Most modern manufacturing centers have both milling machines and lathe machines. Each machine follows the same machining principle, known as subtractive machining, where you begin with a block of material and then shape that material into the desired specifications. How the part is actually shaped is the key difference between the two machines. Understanding the differences in more depth will help in putting the right part in the right machine to maximize their capabilities.
An Example of a Lathe Machine
An Example of a Milling Machine
Operation
The major difference between a milling machine and a lathe machine is the relationship of the workpiece and the tool.
Lathe Machines
In a lathe, the workpiece that is being machined spins about it’s axis, while the cutting tool does not. This is referred to as “turning”, and is effective for creating cylindrical parts. Common operations done on a lathe include drilling, boring, threading, ID and OD grooving, and parting. When looking to create quick, repeatable, and symmetrical cylindrical parts, the lathe machine is the best choice.
Milling Machines
The opposite is true for milling machines. The tool in a milling machine rotates about its axis, while the workpiece does not. This allows the tool to approach the workpiece in many different orientations that more intricate and complex parts demand. If you can program it, you can make it in a milling machine as long as you have the proper clearance and choose the proper tooling.
Best Practice
The best reason to use a milling machine for an upcoming project is the versatility. The tooling options for a milling machine are endless, with hundreds of available specialty cutting tools and various styles of end mills which make sure you are covered from start to finish on each job. A mill can also cut more complex pieces than a lathe. For example, it would impossible to efficiently machine something like an intake manifold for an engine on a lathe. For intricate parts like that, a milling machine would be required for successful machining.
While lathe machines are more limited in use than a milling machine, they are superior for cylindrical parts. While a mill can make the same cuts that a lathe does, it may need multiple setups to create the same part. When continuous production of cylindrical parts is necessary, a lathe will outperform the mill and increase both performance and efficiency.
Running It Too Fast or Too Slow Can Impact Tool Life
Determining the right speeds and feeds for your tool and operation can be a complicated process, but understanding the ideal speed (RPM) is necessary before you start running your machine to ensure proper tool life. Running a tool too fast can cause suboptimal chip size or even catastrophic tool failure. Conversely, a low RPM can result in deflection, bad finish, or simply decreased metal removal rates. If you are unsure what the ideal RPM for your job is, contact the tool manufacturer.
Feeding It Too Little or Too Much
Another critical aspect of speeds and feeds, the best feed rate for a job varies considerably by tool type and workpiece material. If you run your tool with too slow of a feed rate, you run the risk of recutting chips and accelerating tool wear. If you run your tool with too fast of a feed rate, you can cause tool fracture. This is especially true with miniature tooling.
Using Traditional Roughing
While traditional roughing is occasionally necessary or optimal, it is generally inferior to High Efficiency Milling (HEM). HEM is a roughing technique that uses a lower Radial Depth of Cut (RDOC) and a higher Axial Depth of Cut (ADOC). This spreads wear evenly across the cutting edge, dissipates heat, and reduces the chance of tool failure. Besides dramatically increasing tool life, HEM can also produce a better finish and higher metal removal rate, making it an all-around efficiency boost for your shop.
Using Improper Tool Holding and its Effect on Tool Life
Proper running parameters have less of an impact in suboptimal tool holding situations. A poor machine-to-tool connection can cause tool runout, pullout, and scrapped parts. Generally speaking, the more points of contact a tool holder has with the tool’s shank, the more secure the connection. Hydraulic and shrink fit tool holders offer increased performance over mechanical tightening methods, as do certain shank modifications, like Helical’s ToughGRIP shanks and the Haimer Safe-Lock™.
Not Using Variable Helix/Pitch Geometry
A feature on a variety of high performance end mills, variable helix, or variable pitch, geometry is a subtle alteration to standard end mill geometry. This geometrical feature ensures that the time intervals between cutting edge contact with the workpiece are varied, rather than simultaneous with each tool rotation. This variation minimizes chatter by reducing harmonics, which increases tool life and produces superior results.
Choosing the Wrong Coating Can Wear on Tool Life
Despite being marginally more expensive, a tool with a coating optimized for your workpiece material can make all the difference. Many coatings increase lubricity, slowing natural tool wear, while others increase hardness and abrasion resistance. However, not all coatings are suitable to all materials, and the difference is most apparent in ferrous and non-ferrous materials. For example, an Aluminum Titanium Nitride (AlTiN) coating increases hardness and temperature resistance in ferrous materials, but has a high affinity to aluminum, causing workpiece adhesion to the cutting tool. A Titanium Diboride (TiB2) coating, on the other hand, has an extremely low affinity to aluminum, and prevents cutting edge build-up and chip packing, and extends tool life.
Using a Long Length of Cut
While a long length of cut (LOC) is absolutely necessary for some jobs, especially in finishing operations, it reduces the rigidity and strength of the cutting tool. As a general rule, a tool’s LOC should be only as long as needed to ensure that the tool retains as much of its original substrate as possible. The longer a tool’s LOC the more susceptible to deflection it becomes, in turn decreasing its effective tool life and increasing the chance of fracture.
As simple as it seems, a tool’s flute count has a direct and notable impact on its performance and running parameters. A tool with a low flute count (2 to 3) has larger flute valleys and a smaller core. As with LOC, the less substrate remaining on a cutting tool, the weaker and less rigid it is. A tool with a high flute count (5 or higher) naturally has a larger core. However, high flute counts are not always better. Lower flute counts are typically used in aluminum and non-ferrous materials, partly because the softness of these materials allows more flexibility for increased metal removal rates, but also because of the properties of their chips. Non-ferrous materials usually produce longer, stringier chips and a lower flute count helps reduce chip recutting. Higher flute count tools are usually necessary for harder ferrous materials, both for their increased strength and because chip recutting is less of a concern since these materials often produce much smaller chips.
https://www.harveyperformance.com/wp-content/uploads/2018/02/Featured-Image-Killing-End-Mill-IMG.jpg3931400Harvey Performance Companyhttp://www.harveyperformance.com/wp-content/uploads/2018/08/Logo_HarveyPerformanceCompany-4.pngHarvey Performance Company2018-02-07 09:08:092023-10-12 09:59:088 Ways You’re Killing Your End Mill
Material Removal Rate (MRR), otherwise known as Metal Removal Rate, is the measurement for how much material is removed from a part in a given period of time. Every shop aims to create more parts in a shorter period of time, or to maximize money made while also minimizing money spent. One of the first places these machinists turn is to MRR, which encompasses Radial Depth of Cut (RDOC), Axial Depth of Cut (ADOC), and Inches Per Minute (IPM) to create the MRR triangle where all three figures impact each other. If you’re aiming to boost your shop’s efficiency, increasing your MRR even minimally can result in big gains by decreasing cycle times and ultimately freeing up machines for increased productivity.
The Material Removal Rate equation is RDOC x ADOC x Feed Rate (IPM). As an example, if your RDOC is .500″, your ADOC is .100″ and your Feed Rate is 41.5 inches per minute, you’d calculate MRR the following way:
MRR = .500″ x .100″ x 41.5 in/min = 2.08 cubic inches per minute.
Optimizing Efficiency
A machinists’ depth of cut strategy is directly related to the Material Removal Rate. Using the proper RDOC and ADOC combination can boost MRR rates, shaving minutes off of cycle times and opening the door for greater production. Utilizing the right approach for your tool can also result in prolonged tool life, minimizing the rate of normal tool wear. Combining the ideal feed rate with your ADOC and RDOC to run at your tool’s “sweet spot” can pay immediate and long term dividends for machine shops.
The following MRR machining chart illustrates how a 1/2″, 5-flute tool will perform in Steel when varying ADOC and RDOC parameters are used. You can see that by varying the ADOC and RDOC, a higher feed rate is achievable, and thus, a higher MRR. In this case, pairing a high ADOC, low RDOC approach with an increased feed rate was most beneficial. This method has become known as High Efficiency Milling.
Axial Depth of Cut
Radial Depth of Cut
Feed Rate
Material Removal Rate
.125″
.200″
19.5 IPM
.488 in.³/min.
.250″
.150″
26.2 IPM
.983 in.³/min.
.500″
.100″
41.5 IPM
2.08 in.³/min.
.750″
.050″
89.2 IPM
3.35 in.³/min.
1.00″
.025″
193 IPM
4.83 in.³/min.
High Efficiency Milling
High Efficiency Milling (HEM) is a milling technique for roughing that utilizes a lower RDOC and a higher ADOC strategy. This spreads wear evenly across the cutting edge, dissipates heat, and reduces the chance of tool failure. This results in a greater ability to increase your MRR in machining, while maintaining and even prolonging tool life versus traditional machining methods.
HEM VS Traditional Milling
The image referenced below compares the differences between traditional milling and the newer High Efficiency Milling technique in achieving adequate material removal. A traditional milling strategy requires the application of work and heat along a smaller portion of the cutting edge, while the HEM technique disperses heat more evenly across the entire cutting edge. This method calls for more radial passes which utilize a larger portion of the cutting edge, as opposed to axial passes that lead to a higher likelihood of tool failure over time.
Obviously, with higher MRR’s, chip evacuation becomes vitally important as more chips are evacuated in a shorter period of time. Utilizing a tool best suited for the operation – in terms of quality and flute count – will help to alleviate the additional workload. For softer materials lower flute count tools will traditionally be the best choice. The thinner core allows for deeper flute valleys which aid in enhanced chip evacuation and ultimately increased MRR. On the other hand, harder materials require higher flute count tools with shallower flute valleys. This leads to less material removed per tooth, however tool life is substantially increased over the historic usage of lower flute count tools in these materials.
Additionally, a tool coating optimized for your workpiece material can significantly help with chip packing. First, tool coatings increase heat resistance of the tool allowing for faster cutting speeds leading to increased MRR. Secondly, coatings increase the lubricity of the cutting tool allowing for enhanced chip evacuation and lessened friction. This enhanced chip evacuation allows for the most efficient metal removal rate possible.
Further, compressed air or coolant can help to properly remove chips from the tool and workpiece. There are different three types of coolant delivery methods one could utilize in increasing metal removal rate.
Compressed Air
While having no lubricity purpose, the air coolant delivery method is made to cool and clear chips. This method does not cool as effectively as other coolant-based solutions, however it is preferred for more sensitive materials where thermal shock is a concern.
Flood
Flooding is a low pressure coolant delivery method which creates lubricity in order to evacuate chips from a part. This is necessary to prevent chip recutting which is likely to damage a cutting tool. This method of delivery is the most common choice for the widest range of machining operations.
High Pressure
This method is similar to flood coolant, however it is used to instantly cool a part and blast chips away with a high pressure of delivery. While highly effective at chip evacuation, this option is most likely to damage or break more fragile cutting tools. High pressure coolant delivery is most often utilized in deep pocket machining and drilling operations due to its increased ability to flush chips.
In conclusion, optimizing workplace efficiency is vital to sustained success and continued growth in every business. This is especially true in machine shops, as even a very minor adjustment in operating processes can result in a massive boost in company revenue. Proper machining methods will boost MRR, minimize cycle times, prolong tool life, and maximize shop efficiency.
https://www.harveyperformance.com/wp-content/uploads/2018/01/Featured-Image-Optimizing-MRR-IMG.jpg5251400Harvey Performance Companyhttp://www.harveyperformance.com/wp-content/uploads/2018/08/Logo_HarveyPerformanceCompany-4.pngHarvey Performance Company2018-01-15 10:25:152024-02-12 10:29:03Optimizing Material Removal Rates
Coolant in purpose is widely understood – it’s used to temper high temperatures common during machining, and aid in chip evacuation. However, there are several types and styles, each with its own benefits and drawbacks. Knowing which cnc coolant – or if any – is appropriate for your job can help to boost your shop’s profitability, capability, and overall machining performance.
Coolant or Lubricant Purpose
Coolant and lubricant are terms used interchangeably, though not all coolants are lubricants. Compressed air, for example, has no lubricating purpose but works only as a cooling option. Direct coolants – those which make physical contact with a part – can be compressed air, water, oil, synthetics, or semi-synthetics. When directed to the cutting action of a tool, these can help to fend off high temperatures that could lead to melting, warping, discoloration, or tool failure. Additionally, coolant can help evacuate chips from a part, preventing chip recutting and aiding in part finish.
Coolant can be expensive, however, and wasteful if not necessary. Understanding the amount of coolant needed for your job can help your shop’s efficiency.
CNC coolant is delivered in several different forms – both in properties and pressure. The most common forms include air, mist, flood coolant, high pressure, and Minimum Quantity Lubricant (MQL). Choosing the wrong pressure can lead to part or tool damage, whereas choosing the wrong amount can lead to exhausted shop resources.
Air: Cools and clears chips, but has no lubricity purpose. Air coolant does not cool as efficiently as water or oil-based coolants. For more sensitive materials, air coolant is often preferred over types that come in direct contact with the part. This is true with many plastics, where thermal shock – or rapid expansion and contraction of a part – can occur if direct coolant is applied.
Mist: This type of low pressure coolant is sufficient for instances where chip evacuation and heat are not major concerns. Because the pressure applied is not great in a mist, the part and tool do not undergo additional stresses.
Flood: This low pressure method creates lubricity and flushes chips from a part to avoid chip recutting, a common and tool damaging occurrence.
High Pressure: Similar to flood coolant, but delivered in greater than 1,000 psi. This is a great option for chip removal and evacuation, as it blasts the chips away from the part. While this method will effectively cool a part immediately, the pressure can be high enough to break miniature diameter tooling. This method is used often in deep pocket or drilling operations, and can be delivered via coolant through tooling, or coolant grooves built into the tool itself. Harvey Tool offers Coolant Through Drills, while Titan USA proudly offers Coolant-Fed ThreadMills
Minimum Quantity Lubricant (MQL): Every machine shop focuses on how to gain a competitive advantage – to spend less, make more, and boost shop efficiency. That’s why many shops are opting for MQL, along with its obvious environmental benefits. Using only the necessary amount of coolant will dramatically reduce costs and wasted material. This type of lubricant is applied as an aerosol, or an extremely fine mist, to provide just enough coolant to perform a given operation effectively.
To see all of these coolant styles in action, check out the video below from our partners at CimQuest.
In Conclusion
CNC coolant is all-too-often overlooked as a major component of a machining operation. The type of coolant or lubricant, and the pressure at which it’s applied, is vital to both machining success and optimum shop efficiency. Coolant can be applied as compressed air, mist, in a flooding property, or as high pressure. Certain machines also are MQL able, meaning they can effectively restrict the amount of coolant being applied to the very amount necessary to avoid being wasteful.
https://www.harveyperformance.com/wp-content/uploads/2017/12/Feature-Image-Coolant-for-CNC-Machining-IMG.jpg5251400Harvey Performance Companyhttp://www.harveyperformance.com/wp-content/uploads/2018/08/Logo_HarveyPerformanceCompany-4.pngHarvey Performance Company2017-12-05 15:09:342022-04-20 16:52:22What You Need to Know About Coolant for CNC Machining
Cutting tools undergo a great deal of force during the machining process, which cause vibrations – also known as chatter or harmonics. Avoiding these vibrations entirely is not possible, though minimizing them is pivotal for machining success. Vibrations become damaging when proper machining steps are not followed. This leads to strong, part-ruining chatter. In these situations, parts have what is known as “chatter marks,” or clear vibration marks along the surface of a part. Tools can experience an increased rate of wear due to excess vibration.
It seems elementary, but selecting the best tool for your application can be confusing. With so many different geometric styles for tooling – overall length, length of cut, reach, number of flutes – it can sometimes be difficult to narrow down one specific tool for your job. Oftentimes, machinists opt for general purpose tooling that can perform a variety of operations, overlooking the option that’s optimized for one material and job.
Use Material Specific Tooling
Opting for Material Specific Tooling is helpful, as each material has different needs. For example, steels are machined differently than aluminum materials. Everything from the chip size, to chip evacuation, is different. Variable Helix or Variable Pitch designs help to minimize chatter by reducing harmonics, which are caused by the cutting edge having repeated contact with the workpiece. In order to reduce harmonics, the time intervals between flute contact with the workpiece are varied.
Consider Tool Length
Overall length is another important factor to consider when deciding on a tool for your job. The more overhang, or length the tool hangs from the spindle, the less secure the spindle-to-tool connection is, and the more vibration. Ensuring that your tool is only as long as needed for your operation is important to minimizing chatter and harmonics. If machining deep within a part, opt for reached tooling or an extended reach tool holder to help solidify the connection.
Ensure a Secure Connection
Tool Holder & Shank Relationship
When it comes to secure tool holding approaches, both the tool shank and the collet are important. A loose tool, unsurprisingly, has more ability to move, or vibrate, during machining. With this in mind, Helical offers Shank Configurations to help the connection including the ToughGRIP Shank, which replaces a smooth, mirror-like surface with a rougher, coarser one for increased friction. Helical is also a licensee of the HAIMER Safe-Lock™, added grooves on the shank of a tool that work opposite of the spindle rotation, securely fastening the tool in place.
Choosing Collet Types
Machinists must also know the different types of collets available to them to identify if a better solution might be necessary. For example, Hydraulic Tool Holders or Shrink Fit Tool Holders promote a stronger connection than a Mechanical Spindle Tightening method.
How a tool is run can mean the difference between stellar job results and a ruined part. This includes both the parameters a tool is run at, as well as the direction by which it rotates – either a Conventional Milling or a Climb Milling technique. The key distinction between these two methods lies in the relationship between the cutter’s rotation and the direction of the feed.
Conventional Milling
In conventional milling, the chip width starts from zero and increases gradually, causing the process of heat generation onto the workpiece rather than the chips. Heat generation causes deformities and tool failure such as work hardening, creating more headaches for a machinist. For this reason, conventional milling is generally only recommended for tools with high toughness or for breaking into case hardened materials.
Climb Milling
Most modern machine shops will use a climb milling technique, or when the chip width starts at its maximum and decreases during the cut. Climb Milling will offer a more consistent cut than traditional methods, and puts less stress on the tool. Think of it like weight lifting – doing the heavy lifting will be easiest at the beginning of your workout. Similarly, a cut in which the thickest chip is removed first helps the tool maintain its strength. Because the chip cutting process is more swift, vibrations are minimized.
Vibrations are unavoidable during the machining process, but minimizing them can mean the difference between successful machining and scrapped parts. Following three simple rules can help to keep your chatter and harmonics under control, including: Selecting the right tool, ensuring a secure machine-tool connection, and using it in a climb milling strategy. Both Harvey Tool and Helical Solutions have tools that can help, including shank modifications and Variable Helix or Variable Pitch end mills.
https://www.harveyperformance.com/wp-content/uploads/2017/11/Feature-Image-Tool-Chatter-IMG.jpg5251400Harvey Performance Companyhttp://www.harveyperformance.com/wp-content/uploads/2018/08/Logo_HarveyPerformanceCompany-4.pngHarvey Performance Company2017-11-08 09:30:472023-12-01 16:08:473 Steps to Shutting up Tool Chatter
NOTE: This article covers speeds and feed rates for milling tools, as opposed to turning tools.
Before using a cutting tool, it is necessary to understand tool cutting speeds and feed rates, more often referred to as “speeds and feeds.” Speeds and feeds are the cutting variables used in every milling operation and vary for each tool based on cutter diameter, operation, material, etc.
Understanding the right speeds and feeds for your tool and operation before you start machining is critical. These are to be used to set baselines for a particular tool, ensuring proper performance without compromising part finish and tool life.
NOTE: This article covers speeds and feed rates for milling tools, as opposed to turning tools.
Understanding SFM Calculations
It is first necessary to define each of these factors. Cutting speed, also referred to as surface speed, is the difference in speed between the tool and the workpiece, expressed in units of distance over time known as SFM (surface feet per minute).
For set-ups with stationary workpieces, SFM is the speed at which a tool moves across the part in the cut. The speed difference must be calculated in set ups where the part and tool are both moving in multi-axis machining set-ups.
Surface Foot is based on the various properties of the given material. Speed, referred to as Rotations Per Minute (RPM) is based off of the SFM and the cutting tool’s diameter. As SFM is tied to the properties of a material, it does not change based upon the operation being performed and remains constant despite changes in chip load calculation.
How Do You Calculate Surface Feet per Minute (SFM)?
The SFM calculation utilizes the industry standard of 3.82. Here, the cutter diameter of the chosen tool is multiplied by the speed or RPM. This figure is then divided by 3.82 to generate the SFM or Surface Feet per Minute.
Feed Rate and Chip Load Calculations
While speeds and feeds are common terms used in the programming of the cutter, the ideal running parameters are also influenced by a myriad of other variables. As speeds and feeds must be well-matched to be effective, the speed of the cutter is used in the calculation of the cutter’s feed rate, measured in Inches Per Minute (IPM).
The other part of the equation is the chip load, or material being removed per revolution. It is important to note that chip load per tooth and chip load per tool are different:
Chip load per tooth is the appropriate amount of material that one cutting edge of the tool should remove in a single revolution. This is measured in Inches Per Tooth (IPT).
Chip load per tool is the appropriate amount of material removed by all cutting edges on a tool in a single revolution. This is measured in Inches Per Revolution (IPR).
A chip load that is too large can pack up chips in the cutter, causing poor chip evacuation and eventual breakage. A chip load that is too small can cause rubbing, chatter, tool deflection, and a poor overall cutting action. Finding the correct balance will not only allow for the most efficient cut possible, but also ensures the most efficiency in regard to tool wear. When calculating chip load per tool or IPR, the per tooth chip load is aptly multiplied by the number of flutes on the tool itself.
Material Removal Rate
Material Removal Rate (MRR), while not part of the cutting tool’s program, is a helpful way to calculate a tool’s efficiency. MRR takes into account two very important running parameters: Axial Depth of Cut (ADOC), or the distance a tool engages a workpiece along its centerline, and Radial Depth of Cut (RDOC), or the distance a tool is stepping over into a workpiece.
The MRR calculation (seen below) relies on the calculated feed rate. The feed rate (IPM) is multiplied by the radial and axial depths of cut to produce the rate of removal.
The tool’s depth of cuts and the rate at which it is cutting can be used to calculate how many cubic inches per minute (in3/min) are being removed from a workpiece. This equation is extremely useful for comparing cutting tools and examining how cycle times can be improved. Decreased cycle times leads to higher productivity within a shop, which is what all machinists aim for during production.
Adjusting depths of cut can decrease time in cut and overall production time, freeing up machines for additional manufacturing. An example of depth of cut adjustment is seen in High Efficiency Milling, where RDOC is decreased and ADOC is increased. In this method, MRR is increased while also reducing tool wear, leading to higher productivity and more parts per tool.
Speeds and Feeds In Practice
While many of the cutting parameters are set by the tool and workpiece material, the depths of cut taken also affect the feed rate of the tool. The depths of cuts are dictated by the operation being performed – this is often broken down into slotting, roughing, and finishing. Though there are many other more specific types of operations.
These unique operations utilize much different depths of cut, with industry standardized terms as description. Slotting can be described as utilizing 180° of the diameter of the tool engaged in the cut.
Roughing on the other hand will typically disperse both ADOC and RDOC relatively evenly. Finally, finishing operations will use substantially more axial depths of cut in relation to radial, leaving the best finish possible on the workpiece.
Many tooling manufacturers provide useful speeds and feeds charts calculated specifically for their products. For example, Harvey Tool provides the following chart for a 1/8” diameter end mill, tool #50308.
A customer can find the SFM for the material on the left, in this case 304 stainless steel (highlighted in yellow). The chip load (per tooth) can be found by intersecting the tool diameter on the top (blue heading) with the material and operations (based on axial and radial depth of cut), highlighted in the image below.
The following table calculates the speeds and feeds for this tool (#50308) and material (304 Stainless) for each operation, based on the chart above:
Each operation recommends a unique chip load per the depths of cut depending on the operation, thus resulting in different feed rates for the desired application. Since the SFM is based on the material, it will always remain constant for each of the three defined operations.
Milling speeds between materials vary drastically. For example, the milling speed for stainless will differ than that of much softer aluminum. Therefore, it is always important to factor in materials when examining speeds and feeds chart and performing calculations.
Spindle Speed Cap
As shown above, the cutter speed (RPM) is defined by the SFM (based on material) and the cutter diameter. With miniature tooling and/or certain materials the speed calculation sometimes yields an unrealistic spindle speed.
For example, a .047” cutter in 6061 aluminum (SFM 1,000) would return a speed of ~81,000 RPM. Since this speed is only attainable with high speed air spindles, the full SFM of 1,000 may not be achievable. In a case like this, it is recommended that the tool is run at the machine’s max speed (that the machinist is comfortable with) and that the appropriate chip load for the diameter is maintained. This produces optimal parameters based on the machine’s top speed.
All machines are unique and provide different max speed, therefore these calculations will vary based on machine capabilities within your shop.
Effective Cutter Diameter
On angled tools the cutter diameter changes along the LOC. For example, Helical tool #07001, a flat-ended chamfer cutter with helical flutes, has a tip diameter of .060” and a major/shank diameter of .250”. In a scenario where it was being used to create a 60° edge break, the actual cutting action would happen somewhere between the tip and major/shank diameters. To compensate, the equation below can be used to find the average diameter along the chamfer.
Using this calculation, the effective cutter diameter is .155”, which would be used for all Speeds and Feeds calculations.
Non-linear Path
Feed rates assume a linear motion. However, there are cases in which the path takes an arc, such as in a pocket corner or a circular interpolation. Just as increasing the DOC increases the angle of engagement on a tool, so does taking a nonlinear path. For an internal corner, more of the tool is engaged and, for an external corner, less is engaged. The feed rate must be appropriately compensated for the added or lessened engagement on the tool to provide the most effective and desired IPM for the chosen application.
In the below graphic, Figure A is showcasing a linear path on a part, with a standard engagement. Figure’s B and C demonstrate the increase and decrease of engagement in non-linear, circular toolpaths. Utilizing identical feed rates between the three paths would generate three wildly different IPMs despite similar setups.
This adjustment is even more important for circular interpolation. Take, for example, a threading application involving a cutter making a circular motion about a pre-drilled hole or boss. For internal adjustment, the feed rate must be lowered to account for the additional engagement. For external adjustment, the feed rate must be increased due to less tool engagement.
An adjustment in internal feed subtracts the differences in cutter diameters from the differences in outer diameters before dividing by the outer dia. difference. On the other hand, adjusting for external feed adds the differences between cutter diameters to the differences in inner diameters before dividing by the inner dia. difference.
Take this example, in which a Harvey Tool threadmill #70094, with a .370” cutter diameter, is machining a 9/16-18 internal thread in 17-4 stainless steel. The calculated speed is 2,064 RPM and the linear feed is 8.3 IPM. The thread diameter of a 9/16 thread is .562”, which is used for the inner and outer diameter in both adjustments. After plugging these values into the equations below, the adjusted internal feed becomes 2.8 IMP, while the external feed becomes 13.8 IPM.
SFM in Conclusion
These calculations are useful guidelines for running a cutting tool optimally in various applications and materials. However, the tool manufacturer’s recommended parameters are the best place to start for initial numbers and to set a baseline for the best tool performance.
After that, it is up to the machinist’s eyes, ears, and experience to help determine the best running parameters, which will vary by set-up, tool, machine, and chosen material. No operation is exactly the same, and nothing occurs in a vacuum. Experience and continued learning will always aid machinists in ensuring the most efficient performance possible in the cut.
The following links have the most up to date information on running parameters for Harvey Tool, Helical, Titan USA, and CoreHog CNC products.
https://www.harveyperformance.com/wp-content/uploads/2017/10/Feature-Image-Speeds-Feeds-IMG.jpg5251400Harvey Performance Companyhttp://www.harveyperformance.com/wp-content/uploads/2018/08/Logo_HarveyPerformanceCompany-4.pngHarvey Performance Company2017-10-02 17:00:172025-02-14 10:48:58Speeds and Feeds 101
Tool runout is a given in any machine shop, and can never be 100% avoided. Thus, it is important to establish an acceptable level of runout for any project, and stay within that range to optimize productivity and prolong tool life. Smaller runout levels are always better, but choice of machine and tool holder, stick-out, tool reach, and many other factors all have an influence on the amount of runout in every setup.
Defining Tool Runout
Tool runout is the measurement of how far a cutting tool, holder, or spindle rotates off of its true axis. This can be seen in low quality end mills where the cutting diameter is true to size when measured while stationary, but measures above tolerance while rotating.
The first step to minimizing runout is understanding what individual factors cause runout in every machine setup. Runout is seen in the accuracy of every cutting tool, collet, tool holder, and spindle. Every added connection between a machine and the workpiece it is cutting will introduce a higher level of runout. Each increase can add to the total runout further and further. Steps should be taken with every piece of tooling and equipment to minimize runout for best performance, increased tool life, and quality finished products.
Measuring Runout
Determining the runout of your system is the first step towards finding how to combat it. Runout is measured using an indicator that measures the variation of a tool’s diameter as it rotates. This is done with either a dial/probe indicator or a laser measuring device. While most dial indicators are both portable and easy to use, they are not as accurate as the available laser indicators, and can also make a runout measurement worse by pushing on a tool. This is mostly a concern for miniature and micro-tooling, where lasers should be strictly used due to the tool’s fragile nature. Most end mill manufacturers recommend using a laser runout indicator in place of a dial indicator wherever possible.
Z-Mike laser measurement devices are common instruments used to measure levels of tool runout.
Runout should be measured at the point where a tool will be cutting, typically at the end of the tools, or along a portion of the length of cut. A dial indicator may not be plausible in these instances due to the inconsistent shape of a tool’s flutes. Laser measuring devices offer another advantage due to this fact.
High Quality Tools
The amount of runout in each component of a system, as-manufactured, often has a significant impact on the total runout of a given setup. Cutting tools all have a restriction on maximum runout allowed when manufactured, and some can have allowances of .0002” or less. This is often the value that should be strived for in a complete system as well. For miniature tooling down to .001” diameter, this measurement will have to be held to an even smaller value. As the ratio of tool runout to tool diameter becomes larger, threats of tool failure increase. As stated earlier, starting with a tool that has minimal runout is pivotal in keeping the total runout of a system to a minimum. This is runout that cannot be avoided.
Precision Tool Holders
The next step to minimizing runout is ensuring that you are using a high quality, precision tool holder. These often come in the form of shrink-fit, or press-fit tool holders offering accurate and precise tool rotation. Uniform pressure around the entire circumference of a shank is essential for reducing runout. Set screw based holders should be avoided, as they push the tool off-center with their uneven holding pressure. Collet-based tool holders also often introduce an extra amount of runout due to their additional components. Each added connection in a tool holding system allows more methods of runout to appear. Shrink-fit and press-fit tool holders are inherently better at minimizing runout due to their fewer components.
Included in your tool holding considerations should be machine tool cleanliness. Often, chips can become lodged in the spindle, and cause an obstruction between two high-precision surfaces in the system. Ensuring that your tool holder and spindle are clean and free of chips and debris is paramount when setting up for every job.
Shank Modifications
Apart from equipment itself, many other factors can contribute to an increasing amount of tool runout. These can include how long a tool is, how rigid a machine setup is, and how far a tool is hanging out of its holder. Shank modifications, along with their methods of tool holding can have a large impact. Often thought of as an older, obsolete technology, Weldon flats are found guilty of adding large amounts of runout in many shops. While many shops still use Weldon flats to ensure a secure grip on their tools, having a set screw pushing a tool to one side can push it off center, yielding very high levels of runout. Haimer Safe Lock™ is another option increasing in popularity that is a much higher performance holding technology. The Safe-Lock™ system is designed with the same tolerances as shrink fit and other high precision tool holders. It is able to minimize runout, while firmly holding a tool in place with no chance of pull-out.
The Haimer Safe-Lock™ system is one option to greatly reduce tool runout.
Runout will never be completely eliminated from a machining system. However, steps can (and should) be taken to keep it to a minimum using every method possible. Keeping a tool running true will extend tool life, increase performance, and ultimately save your shop time and money. Runout is a common concern in the metalworking industry, but it is often overlooked when it could be main issue causing part rejections and unacceptable results. Every piece of a machine tool plays a part in the resultant runout, and none should be overlooked.
The following is just one of several blog posts relevant to High Efficiency Milling. To achieve a full understanding of this popular machining method, view any of the additional HEM posts below!
Tool wear is the breakdown and gradual failure of a cutting tool due to regular operation. Every tool will experience tool wear at some point in its life. Excessive wear will show inconsistencies and have unwanted effects on your workpiece, so it is important to avoid tool wear in order to achieve optimal end mill performance. Tool wear can also lead to failure, which in turn can lead to serious damage, rework, and scrapped parts.
An example of a tool with no wearAn example of a tool with excessive wear
To prolong tool life, identifying and mitigating the various signs of cutting tool wear is key. Both thermal and mechanical stresses cause tool wear, with heat and abrasion being the major culprits. Learning how to identify the most common types of tool wear and what causes them can help machinists remedy issues quickly and extend tool longevity.
Types of Tool Wear And Their Solutions
Abrasive Wear
The wear land is a pattern of uniform abrasion on the cutting edge of the tool, caused by mechanical abrasion from the workpiece. This dulls the cutting edge of a tool, and can even alter dimensions such as the tool diameter. At higher speeds, excessive heat becomes more of an issue, causing more damage to the cutting edge, especially when an appropriate tool coating is not used.
Utilizing Proper Tool Coatings
Using a tool coating with a high microhardness rating is crucial to avoiding abrasive wear. Microhardness ratings help determine a cutting tool’s level of wear resistance. For example, bare tungsten carbide has a Vickers Hardness (HV) ranging from 760 HV to 1740 HV while coatings such as TiN have an HV of 2213 or more. Despite facing maximum forces during cutting operations, the addition of coating on a tool significantly improves its ease of material removal due to higher hardness. When hardness in a coating is elevated wear is mitigated due to the stack up.
Coolant Usage
If the wear land becomes excessive or causes premature tool failure, reducing the cutting speed and optimizing coolant usage can help. Coolant is directed towards the cutting action of a tool during CNC operations. It prevents tool failure by countering high temperatures. Generally machinists opt for either Flood or High Pressure coolant methods. Flooding allows for low pressure chip flushing by providing lubricity. High Pressure coolant provides almost instant cooling of a part and works to evacuate chips at a faster rate. Both methods improve part finish and minimize chip recutting, which can damage a cutting tool.
High Efficiency Milling
High Efficiency Milling (HEM) toolpaths can help reduce wear by spreading the work done by the tool over its entire length of cut. This prevents localized wear and will prolong tool life by using the entire cutting edge available. The image referenced below compares traditional (standard) milling and the newer HEM method. HEM evenly disperses heat across the cutting edge by employing a lower radial depth of cut (RDOC) and a higher axial depth of cut (ADOC). This reduces the likelihood of tool failure and lengthens the tool wear process.
Chipping
Chipping can be easily identified by a nicked or flaked edge on the cutting tool, or by examining the surface finish of a part. A poor surface finish can often indicate that a tool has experienced some sort of chipping, which can lead to eventual catastrophic tool failure if it is not caught. \When a chipped tool engages with a workpiece the cutting edges are not even leading to high and low spots within the surface finish.
Chipping is typically caused by excessive loads and shock-loading during operation, but it can also be caused by thermal cracking, another type of tool wear which is explored in further detail below.
Reduce Chatter
To counter chipping, ensure the milling operation is completely free of vibration and chatter. Chatter occurs because cutting tools experience high forces during CNC machining operations. While machinists cannot entirely avoid chatter, minimizing it prevents vibration marks and excess wear from appearing along the surface of a tool or part. Taking a look at the speeds and feeds can also help. Interrupted cuts and repeated part entry can also have a negative impact on a tool. Reducing feed rates for these situations can mitigate the risk of chipping.
Thermal Cracking
Thermal cracking is often identified by cracks in the tool perpendicular to the cutting edge. Cracks form slowly, but they can lead to both chipping and premature tool failure.
Thermal cracking, as its name suggests, is caused by extreme temperature fluctuations during milling. Adding a proper coating to an end mill is beneficial in providing heat resistance and reduced abrasion on a tool.
HEM Toolpaths
HEM toolpaths provide excellent protection against thermal cracking. As previously mentioned, these toolpaths spread the heat across the cutting edge of the tool, reducing the overall temperature and preventing serious fluctuations in heat.
Fracture
Fracture is the complete loss of tool usage due to sudden breakage, often as a result of improper speeds and feeds, an incorrect coating, or an inappropriate depth of cut.
Optimal Tool Holding
Tool holder issues or loose work holding can also cause a fracture, as can inconsistencies in workpiece material properties. Establishing a secure connection between the tool and machine reduces the risk of tool runout and scrapped parts. Machinists generally experience improved performance in hydraulic and shrink fit tool holders compared to more mechanical tightening methods.
Adjusting the speeds, feeds, and depth of cut and checking the setup for rigidity will help to reduce fracturing. The tool’s axial engagement with a part must be appropriate in order to prevent tool deflection, especially during slotting operations. As pictured below, with increasing slot lengths comes the necessity for longer lengths of cut. Above all, you should choose a tool that offers the highest productivity and least amount of deflection.
Optimizing coolant usage can also be helpful to avoid hot spots in materials which can dull a cutting edge and cause a fracture. HEM toolpaths prevent fracture by offering a more consistent load on a tool. Shock loading is reduced, causing less stress on a tool, which lessens the likelihood of breakage and increases tool life.
It is important to monitor tools and keep them in good, working condition to avoid downtime and save money. Wear is caused by both thermal and mechanical forces, which can be mitigated by running with appropriate running parameters and HEM toolpaths to spread wear over the entire length of cut. While every tool will eventually experience some sort of tool wear, the effects can be delayed by paying close attention to speeds and feeds and depth of cut. Preemptive action should be taken to correct issues before they cause complete tool failure.
https://www.harveyperformance.com/wp-content/uploads/2017/07/Feature-Image-Tool-Wear-IMG.jpg5251400Harvey Performance Companyhttp://www.harveyperformance.com/wp-content/uploads/2018/08/Logo_HarveyPerformanceCompany-4.pngHarvey Performance Company2017-07-11 16:30:432023-11-17 14:56:39How to Avoid 4 Major Types of Tool Wear
Ball nose end mills are ideal for machining 3-dimensional contour shapes typically found in the mold and die industry, the manufacturing of turbine blades, and fulfilling general part radius requirements. To properly employ a ball nose end mill (with no tilt angle) and gain the optimal tool life and part finish, follow the 2-step process below (see Figure 1).
Step One: Calculate Your Effective Cutting Diameter
A ball nose end mill’s Effective Cutting Diameter (Deff) differs from its actual cutting diameter when utilizing an Axial Depth of Cut (ADOC) that is less than the full radius of the ball. Calculating the effective cutting diameter can be done using the chart below that represents some common tool diameters and ADOC combinations or by using the traditional calculation (see Figure 2).
Step Two: Calculate Your Compensated Speed
Given the new effective cutting diameter a “Compensated Speed” will need to be calculated. If you are using less than the cutter diameter, then its likely your RPM’s will need to be adjusted upward (see Figure 3).
KEY ADOC = Axial Depth of Cut D = Cutting Diameter Deff = Effective Cutting Diameter R = Tool Radius (Dia./2) RDOC = Radial Depth of Cut SFM = Surface Feet per Minute Sc = Compensated Speed
Ball Nose Milling With a Tilt Angle
If possible, it is highly recommended to use ball nose end mills on an incline (ß) to avoid a “0” SFM condition at the center of the tool, thus increasing tool life and part finish (Figure 4). For ball nose optimization (and in addition to tilting the tool), it is highly recommended to feed the tool in the direction of the incline and utilize a climb milling technique.
To properly employ a ball nose end mill with a tool angle and gain the most optimal tool life and part finish, follow the 2-step process below.
Step One: Calculate Your Effective Cutting Diameter
The chart below that represents some common effective cutting diameters and ADOCs at a 15º tilt angle. Otherwise, the traditional calculation below may be used (see Figure 5).
Step Two: Calculate Your Compensated Speed
Given the new effective cutting diameter a compensated speed will need to be calculated. If you are using less than the cutter diameter, then its likely your RPM’s will need to be adjusted upward (see Figure 6).
Machining is one of the fastest growing occupations in the US, with thousands of open positions listed all across various job boards and websites. Because graduating students are more likely to head to college than join the trades, there is currently a major shortage in the workforce for machinists. As the “Baby Boomer” generation inches closer to retirement, this shortage will only continue to grow. According to American Machinist, nearly 70% of the current machinist workforce is over the age of 45, which means there is a great need for younger workers over the next two decades. The Bureau of Labor Statistics (BLS) is predicting a 10% increase in the machinist workforce with opportunities for 29,000 additional skilled machinists by 2024, so it is certainly an exciting time to start thinking about the available career opportunities in the machining industry.
Getting Started
One of the best things about becoming a machinist is that there is a fairly low barrier to entry level positions. Many machinists start working right out of high school, with 12-18 months of on-the-job training or a 1-2 year apprenticeship. This path generally does not require any experience past a high school education, but prospective machinists are encouraged to take math classes including geometry and trigonometry, and participate in metalworking, drafting, and blueprint reading classes if possible. Chris Metayer, a CNC Operator with Helical Solutions, took this same route to begin his career. “I didn’t know anything about machining when I started, but I trained side by side with other employees. I am a hands-on learner, so it was a perfect learning experience for me.” said Metayer. In the end, most of an entry-level machinists’ learning will be done hands-on in the machine shop while getting paid to learn the craft.
Others may take a two-year machining-based program at a community college or technical school, where they can learn more advanced skills like Computer Numerical Control (CNC) Machining and Computer Aided Design (CAD) or Computer Aided Manufacturing (CAM) programming. They would then enter the workforce following the completion of an associate’s degree. These machinists tend to earn higher salaries and are more apt to advance to a management role, but they will also need to pay for the costs of their continued education and will still require some hands-on training before they can jump into their new positions. However, there are added benefits to continuing your education. Jake Barnes, another member of the CNC team at Helical, earned his associates degree in Integrated Manufacturing Technology at Southern Maine Community College, and has worked in various departments since joining Helical. Jake started as a manual grinder, then moved to inspection before landing with the CNC team. “I personally recommend going to a trade school” said Barnes, “You will get exposure to many different classes, which opens up new career opportunities across the industry.”
Some machinists who want to work in more advanced industries like aerospace or tech may attend a four-year college and take advanced courses in calculus, physics, and engineering. All of these options are widely accepted in the machining community, so it is more a matter of personal preference and an individual’s specific situation that determine which path to take.
Location Matters
While there are open jobs for machinists all over the country, there are certainly a few areas that would be considered machinist “hot spots.” These areas of the country have increased job openings in the industry and often pay better wages, since machining skills are in higher demand. The Great Lakes Region (Michigan, Ohio, Illinois, Indiana, Upstate New York, Pennsylvania), and the Southeast (The Carolinas, Louisiana, Georgia, Alabama, Mississippi) are great places to look for work, with over 150,000 currently employed machinists. Most of the work in the Great Lakes Region is dominated by the automotive industry, especially in Michigan. In the Southeast US, there has been a recent influx of manufacturing jobs after plants owned by Apple, Boeing, General Electric, Haier, and LeNovo all opened in the area. In fact, Mississippi offers the highest annual salaries for machinists of any state in the country.
Texas, California, and Washington (especially Seattle) are also hot spots for machining jobs. The west coast holds some of the world’s largest aerospace manufacturing plants, so these areas have plenty of job opportunities for machining and manufacturing.
A career as a machinist can be rewarding and fun, especially when it comes to working with different materials and creating amazing and intricate parts. But in the end, compensation matters as well. What is often misunderstood most about this industry is that the salary range for machinists is above the national median.
The Bureau of Labor Statistics (BLS) reported in 2016 that those in the workforce with a high school diploma earned an annual median salary of $36,000, while those with an associate’s degree earned $42,000 across all occupations. The BLS also reported the median salaries for machinists in 2016, with median earnings at $43,200, across all levels of education.
The top 10% of machinists earn over $62,500, and depending on what projects they work on, those wages can go even higher. For example, someone working in the aerospace industry or tech industry can expect to make a higher salary as a machinist, but will likely need to have a more extensive education, which can get costly. Experience also matters, as salaries are likely to increase as machinists get more years under their belts. However, many entry level machinist jobs require little to no educational cost and no experience, so the return on investment can be very high once hired into the industry.
Machinist Career Paths
There are quite a few career paths that a machinist can take once they begin working on their craft. Some machinists will work their way up the shop ladder, going from an entry level CNC operator, to a full-on CNC machinist, and possibly finding themselves in a shop management position at some point in their careers. Others may transition away from machining and begin to work with CAD/CAM or CNC Programming applications, working with the machinists on the floor to program and troubleshoot the machines and design new parts to be created. Many machinists also move into careers in inspection, quality control, or production planning, which can be an excellent way to move up the corporate ladder.
Working in Inspection is a possible career path for a machinist.
Those who do earn an associate’s degree in a machining-based program should consider a path in engineering. The experiences learned as a machinist translate well to this field, and having an associate’s degree allows for the flexibility of going back to school to finish up a Bachelor’s degree in mechanical engineering. For those who may be unable to go to school full-time, there are many online and part-time courses available. These courses make it possible to work full-time or part-time to advance your skills and attain hands-on experience while earning a degree. Both Barnes and Matayer talked about heading back to school to complete an engineering program at some point, taking advantage of the Harvey Performance Company tuition reimbursement program to advance their education and careers.
The skills learned as a machinist also lay a foundation for becoming an entrepreneur or starting a business. Some machinists will open their own machine shops, manufacturing outsourced parts from other companies, while others will take their skills and create a unique product to fulfill a need they identify in the market.
Do Your Research
As the manufacturing industry continues to grow in America, the shortage of machinists in the workforce will become an incredible source of opportunity for our youth. Breaking into the industry now can set young machinists up for great career opportunities. The skills learned as a machinist also translate well to many different jobs, especially in manufacturing and engineering.
However, not every machine shop should be treated equal. Potential machinists will want to research shops in their area to find the right fit. As Matayer puts it, “Finding the right shop matters. You want to find a place with newer equipment, great benefits, and clean air in a safe environment.” Poor air quality or unsafe working conditions can directly affect a machinist’s long-term health, so doing the proper research before accepting a position can prevent any serious issues.
If you are curious and want to learn more, reach out to your local trade school or college, talk to a machinist, check out some online forums, and read about the profession. You should also check out the machinist community on Instagram, which is full of amazing customer projects, helpful tips and tricks, and videos that will give you a better idea of what is possible in this field! Machinists are always more than happy to share their experiences, but the biggest thing you can do is try. Get out there, start creating, and see where it takes you – the possibilities are endless!
https://www.harveyperformance.com/wp-content/uploads/2017/06/Feature-Image-How-to-Become-a-Machinist-IMG.jpg5251400Harvey Performance Companyhttp://www.harveyperformance.com/wp-content/uploads/2018/08/Logo_HarveyPerformanceCompany-4.pngHarvey Performance Company2017-06-05 16:04:562023-10-12 08:52:45How to Become a Machinist
