Technical Blog excerpt courtesy of Techniks USA
It is important to understand how collets work, what impacts their performance, how to maintain collets for long service life, and how to recognize when to replace them.
Collets are a high-precision wear component of a tool holding system and require maintenance to ensure accuracy. First, it’s important to remember that collets are the softest component in a collet-based tool-holding system assembly and are designed to wear out.
Here is an overview of the wear pattern of a collet-based tool-holding system. The machine spindle is harder than the tool holder/collet chuck that fits into the spindle, so any wear between these two components will mostly occur to the collet chuck. That’s good. It protects the spindle from expensive maintenance.
Collets are softer than both the collet chuck body and the cutting tool, so any wear forces between these items will mostly occur to the collet. Since collets are generally the least expensive component in a collet chuck tool holding system, it is preferred that the collets wear out before the other components.
Worn-out collets will not achieve the same level of accuracy and rigidity that newer collets can provide. The result is more chatter when cutting workpieces, less accuracy, and shorter cutting tool life.
When to Replace Collets
Collets are designed to wear out as they lose accuracy and rigidity with use. High side-load forces during milling operations cause cutting tool deflection as illustrated below.
Over time, these side-load forces will bell-mouth the collet at its face.
As the collet experiences bell-mouthing, the cutting tool is allowed to deflect more and more during milling operations.
Unfortunately, the collet may still indicate good accuracy on a presetter where there are no side-load forces. However, once the tool is put into service and begins experiencing side-load forces, the cutting tool is allowed more room to deflect, resulting in increased chatter and reduced tool life.
It is recommended to change collets out every 4-6 months, depending on usage, to ensure the most rigid and accurate collet chuck assembly.
A good rule of thumb is to replace collets every 4-6 months to maximize the performance of your tooling.
Again, collets are designed to wear out and are generally the least expensive component in the system. It is much less expensive to replace the collets as opposed to prematurely wearing out cutting tools.
The following tips will help you in maintaining collets:
Signs that Your Collet Should be Replaced
Technical Blog excerpt courtesy of Techniks USA
Collets come in many different types and sizes. Here is an overview of three of the more popular types of collets, along with the pros and cons of each system.
The ER collet system has become very popular due to the flexibility of the system to hold a variety of cutting tool shank types including drills, end mills, and taps. Also, ER collets provide several solutions for increasingly popular coolant-through cutting tools.
Most standard ER collets have between a 0.020” and 0.040” holding range, making them a good choice when needing to hold odd-sized cutting tool shanks. This holding range also means fewer ER collets are required to hold a range of cutting tool shank diameters as opposed to other collet systems like TG.
The popularity of the ER collet system has led to several variations to hold a wide assortment of cutting tool shanks. Some ER collets have been modified with squares at the bottom to hold taps. Others have been modified to provide quick-change capabilities or compensation, also called “float”, for rigid tapping cycles as shown in the images below.
Specialized ER Collets
Other modifications include special slotting designs that seal around the cutting tool shank and force coolant through channels in coolant-through tooling, as well as modifications to include coolant ports in the collet that direct coolant to the cutting area.
TG collets have about the same accuracy as DA collets, but because there are more slots, and therefore more faces clamping on the cutting tool shank, they tend to deliver greater holding power.
TG can be a good solution for larger shank diameter cutting tools, but they generally limit how far down into a pocket you can reach due to interference with the collet nut, as TG collet nuts tend to be quite large.
TG collets are not as popular as ER collets for several reasons. Most notably, the larger diameter collet nuts can require the use of extended end mills to avoid interference from the collet nut when milling pockets.
Also, since TG collets have a very small collapse range, they are intended for use with one size cutting tool shank.
ER collets, by contrast, offer a large collapse range that can be helpful when clamping odd-shank diameter tools.
On the flip side, TG collets tend to have a bit more holding power than ER collets due to the collet base having a 4° taper as opposed to the 8° taper found in ER collets. This can make TG collets a good choice when machining with longer-length cutting tools.
Double-Angle (DA) Collets
Double-Angle (DA) collets have been around for a long time and continue to be used in the market. There are, however, many issues associated with DA collets of which users should be aware.
Let's just clear the air and say it: Don't use them. If you have them in your shop, replace them with ER Collets and ER Collet Chucks as soon as possible and you will recoup the cost of the new holders and collets in your tool life probably within a month or two.
One of the primary issues with DA collets is that they essentially clamp on the cutting tool shank with only two opposing faces in the I.D. bore.
DA collets have four slots in the front of the collet and four slots in the back of the collet creating four clamping faces.
However, when DA collets are tightened towards the lower end of their collapse range, two of the faces tend to be pushed out of the way so only two of the faces are clamping on the cutting tool shank. This may cause some runout at the nose when the tool is inspected in a presetter.
Additionally, when the tool begins cutting and side forces are applied to the cutting tool, the cutting tool tends to deflect into the area where the faces are not clamping on the tool shank.
This results in excessive chatter that dramatically reduces tool life and results in rough surface finishes. You will be hard-pressed to find a quality end mill holder manufacturer endorsing the performance of their tooling in DA collets.
It’s been estimated that a tool with a run-out of 50% of the tool’s chip load will reduce its tool-life by 40%.
That means that a 1/8” tool with a 0.00019” chip load per tooth will lose 40% of its tool-life with a run-out of less than 0.0001”.
Excessive and inconsistent run-out from a properly setup ER collet chuck assembly typically occurs due to friction build-up between the 30° face of the collet and the collet nut.
Other Parlec P3 collet advantages:
Don’t throw away you ER collet chucks to improve accuracy
Try Parlec P3 collets and supercharge your ER collet system.
Written and edited by Bernard Martin
PowerCOAT Collet Nuts provide up to a 75% increase in holding power!
One of the most important elements of the toolholding 'system' is the collet nut. Each toolholder "system" consists of a precision ER tool holder that comes with a special "Power Coated" high power nut that holds tighter than any other nuts.
According to Techniks, the 'Power Coat' nut is the secret to their high holding power. Because it holds so tight, the 'Power Coat' nut improves T.I.R., extends carbide tool life, and improves finish in heavy milling operations.
Techniks recommends that for best results always tighten the nut to the proper torque using a torque wrench with a tightening stand, and never over-tighten the nut because this can damage both the collet and the collet pocket.
To demonstrate the difference between an uncoated and coated collet nut, Mike Eneix, from Techniks did some testing.
He took an uncoated, imported nut and put it to the test against the Parlec PowerCOAT nut. Mike took them to the limit to see which one gives you more holding power. Check out the video below!
What makes the difference?
As anyone knows who has changed a flat tire on their car, tightening down a nut on a 60 degree thread involves some friction as the mating metal surfaces interact. That's why nuts can be a bit 'hot' to the touch when you take them off. The objective with the "Power Coated" nuts was multifold:
First Techniks needed to reduce the coefficient of friction on the thread angle to enable more lubricity for the nut to tighten down farther. As we all know 'heat' causes metal to "grow" so what may at first appear to be tight, in fact, loosens, as soon as you stop tightening it.
Second they needed to make sure that the front surface of the collet that engages the shorter 30 degree taper on the front of an ER collet did not 'twist' as the night tightened down.
Both problems really involved reducing friction and through a combination of engineering tolerances and unique coating process we believe that we've found the most economical solution to eliminate the use of cheater bars and collet over torque. Here's what they've found out in testing the "Power Coated" Nuts:
“Power Coat” is an innovative, permanent coating that increases clamping pressure of the nut up to 75% compared to standard ER nuts. More holding power reduces the chance of spinning the shank of the tool inside the collet, which can cause premature failure of the collet.
Technical Support Blog
At Next Generation Tool we often run into many of the same technical questions from different customers. This section should answer many of your most common questions.
We set up this special blog for the most commonly asked questions and machinist data tables for your easy reference.
If you've got a question that's not answered here, then just send us a quick note via email or reach one of us on our CONTACTS page here on the website
Our technical section is written by several different people. Sometimes, it's from our team here at Next Generation Tooling & at other times it's by one of the innovative manufacturer's we represent in California and Nevada.
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