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Show Us What You #MadeWithMicro100

Are you proud of the parts you #MadeWithMicro100? Show us with a video of the parts you are making, the Micro 100 Tool used, and the story behind how that part came to be, for a chance to win a $1,000 Amazon gift card grand prize!

With the recent addition of the Micro 100 brand to the Harvey Performance Company family, we want to know how you have been utilizing its expansive tooling offering. Has Micro 100’s Micro-Quik™ system helped you save time and money? Do you have a favorite tool that gets the job done for you every time? Has Micro 100 tooling saved you from a jam? We want to know! Send us a video on Instagram and show us what you #MadeWithMicro100!

How to Participate

Using #MadeWithMicro100 and @micro_100, tag your video of the Micro 100 tools machining your parts on Instagram or Facebook. Remember, don’t share anything that could get you in trouble! Proprietary parts and trade secrets should not be on display.

Official Contest Rules

Contest Dates:

  • The contest will run between December 5, 2019 to January 17, 2020. Submit as many entries as you’d like! Entries that are submitted before or after the contest period will not be considered for the top prizes (But we’d still like to see them!)

The Important Stuff:

  1. Take a video of your Micro 100 tool in action, clear and visible.
  2. Share your video on social media using #MadeWithMicro100 and tagging @Micro_100.
  3. Detail the story behind the project (tool number(s), operation, running parameters, etc.)

Prizes

All submissions will be considered for the $1,000 Amazon gift card grand prize. Of these entries, the most impressive (10) will be put up to popular vote. All entries put up to vote will be featured on our new customer testimonial page on our website with their name, social media account, and video displayed for everybody to see.

We’ll pick our favorites, but the final say is up to you. Public voting will begin on January 21, 2020, and a winner will be announced on January 28, 2020.

The top five entries will be sent Micro 100’s Micro-Quik™ tool change system with a few of our quick change tools. The top three entries will be offered a spot as a “Featured Customer” on our “In The Loupe” blog!

The Fine Print:

  • Please ensure that you have permission from both your employer and customer to post a video.
  • All entries must be the original work of the person identified in the entry.
  • No purchase necessary to enter or win. A purchase will not increase your chances of winning.
  • On January 28, 2020, the top 5 winners will be announced to the public. The Top 5 selected winners will receive a prize. The odds of being selected depend on the number of entries received. If a potential winner cannot be contacted within five (5) days after the date of first attempt, an alternative winner may be selected.
  • The potential winners will be notified via social media. Each potential winner must complete a release form granting Micro 100 full permission to publish the winner’s submitted video. If a potential winner cannot be contacted, or fails to submit the release form, the potential winner forfeits prize. Potential winners must continue to comply with all terms and conditions of these official contest rules, and winning is contingent upon fulfilling all requirements.
  • Participation in the contest constitutes entrants’ full and unconditional agreement to and acceptance of these official rules and decisions. Winning a prize is contingent upon being compliant with these official rules and fulfilling all other requirements.
  • The Micro 100 Video Contest is open to residents in US and Canada who are at least 18 years old at the time of entry.

Selecting the Right Chamfer Cutter Tip Geometry

A chamfer cutter, or a chamfer mill, can be found at any machine shop, assembly floor, or hobbyist’s garage. These cutters are simple tools that are used for chamfering or beveling any part in a wide variety of materials. There are many reasons to chamfer a part, ranging from fluid flow and safety, to part aesthetics.

Due to the diversity of needs, tooling manufacturers offer many different angles and sizes of chamfer cutters, and as well as different types of chamfer cutter tip geometries. Harvey Tool, for instance, offers 21 different angles per side, ranging from 15° to 80°, flute counts of 2 to 6, and shank diameters starting at 1/8” up to 1 inch.

After finding a tool with the exact angle they’re looking for, a customer may have to choose a certain chamfer cutter tip that would best suit their operation. Common types of chamfer cutter tips include pointed, flat end, and end cutting. The following three types of chamfer cutter tip styles, offered by Harvey Tool, each serve a unique purpose.

Three Types of Harvey Tool Chamfer Cutters

Type I: Pointed

This style of chamfer cutter is the only Harvey Tool option that comes to a sharp point. The pointed tip allows the cutter to perform in smaller grooves, slots, and holes, relative to the other two types. This style also allows for easier programming and touch-offs, since the point can be easily located. It’s due to its tip that this version of the cutter has the longest length of cut (with the tool coming to a finished point), compared to the flat end of the other types of chamfer cutters. With only a 2 flute option, this is the most straightforward version of a chamfer cutter offered by Harvey Tool.

Type II: Flat End, Non-End Cutting

Type II chamfer cutters are very similar to the type I style, but feature an end that’s ground down to a flat, non-cutting tip. This flat “tip” removes the pointed part of the chamfer, which is the weakest part of the tool. Due to this change in tool geometry, this tool is given an additional measurement for how much longer the tool would be if it came to a point. This measurement is known as “distance to theoretical sharp corner,” which helps with the programming of the tool. The advantage of the flat end of the cutter now allows for multiple flutes to exist on the tapered profile of the chamfer cutter. With more flutes, this chamfer has improved tool life and finish. The flat, non-end cutting tip flat does limit its use in narrow slots, but another advantage is a lower profile angle with better angular velocity at the tip.

Type III: Flat End, End Cutting

Type III chamfer cutters are an improved and more advanced version of the type II style. The type III boasts a flat end tip with 2 flutes meeting at the center, creating a center cutting-capable version of the type II cutter. The center cutting geometry of this cutter makes it possible to cut with its flat tip. This cutting allows the chamfer cutter to lightly cut into the top of a part to the bottom of it, rather than leave material behind when cutting a chamfer. There are many situations where blending of a tapered wall and floor is needed, and this is where these chamfer cutters shine. The tip diameter is also held to a tight tolerance, which significantly helps with programing it.

In conclusion, there could be many suitable cutters for a single job, and there are many questions you must ask prior to picking your ideal tool. Choosing the right angle comes down to making sure that the angle on the chamfer cutter matches the angle on the part. One needs to be cautious of how the angles are called out, as well. Is the angle an “included angle” or “angle per side?” Is the angle called off of the vertical or horizontal? Next, the larger the shank diameter, the stronger the chamfer and the longer the length of cut, but now, interference with walls or fixtures need to be considered. Flute count comes down to material and finish. Softer materials tend to want less flutes for better chip evacuation, while more flutes will help with finish. After addressing each of these considerations, the correct style of chamfer for your job should be abundantly clear.

How Boring Bar Geometries Impact Cutting Operations

Boring is a turning operation that allows a machinist to make a pre-existing hole bigger through multiple iterations of internal boring. It has a number of advantages over traditional drilling methods:

  • The ability to cost-effectively produce a hole outside standard drill sizes
  • The creation of more precise holes, and therefore tighter tolerances
  • A greater finish quality
  • The opportunity to create multiple dimensions within the bore itself

 

Solid carbide boring bars, such as those offered by Micro 100,  have a few standard dimensions that give the tool basic functionality in removing material from an internal bore. These include:

Minimum Bore Diameter (D1): The minimum diameter of a hole for the cutting end of the tool to completely fit inside without making contact at opposing sides

Maximum Bore Depth (L2): Maximum depth that the tool can reach inside a hole without contact from the shank portion

Shank Diameter (D2): Diameter of the portion of the tool in contact with the tool holder

Overall Length (L1): Total length of the tool

Centerline Offset (F): The distance between a tool’s tip and the shank’s centerline axis

Tool Selection

In order to minimize tool deflection and therefore risk of tool failure, it is important to choose a tool with a max bore depth that is only slightly larger than the length it is intended to cut. It is also beneficial to maximize the boring bar and shank diameter as this will increase the rigidity of the tool. This must be balanced with leaving enough room for chips to evacuate. This balance ultimately comes down to the material being bored. A harder material with a lower feed rate and depths of cut may not need as much space for chips to evacuate, but may require a larger and more rigid tool. Conversely, a softer material with more aggressive running parameters will need more room for chip evacuation, but may not require as rigid of a tool.

Geometries

In addition, they have a number of different geometric features in order to adequately handle the three types of forces acting upon the tool during this machining process. During a standard boring operation, the greatest of these forces is tangential, followed by feed (sometimes called axial), and finally radial. Tangential force acts perpendicular to the rake surface and pushes the tool away from the centerline. Feed force does not cause deflection, but pushes back on the tool and acts parallel to the centerline. Radial force pushes the tool towards the center of the bore.

 

Defining the Geometric Features of Boring Bars:

Nose Radius: the roundness of a tool’s cutting point

Side Clearance (Radial Clearance): The angle measuring the tilt of the nose relative to the axis parallel to the centerline of the tool

End Clearance (Axial Clearance): The angle measuring the tilt of the end face relative to the axis running perpendicular to the centerline of the tool

Side Rake Angle: The angle measuring the sideways tilt of the side face of the tool

Back Rake Angle: The angle measuring the degree to which the back face is tilted in relation to the centerline of the workpiece

Side Relief Angle: The angle measuring how far the bottom face is tilted away from the workpiece

End Relief Angle: The angle measuring the tilt of the end face relative to the line running perpendicular to the center axis of the tool

Effects of Geometric Features on Cutting Operations:

Nose Radius: A large nose radius makes more contact with the workpiece, extending the life of the tool and the cutting edge as well as leaving a better finish. However, too large of a radius will lead to chatter as the tool is more exposed to tangential and radial cutting forces.

Another way this feature affects the cutting action is in determining how much of the cutting edge is struck by tangential force. The magnitude of this effect is largely dependent on the feed and depth of cut. Different combinations of depth of cuts and nose angles will result in either shorter or longer lengths of the cutting edge being exposed to the tangential force. The overall effect being the degree of edge wear. If only a small portion of the cutting edge is exposed to a large force it would be worn down faster than if a longer portion of the edge is succumb to the same force. This phenomenon also occurs with the increase and decrease of the end cutting edge angle.

End Cutting Edge Angle: The main purpose of the end cutting angle is for clearance when cutting in the positive Z direction (moving into the hole). This clearance allows the nose radius to be the main point of contact between the tool and the workpiece. Increasing the end cutting edge angle in the positive direction decreases the strength of the tip, but also decreases feed force. This is another situation where balance of tip strength and cutting force reduction must be found. It is also important to note that the angle may need to be changed depending on the type of boring one is performing.

Side Rake Angle: The nose angle is one geometric dimension that determines how much of the cutting edge is hit by tangential force but the side rake angle determines how much that force is redistributed into radial force. A positive rake angle means a lower tangential cutting force as allows for a greater amount of shearing action. However, this angle cannot be too great as it compromises cutting edge integrity by leaving less material for the nose angle and side relief angle.

Back Rake Angle: Sometimes called the top rake angle, the back rake angle for solid carbide boring bars is ground to help control the flow of chips cut on the end portion of the tool. This feature cannot have too sharp of a positive angle as it decreases the tools strength.

Side and End Relief Angles: Like the end cutting edge angle, the main purpose of the side and end relief angles are to provide clearance so that the tools non-cutting portion doesn’t rub against the workpiece. If the angles are too small then there is a risk of abrasion between the tool and the workpiece. This friction leads to increased tool wear, vibration and poor surface finish. The angle measurements will generally be between 0° and 20°.

Boring Bar Geometries Summarized

Boring bars have a few overall dimensions that allow for the boring of a hole without running the tool holder into the workpiece, or breaking the tool instantly upon contact. Solid carbide boring bars have a variety of angles that are combined differently to distribute the 3 types of cutting forces in order to take full advantage of the tool. Maximizing tool performance requires the combination of choosing the right tool along with the appropriate feed rate, depth of cut and RPM. These factors are dependent on the size of the hole, amount of material that needs to be removed, and mechanical properties of the workpiece.

 

The Geometries and Purposes of a Slitting Saw

When a machinist needs to cut material significantly deeper than wide, a Slitting Saw is an ideal choice to get the job done. A Slitting Saw is unique due to its composition and rigidity, which allows it to hold up in a variety of both straightforward and tricky to machine materials.

What is a Slitting Saw?

A Slitting Saw is a flat (with or without a dish), circular-shaped saw that has a hole in the middle and teeth on the outer diameter. Used in conjunction with an arbor, a Slitting Saw is intended for machining purposes that require a large amount of material to be removed within a small diameter, such as slotting or cutoff applications.

Other names for Slitting Saws include (but are not limited to) Slitting Cutters, Slotting Cutters, Jewelers Saws, and Slitting Knives. Both Jewelers Saws and Slitting Knives are particular types of Slitting Saws. Jewelers Saws have a high tooth count enabling them to cut tiny, precise features, and Slitting Knives are Slitting Saws with no teeth at all. On Jewelers Saws, the tooth counts are generally much higher than other types of saws in order to make the cuts as accurate as possible.

Key Terminology

Why Use a Slitting Saw?

These saws are designed for cutting into both ferrous and non-ferrous materials, and by utilizing their unique shape and geometries, they can cut thin slot type features on parts more efficiently than any other machining tool.

Common Applications:

  1. Separating Two Pieces of Material
    1. If an application calls for cutting a piece of material, such as a rod, in half, then a slitting saw will work well to cut the pieces apart while increasing efficiency.
  2. Undercutting Applications
    1. Saws can perform undercutting applications if mounted correctly, which can eliminate the need to remount the workpiece completely.
  3. Slotting into Material
    1. Capable of creating thin slots with a significant depth of cut, Slitting Saws can be just the right tool for the job!

When Not to Use a Slitting Saw

While it may look similar to a stainless steel circular saw blade from a hardware store, a Slitting Saw should never be used with construction tools such as a table or circular saw.  Brittle saw blades such as slitting saws will shatter when used on manual machines, and can cause injury when not used on the proper set up.

In Conclusion

Slitting Saws can be beneficial to a wide variety of machining processes, and it is vital to understand their geometries and purpose before attempting to utilize them in the shop. They are a great tool to have in the shop and can assist with getting jobs done as quickly and efficiently as possible.

Get to Know Machining Advisor Pro

Machining Advisor Pro (MAP) is a tool to quickly, seamlessly, and accurately deliver recommended running parameters to machinists using Helical Solutions end mills. This download-free and mobile-friendly application takes into account a user’s machine, tool path, set-up, and material to offer tailored, specific speeds and feed parameters to the tools they are using.

How to Begin with Machining Advisor Pro

This section will provide a detailed breakdown of Machining Advisor Pro, moving along step-by-step throughout the entire process of determining your tailored running parameters.

Register Quickly on Desktop or Mobile

To begin with Machining Advisor Pro, start by accessing its web page on the Harvey Performance Company website, or use the mobile version by downloading the application from the App Store or Google Play.

Whether you are using Machining Advisor Pro from the web or your mobile device, machinists must first create an account. The registration process will only need to be done once before you will be able to log into Machining Advisor Pro on both the mobile and web applications immediately.

machining advisor pro

Simply Activate Your Account

The final step in the registration process is to activate your account. To do this, simply click the activation link in the email that was sent to the email address used when registering. If you do not see the email in your inbox, we recommend checking your spam folders or company email filters. From here, you’re able to begin using MAP.

Using MAP

A user’s experience will be different depending on whether they’re using the web or mobile application. For instance, after logging in, users on the web application will view a single page that contains the Tool, Material, Operation, Machine, Parameter, and Recommendation sections.

 

 

On the mobile application, however, the “Input Specs” section is immediately visible. This is a summary of the Tool, Material, Operation, and Machine sections that allow a user to review and access any section. Return to this screen at any point by clicking on the gear icon in the bottom left of the screen.

machining advisor pro

Identify Your Helical Tool

To get started generating your running parameters, specify the Helical Solutions tool that you are using. This can be done by entering the tool number into the “Tool #” input field (highlighted in red below). As you type the tool number, MAP will filter through Helical’s 4,800-plus tools to begin identifying the specific tool you are looking for.

 

Once the tool is selected, the “Tool Details” section will populate the information that is specific to the chosen tool. This information will include the type of tool chosen, its unit of measure, profile, and other key dimensional attributes.

 

Select the Material You’re Working In

Once your tool information is imported, the material you’re working in will need to be specified. To access this screen on the mobile application, either swipe your screen to the left or click on the “Material” tab seen at the bottom of the screen. You will move from screen to screen across each step in the mobile application by using the same method.

In this section, there are more than 300 specific material grades and conditions available to users. The first dropdown menu will allow you to specify the material you are working in. Then, you can choose the subgroup of that material that is most applicable to your application. In some cases, you will also need to choose a material condition. For example, you can select from “T4” or “T6” condition for 6061 Aluminum.

 

Machining Advisor Pro provides optimized feeds and speeds that are specific to your application, so it is important that the condition of your material is selected.

Pick an Operation

The next section of MAP allows the user to define their specific operation. In this section, you will define the tool path strategy that will be used in this application. This can be done by either selecting the tool path from the dropdown menu or clicking on “Tool Path Info” for a visual breakdown and more information on each available toolpath.

 

Tailor Parameters to Your Machine’s Capabilities

The final section on mobile, and the fourth web section, is the machine section. This is where a user can define the attributes of the machine that you are using. This will include the Max RPM, Max IPM, Spindle, Holder, and work holding security. Running Parameters will adjust based on your responses.

 

Access Machining Advisor Pro Parameters

Once the Tool, Material, Operation, and Machine sections are populated there will be enough information to generate the initial parameters, speed, and feed. To access these on the mobile app, either swipe left when on the machine tab or tap on the “Output” tab on the bottom menu.

 

Please note that these are only initial values. Machining Advisor Pro gives you the ability to alter the stick out, axial depth of cut, and radial depth of cut to match the specific application. These changes can either be made by entering the exact numeric value, the % of cutter diameter, or by altering the slider bars. You are now able to lock RDOC or ADOC while adjusting the other depth of cut, allowing for more customization when developing parameters.

The parameters section also offers a visual representation of the portion of the tool that will be engaged with the materials as well as the Tool Engagement Angle.

MAP’s Recommendations

At this point, you can now review the recommended feeds and speeds that Machining Advisor Pro suggests based on the information you have input. These optimized running parameters can then be further refined by altering the speed and feed percentages.

 

Machining Advisor Pro recommendations can be saved by clicking on the PDF button that is found in the recommendation section on both the web and mobile platforms. This will automatically generate a PDF of the recommendations, allowing you to print, email, or share with others.

Machining Advisor Pro Summarized

The final section, exclusive to the mobile application, is the “Summary” section. To access this section, first tap on the checkmark icon in the bottom menu. This will open a section that is similar to the “Input Specs” section, which will give you a summary of the total parameter outputs. If anything needs to change, you can easily jump to each output item by tapping on the section you need to adjust.

 

 

This is also where you would go to reset the application to clear all of the inputs and start a new setup. On the web version, this button is found in the upper right-hand corner and looks like a “refresh” icon on a web browser.

Contact Us

For the mobile application, we have implemented an in-app messaging service. This was done to give the user a tool to easily communicate any question they have about the application from within the app. It allows the user to not only send messages, but to also include screenshots of what they are seeing! This can be accessed by clicking on the “Contact Us” option in the same hamburger menu that the Logout and Help & Tips are found.

Click this link to sign up today!

Best Practices of Tolerance Stacking

Tolerance stacking, also known as tolerance stack-up, refers to the combination of various part dimension tolerances. After a tolerance is identified on the dimension of a part, it is important to test whether that tolerance would work with the tool’s tolerances: either the upper end or lower end. A part or assembly can be subject to inaccuracies when its tolerances are stacked up incorrectly.

The Importance of Tolerances

Tolerances directly influence the cost and performance of a product. Tighter tolerances make a machined part more difficult to manufacture and therefore often more expensive. With this in mind, it is important to find a balance between manufacturability of the part, its functionality, and its cost.

Tips for Successful Tolerance Stacking

Avoid Using Tolerances that are Unnecessarily Small

As stated above, tighter tolerances lead to a higher manufacturing cost as the part is more difficult to make. This higher cost is often due to the increased amount of scrapped parts that can occur when dimensions are found to be out of tolerance. The cost of high quality tool holders and tooling with tighter tolerances can also be an added expense.

Additionally, unnecessarily small tolerances will lead to longer manufacturing times, as more work goes in to ensure that the part meets strict criteria during machining, and after machining in the inspection process.

Be Careful Not to Over Dimension a Part

When an upper and lower tolerance is labeled on every feature of a part, over-dimensioning can become a problem. For example, a corner radius end mill with a right and left corner radii might have a tolerance of +/- .001”, and the flat between them has a .002” tolerance. In this case, the tolerance window for the cutter diameter would be +/- .004”, but is oftentimes miscalculated during part dimensioning. Further, placing a tolerance on this callout would cause it to be over dimensioned, and thus the reference dimension “REF” must be left to take the tolerance’s place.

stacking tolerances

Figure 1: Shape of slot created by a corner radius end mill

Utilize Statistical Tolerance Analysis:

Statistical analysis looks at the likelihood that all three tolerances would be below or above the dimensioned slot width, based on a standard deviation. This probability is represented by a normal probability density function, which can be seen in figure 2 below. By combining all the probabilities of the different parts and dimensions in a design, we can determine the probability that a part will have a problem, or fail altogether, based on the dimensions and tolerance of the parts. Generally this method of analysis is only used for assemblies with four or more tolerances.

stacking tolerances

                                                               Figure 2: Tolerance Stacking: Normal distribution

Before starting a statistical tolerance analysis, you must calculate or choose a tolerance distribution factor. The standard distribution is 3 . This means that most of the data (or in this case tolerances) will be within 3 standard deviations of the mean. The standard deviations of all the tolerances must be divided by this tolerance distribution factor to normalize them from a distribution of 3  to a distribution of 1 . Once this has been done, the root sum squared can be taken to find the standard deviation of the assembly.

Think of it like a cup of coffee being made with 3 different sized beans. In order to make a delicious cup of joe, you must first grind down all of the beans to the same size so they can be added to the coffee filter. In this case, the beans are the standard deviations, the grinder is the tolerance distribution factor, and the coffee filter is the root sum squared equation. This is necessary because some tolerances may have different distribution factors based on the tightness of the tolerance range.

The statistical analysis method is used if there is a requirement that the slot must be .500” wide with a +/- .003” tolerance, but there is no need for the radii (.125”) and the flat (.250”) to be exact as long as they fit within the slot. In this example, we have 3 bilateral tolerances with their standard deviations already available. Since they are bilateral, the standard deviation from the mean would simply be whatever the + or – tolerance value is. For the outside radii, this would be .001” and for the middle flat region this would be .002”.

For this example, let’s find the standard deviation (σ) of each section using equation 1. In this equation represents the standard deviation.

standard deviation

The standard assumption is that a part tolerance represents a +/- 3  normal distribution. Therefore, the distribution factor will be 3. Using equation 1 on the left section of figure 1, we find that its corrected standard deviation equates to:

tolerance stacking

This is then repeated for the middle and right sections:

standard deviation

After arriving at these standard deviations, we input the results into equation 2 to find the standard deviation of the tolerance zone. Equation 2 is known as the root sum squared equation.

root sum

At this point, it means that 68% of the slots will be within a +/- .0008” tolerance. Multiplying this tolerance by 2 will result in a 95% confidence window, where multiplying it by 3 will result in a 99% confidence window.

68% of the slots will be within +/- .0008”

95% of the slots will be within +/- .0016”

99% of the slots will be within +/- .0024”

These confidence windows are standard for a normal distributed set of data points. A standard normal distribution can be seen in Figure 2 above.

Statistical tolerance analysis should only be used for assemblies with greater than 4 toleranced parts. A lot of factors were unaccounted for in this simple analysis. This example was for 3 bilateral dimensions whose tolerances were representative of their standard deviations from their means. In standard statistical tolerance analysis, other variables come into play such as angles, runout, and parallelism, which require correction factors.

Use Worst Case Analysis:

Worst case analysis is the practice of adding up all the tolerances of a part to find the total part tolerance. When performing this type of analysis, each tolerance is set to its largest or smallest limit in its respective range. This total tolerance can then be compared to the performance limits of the part to make sure the assembly is designed properly. This is typically used for only 1 dimension (Only 1 plane, therefore no angles involved) and for assemblies with a small number of parts.

Worst case analysis can also be used when choosing the appropriate cutting tool for your job, as the tool’s tolerance can be added to the parts tolerance for a worst case scenario. Once this scenario is identified, the machinist or engineer can make the appropriate adjustments to keep the part within the dimensions specified on the print. It should be noted that the worst case scenario rarely ever occurs in actual production. While these analyses can be expensive for manufacturing, it provides peace of mind to machinists by guaranteeing that all assemblies will function properly. Often this method requires tight tolerances because the total stack up at maximum conditions is the primary feature used in design. Tighter tolerances intensify manufacturing costs due to the increased amount of scraping, production time for inspection, and cost of tooling used on these parts.

Example of worst case scenario in context to Figure 1:

Find the lower specification limit.

For the left corner radius

.125” – .001” = .124”

For the flat section

.250” – .002” = .248”

For the right corner radius

.125” – .001” = .124”

Add all of these together to the lower specification limit:

.124” + .248” + .124” = .496”

Find the upper specification limit:

For the left corner radius

.125” + .001” = .126”

For the flat section

.250” + .002” = .252”

For the right corner radius

.125” + .001” = .126”

Add all of these together to the lower specification limit:

.126” + .252” + .126” = .504”

Subtract the two and divide this answer by two to get the worst case tolerance:

(Upper Limit – Lower Limit)/2 = .004”

Therefore the worst case scenario of this slot is .500” +/- .004”.

4 Essential Corner Rounding End Mill Decisions

A Corner Rounding End Mill is typically used to add a specific radius to a workpiece, or in a finishing operation to remove a sharp edge or burr. Prior to selecting your Corner Rounding End Mill, mull the following considerations over. Choosing the right tool will result in a strong tool with a long usable life, and the desired dimensional qualities on your part. Choosing wrong could result in part inaccuracies and a subpar experience.

Selecting the Right Pilot Diameter

The pilot diameter (D1 in the image above) determines the tool’s limitations. When pilot diameters are larger, the tool is able to be run at lower speeds. But with smaller pilot diameters, the tool can be run faster because of its larger effective cutter radius. The effective cutter diameter is determined by the following equations depending on the radius to pilot ratio:

For a Radius/Pilot Ratio < 2.5, Effective Cutter Diameter = Pilot Diameter + Radius
For a Radius/Pilot Ratio ≥ 2.5, Effective Cutter Diameter = Pilot Diameter + .7x Radius

Larger pilot diameters also have more strength than smaller pilot diameters due to the added material behind the radius. A smaller pilot may be necessary for clearance when working in narrow slots or holes. Smaller pilots also allow for tighter turns when machining an inside corner.

Flared or Unflared

Putting a full radius on a part has the potential to leave a step or an over-cut on a workpiece. This can happen if the tool isn’t completely dialed in or if there is minor runout or vibration. A slight 5° flare on the pilot and shoulder blends the radius smoothly on the workpiece and avoids leaving an over-cut.

A flared Corner Rounding End Mill leaves an incomplete radius but allows for more forgiveness. Additionally, this tool leaves a clean surface finish and does not require a second finishing operation to clean leftover marks. An unflared corner radius leaves a complete radius on the workpiece, but requires more set-up time to make sure there is no step.

Front or Back

Choosing between a Corner Rounding End Mill and a Back Corner Rounding End Mill boils down to the location on the part you’re machining. A Back Corner Rounding End Mill should be utilized to put a radius on an area of the part facing the opposite direction as the spindle. While the material could be rotated, and a front Corner Rounding End Mill used, this adds to unnecessary time spent and increased cycle times. When using a Back Corner Rounding End Mill, ensure that you have proper clearance for the head diameter, and that the right reach length is used. If there is not enough clearance, the workpiece will need to be adjusted.

Flute Count

Corner Rounding End Mills are often offered in 2, 3, and 4 flute styles.  2 flute Corner Rounding End Mills are normally used for aluminum and non-ferrous materials, although 3 flutes is quickly becoming a more popular choice for these materials, as they are softer than steels so a larger chip can be taken without an impact on tool life. 4 flutes should be chosen when machining steels to extend tool life by spreading out the wear over multiple teeth. 4 flute Corner Rounding End Mills can also be run at higher feeds compared to 2 or 3 flute tools.

Corner Rounding End Mill Selection Summarized

The best corner rounding end mill varies from job-to-job. Generally speaking, opting for a tool with the largest pilot diameter possible is your best bet, as it has the most strength and requires less power due to its larger effective cutter diameter. A flared Corner Rounding End Mill is preferred for blending purposes if the workpiece is allowed to have an incomplete radius as this allows more forgiveness and can save on set up time. If not, however, an unflared Corner Rounding End Mill should be utilized. As is often the case, choosing between number of flutes boils down to user preference, largely. Softer materials usually require fewer flutes. As material gets harder, the number of flutes on your tool should increase.

The Advances of Multiaxis Machining

CNC Machine Growth

As the manufacturing industry has developed, so too have the capabilities of machining centers. CNC Machines are constantly being improved and optimized to better handle the requirements of new applications. Perhaps the most important way these machines have improved over time is in the multiple axes of direction they can move, as well as orientation. For instance, a traditional 3-axis machine allows for movement and cutting in three directions, while a 2.5-axis machine can move in three directions but only cut in two. The possible number of axes for a multiaxis machine varies from 4 to 9, depending on the situation. This is assuming that no additional sub-systems are installed to the setup that would provide additional movement. The configuration of a multiaxis machine is dependent on the customer’s operation and the machine manufacturer.

Multiaxis Machining

With this continuous innovation has come the popularity of multiaxis machines – or CNC machines that can perform more than three axes of movement (greater than just the three linear axes X, Y, and Z). Additional axes usually include three rotary axes, as well as movement abilities of the table holding the part or spindle in place. Machines today can move up to 9 axes of direction.

Multiaxis machines provide several major improvements over CNC machines that only support 3 axes of movement. These benefits include:

  • Increasing part accuracy/consistency by decreasing the number of manual adjustments that need to be made.
  • Reducing the amount of human labor needed as there are fewer manual operations to perform.
  • Improving surface finish as the tool can be moved tangentially across the part surface.
  • Allowing for highly complex parts to be made in a single setup, saving time and cost.

9-Axis Machine Centers

The basic 9-axis naming convention consists of three sets of three axes.

Set One

The first set is the X, Y, and Z linear axes, where the Z axis is in line with the machine’s spindle, and the X and Y axes are parallel to the surface of the table. This is based on a vertical machining center. For a horizontal machining center, the Z axis would be aligned with the spindle.

Set Two

The second set of axes is the A, B, and C rotary axes, which rotate around the X, Y, and Z axes, respectively. These axes allow for the spindle to be oriented at different angles and in different positions, which enables tools to create more features, thereby decreasing the number of tool changes and maximizing efficiency.

Set Three

The third set of axes is the U, V, and W axes, which are secondary linear axes that are parallel to the X, Y, and Z axes, respectively. While these axes are parallel to the X, Y, and Z axes, they are managed by separate commands. The U axis is common in a lathe machine. This axis allows the cutting tool to move perpendicular to the machine’s spindle, enabling the machined diameter to be adjusted during the machining process.

A Growing Industry

In summary, as the manufacturing industry has grown, so too have the abilities of CNC Machines. Today, tooling can move across nine different axes, allowing for the machining of more intricate, precise, and delicate parts. Additionally, this development has worked to improve shop efficiency by minimizing manual labor and creating a more perfect final product.

8 Ways You’re Killing Your End Mill

1. Running It Too Fast or Too Slow

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. 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.

2. 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.

3. Using Traditional Roughing

high efficiency milling

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.

4. Using Improper Tool Holding

tool holding

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™.

5. Not Using Variable Helix/Pitch Geometry

variable helix

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.

6. Choosing the Wrong Coating

end mill coatings

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.

7. Using a Long Length of Cut

optimal 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.

8. Choosing the Wrong Flute Count

flute count

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.

Optimizing Material Removal Rates

 What is the Material Removal Rate?

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). If you’re aiming to boost your shop’s efficiency, increasing your MRR even minimally can result in big gains.

Calculating MRR

The calculation for Material Removal Rate is RDOC x ADOC x Feed Rate. 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 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, while maintaining and even prolonging tool life versus traditional machining methods.

High Efficiency Milling

The following video provides an excellent look into the efficiency-boosting power of HEM operations. By following the MRR calculation, we can see that @jcast.cnc will have experienced 40.6 cu.in.³ MRR.

MRR = .145″ x .800″ x 350 in./min. = 40.6 in.³/min.

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. Additionally, a tool coating optimized for your workpiece material can significantly help with chip packing. Further, compressed air or coolant can help to properly remove chips from the tool and workpiece.

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 output.