Multi-Axis Finishers: The Key to Amazing Surface Finish

A Key to Improving Surface Finish

In today’s Manufacturing Industry, part finish and machining efficiency are key to a successful machine shop. It’s no surprise, therefore, that the popularity Multi-Axis Finishers has never been greater. Helical Solutions is a leader in the manufacturing of Multi-Axis Finishers, and its customers utilize this impressive tool when faced with extremely high surface finish requirements, oftentimes swapping out a traditional Ball End Mill to dramatically improve finish while minimizing cycle times.

Multi-Axis Finisher Basic Principles

A Multi-Axis Finisher can be easily recognized by its large radius included in the profile of the tool. With a larger radius, a far greater stepover can be used pass-to-pass while keeping the same cusp height as a Ball End Mill. This decreases the cycle time by a known value called the Benefit Multiple.

A Multi-Axis Finisher with a Benefit Multiple of 8 will reduce the cycle time to 1/8 of the cycle time for a Ball End Mill of the same shank diameter – an 87.5% time savings! If a Multi-Axis Finisher is used with the same pass-to-pass stepover as a Ball End Mill, the finish will be drastically improved due to exponentially smaller cusp heights. Most situations allow both reduced cycle time and improved surface finish to be achieved.

The images below show the comparison of a ball end mill to an Oval Shape Multi-Axis Finisher with a benefit multiple of 4.

Due to their large radii, Multi-Axis Finishers are best suited for wide open, flowing, and somewhat flat surfaces. Smaller spaces, especially tight corners, will generally not see as much benefit from these tools due to limited use of the major radius.

Multi-Axis Finisher Tool Selection

The Manufacturing Industry’s leader in Multi-Axis Finishers, Helical Solutions offers 3 distinct profiles, each fully stocked and available to ship the day of purchase.

Oval Form Multi-Axis Finishers

The oval form includes 2 tangential radii and offers the most versatility in smaller spaces where a slightly varied approach angle is required, such as impellers or fan blades.

Taper Form Multi-Axis Finishers

The taper form includes 3 tangential radii and a taper angle. It allows for the largest radius, and therefore greatest potential improvement of finish and reduction of cycle time. They are best used where a specific approach angle is needed and where maximum performance gain is desired.

Lens Form Multi-Axis Finishers

The lens form includes 2 tangential radii on the end of the tool and is used for work mostly on the face of a part. Tilt angles of approximately 5 degrees are recommended for these tools to avoid working on-center.

Programming Multi-Axis Finishers

Programming Multi-Axis Finishers requires some additional consideration compared to a typical end mill. Luckily, many modern CAM packages offer support for these unique profiles, including many of Helical’s CAM partners. Each software has their own name for these toolpaths, so reach out to your CAM or Helical sales rep to find how you can program yours!

For more information on Multi-Axis Finishers, and to learn if this advantageous tool is right for you, read our Multi-Axis Finishers Q&A.

10 CNC Drill Geometries Every Machinist Must Know

A CNC drill has many different features and geometries that directly impact the tool’s performance, productivity, and tool life in the specific material it’s machining. It is important to understand the different geometries of a drill to ensure you’re not only recognizing how they affect an application, but also which geometries you should be looking for when selecting your next drill.

1.    Point Angle

This drill geometry refers to the angle of the cutting edge of the drill. As the point angle increases on a drill, the radial forces decrease, making the angle size a huge factor in what type of material the drill is optimized for and what types of applications should be run. The smaller the point angle, the better it will perform in through hole applications. This is because the smaller angle reduces the axial forces, allowing less of the chip to be pushed out and more cutting to occur.

118° & 120° Point Angle

Many machinists opt for this angle when machining soft gummy materials.

135° Point Angle

This point angle size is an excellent choice for machining aluminum and stainless steels.

140° Point Angle

This larger point angle size is great for machining steels.

150° Point Angle

Large angles are often used for spot drilling applications, but the optimal spot drill angle is determined by the size of the angle of the final drill being used. Selecting the proper spot drill is essential to eliminating the chance of drill walking and ensuring a more accurate final product. Learn which spot angle should be used for your next drilling job in this in-depth guide.

2.    Chisel and Cutting Edges


Although the chisel edge of a CNC drill does not provide any cutting action, it is responsible for the centering of the drill, as it extrudes the material towards the cutting edges. The cutting edges are then able to start the process of producing chips, which then travel up the flutes of the drill.

3.    Flutes

The most recognizable part of a drill is its flutes. They are the deep grooves that allow for chip evacuation to occur. When one thinks of a drill, they are likely imagining a spiral flute drill. These spiral flutes complement the point angle, chisel edge, and the cutting edges. They work like an elevator system to lift the chips out of the hole, allowing them to provide excellent chip evacuation. They work great in most material types and provide good hole quality.

4.    Helix Angle

The helix angle is the angle formed by the leading edge of the land with a plane containing the axis of the drill. The main function of the helix angle is to transfer the chips out of the hole and a specific angle is relevant to the type of material that is being machined in and the particular application being run.

Low Helix

A low helix of 12° – 22° is recommended for materials like cast iron, brass, and hardened steels. In these “short chipping” materials, the chips move more freely, and the coolant provides enough assistance to properly evacuate the chips out of the hole.

Medium Helix

The most widely used helix angles are medium as they provide optimal chip evacuation and strength to the drill. Medium helix angles range from 28° – 32° and are recommended for any general purpose drilling applications.

High Helix

A high helix angle of 34° – 38° is recommended for long chipping material such as softer non-ferrous materials like brass, aluminum, and plastics. Drills with a high helix are also beneficial in deep hole applications as the chips can evacuate more easily.

5.    Web Thickness (Core)

The web is the core section of the drill body, which connects the two flutes. The thickness of the web determines the torsional strength of a drill. A drill with a larger web diameter will have more torsional strength than a drill with a smaller web diameter.

The proper web thickness is determined by the material type to be machined. Long chipping materials will require a drill with a smaller web thickness to provide adequate clearance for chip removal. When drilling short chipping materials such as cast iron, the drill web can be increased for additional strength.

6.    Corner Chamfer


A corner chamfer or radius is often added to eliminate the sharp edge at the intersection of the flutes and the outside diameter of a drill. This helps to eliminate material breakout when exiting a hole, while also helping to reduce the size of the entrance and exit burrs. This feature is also widely known to significantly extend tool life.

7.    Drill Margin

Margin(s) are the surfaces along the outer diameter of the drill which provide stability to the hole as they support the radial forces that are directed radially by the drill point.

Size of Drill Margin

The size of the margin will determine the overall quality of the hole. Wide marginswill stabilize the drill better, hold a tighter hole diameter tolerance, and improve the circularity of the hole. Narrow margins reduce friction and heat, eliminate work hardening, mitigate built-up edge, and provide better tool life.

Number of Drill Margins

The number of margins on a drill is usually determined by the type of hole being machined. Single margin drills are very common in non-interrupted holes. Double or triple margin drills are common in interrupted or intersecting holes. The more margins there are, the better the guidance is to help the drill stay straight through interrupted cuts, cross holes, and irregular or angled surfaces on exit. While adding margins does provide these benefits for irregular style cuts, they also increase friction, which causes the drill to produce more heat. This causes wear to be accelerated, reducing the life of the tool.

8.    Land of a Drill

The land is the outer portion of the body of the drill between two adjacent flutes. Land width will determine how much torsional force a drill can withstand before catastrophic failure. The smaller the land is, the more chip space there is, producing less torsional strength. The larger the land is, the less chip space there is, providing more torsional strength.

9.    Coolant-Through Channels


Not only do coolant-through channels offer any drilling application a multitude of benefits, but they are also highly recommended for hole depths that exceed 4XD (4 times diameter). Coolant-Through Drills allow for higher speed and feed rate capabilities, increased lubricity, better chip control, improved surface finish, and enhanced tool life.

10.  Shank

The shank is a very important yet overlooked drill geometry as it is the drive mechanism and is what is mounted into a Tool Holder. It is essential that the shank is held to proper diameter tolerance and considerations are being made depending on the holder being used. For example, a shank with an h6 tolerance is essential when a shrink fit style tool holder is being used.

Learning the different geometries of a CNC drill can greatly assist you in ensuring you are selecting the right drill for your next job, while understanding the functions of these features will allow you to trouble shoot any potential machining hiccups you may encounter in your future CNC drilling applications.

3 Tips for Avoiding Misaligned Holes


One of the most common issues machinists face during a drilling operation is hole misalignment. Hole alignment is an essential step in any assembly or while mating cylindrical parts. When holes are properly aligned, the mating parts fit easily in each other. When one of the pieces to the puzzle is inaccurate, however, machinists run into issues and parts can be scrapped. The two types of common misalignment woes are Angular Misalignment and Offset Misalignment.

Angular Misalignment

Angular misalignment is the difference in slope of the centerlines of the holes. When the centerlines are not parallel, a shaft will not be able to fit through the hole properly.

Offset Misalignment

Offset misalignment is the distance between the centerlines of the hole. This is the position of the hole from its true position or mating part. Many CAD software programs will help to identify if holes are misaligned, but proper technique is still paramount to creating perfect holes.

1.    Utilize a Spotting Drill

Using a spotting drill is a common way to eliminate the chance of the drill walking when it makes contact with the material. A spotting drill is designed to mark a precise location for a drill to follow, minimizing the drill’s ability to walk from a specific area.

valor holemaking high performance spotting drill

Valor Holemaking High Performance Spotting Drill

Although using a spotting drill would require an additional tool change during a job, the time spent in a tool change is far less than the time required to redo a project due to a misaligned hole. A misaligned hole can result in scrapping the entire part, costing time and money.

Do you know how to choose the perfect spot drill angle? Learn how in this in-depth guide so you can eliminate the chance of drill walking and ensure a more accurate final product.

2.    Be Mindful of Web Thickness

A machinist should also consider the web thickness of the drill when experiencing hole misalignment. A drill’s web is the first part of the drill to make contact with the workpiece material.

Essentially, the web thickness is the same as the core diameter of an end mill. A larger core will provide a more rigid drill and a larger web. A larger web, however, can increase the risk of walking, and may contribute to hole misalignment. To overcome this machining dilemma, machinists will oftentimes choose to use a drill that has a thinned web.

Web Thinning

Also known as a split point drill, web thinning is a drill with a thinned web at the point, which helps to decrease thrust force and increase point accuracy. There are many different thinning methods, but the result allows a drill to have a thinner web at the point while having the benefit of a standard web through­out the rest of the drill body.

A thinner web will:

  1. Be less susceptible to walking
  2. Need less cutting resistance
  3. Create less cutting force

3.    Select a Material Specific Drill

Choosing a material specific drill is one of the easiest ways to avoid hole misalignment. A material specific drill design has geometries that will mitigate the specific challenges that each unique material presents. Further, material specific drills fea­ture tool coatings that are proven to succeed in the specific material a machinist is working in.

Valor Holemaking High Performance Drills for Steels and High Performance Drills for Aluminum

Helical Solutions Teams up With Mastercam to Test Different Levels of Continuous Time In Cut (CTIC)

Don Grandt, Harvey Performance Company National Application Engineer, met up with Jesse Trinque at the Mastercam Manufacturing Lab to demo some Helical Solutions End Mills and discuss Continuous Time In Cut (CTIC).

Continuous Time in Cut (CTIC) is the amount of time that a tool is engaged with a material. When an end mill is in a cut for too long, the friction can build and surface foot can be sacrificed, greatly affecting the performance and wear of a tool.

Check out this video to watch Jesse and Don test out how different levels of CTIC directly affect tool life and performance. This series of tests, which were facilitated by Mastercam, were conducted in Okuma’s GENOS M560-V, and utilized tool paths from Mastercam. For tooling, a standard ½” Helical Solutions HEV-6, a 6 flute, variable pitch end mill with a .03” corner radius, was used to machine 17-4 stainless steel.

All tests used the same cutting parameters, setup, material, and tool, with altered CTIC.

Take a Deeper Dive Into CTIC

Tune into this episode of In The Loupe TV to learn how you can manipulate Continuous Time In Cut (CTIC) and surface foot to reduce heat in your machining applications.

Carbon Fiber Reinforced Polymers (CFRP): Running Parameters, Tool Life, & Safety Tips


Carbon Fiber Reinforced Polymers (CFRP) is a collection of carbon fibers that, when bound together via resin, creates a material with a wide range of application possibilities. It’s strong, durable, and resistant to corrosion, making it an advantageous material for use in several advanced industries, including the aerospace and automotive industries. Despite its unique abilities, however, machining CFRP is not without its set of challenges, all of which machinists must be cognizant of to achieve desired results. Once CFRP is properly understood and the right cutting tool is selected for the job, the next step is to properly set running parameters for your application.

Square piece of cfrp laminate carbon fiber material

Running Parameters

Comparison of Metal Machining vs Composite Machining

When machining CFRP, the suggested running parameters are to have a high RPM with low feed rates. Feed rates will need to be adjusted to account for heat minimization, while RPMs may need to be dialed back to prevent excessive fraying, tearing, or splitting of fibers when cutting.

In metal machining, the tool cuts away at material, forming chips. This is possible due to the formation of the metal having natural fracture and stress lines that can be wedged by the cutting tool to create a chip. Unlike metals, machining carbon fiber does not peel away material but rather fracture and break the fibers and resin.

Milling vs Drilling Carbon Fiber

Composite holemaking or drilling is found to be more challenging than milling carbon fiber. It generates more dust due to the drilling speed. Using specific tooling for composites will be crucial in effective drilling. When machining holes, the carbon fiber will relax, creating undersized holes which requires extensive adjustments that are best automated for efficiency.

For help mitigating the challenges of composite holemaking, read Overcoming Composite Holemaking Challenges and browse CoreHog’s offering of drills, specially engineered to mitigate all-too-common holemaking headaches. To achieve better finish and avoid delamination, it is recommended to utilize conventional milling over climb milling within composites contrary to what is recommended in metal machining.

Combination of corehog specific cfrp drills including helical step, dagger, 8 facet, and tapered drill reamer

Within the aerospace industry, drilling is the most common application in machining. Like milling, performing operations such as pecking may be preferred even with increased cycle time if it reduces any chances of error that result in scrapping of the part.

Running Parallel to Grain of Fibers

While every part is different, there is a method for reducing fraying, chipping, or delamination by cutting parallel to the fiber direction when possible. This can be like cutting along the grain of wood instead of cutting perpendicular or at an angle to the grain.

Coolant Applications

The use of coolant when machining CFRP can either benefit or negatively affect the part depending on the application. The preferred coolant of choice for machining carbon fiber is typically using water or a water-soluble coolant. This is due to composites having a porous surface that could allow contaminates to enter the part itself. By using water, it prevents any issues after machining where adhesives or paint may need to be applied to the part that otherwise would not have adhered properly with contaminates present.

cnc machine looking through glass window focusing on a tool in the cut with external coolant spraying the workpiece

High Scrapping Costs

Many composite parts are unique in shape and size with custom molded designs that create a large initial cost prior to the machining stage. After the part is molded near to its shape, machining is often used to finish the part or drill holes where needed to finalize the part.

Importance of Considering Machining Challenges to Avoid Scrapping

Having a set process that is consistent and reliable is important in helping to prevent scrapping. Eliminating human error with machines that can monitor the entire process while automating tool changes when tools are worn, avoids issues before they can happen. A key factor is ensuring the setup is correct, having the right tooling, tool path, and coolant option to perform the operation effectively and accurately. With some parts serving critical functions and with a high cost, there is no exception for poor finish or incorrect cuts emphasizing the importance of having a procedure that gets the job done the right way.

Composite Cutting Tool Life Management

Wear Rate & its Effects 

Due to carbon fiber’s abrasion on the cutting tools, a rapid decrease in cutting quality will occur as soon as the tool begins to dull. Fibers will be grabbed instead of fractured, causing fraying and damage to the part. Therefore, tool life should be vigilantly monitored to replace the tool before reaching the point of dullness.

Developing a Process for Success

Unlike metal machining where tools may be utilized until they show signs of wear, this method would be unideal for CFRP as the highly expensive part could be ruined or damaged causing scrapping costs and time. It is good practice to take preventative measures by taking note of typical wear of your tools and using that information to set tool changes before it dulls. Noting tool changes and having high interval checks on cutting and dimension quality will aid in avoiding poor finish or scrapping. Some machines are equipped with tool life management systems which will greatly reduce the chances of having to scrap a part because of tool dullness.

Safety Practices When Machining CFRP

Being that chips are not formed when machining CFRP, and instead, the material is fractured, it creates dust that can spread throughout the air and other surfaces. Not only does this cause hazardous conditions for anyone nearby who may inhale the dust, but the dust is also conductive, which can ruin electronics. To avoid these issues, two different extraction methods can be used depending on the needs of the application.

Wet vs Dry Extraction

The two options for dust extraction are using coolant (wet) or vacuuming (dry). Choosing between the two is dependent on the application, but mostly dictated by the size of the application. Smaller scale machining can be contained through vacuuming, but larger applications would require coolant as vacuuming a large area may be challenging. If a lot of heat will be generated, then it is necessary to have a water-soluble coolant. This would also benefit the use of diamond tooling as they will wear faster at lower temperatures in comparison to carbide tooling. Another would be the dust collection would remain contained with the liquid preventing any airborne exposure.

Disposal Considerations

One benefit of vacuuming over coolant is the disposal process. After machining, the coolant/dust mix would require post-treatment to remove excess water before being transferred to a landfill. This would incur additional costs to the process which may cause some to lean towards vacuuming if heat is not an issue.

Conclusion

With CFRP’s wide range of uses and desirable mechanical properties for its applications, comes the effect of its challenges in machining and high cost of scrapping. Refining this process will be essential for the growing demand of carbon fiber machining in the near future. For more information on CFRP, specifically related to material properties and tool selection, read In the Loupe’s complementary post “Carbon Fiber Reinforced Polymers (CFRP): Material Properties & Tool Selection”.

The Benefits of CoreHog’s Assembly Style Tooling in Composites


Harvey Performance Company brand CoreHog, which focuses on the manufacturing of the world’s most advanced composite and honeycomb core cutting tools, fully stocks an array of “Assembly Style Cutting Tools,” which allow a machinist to build the perfect solution for their specific application’s needs. In doing so, a cutting tool can be optimized for specific materials, densities, and manufacturing styles to increase efficiency, decrease costs, and provide unbelievable machining flexibility.

Corehog tooling for machining composites

How Does Assembly Style Tooling Work?

CoreHog’s Assembly Style Tooling works by taking multiple pieces and tool components, and assembling them together to create one finished cutting tool. The concept of assembling a completed tool allows machinists greater flexibility in choosing cutting edges that are best suited for their application or material type. Further, this type of tooling is often utilized by machinists because it’s often a less expensive alternative to solid round, non-assembled tooling, as a machinist would only need to replace the cutting end components when they begin to dull, and not the arbors or shank pieces.

CoreHog’s offering of Assembly Style Tooling includes Small Size, Medium Size, and Large Size Finishing Core Tools, as well as Valve Stem Cutters and Rebating Cutters. The way in which each system is built varies by tool type.

Finishing Core Tools

Small Finishing Core Tools

Optimized to machine small, closed features in composites, such as pockets, joggles, and closed walls, Small Size Finishing Tools are engineered for the superior finishing of honeycomb core materials. This configuration includes a Small Coreslicer with three different edge options: Smooth, Sawtooth, or Staggered Tooth, and an optional Small CoreHogger. The right edge style for the Coreslicer depends largely on the material you’re working in. While a Smooth edge style works well in lighter density honeycomb core materials such as Kevlar®, Nomex®, and Aluminum, Sawtooth and Staggered Tooth options work best for honeycomb core materials with densities of 6 pounds or higher, such as aluminum core, Kevlar®, or Nomex®.


Key Benefits: Eliminating the risk of material wrapping around the spindle by disintegrating them as they approach the face of the slicer.

Browse Small Finishing Core Tools

Medium Finishing Core Tools

Designed for finishing honeycomb core materials, this assembly style CNC tooling is engineered for shaping smaller complex surfaces, bevels, and external radii. For this configuration, a Medium CoreHogger and a Medium Coreslicer must be utilized and fastened with a screw. Similar to the Small Finishing Core Tool options, this assembly can be used with a Smooth, Sawtooth, or Staggered Tooth Coreslicer edge.

Key Benefits: This Medium Size Finishing Tool offering includes both carbide and high speed steel options. The carbide version is uncoated, whereas the high speed steel version is TiCN coated for extended tool life and improved wear resistance.

Browse Medium Finishing Core Tools

Large Finishing Core Tools

Designed to vastly reduce cycle times while finishing honeycomb core materials, this assembly style tooling removes large volumes of material quickly, while providing excellent surface finish and keeping tool pressure and heat low.


Large Finishing Core Tools require a slightly more complex configuration. This type of modular tool features an Arbor, which includes a washer and screw; Large CoreHogger; and Large Coreslicer. For this assembly, four types of Coreslicer edge options are available: Smooth, Sawtooth, Staggered Tooth, or Wavy. Wavy style options are best utilized in heavier density types of Kevlar®, Nomex®, and Aluminum Core, and are engineered to be useful when machining parts that contain bond lines.

Key Benefits: The Arbors in this configuration are heat treated and finish ground for extremely tight tolerances in runout, concentricity, and perpendicularity. With tighter tolerances, harmonics are minimized while longer tool life and better part finish are observed.

Browse Large Finishing Core Tools

Valve Stem Cutters


Different from CoreHog’s Finishing Core Tools, Valve Stem Cutters are assembly tooling engineered for machining honeycomb core materials and finishing thin features, such as bevels and knife edge parts. To build a Valve Stem Cutter, utilize an Arbor, a Valve Stem Slicer, and a screw to fasten the two together. Similar to Small and Medium Finishing Core Tools, the Valve Stem Slicer can feature a Smooth, Sawtooth, or Staggered Tooth edge profile.

Key Benefits: The Stem design of CoreHog’s Valve Stem Arbors is optimized for free flowing applications, eliminating grabbing when machining Honeycomb Core Materials.

Browse Valve Stem Cutters

Rebating Cutters


Machinists may opt to use a Modular Rebating Tool if they are aiming to reduce setup, minimize cost per cutter, and obtain flexibility with varying sandwich panel configurations. For this configuration, an Arbor connects to a Core Insert, Skin Insert, and is fastened with a screw. Here, the Arbor, which features a .500” shank diameter and a 3” overall length, can be paired with multiple sizes of Core Inserts. As of September 2022, CoreHog’s offering of Core Inserts range in diameter from .875” to 1”, with a length of cut spanning from .160” to .312”. All Inserts feature TiAlN coating, which provides high hardness and high temperature resistance. Finally, the Skin Insert features a ½” diameter, and provides a machinist with the option of DLC or CVD Coating. While DLC coating provides optimal performance, true crystalline CVD diamond coating works to significantly extend tool life.

Key Benefits: The complex geometry of Sandwich Panel Cutters – Arbors helps to reduce tearing, flagging, and fuzz, while providing a rebated area to allow for edge filling or fasteners, later on.

Browse Rebating Cutters

For more information on CoreHog’s Assembly Style Tooling, visit its website at corehog.com.

Reduce Tool Chatter by Avoiding These 5 Boring Bar Application Mistakes

Boring bar applications are very popular in the lathe and CNC machining industry, as they provide a shop with extreme diversity and accuracy. Running a boring bar properly, however, is essential to ensuring you’re maximizing shop efficiency and achieving outstanding part finish. There are many mistakes that can be made when running boring bars and many that cause excessive machining vibrations or chatter that must be avoided. Learn the five mistakes that could be causing tool chatter in your boring applications and how you can stop chatter once and for all.

Lathe Boring Bar Application Mistakes

Using a Dull Cutter

Boring with a worn-out tool significantly increases cutting forces generated by the cut, leading to chatter. The more a tool is run, the more chance it has for galling, or in other words, built-up edge (BUE), making it imperative to inspect your boring bar before each application. BUE occurs when material is welded onto the cutting tool due to high friction and heat generation during a CNC machining operation. This condition is not desirable because it leads to poor tool life and increased vibrations due to an uneven cutting edge. Stocking your tool crib with great quality boring bars can help reduce BUE by providing a sharp, long lasting cutting edge, catered for your exact application. Learn other ways to reduce BUE in your turning applications, today.

Shows zoomed in effects of built-up edge and wear failure on carbide boring bar
Image Source: Carbide inserts Wear Failure modes. | machining4.eu, 2022

Utilizing Incorrect Speeds & Feeds

Like many applications, using improper turning speeds & feeds can lead to poor performance. In boring applications, using too high of a chip load can cause deflection, greatly increasing the chances of tool failure. Using too low of a chip load doesn’t allow the tool to cut enough, which causes the tool to bounce off the material, leading to increased tool wear and poor part finish. Discovering the right balance for using chip load is crucial in order to produce a more efficient cut.

lathe turning speeds and feeds

When running a boring bar, it is imperative to use the speeds & feeds recommended for the tool being used. Micro 100 provides downloadable and printer-friendly Speeds & Feeds for all Standard and Quick Change Micro-Quik turning tools.

Lacking Workpiece Support

A main cause of chatter in boring applications is lack of support on the workpiece. If a workpiece is not properly supported when entering a boring application, the tool will begin to chatter. Not only is it essential to confirm the proper workholding device is being used, but it’s also important to ensure that your setup is as rigid as possible. Learn more about workholding styles and considerations to make sure you’re supporting your workpiece properly in your next boring application.

Uneven Tool Holding

Similarly, tool holding also plays a vital role in the performance of a boring bar application. It is important to select a tool holder that accommodates the tooling being used and is as rigid as possible. Using an improper method of tool holding can lead to tool runout, which occurs when the tool or holder deviates too far off its axis.

Micro-Quik tool holder with a tool inserted and pointing towards workpiece
Image Source: @abom79

Many machinists opt for tools that promote machining efficiency by boosting the speed at which tool changes occur. For example cutting tool manufacturer Micro 100 offers Micro-Quik Holders, which offer unmatched rigidity, axial and radial repeatability, tip-to-tip consistency, and part-to-part accuracy in tool changes totaling fewer than 30 seconds.

Drilling an Improper Starter Hole

Before starting a boring application, drilling the proper hole is vital to ensuring that the boring bar has sufficient contact with the workpiece to properly stabilize the cut. If a hole is too large, the boring bar could deflect off of the workpiece. If the hole is too small, there will not be enough clearance for the tool, increasing chances of tool wear and possibly tool failure. When selecting a drill to prepare the workpiece for your boring applications, there are two dimensions that should be considered: the Head Width and the Minimum Bore Diameter.

Boring bar with line drawing showing where different dimensions are located on the tool

The Head Width, or “H” value on the above line drawing, is the actual width of the boring tool. The Minimum Bore Diameter is a calculated dimension slightly larger in size compared to the head with that is associated with the smallest drill size that should be used to start a boring application. It is recommended to opt for a drill that is the same or slightly larger than the Minimum Bore Diameter of the boring bar being used, to ensure there is proper clearance for the cutting edge.

Utilizing an Inefficient Coolant Strategy

If coolant isn’t aimed properly on the workpiece or if improper coolant is being used, tool life and quality part finish can be significantly reduced. Additionally, if coolant lines are aimed directly at the bore, the pressure of the coolant holds the chips in the bore, causing them to evacuate improperly. This then causes chip recutting, leading to chatter and finish problems. Opting for a Plumbed and Ported Tool Holder can mitigate this problem, ensuring chips are being properly evacuated out of the cut.

coolant being sprayed onto a part during a cnc machining operation

Machinists generally utilize Flood or High Pressure coolant methods for chip removal. Flood coolant uses low pressure to create lubricity and aid in chip evacuation. On the other hand, high pressure coolant delivers instant cooling of a part and quickly shoots chips away to prevent recutting.

Spot Drilling: The First Step to Precision Drilling

Drilling an ultra-precise hole can be tough. Material behavior, surface irregularities, and drill point geometry can all be factors leading to inaccurate holes. A Spot Drill, if used properly, will eliminate the chance of drill walking and will help to ensure a more accurate final product.

Choosing a Spot Drill

Ideally, the center of a carbide drill should always be the first point to contact your part. Therefore, a spotting drill should have a slightly larger point angle than that of your drill. Common drill point angles range from 118° to 140° and larger. Shallower drill angles are better suited to harder materials like steels due to increased engagement on the cutting edges. Aluminums can also benefit from these shallower angles through increased drill life. While these drills wear less and more evenly, they are more prone to walking, therefore creating a need for a proper high performance spot drill in a shallow angle to best match the chosen drill.

Five Valor holemaking high performance spot drills displayed on top of a workpiece with a purple product packaging container in front

If a spotting drill with a smaller point angle than your drill is used, your drill may be damaged due to shock loading when the outer portion of its cutting surface contacts the workpiece before the center. Using a drill angle equal to the drill angle is also an acceptable situation. Figure 1 illustrates the desired effect. On the left, a drill is entering a previously drilled spot with a slightly larger angle than its point. On the right, a drill is approaching an area with an angle that is far too small for its point.

Proper Spot Angle Diagram

Marking Your Spot

A Spotting Drill’s purpose is to create a small divot to correctly locate the center of a drill when initiating a plunge. However, some machinists choose to use these tools for a different reason – using it to chamfer the top of drilled holes. By leaving a chamfer, screw heads sit flush with the part once inserted.

Spot Drill

What Happens if I Use a Spot Drill with an Improper Angle?

Using a larger angle drill will allow the drill to find the correct location by guiding the tip of the drill to the center. If the outer diameter of a carbide drill were to contact the workpiece first, the tool could chip. This would damage the workpiece and result in a defective tool. If the two flutes of the drill were slightly different from one another, one could come into contact before the other. This could lead to an inaccurate hole, and even counteract the purpose of spot drilling in the first place.

Avoiding CNC Drill Walking With a Spotting Drill

Few CNC machining applications demand precision like drilling. The diameter hole size, hole depth, part location, and finish are all important and provide little recourse if not up to specifications. That said, accuracy is paramount – and nothing leads to inaccurate final parts faster than drill walking, or the inadvertent straying from a drill’s intended location during the machining process. So how does drill walking occur, and how can one prevent it?

To understand drill walking, think about the act of striking a nail with a hammer, into a piece of wood. Firm contact to a sharp nail into an appropriate wood surface can result in an accurate, straight impact. But if other variables come into play – an uneven surface, a dull nail, an improper impact – that nail could enter a material at an angle, at an inaccurate location, or not at all. With CNC Drilling, the drill is obviously a critical element to a successful operation – a sharp, unworn cutting tool – when used properly, will go a long way toward an efficient and accurate final part.

To mitigate any variables working against you, such as an uneven part surface or a slightly used drill, a simple way to avoid “walking” is to utilize a Spotting Drill. This tool is engineered to leave a divot on the face of the part for a drill to engage during the holemaking process, keeping it properly aligned to avoid a drill from slipping off course.

When Won’t a Spot Drill Work for My Application?

When drilling into an extremely irregular surface, such as the side of a cylinder or an inclined plane, this tool may not be sufficient to keep holes in the correct position. For these applications, flat bottom versions or Flat Bottom Counterbores may be needed to creating accurate features.

Harvey tool spot drill zoomed in on the tip of the drill
Harvey Tool Spot Drill

Machining Nickel Alloys: Avoiding All-Too-Common Mishaps


Nickel-based alloys are growing in popularity across many industries such as aerospace, automotive, and energy generation due to their unique and valuable mechanical and chemical properties. Nickel alloys exhibit high yield and tensile strengths at low weights and have high corrosion resistance in acidic and high temperature environments. Because of these advantageous properties, nickel alloys have increasingly become popular in machine shops.

Unfortunately, nickel alloys have a reputation for creating issues at the spindle. These metals present themselves to be problematic as they easily work harden. Further, nickel alloys generate high temperatures during machining, and have gummy chips that can weld onto cutting tools, creating built-up edge (BUE). Fortunately, with the correct approach, one can be successful in cutting nickel alloys.

Work Hardening

Across machine shops, nickel alloys are notorious for being difficult to machine. This reputation stems, largely, from work hardening, or a metal’s microhardness increasing due to the addition of heat. According to the Nickel Development Institute, this heat is generated through friction and plastic deformation of the metal. As the metal is cut, the friction between the cutting tool and workpiece generates heat which is concentrated around the cutting area.

Simultaneously, the metal is being physically worked. This means that as it is being machined, it is experiencing plastic deformation, which is a physical property that measures how much a material can be deformed to the point that it cannot return to its original shape.

This physical working of a nickel alloy increases its hardness faster than it does most other metals. The combination of high heat generation and physical work quickly increases the alloy’s hardness, causing tools to dull quickly and fail. This may result in scrapped parts and broken tools.

8 flute HVNI End Mill for Machining Nickel Alloys
Shown above is Helical Solutions’ End Mill for Nickel Alloys. This tool, engineered to excel in Inconel 718 and other nickel-based superalloys, is fully stocked in 6 and 8 flute styles.

Tool Adhesion

As nickel alloys are being machined and heat is generated, chips tend to become stringy and weld themselves to a tool’s cutting edge. This phenomenon, built up edge or BUE, rounds the cutting edge of the tool, resulting in poor cuts and increased friction, thus further contributing to work hardening. An example of BUE is seen in the image below.

Zoomed in display of built-up edge on End Mill Flutes
On the above tool, chips from the workpiece (Inconel 718) have welded onto the cutting edge, severely decreasing the tool’s effectiveness. Image Source: International Journal of Extreme Manufacturing

Built-up edge also speeds up tool wear, as the rotational forces involved in the cut increase. Now that the cutting edge is rounded from welded chips, a blunt tool is being forced into the workpiece.

With a blunt edge, the cutting motion changes from a shearing action to plowing. In other words, instead of cutting through the metal, the tool is pushing the material, resulting in poor cuts and increased friction.

Excessive Heat Generation

With poor cutting, internal heat of the tool rises, which can cause thermal cracking, defined by cracks that form perpendicular to the cutting edge. The fractures within the tool are created by extreme internal tool temperature fluctuations.

As a cutting tool rapidly overheats while cutting nickel alloys, cracks may form which can lead to catastrophic tool failure. With high temperatures, galling may also occur, which is characterized by pieces of the tool flaking off due to the same adhesion that causes BUE. As the tool is being welded to the workpiece and the machine continues to rotate it, pieces of the tool may start to break off resulting in tool failure.

Overcoming Nickel Alloy Difficulties

Temperature Control and Coolant Usage

The first step to effectively machine nickel alloys is to keep temperatures manageable as the workpiece is cut. Using high pressure coolant is mandatory. Coolant pressure should be 1000 psi or greater. This high pressure concentrating on the cutting zone of the workpiece will dissipate heat within both the cutting tool and workpiece. By doing so, the chances of work hardening lessen.

High pressure coolant will also aid in clearing out chips from the cutting area. Those hot gummy chips are responsible for BUE. Removing them as quickly as possible reduces the risk of BUE forming on the cutting edge. Additionally, chip removal is important to avoid chip recutting.

Chips absorb much of the heat and often work harden themselves. Recutting these hardened chips will dull the cutting edge resulting in poor cuts and decrease tool life. In general, water-based cutting fluids are preferable as they have higher heat removal rates and have a lower viscosity, which is needed for high metal removal operations.

Using the Proper Techniques

To also assist with heat removal, utilize climb milling techniques, where possible. When climb milling, the chip thickness is at its maximum at the beginning of the cut and tapers off until the cut is complete. Due to this, less heat is generated, as the cutting tool does not rub on the workpiece. Most of the heat from the cut is transferred into the chip.

Selecting the Proper Tooling and Coating

The next step is selecting the right end mill. Your end mill of choice should have a proper tool coating, such as Helical’s Tplus coating. Tool coatings are specifically engineered to improve tool performance by reducing friction, increasing tool microhardness, and extending tool life.

Next is selecting flute count. Tools used for nickel alloys need to be rigid to withstand the cutting forces present when machining high hardness alloys. Therefore, higher flute counts are necessary. If using traditional roughing toolpaths, your end mill should have at least 6 flutes. With 6 flutes, there is sufficient flute valley depth to allow for chip evacuation, while having a larger core diameter keeps the tool strong and rigid.

For finishing operations and instances of implementing high efficiency milling, higher flute counts should be considered. A tool used this way should have 8 flutes to provide excellent surface finish.

Helical’s End Mills for Nickel Alloys

CNC tooling manufacturer Helical Solutions’ End Mills for Nickel Alloys product offering, its HVNI tool family, specializes in machining nickel alloys as it exhibits these key tool features.

Four Helical Solutions End Mills for Nickel Alloys positioned over a Helical product container
The tools shown above are Helical Solutions’ End Mills for Nickel Alloys. These tools are coated in Tplus for high hardness, resulting in improved tool life and increased strength,

With its Tplus coating and variable pitch to minimize chatter, these solid carbide end mills are engineered to perform in all grades of nickel alloys. Coupled with their geometry to maximize cutting performance, Helical’s End Mills for Nickel Alloys utilize faster speeds and feeds, which are readily available on the Helical Solutions website and Machining Advisor Pro.

For more information about the chemical make-up, uses, and categorization of nickel alloys, read “In the Loupe’s” post “Understanding Nickel Alloys: Popularity, Chemical Composition, & Classification”.

PVD Coating vs. CVD: Two Common Coating Application Methods

Most tool manufacturers offer tool coatings, made up of a layer of metal compounds adhered to the surface of the tool to enhance its performance. The most common methods for adding coatings to a tool are Physical Vapor Deposition (PVD coating) and Chemical Vapor Deposition (CVD coating). This article will take a deep dive into PVD vs CVD to identify their unique and shared characteristics.

Physical Vapor Deposition (PVD) Coatings

The PVD coating method is a process in which metals go through a cycle of vaporization and condensation to be transferred from their original solid state to the tool. The metal compounds that make up the coatings are often referred to as the “metal material” in this process. The metal material starts as a solid wafer and is vaporized into a plasma, which can then be put onto the tools in the chamber. In this process, the tools are referred to as the “substrate.”

There are two different ways in which PVD coatings can be performed: arc ion plating and sputtering.

Arc Ion Plating & Sputtering

Key Differences

The main difference between arc ion plating and sputtering is that arc ion plating uses high electrical currents to vaporize the metallic material, and the metal ions are steered onto the tool for coating. Sputtering, in contrast, uses the properties of magnetic fields to direct reactive gasses to collide with a target made up of metallic material. During these collisions, metallic surface ions fall from the target and land on the substrate, slowly bombarding it until it is sufficiently coated. Both arc ion plating and sputtering are high temperature, ultrahigh vacuum processes. The term “vacuum” refers to any pressure below atmospheric pressure at sea level.

Three Harvey tool AlTiN coated end mills
Above is an example of a Harvey Tool AlTiN Coated tool, which is applied using a PVD process.

Application Processes of Arc Ion Plating & Sputtering

Arc Ion Plating

  1. The internal pressure within the reaction chamber is dropped to form a vacuum to around 1 Pa (0.0000145 psi). Creating a vacuum is crucial as it removes any moisture and impurities, on or surrounding the tools.
  2. The chamber is heated to temperatures ranging from 150 – 750°C (302 – 1382°F). The temperature of the chamber is dependent on the coating that is being applied to create an ideal chemical reaction and adhesion between the plasma and substrate. A high current of around 100 A is applied to the metallic material causing an explosive reaction.
  3. The high current positively ionizes the metal and vaporizes it into a dense plasma.
  4. The substrate is negatively charged to attract the positive metal ions.
  5. The ions collide into tools with force and are deposited, forming a film that builds up in thickness to create the desired coating.

Sputtering

  1. The internal pressure within the reaction chamber is dropped to form a vacuum to around 1 Pa (0.0000145 psi) to remove any moisture and impurities on or surrounding the tools.
  2. An inert gas is pumped into the chamber to create a low pressure atmosphere. Inert gases are specifically used, as it is non-reactive with the metal elements and ensures that impurities are not mixed in with the tool coatings.
  3. The gas used is dependent on the atomic weight of the metal material; a heavier gas is commonly used with heavier metals.
  4. The chamber is heated to temperatures anywhere from 150 – 750°C (302 – 1382°F) depending on the coating that is being applied.
  5. The tools are placed between the metallic materials (called the “target” in sputtering) and an electromagnet, so that when turned on, a magnetic field runs along and around the tools.
  6. A high voltage is then applied along the magnetic field ionizing the argon atoms.
  7. Voltage ranges from 3-5 kV, and if using AC, with a frequency of around 14 MHz.
  8. The target is negatively charged attracting the positively charged Argon gas.
  9. The inert gas collides with the target ejecting metallic compounds onto the substrate to create a coating.

Key PVD Coating Differences, Summarized

Arc ion plating and sputtering are both effective methods of applying a PVD coating. So why use one over the other? Arc ion plating has a significantly higher ionization rate than sputtering, allowing for much faster deposition rates, shortening coating times. In turn, since sputtering is a slower process, it allows for more control when applying multi-metal compositions and ensuring that the stoichiometry of the coating is even throughout the tool. Finally, during the PVD coating process, micro-droplets are formed as the vaporized metals condense and solidify onto the tools. As these droplets impact the newly applied coating, they can cause defects and craters, producing residual stress points. In order to achieve a perfect coating, droplet size must be minimized. Arc ion plating produces droplets up to 3µm (micrometers) in diameter, while sputtering has droplets with diameters up to 0.3µm. With droplets up to ten times smaller, sputtering produces much smoother and defect-free surfaces which have been proven to slow corrosion rates.

Chemical Vapor Deposition (CVD)

Harvey tool CVD ball end mill held in person's hand
Above is an example of a Harvey Tool CVD Ball End Mill.


Unlike PVD coating operations, which use high electrical charges and atomic collisions to deposit coatings onto a tool, the CVD method utilizes the chemical properties of the metals to transfer metallic compounds onto the tool. The following steps are required to carry out the CVD operation:

  1. Much like the PVD method, the first step is creating an ultrahigh vacuum within the reaction chamber of around 1 Pa (0.0000145 psi) to eliminate all moisture and impurities.
  2. The internal temperature of the chamber is increased between 600 – 1000°C (1112 – 2012°F).
  3. The temperatures required in the CVD process are significantly higher than PVD coating because this method requires a chemical reaction to occur between gases flowed into the chamber and the substrate. High temperatures are required to initiate and maintain these reactions.
  4. Once the substrate is heated to its desired temperature, the metals intended to be coated onto the tools, which are already in their vapor state, are chemically bonded with a reactive gas (typically chlorine), and flowed into the chamber.
  5. The metallic materials being bonded to a gas keeps it in a gaseous state while it is being transported through the chamber and around the tools.
  6. Hydrogen gas is then pumped into the chamber and mixes with the chlorine and metals.
  7. When this mixture meets the heated substrate, the thermal energy creates a reaction where hydrogen and chlorine bond and leave the metallic materials behind on the tools.
  8. In the chamber, there is an exit vent where the waste gas (H2Cl) is removed.

PVD Coating & CVD Coating, Summarized

Tool coatings are utilized by machinists every day to accomplish prolonged tool life, a more efficient machining operation, and an overall higher quality final part. Most manufacturers use two different types of application techniques, PVD coating and CVD coating. Stay on “In the Loupe” to learn more about tool coatings by reading the following blog posts: Overview of Harvey Tool Coatings: Maximizing Performance and 3 Ways Tool Coatings Increase Tool Life.

Citation:
[1] Ucun, İ., Aslantas, K., & Bedir, F. (2013). An experimental investigation of the effect of coating material on tool wear in micro milling of Inconel 718 super alloy. Wear, 300(1-2), 8–19. https://doi.org/10.1016/j.wear.2013.01.103