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How to Extend the Life of Your End Mill

Breaking and damaging an end mill is oftentimes an avoidable mistake that can be extremely costly for a machine shop. To save time, money, and your end mill it is important to learn some simple tips and tricks to extend your tool’s life.

Properly Prepare Before the Tool Selection Process

The first step of any machining job is selecting the correct end mill for your material and application. However, this doesn’t mean that there should not be an adequate amount of legwork done beforehand to ensure the right decision on a tool is being made. Harvey Tool and Helical Solutions have thousands of different tools for different operations – a vast selection which, if unprepared – can easily result in selecting a tool that’s not the best for your job. To start your preparation, answer the 5 Questions to Ask Before Selecting an End Mill to help you quickly narrow down your selection and better understand the perfect tool you require.

Understand Your Tooling Requirements

It’s important to understand not only what your tool needs, but also general best practices to avoid common machining mishaps. For instance, it is important to use a tool with a length of cut only as long as needed, as the longer a tools length of cut is, the greater the chance of deflection or tool bending, which can decrease its effective life.

tool life

Another factor to consider is the coating composition on a tool. Harvey Tool and Helical Solutions offer many varieties of coatings for different materials. Some coatings increase lubricity, slowing tool wear, while others increase the hardness and abrasion resistance of the tool. Not all coatings increase your tool’s life in every material, however. Be wary of coatings that don’t perform well in your part’s material – such as the use of AlTiN coating in Aluminum (Both coating and material are aluminum-based and have a high affinity for each other, which can cause built-up edge and result in chip evacuation problems).

Consider Variable Helix & Pitch Geometry

A feature on many of our high performance end mills is variable helix or variable pitch geometry, which have differently-spaced flutes. As the tool cuts, there are different time intervals between the cutting edges contacting the workpiece, rather than simultaneously on each rotation. The varying time intervals minimizes chatter by reducing harmonics, increasing tool life and producing better results.

Ensure an Effective Tool Holding Strategy

Another factor in prolonging tool life is proper tool holding. A poor tool holding strategy can cause runout, pullout, and scrapped parts. Generally, the most secure connection has more points of contact between the tool holder and tool shank. Hydraulic and Shrink Fit Tool Holders provide increased performance over other tightening methods.

tool life

Helical also offers shank modifications to all stocked standards and special quotes, such as the ToughGRIP Shank, which provides added friction between the holder and the shank of the tool for a more secure grip; and the Haimer Safe-Lock™, which has grooves on the shank of the tool to help lock it into place in a tool holder.

tool life

Trust Your Running Parameters, and their Source

After selecting the correct end mill for your job, the next step is to run the tool at the proper speeds and feeds.

Run at the Correct Speed

Understanding the ideal speed to run your machine is key to prolonging tool life. If you run your tool too fast, it can cause suboptimal chip size, ineffective chip evacuation, or even total tool failure. Adversely, running your tool too slowly can result in deflection, bad finish, or decreased metal removal rates.

Push at the Best Feed Rate

Another critical parameter of speeds and feeds is finding the best possible feed rate for your job, for sake of both tool life and achieving maximum shop efficiency. Pushing your tool too aggressively can result in breakage, but being too conservative can lead to recutting chips and excess heat generation, accelerating tool wear.

Use Parameters from Your Tooling Manufacturer

A manufacturer’s speeds and feeds calculations take into account every tool dimension, even those not called out in a catalog and readily available to machinists. Because of this, it’s best to rely on running parameters from tooling manufacturers. Harvey Tool offers speeds and feeds charts for every one of its more than 21,000 tools featured in its catalog, helping machinists to confidently run their tool the first time.

Harvey Performance Company offers the Machining Advisor Pro application, a free, cutting-edge resource that generates custom running parameters for optimized machining with all of Helical’s products.

tool life

Opt for the Right Milling Strategy: Climb vs Conventional

There are two ways to cut material when milling: Climb Milling and Conventional Milling. In conventional milling, the cutter rotates against the feed. In this method, chips will start at theoretical zero and increase in size. Conventional milling is usually recommended for tools with higher toughness, or for breaking through case hardened materials.

In Climb Milling, the cutter rotates with the feed. Here, the chips start at maximum width and decrease, causing the heat generated to transfer into the chip instead of being left in the tool or work piece. Climb milling also produces a cleaner shear plane, causing less rubbing, decreasing heat, and improving tool life. When climb milling, chips will be removed behind the cutter, reducing your chances of recutting.

Utilize High Efficiency Milling

High Efficiency Milling (HEM), is a roughing technique that uses the theory of chip thinning by applying a smaller radial depth of cut (RDOC) and a larger axial depth of cut (ADOC). The parameters for HEM are similar to that of finishing, but with increased speeds and feeds, allowing for higher material removal rates (MRR). HEM utilizes the full length of cut instead of just a portion of the cutter, allowing heat to be distributed across the cutting edge, maximizing tool life and productivity. This reduces the possibility of accelerated tool wear and breakage.

Decide On Coolant Usage & Delivery

Coolant can be an extremely effective way to protect your tool from premature wear and possible tool breakage. There are many different types of coolant and methods of delivery to your tool. Coolant can come in the form of compressed air, water-based, straight oil-based, soluble oil-based, synthetic or semi-synthetic. It can be delivered as mist, flood, high pressure or minimum quantity lubricant.

Appropriate coolant type and delivery vary depending on your application and tool. For example, using a high pressure coolant with miniature tooling can lead to tool breakage due to the fragile nature of extremely small tools. In applications of materials that are soft and gummy, flood coolant washes away the long stringy chips to help avoid recutting and built-up edge, preventing extra tool wear.

Extend Your Tool’s Life

The ability to maximize tool life saves you time, money and headaches. To get the best possible outcome from your tool, you first need to be sure you’re using the best tool for your job. Once you find your tool, ensure that your speeds and feeds are accurate and are from your tooling manufacturer. Nobody knows the tools better than they do. Finally, think about how to run your tool: the rotation of your cutter, whether utilizing an HEM approach is best, and how to introduce coolant to your job.

 

Using Tool Libraries in Autodesk HSM & Fusion 360

The days of modeling your tools in CAM are coming to an end. Harvey Performance Company has partnered with Autodesk to provide comprehensive Harvey Tool and Helical Solutions tool libraries to Fusion 360 and Autodesk HSM users. Now, users can access 3D models of Harvey and Helical tools with a quick download and a few simple clicks. Keep reading to learn how to download these libraries, find the tool you are looking for, how to think about speeds and feeds for these libraries, and more.

Downloading Tool Libraries

To download one of our tool libraries, head to https://cam.autodesk.com/hsmtools. There you will find Harvey Tool and Helical Solutions tool libraries. You will be able to sort by vendor or use the search bar to filter results. There will be a download option for both Fusion and HSM.

From there, you will need to import the tool libraries from your Downloads folder into Fusion 360 or HSM. These tool libraries can be imported into your “Local” or “Cloud” libraries in Fusion 360, depending on where you would like them to appear. For HSM, simply import the HSMLIB file you have downloaded as you would any other tool library.

Curt Chan, Autodesk MFG Marketing Manager, takes a deeper dive into the process behind downloading, importing, and using CAM tool libraries to Fusion in the instructional video below.

For HSM users, jump to the 2:45 mark in this video from Autodesk’s Lars Christensen, who explains how to download and import these libraries into Autodesk HSM.


Selecting a Tool

Once you have downloaded and imported your tool libraries, selecting a specific tool or group of tools can be done in several ways.

Searching by Tool Number

To search by tool number, simply enter the tool number into the search bar at the top of your tool library window. For example, if you are looking for Helical Tool EDP 00015, enter “00015” into the search bar and the results will narrow to show only that tool.

Fusion 360 Tool Libraries

In the default display settings for Fusion 360, the tool number is not displayed in the table of results, where you will find the tool name, flute count, cutter diameter, and other important information. If you would like to add the tool number to this list of available data, you can right click on the top menu bar where it says “Name” and select “Product ID” from the drop down menu. This will add the tool number (ex. 00015) to the list of information readily available to you in the table.

Harvey Tool Tool Libraries

Searching by Keyword

To search by a keyword, simply input the keyword into the search bar at the top of the tool library window. For example, if you are looking for metric tooling, you can search “metric” to filter by tools matching that keyword. This is helpful when searching for Specialty Profile tools which are not supported by the current profile filters, like the Harvey Tool Double Angle Shank Cutters seen in the example below.

Fusion 360 Tool Libraries

Searching by Tool Type

To search by tool type, click the “Type” button in the top menu of your tool library window. From there, you will be able to segment the tools by their profile. For example, if you only wanted to see Harvey Tool ball nose end mills, choose “Ball” and your tool results will filter accordingly.

Tool Libraries

As more specialty profiles are added, these filters will allow you to filter by profiles such as chamfer, dovetail, drill, threadmill, and more. However, some specialty profile tools do not currently have a supported tool type. These tools show as “form tools” and are easier to find by searching by tool number or name. For example, there is not currently a profile filter for “Double Angle Shank Cutters” so you will not be able to sort by that profile. Instead, type “Double Angle Shank Cutter” into the search bar (see “Searching by Keyword”) to filter by that tool type.

Searching by Tool Dimensions

To search by tool dimensions, click the “Dimensions” button in the top menu of your tool library window. From there, you will be able to filter tools by your desired dimensions, including cutter diameter, flute count, overall length, radius, and flute length (also known as length of cut). For example, if you wanted to see Helical 3 flute end mills in a 0.5 inch diameter, you would check off the boxes next to “Diameter” and “Flute Count” and enter the values you are looking for. From there, the tool results will filter based on the selections you have made.

Tool Libraries

Using Specialty Profile Tools

Due to the differences in naming conventions between manufacturers, some Harvey Tool/Helical specialty profile tools will not appear exactly as you think in Fusion 360/HSM. However, each tool does contain a description with the exact name of the tool. For example, Harvey Tool Drill/End Mills display in Fusion 360 as Spot Drills, but the description field will call them out as Drill/End Mill tools, as you can see below.

Below is a chart that will help you match up Harvey Tool/Helical tool names with the current Fusion 360 tool names.

Tool Name Fusion 360 Name
Back Chamfer Cutter Dovetail Mill
Chamfer Cutters Chamfer Mill
Corner Rounding End Mill – Unflared Radius Mill
Dovetail Cutter Dovetail Mill
Drill/End Mill Spot Drill
Engraving Cutter/Marking Cutter – Tip Radius Tapered Mill
Engraving Cutter – Tipped Off & Pointed Chamfer Mill
Keyseat Cutter Slot Mill
Runner Cutter Tapered Mill
Undercutting End Mill Lollipop Mill
All Other Specialty Profiles Form Mill

Speeds and Feeds

To ensure the best possible machining results, we have decided not to pre-populate speeds and feeds information into our tool libraries. Instead, we encourage machinists to access the speeds and feeds resources that we offer to dial accurate running parameters based on their material, application, and machine capabilities.

Harvey Tool Speeds & Feeds

To access speeds and feeds information for your Harvey Tool product, head to http://www.harveytool.com/cms/SpeedsFeeds_228.aspx to find speeds and feeds libraries for every tool.

If you are looking for tool specific speeds and feeds information, you will need to access the tool’s “Tech Info” page. You can reach these pages by clicking any of the hyperlinked tool numbers across all of our product tables. From there, simply click “Speeds & Feeds” to access the speeds and feeds PDF for that specific tool.

If you have further questions about speeds and feeds, please reach out to our Technical Support team. They can be reached Monday-Friday from 8 AM to 7 PM EST at 800-645-5609, or by email at harveytech@harveyperformance.com.

Helical Solutions Speeds & Feeds

To access speeds and feeds information for your Helical Solutions end mills, we recommend using our Machining Advisor Pro application. Machining Advisor Pro (MAP) generates specialized machining parameters by pairing the unique geometries of your Helical Solutions end mill with your exact tool path, material, and machine setup. MAP is available free of charge as a web-based desktop app, or as a downloadable application on the App Store for iOS and Google Play.

machining advisor pro

To learn more about Machining Advisor Pro and get started today, visit www.machiningadvisorpro.com. If you have any questions about MAP, please reach out to us at webapps@harveyperformance.com.

If you have further questions about speeds and feeds, please reach out to our Technical Support team. They can be reached Monday-Friday from 8 AM to 7 PM EST at 866-543-5422, or by email at helicaltech@harveyperformance.com.


For additional questions or help using tool libraries, please send an email to webapps@harveyperformance.com. If you would like to request a Harvey Performance Company tool library be added to your CAM package, please fill out the form here and let us know! We will be sure to notify you when your CAM package has available tool libraries.

Understanding Threads & Thread Mills

Thread milling can present a machinist many challenges. While thread mills are capable of producing threads with relative ease, there are a lot of considerations that machinists must make prior to beginning the job in order to gain consistent results. To conceptualize these features and choose the right tool, machinists must first understand basic thread milling applications.

 

What is a thread?

The primary function of a thread is to form a coupling between two different mechanisms. Think of the cap on your water bottle. The cap couples with the top of the bottle in order to create a water tight seal. This coupling can transmit motion and help to obtain mechanical advantages.  Below are some important terms to know in order to understand threads.

Root – That surface of the thread which joins the flanks of adjacent thread forms and is immediately adjacent to the cylinder or cone from which the thread projects.

Flank – The flank of a thread is either surface connecting the crest with the root. The flank surface intersection with an axial plane is theoretically a straight line.

Crest – This is that surface of a thread which joins the flanks of the thread and is farthest from the cylinder or cone from which the thread projects.

Pitch – The pitch of a thread having uniform spacing is the distance measured parallelwith its axis between corresponding points on adjacent thread forms in the same axial plane and on the same side of the axis. Pitch is equal to the lead divided by the number of thread starts.

Major Diameter – On a straight thread the major diameter is that of the major cylinder.On a taper thread the major diameter at a given position on the thread axis is that of the major cone at that position.

Minor Diameter – On a straight thread the minor diameter is that of the minor cylinder. On a taper thread the minor diameter at a given position on the thread axis is that of the minor cone at that position.

Helix Angle – On a straight thread, the helix angle is the angle made by the helix of the thread and its relation to the thread axis. On a taper thread, the helix angle at a given axial position is the angle made by the conical spiral of the thread with the axis of the thread. The helix angle is the complement of the lead angle.

Depth of Thread Engagement – The depth (or height) of thread engagement between two coaxially assembled mating threads is the radial distance by which their thread forms overlap each other.

External Thread – A thread on a cylindrical or conical external surface.

Internal Thread – A thread on a cylindrical or conical internal surface.

Class of Thread – The class of a thread is an alphanumerical designation to indicate the standard grade of tolerance and allowance specified for a thread.

Source: Machinery’s Handbook 29th Edition

Types of Threads & Their Common Applications:

ISO Metric, American UN: This thread type is used for general purposes, including for screws. Features a 60° thread form.

British Standard, Whitworth: This thread form includes a 55° thread form and is often used when a water tight seal is needed.

NPT: Meaning National Pipe Tapered, this thread, like the Whitworth Thread Form, is also internal. See the above video for an example of an NPT thread.

UNJ, MJ: This type of thread is often used in the Aerospace industry and features a radius at the root of the thread.

ACME, Trapezoidal: ACME threads are screw thread profiles that feature a trapezoidal outline, and are most commonly used for power screws.

Buttress Threads: Designed for applications that involve particularly high stresses along the thread axis in one direction. The thread angle on these threads is 45° with a perpendicular flat on the front or “load resisting face.”         

Thread Designations

Threads must hold certain tolerances, known as thread designations, in order to join together properly. International standards have been developed for threads. Below are examples of Metric, UN, and Acme Thread Designations. It is important to note that not all designations will be uniform, as some tolerances will include diameter tolerances while others will include class of fit.

Metric Thread Designations              

M12 x 1.75 – 4h – LH

In this scenario, “M” designates a Metric Thread Designation, 12 refers to the Nominal Diameter, 1.75 is the pitch, 4h is the “Class of Fit,” and “LH” means “Left-Hand.”

UN Thread Designations

¾ 10 UNC 2A LH

For this UN Thread Designation, ¾ refers to the thread’s major diameter, where 10 references the number of threads per inch. UNC stands for the thread series; and 2A means the class of thread. The “A” is used to designate external threads, while “B” is for internal threads. For these style threads, there are 6 other classes of fit; 1B, 2B, and 3B for internal threads; and 1A, 2A, and 3A for external threads.

ACME Thread Designations

A 1 025 20-X

For this ACME Thread Designation, A refers to “Acme,” while 1 is the number of thread starts. The basic major diameter is called out by 025 (Meaning 1/4”) while 20 is the callout for number of threads per inch. X is a placeholder for a number designating the purpose of the thread. A number 1 means it’s for a screw, while 2 means it’s for a nut, and 3 refers to a flange.

How are threads measured?

Threads are measured using go and no-go gauges. These gauges are inspection tools used to ensure the that the thread is the right size and has the correct pitch. The go gauge ensures the pitch diameter falls below the maximum requirement, while the no-go gauge verifies that the pitch diameter is above the minimum requirement. These gauges must be used carefully to ensure that the threads are not damaged.

Thread Milling Considerations

Thread milling is the interpolation of a thread mill around or inside a workpiece to create a desired thread form on a workpiece. Multiple radial passes during milling offer good chip control. Remember, though, that thread milling needs to be performed on machines capable of moving on the X, Y, and Z axis simultaneously.

5 Tips for Successful Thread Milling Operations:

1.  Opt for a Quality Tooling Manufacturer

There is no substitute for adequate tooling. To avoid tool failure and machining mishaps, opt for a quality manufacturer for High Performance Drills for your starter holes, as well as for your thread milling solutions. Harvey Tool fully stocks several types of threadmills, including Single Form, Tri-Form, and Multi-Form Thread Milling Cutters. In addition, the 60° Double Angle Shank Cutter can be used for thread milling.

thread milling

Image Courtesy of  @Avantmfg

2. Select a Proper Cutter Diameter

Choose only a cutter diameter as large as you need. A smaller cutter diameter will help achieve higher quality threads.

3. Ensure You’re Comfortable with Your Tool Path

Your chosen tool path will determine left hand or right hand threads.

Right-hand internal thread milling is where cutters move counterclockwise in an upwards direction to ensure that climb milling is achieved.

Left-hand internal thread milling a left-hand thread follows in the opposite direction, from top to bottom, also in a counterclockwise path to ensure that climb milling is achieved.

4. Assess Number of Radial Passes Needed

In difficult applications, using more passes may be necessary to achieve desired quality. Separating the thread milling operation into several radial passes achieves a finer quality of thread and improves security against tool breakage in difficult materials. In addition, thread milling with several radial passes also improves thread tolerance due to reduced tool deflection. This gives greater security in long overhangs and unstable conditions.

5. Review Chip Evacuation Strategy

Are you taking the necessary steps to avoid chip recutting due to inefficient chip evacuation? If not, your thread may fall out of tolerance. Opt for a strategy that includes coolant, lubricant, and tool retractions.

In Summary

Just looking at a threading tool can be confusing – it is sometimes hard to conceptualize how these tools are able to get the job done. But with proper understanding of call, methods, and best practices, machinists can feel confident when beginning their operation.

5 Ways Your Shop is Inefficient

5 Ways Your Shop is Inefficient

In today’s ultracompetitive industry, every machine shop seeks even the slightest edge to gain an advantage on their competition and boost their bottom line. However, what many machinists don’t know is that improving their shop’s efficiency might be easier than they thought. The following five ways your shop is inefficient will provide a clear starting point of where to look for machinists desperate to earn a competitive edge.

1. Premature Tool Decay / Tool Failure

If you’re finding that your tools are failing or breaking at an unacceptable rate, don’t mistake it for commonplace. It doesn’t have to be. Prolonging the life of your tooling starts with finding not just the right tool, but the best one; as well as running it in a way to get its optimal performance. Many machinists mistake premature tool failure with running parameters that were too aggressive. In fact, not pushing the tool to its full potential can actually cause it to decay at an accelerated rate in certain situations.

Tool failure can occur in many different ways: Abrasive Wear, Chipping, Thermal Cracking or Tool Fracture, just to name a few. Understanding each type and its causes can help you to quickly boost your shop’s efficiency by minimizing downtime and saving on replacement tool costs.

tool wear

An example of a tool with excessive wear

For more information on tool wear, view Avoiding 4 Major Types of Tool Wear.

2. Subpar Part Finish

Your shop spends money to employ machinists, run machines, and buy cutting tools. Get your money’s worth, lead the industry, and ensure that you’re providing your customers with the highest quality product. Not only will this help to keep your buyer-seller relationship strong, but it will allow you the flexibility to increase your prices in the future, and will attract prospective customers.

Many factors influence part finish, including the material and its hardness, the speeds and feeds you’re running your tool at, tool deflection, and the tool-to-workpiece orientation.

For more information on ways to improve your part finish, view our Part Finish Reference Guide.

3. Inefficient Coolant Usage

One often forgotten expense of a machine shop is coolant – and it can be pricey. A 55-gallon drum of coolant can run more than $1,500. What’s worse is that coolant is often applied in excess of what’s required for the job. In fact, some machines even feature a Minimum Quantity Lubricant (MQL) functionality, which applies coolant as an extremely fine mist or aerosol, providing just enough coolant to perform a given operation effectively. While drowning a workpiece in coolant, known as a “Flood Coolant,” is sometimes needed, it is oftentimes utilized on jobs that would suffice with much less.

For more information about coolants and which method of application might be best for your job, view What You Need to Know About Coolant for CNC Machining.

4. Not Taking Advantage of Tool Versatility

Did you know that several CNC cutting tools can perform multiple operations? For example, a Chamfer Mill can chamfer, bevel, deburr, and countersink. Some Chamfer Mills can even be used as a Spotting Drill. Of course, the complexity of the job will dictate your ability to reap the benefits of a tool’s versatility. For instance, a Spotting Drill is obviously the best option for spotting a hole. If performing a simple operation, though, don’t go out of your way to buy additional tooling when what’s already in your carousel can handle it.

chamfer mills

To learn more about versatile tools that can perform multiple applications, check out Multi-Functional Tools Every Shop Should Have.

5. High Machine Downtime

What use is a machine that’s not running? Minimizing machine downtime is a key way to ensure that your shop is reaching its efficiency pinnacle. This can be accomplished a variety of ways, including keeping like-parts together. This allows for a simple swap-in, swap-out of material to be machined by the same cutting tool. This saves valuable time swapping out tooling, and lets your machine to do its job for more time per workday. Production planning is a key factor to running an efficient machine shop.

4 Important Keyseat Cutter Considerations

Keyseat cutters, also called woodruff cutters, keyway cutters, and T-slot cutters, are a type of cutting tool used frequently by many machinists – some operations are impractical or even impossible without one. If you need one of these tools for your job, it pays to know when and how to pick the right one and how to use it correctly.

1. Keyseat Cutter Geometry

Selecting and utilizing the right tool is often more complicated than identifying the right diameter and dialing in the speeds and feeds. A keyseat cutter’s strength should be considered carefully, especially in tricky applications and difficult materials.

As with any tool, a longer reach will make a keyseat cutter more prone to deflection and breakage. A tool with the shortest allowable reach should be used to ensure the strongest tool possible.

A keyseat cutter’s neck diameter greatly affects its performance. A thinner neck allows for a comparatively larger radial depth of cut (RDOC) and more clearance, but makes for a weaker tool. A thicker neck reduces the keyseat cutter’s RDOC, but greatly strengthens the tool overall. When clearances allow, a keyseat cutter with a thicker neck and larger cutter diameter should be chosen over one with a thinner neck and smaller cutter diameter (Figure 1).

keyseat cutter geometry

Cutter width has an effect on tool strength as well. The greater a keyseat cutter’s cutter width, the more prone to deflection and breakage it is. This is due to the increased forces on the tool – a greater cutter width equates to an increased length of engagement. You should be particularly careful to use the strongest tool possible and a light RDOC when machining with a keyseat cutter with a thick cutter width.

2. Radial Depth of Cut

Understanding a keyseat cutter’s RDOC is critical to choosing the correct tool, but understanding how it affects your tool path is necessary for optimal results. While it may be tempting to make a cut using a keyseat cutter’s maximum RDOC, this will result in increased stress on the tool, a worse finish, and potential catastrophic tool failure. It is almost always better to use a lighter depth of cut and make multiple passes (Figure 2).

keyseat cutter RDOC
When in doubt about what RDOC is correct for your tool and application, consider consulting the tool manufacturer’s speeds and feeds. Harvey Tool’s keyseat cutter speeds and feeds take into account your tool dimensions, workpiece material, operation, and more.

3. Desired Slot Size

Some machinists use keyseat cutters to machine slots greater than their cutter width. This is done with multiple operations so that, for example, a keyseat cutter with a 1/4” cutter width can create a slot that is 3/8” wide. While this is possible and may save on up-front tooling costs, the results are not optimal. Ideally, a keyseat cutter should be used to machine a slot equal to its cutter width as it will result in a faster operation, fewer witness marks, and a better finish (Figure 3).

ideal keyseat slot

4. Staggered Tooth Geometry

When more versatility is required from a keyseat cutter, staggered tooth versions should be considered. The front and back reliefs allow the tools to cut not only on the OD, but also on the front and back of the head. When circumstances do not allow for the use of a cutter width equal to the final slot dimensions as stated above, a staggered tooth tool can move axially in the slot to expand its width.

staggered tooth keyseat cutter
Machining difficult or gummy materials can be tricky, and using a staggered tooth keyseat cutter can help greatly with tool performance. The shear flutes reduce the force needed to cut, as well as leave a superior surface finish by reducing harmonics and chatter.

Having trouble finding the perfect keyseat cutter for your job? Harvey Tool offers over 1,800 keyseat cutter options, with cutter diameters from 1/16” to 1-1/2” and cutter widths from .010” to ½”.

Speeds and Feeds 101

Understanding Speeds and Feed Rates

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.

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). SFM 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.

While speeds and feeds are common terms used in the programming of the cutter, the ideal running parameters are also influenced by other variables. 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. It is important to note that chip load per tooth and chip load per tool are different:

speeds and feeds formula

 

  • 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, deflection, and a poor overall cutting action.

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 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.

speeds and feeds

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.

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. The chip load (per tooth) can be found by intersecting the tool diameter on the top 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 and material for each operation, based on the chart above:

speeds and feeds

Other Important Considerations

Each operation recommends a unique chip load per the depths of cut. This results in various feed rates depending on the operation. Since the SFM is based on the material, it remains constant for each operation.

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.

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.

non-linear path

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.

adjusted internal feed

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.

adjusted external feed

Click here for the full example.

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. 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 material.

Click the following links for more information about running parameters for Harvey Tool and Helical products.

How to Avoid Composite Delamination with Compression Cutters

Composites are a group of materials made up of at least two unique constituents that, when combined, produce mechanical and physical properties favorable for a wide array of applications. These materials usually contain a binding ingredient, known as a matrix, filled with particles or fibers called reinforcements. Composites have become increasingly popular in the Aerospace, Automotive, and Sporting Goods industries because they can combine the strength of metal, the light weight of plastic, and the rigidity of ceramics.

Unfortunately, composite materials present some unique challenges to machinists. Many composites are very abrasive and can severely reduce tool life, while others can melt and burn if heat generation is not properly controlled. Even if these potential problems are avoided, the wrong tool can leave the part with other quality issues, including delamination.

While composites such as G10 and FR4 are considered “fibrous”, composites can also be “layered,” such as laminated sheets of PEEK and aluminum. Layered composites are vulnerable to delamination, when the layers of the material are separated by a tool’s cutting forces. This yields less structurally sound parts, defeating the purpose of the combined material properties in the first place. In many cases, a single delaminated hole can result in a scrapped part.

Using Compression Cutters in Composite Materials

Composite materials are generally machined with standard metal cutting end mills, which generate exclusively up or down cutting forces, depending on if they have right or left hand flute geometry. These uni-directional forces cause delamination (Figure 1).

delamination

Conversely, compression cutters are designed with both up and down-cut flutes. The top portion of the length of cut, closest to the shank, has a left hand spiral, forcing chips down. The bottom portion of the length of cut, closest to the end, has a right hand spiral, forcing chips up. When cutting, the opposing flute directions generate counteracting up-cut and down-cut forces. The opposing cutting forces stabilize the material removal, which compresses the composite layers, combatting delamination on the top and bottom of a workpiece (Figure 2).

compression cutters

Since compression cutters do not pull up or press down on a workpiece, they leave an excellent finish on layered composites and lightweight materials like plywood. It is important to note, however, that compression cutters are suited specifically to profiling, as the benefits of the up and down-cut geometry are not utilized in slotting or plunging operations.

Something as simple as choosing a tool suited to a specific composite material can have significant effects on the quality of the final part. Consider utilizing tools optimized for different composites and operations or learn how to select the right drill for composite holemaking.

The Multiple Uses of a Chamfer Mill

A chamfer mill, or a chamfer cutter, is one of the most common tools used by machinists daily. When creating a part, machining operations can oftentimes leave a sharp edge on a workpiece. A chamfer mill eliminates sharp edges, leaving a sloped surface, or a chamfer, instead. In doing so, the part will be stronger and more aesthetically appealing to its eventual user.

This singular tool can provide many cost-saving benefits to machinists. Aside from the namesake operation it performs on a part, a chamfer mill can be used for several machining operations including beveling, deburring, countersinking, and spotting.

Chamfer Mill for Beveling

The terms “chamfer” and “bevel” are often used interchangeably. These two features, while similar, actually have two different definitions. While a chamfer impacts a portion of the side of a workpiece – specifically the edge of a part, a bevel angles the entire side of what was a squared-off part feature. Thus, the side of a part can feature two chamfers, or only one bevel (Figure 1).

A chamfer mill, however, can perform both operations. The two features are equivalent in both geometry, and how they are machined.  A chamfer mill will create both part features in the exact same fashion; a bevel just may use a larger portion of the cutting surface, or may require multiple passes to create a large part feature.

Chamfer Mill for Deburring

Like many other versatile tools, a chamfer mill can be used to easily and swiftly deburr a part during the CNC machining process. In doing so, efficiency is maintained as manual deburring – a time exhaustive process – isn’t necessary.

A chamfer mill’s angled cutting surface makes it a great tool for deburring workpiece edges.  Because a very small amount of the chamfer cutter’s cutting face will be used, a simple adjustment to running parameters will allow for simple deburring operations using a very light cut depth.

Chamfer Mill for Spotting & Countersinking

Drilling precise, clean, and aesthetically appealing holes into a part is not a one-step process. In fact, some use up to four different tools to machine a perfect hole: spotting drill, drill, flat bottom counterbore, and countersink. However, a chamfer cutter is often used to perform two of these operations simultaneously.

By using a pointed chamfer cutter with a diameter larger than that of the hole being drilled, a machinist can spot and countersink the hole in one operation prior to its creation. Tipped-off Chamfer  Cutters are unable to perform a spotting operation because they are non-center cutting. By spotting a hole, the drill has a clear starting point. This works to alleviate walking during the drilling process, which in turn drastically reduces the chance of misaligned holes. By countersinking a hole, the screw sits flush with the part, which is often a requirement for many parts in the aerospace industry.

One consideration to keep in mind is that a carbide spot drill should always have an angle larger than that of the drill following it. However, many countersinks have angles that are smaller than most drill points.  This creates a dilemma in choosing a chamfer tool for both spotting and countersinking, as they can reduce the number of tools needed, but do not see the full benefit of a spot drill with a proper angle.

Key Takeaways

A chamfer mill, also known as a chamfer cutter, is a tool that can perform several machining operations including chamfering, beveling, deburring, spotting, and countersinking. Due to this versatility, chamfer mills are an essential part of every machinist’s arsenal.  All that’s needed to run them is these various operations is a slight change to running parameters and depth of cut.

Undercutting End Mills: Well-Rounded Tools That Offer Maximum Versatility

Undercutting end mills, also known as lollipop cutters or spherical ball end mills, are a common choice for machining undercuts. An undercut is a common part feature characterized by one part of a workpiece “hanging” over another. Undercuts are typically difficult, or even impossible, to machine with a standard end mill, especially on 3-axis machines. In many cases, a specialty tool is needed to tackle this feature. Although they are frequently associated with a singular use, undercutting end mills are actually very versatile tools that are worth keeping on hand for a variety of operations.

Undercutting

undercutting machining

Unsurprisingly, undercutting end mills are very well suited to undercutting operations. Creating an undercut on a part can be tricky and time consuming, especially when forced to rotate the workpiece. Fortunately, this can be greatly simplified with an undercutting end mill.

Exactly what tool to use depends on the geometry of the feature and the part. Undercutting end mills are available with a range of wrap angles like 220°, 270°, and 300°. Greater wrap angles are the result of a thinner neck and create a more spherical cutting end. This style offers more clearance at the cost of rigidity. Likewise, undercutting end mills with lower wrap angles sacrifice clearance for greater rigidity.

Deburring & Edgebreaking

deburring

Since undercuts have a wrap angle that is greater than 180°, they are very well-suited to deburring or edgebreaking anywhere on your workpiece, including the underside. Deburring your parts by hand can be inefficient for your shop – using an undercutting end mill instead will save you time and money. Edgebreaking operations are often a critical final step to create a part that looks and feels like a finished product and that is safe to handle.

All undercutting end mills can be used to deburr and edgebreak, which makes them a useful tool to have on hand in any shop. Some manufacturers also offer specialized deburring undercutting end mills that are designed with a right and left hand flute orientation, giving them “teeth” that make them particularly useful for deburring complex shapes. Using a deburring undercutting end mill in a 5-axis machine often makes it possible to deburr or edgebreak an entire workpiece in one shot.

Slotting

slotting

Most machinists might not think of undercutting end mills for slotting, but they are fully capable of this operation. An equivalent slot can be machined with a regular ball end mill, but doing so might not be feasible due to clearance issues – an undercutting end mill has a reduced neck, unlike a standard ball end mill. Additionally, using an undercutter to slot can save time switching to an equivalent ball end mill.

Since only 180° of the cutting end can be used to slot, undercutting end mills with lower wrap angles and thicker necks are best suited to slotting. However, high helix undercutting end mills may be ideal if improved finish and increased chip removal are important to the operation.

Contouring & Profiling

contouring

With their wrap angle and increased clearance, undercutting end mills are very useful for both simple and complicated contouring and profiling operations. Their versatility means that it is sometimes possible to accomplish the entire operation with a single tool, rather than several, especially when 5-axis milling.

Reduced shank undercutting end mills offer the most versatility in complex contouring and profiling operations. The ability to chuck these tools at any depth means that they are capable of maximum clearance.

Choosing An Undercutting End Mill

While most undercutting end mills are conceptually similar, there are a few key differences that must be considered when picking the right tool for your job. Harvey Tool offers the following undercutting end mill styles as stock standard tools.

undercutting end mills

Introduction to High Efficiency Milling

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!

High Speed Machining vs. HEM I How to Combat Chip Thinning I Diving into Depth of Cut I How to Avoid 4 Major Types of Tool Wear I Intro to Trochoidal Milling


High Efficiency Milling (HEM) is a strategy that is rapidly gaining popularity in the metalworking industry. Most CAM packages now offer modules to generate HEM toolpaths, each with their own proprietary name. In these packages, HEM can also be known as Dynamic Milling or High Efficiency Machining, among others. HEM can result in profound shop efficiency, extended tool life, greater performance, and cost savings. High performance end mills designed to achieve higher speeds and feeds will help machinists to reap the full benefits of this popular machining method.

High Efficiency Milling Defined

HEM is a milling technique for roughing that utilizes 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.

This strategy differs from traditional or conventional milling, which typically calls for a higher RDOC and lower ADOC. Traditional milling causes heat concentrations in one small portion of the cutting tool, expediting the tool wear process. Further, while Traditional Milling call for more axial passes, HEM toolpaths use more passes radially.

For more information on optimizing Depth of Cut in relation to HEM, see Diving into Depth of Cut: Peripheral, Slotting & HEM Approaches.

High Efficiency Milling

Built-In CAM Applications

Machining technology has been advancing with the development of faster, more powerful machines. In order to keep up, many CAM applications have developed built-in features for HEM toolpaths, including Trochoidal Milling, a method of machining used to create a slot wider than the cutting tool’s cutting diameter.

HEM is largely based on the theory surrounding Radial Chip Thinning, or the phenomenon that occurs with varying RDOC, and relates to the chip thickness and feed per tooth. HEM adjusts parameters to maintain a constant load on the tool through the entire roughing operation, resulting in more aggressive material removal rates (MRR). In this way, HEM differs from other high performance toolpaths, which involve different methods for achieving significant MRR.

Virtually any CNC machine can perform HEM – the key is a fast CNC controller. When converting from a regular program to HEM, about 20 lines of HEM code will be written for every line of regular code. A fast processor is needed to look ahead for the code, and keep up with the operation. In addition, advanced CAM software that intelligently manages tool load by adjusting the IPT and RDOC is also needed.

HEM Case Studies

The following example shows the result a machinist had when using a Helical Solutions HEV-5 tool to perform an HEM operation in 17-4PH stainless steel. While performing HEM, this ½” diameter, 5-flute end mill engaged the part just 12% radially, but 100% axially. This machinist was able to reduce tool wear and was able to complete 40 parts with a single tool, versus only 15 with a traditional roughing toolpath.

The effect of HEM on a roughing application can also be seen in the case study below. While machining 6061 aluminum with Helical’s H45AL-C-3, a 1/2″, 3-flute rougher, this machinist was able to finish a part in 3 minutes, versus 11 minutes with a traditional roughing toolpath. One tool was able to make 900 parts with HEM, a boost of more than 150% over the traditional method.

Importance of Tooling to HEM

Generally speaking, HEM is a matter of running the tool – not the tool itself. Virtually every tool can perform HEM, but using tooling built to withstand the rigors of HEM will result in greater success. While you can run a marathon in any type of shoes, you’d likely get the best results and performance from running shoes.

HEM is often regarded as a machining method for larger diameter tooling because of the aggressive MRR of the operation and the fragility of tooling under 1/8” in size. However, miniature tooling can be used to achieve HEM, too.

Using miniature tooling for HEM can create additional challenges that must be understood prior to beginning your operation.

Best Tools for HEM:

  • High flute count for increased MRR.
  • Large core diameter for added strength.
  • Tool coating optimized for the workpiece material for increased lubricity.
  • Variable Pitch/Variable Helix design for reduced harmonics.

Key Takeaways

HEM is a machining operation which continues to grow in popularity in shops worldwide. A milling technique for roughing that utilizes a lower RDOC and higher ADOC than traditional milling, HEM distributes wear evenly across the cutting edge of a tool, reducing heat concentrations and slowing the rate of tool wear. This is especially true in tooling best suited to promote the benefits of HEM.