Tool Holding Explained

16 Dec.,2024

 

Tool Holding Explained

There are many different types of tool holders that can be used for different applications. Using the right tool holder for your job can impact many aspects of the machining process, including the speed at which the machine is able to run. If the tool holder you are using is high, with a low runout and high rigidity, it allows the cutting tools to run at a much higher RPM. The biggest advantage to this, and why we recommend high performance tooling alongside suitably high-performance tool holders, is the cost-saving benefits; saving the amount of downtime you will experiencing and allowing you to complete more jobs in a set time in a time-effective manner. On the flip side, if the tool holder you are using is not suitable for your set-up (for instance, using a standard ER collet chuck for high-speed cutting of a tough material), this can cause wear on the tool holder and also tool wear, potentially causing it to chip or even snap. Collets can also not be evenly pressed into the tool holder.

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Having the right tool holder in your machine can also significantly help with the repeatability of high-volume jobs and ensure that all your workpieces are machined to the same standards. This can increase productivity, improve process efficiencies and allow more high-volume jobs to run in a shorter time period, without the worry that workpieces will need to be scrapped due to not conforming to specified tolerances. Sometimes, when using tool holders that aren&#;t suitable for your machining set-up, it can cause the machine to stall or even damage the spindle &#; having huge cost implications and also causing major downtime whilst the machine is serviced or replaced.

 

What is spindle tooling?

Spindle tooling refers to a collection of tooling which fits into a manual or CNC machine&#;s spindle, hence the name &#;spindle tooling&#;. The end of the tool holder which connects to the machine will feature the same taper as the machines. Common tapers include BT MAS (JIS B ), SK (DIN ), HSK (DIN ), ISO (DIN ), Straight Shank and Morse Taper (MT). The connection chosen will have little bearing on the quality of the toolholder but is just a reflection of the make and model of the machine. At the other end of a tool holder will be the cutting tool.Usually, the cutting tool is directly clamped into the tool holder, with certain types of spindle tooling (commonly ER Collet Chucks) instead use an intermediatory to clamp the tool into the holder, usually a collet. A collet will have a clamping range, by which tools with diameter shanks within this range can be clamped. The collet is then clamped within the tool holder, which is then ready to be used.

Depending on the application or performance level required, there are different tool holding options available. If you&#;re using very cost-efficient tooling (for instance HSS or powder metal milling cutters or drills), it makes sense for a standard run-out holder to be used. This could be a basic ER collet chuck, end mill holder or face mill holder with standard 10 micron run-out collets. Of course, you can use a high precision collet in a standard tool holder, but you will be limited on the cutting data you can run a tool at and the vibration within such a set-up.

When using carbide tooling (or any tooling which is defined as &#;high performance&#;, &#;premium&#; or has a sizeable cost attached to it), it is important that the tool holding matches that of the tool making contact with the workpiece. Hydraulic chucks and heat shrink chucks (also referred to as shrink fit chucks) are two popular options when dealing with high performance tooling. Both offer higher run-out accuracies and increased tool life over conventional tool holders. Differences between the two are mainly the way in which the tool clamps into the holder; hydraulic chucks fill with hydraulic fluid which pressurises, closing the bore of the holder and clamps the tool in place, whilst shrink fit chucks use specialist machines to heat the chuck, which causes the chuck to &#;shrink&#; and mould around the tool. For tapping, the equivalent high performance tool holder would be a synchro tap chuck.

 

Why would you choose a high-performance tool holder over a standard tool holder?

A high-performance tool holder can offer several different benefits. Most high quality/high-performance tool holders will offer excellent rigidity, accuracy, high clamping power and dynamic balancing &#; this is all to suit the machine and the maximum spindle speed.

Using a high-performance tool holder can also have implications on the outcome of a job or workpiece. By using a performance tool holder, you can decrease the expected run-out, hence increasing the accuracy of your tool and also the tool life. The amount of run-out that a tool will experience will cause it to wear due to the increased vibrations (vibration causes tool wear, spindle wear and tool failure, as well as a poor surface finish on your workpiece).

High-performance tool holders also usually have a higher balance rating. A higher balance rating can affect the efficiency of work. When a tool holder has a high balance rating, the G value will be lower; the lower the G rating, the better the tool holder will be for your work (this can also depend on the application, the machine you are using and the cutting data of the tool you are using).

Another factor that can affect the efficiency of your tool holder is the gripping force. High-performance tool holders will have a higher gripping torque; the higher the gripping torque is on a tool holder, the more efficiently it will be able to run. A tool holder with a low gripping torque is more likely to run the risk of tool pull out.

A huge factor that can impact the performance of a tool holder is rigidity. The higher the rigidity of a tool holder, the longer the tool life will be. The most high-performance tool holders will offer a combination of high rigidity and good dampening qualities, which allows the tools to work through vibration without decreasing the quality of the surface finish or damaging the tool.

Arguably, one of the most crucial things to look at when purchasing a tool holder is the accuracy the tool holder provides. The accuracy of a tool holder can play a huge role in affecting the tolerance of the completed product and the machine&#;s ability to complete instructions and produce components to precise dimensions. When tool holders have increased levels of accuracy (usually characterised by low run-out, higher balancing and a higher quality material body), it is usually accompanied by improved productivity, better surface finish, lower downtime (due to not needing to replace tooling as frequently) and increased cutting speeds without sacrificing precision.

Optimize or Replace Your Tools? Here Are 5 Questions to ...

By Kip Hanson

Whether you call them maintenance-grade or general-purpose, it&#;s essential to know when to replace cutting tools, and what to replace them with.

Maintenance and repair departments, prototype and development firms, academic and government research facilities&#;these are just a few of the manufacturing environments where machine tool operators are not trained machinists, but rather mechanics, design engineers, and university professors or their students, whose grasp of basic machining and cutting tool practices is often incomplete. 

Unfortunately, cutting tools are frequently misapplied in these situations. Edge wear and damage that would set off alarm bells in a production shop are either overlooked or misunderstood. The wrong grade or geometry might be used, with improper feeds, speeds and depths of cut making matters even worse. The result is waste and lost time, with less than stellar performance from machine shops under the same pressures as their skilled CNC counterparts.   

&#;Cutting tool manufacturers are always coming out with new and better technologies, so it&#;s important to stay current, but just as important is the need for sound machining practices.&#;

The good news is that machining isn&#;t rocket science. With a bit of training and the right cutting tool, practically anyone can produce good parts, achieve acceptable tool life, and above all, stay safe while operating machinery.

This article offers some questions you should ask when evaluating your shop&#;s tooling choices&#;whatever its size or experience level&#;and whether cutting tool upgrades or a tool crib makeover is in order:

No. 1: The edge doesn&#;t look too bad, and the drill, end mill or reamer is still cutting. How do I know when to replace a cutting tool, and whether my current tool was the right choice?

The signs of cutting tool wear are manifold. Chipped or worn edges, notch wear on cutting tool at the depth of the cut line, discoloration of the tool or workpiece, material buildup on the cutting surfaces, poor part quality and surface finish, increased noise from the machine spindle&#;it&#;s a long list, and even the most experienced machinists occasionally misdiagnose an application problem. Fortunately, a wealth of online, paper-based and educational resources are available to help troubleshoot cutting tool wear, all of which stress the importance of inspecting tools periodically, then adjusting operating parameters or changing to a different grade, coating or geometry if needed. 

&#;Cutting tool manufacturers are always coming out with new and better technologies, so it&#;s important to stay current, but just as important is the need for sound machining practices,&#; says Jake Rutherford, research and development engineer for KYOCERA SGS Precision Tools Inc. &#;That means using as short a gauge length as possible, making sure you&#;re applying the right feeds and speeds for the material, and why routine toolholder maintenance is critical.&#;


KYOCERA SGS and other cutting tool manufacturers offer a wide variety of application and material-specific grades, coatings and geometries. (Image courtesy of KYOCERA SGS Precision Tools)

No. 2: We cut aluminum one day and stainless the next. Do we really need special grades or coatings for each material? Why not just use a general-purpose or maintenance-grade cutting tool and ease back on the speeds and feeds enough to get through the current task?

If you want to learn more, please visit our website High-performance Toolholders.

It&#;s a fair question, and in some cases, the answer is to do precisely that&#;settle for lower performance in order to get the job done. And yet, the get &#;er done approach can lead to bigger problems down the road. 

Read more: The Latest Toolholding and Workholding Innovations That Help You Increase Productivity

Worn or chipped tools increase the load on expensive machinery, possibly causing damage to spindle bearings and electrical components. They can also damage the workpiece, generating enough heat to work harden the material, or snap off unexpectedly deep inside a hole. This last event might damage the operator as well, which is why it&#;s crucial to avoid overloading tools. 

&#;Let&#;s say you need to drill a series of holes in a stainless steel component, or one made of superalloy, and end up burning through a bunch of tools,&#; says Tim Griebno, technical support specialist at Greenfield Industries. &#;A lot of folks might not realize that there are cutting tools made especially for these materials, and by switching to one, they can save a ton of time and money.&#;


General-purpose tooling like the drill index shown here is an excellent choice in many cases, but that doesn't always mean it's the most cost-effective solution. (Image courtesy of Greenfield Industries)

No. 3: But high-performance and application-specific tooling are a lot more expensive than what we've been buying. How do we justify the additional cost?

As Griebno just mentioned, spending more on an optimized cutting tool solution generally saves money in the long run. 

KYOCERA SGS' Rutherford seconds this, noting that cutting tool consumption represents between 3 percent and 5 percent of the total costs for producing any part; because of this, a 30 percent decrease in tooling cost or 50 percent increase in tool life only reduces part cost by roughly 1 percent. Far more important than either is cycle time. 

Read more: 5 Ways Manufacturers Can Use Data Analytics to Improve Efficiency

&#;That&#;s why the key to higher profitability in practically any situation is the selection of high-performance tools that are optimized for the application,&#; he says. &#;For example, spending a bit more for a coated tool almost always makes sense, as does switching to a tool with higher flute counts on finishing operations. Both serve to reduce cycle time, which means more product out the door at the end of the day.&#;

Because one tool can accept multiple grades and geometries, indexable cutters are another alternative to general-purpose and maintenance-grade tooling. (Image courtesy of KYOCERA Precision Tools)

No. 4: Yes, that all makes sense, but who has time to investigate new cutting tools and learn how to use them. Any suggestions?

It&#;s not as difficult as one might think. Aside from the educational resources mentioned earlier, Rutherford and Griebno both suggested that help is but a call away. That said, shops should set aside some time for testing of new grades and geometries. These often require more aggressive machining parameters than one might expect, and unless applied properly, even an optimized cutting tool will fail. 

&#;A lot of plants will shut down once a year for machine maintenance,&#; Griebno says. &#;This is a great time to go through the tool crib and evaluate what&#;s working, what&#;s not, and do some testing and optimization of new tools. Doing so can reap big benefits when the shop starts up again.&#;

Summer plant shutdowns offer a great opportunity to train up employees on the latest cutting tool technologies and machining practices. (Image courtesy of Greenfield Industries)

No. 5: What should I do with this box of old drills and end mills? And what about my toolholders? Do they need replacing, too?

Let&#;s answer the second question first: quite possibly. Toolholders that are nicked and dented on their locating surfaces or exhibit a rust-like appearance known as fretting should be discarded. If not, this damage will translate into poor tool life and part quality and may damage the machine tool as well. And as with cutting tools, only high-quality replacements should be used in their stead. As for the box of tired soldiers sitting in the bottom of most toolboxes, Drew Strauchen, executive vice president for GWS Tool Group, says to send them his way. 

&#;Maintenance shops in particular are a great place to use refurbished tools,&#; he says. &#;We&#;ll regrind them for a fraction of the cost you&#;ll pay for a new tool and can apply coatings or special grinds to increase their effectiveness. Just be sure that the original tools aren&#;t pushed past the point of no return, otherwise they might not be salvageable. Generally speaking, you can get far more regrinds out of a cutting tool that&#;s been well cared for than one that&#;s been abused. Probably 10 percent or so of our business is on tool reconditioning, and MSC is one of our preferred partners on this as well as custom cutting tools.&#;


Though usually reserved for high-volume work, polycrystalline diamond (PCD) tooling and combo cutters like those shown here can provide excellent results even in low-volume, maintenance and repair facilities. (Image courtesy of GWS Tool Group)

What questions do you ask when evaluating your shop&#;s tooling choices? Share your thoughts and insights in the comments.

For more great content and insights, check out our MSC Knowledge Center.

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