ER collet Accuracy

[enauman]

I am using a CAT-40 ER-16 collet chuck with an 1/8" collet. I'm using 0.030" 4 Flute Carbide Endmills that don't take a lot of vibration before they break. I can't seem to get better than 0.0015" TIR on the endmill shank. I have cleaned my quill, tried different collet holders, different endmills, ETC. The spindle won't even move the dial so it's dead on. Is this the best accuracy I can expect from an ER-16 setup? Thanks.
Fast Eddie

[Matt@RFR]

Try tapping the collet nut lightly with a ball peen hammer or similar as you tighten the nut. That usually works for me.

If it doesn't work, you can try just barely snugging the collet nut, put the toolholder and tool in your spindle and indicate. Tap the tool around until the runout is gone, take it back out of the spindle and tighten fully.

And the obvious: Be sure there are no chips or rust on any of the angled mating surfaces on the collets, nuts toolholder.

[John Welden]

Originally Posted by enauman I am using a CAT-40 ER-16 collet chuck with an 1/8" collet. I'm using 0.030" 4 Flute Carbide Endmills that don't take a lot of vibration before they break. I can't seem to get better than 0.0015" TIR on the endmill shank. I have cleaned my quill, tried different collet holders, different endmills, ETC. The spindle won't even move the dial so it's dead on. Is this the best accuracy I can expect from an ER-16 setup? Thanks. Fast Eddie

Something must be wrong. I use them all the time and wouldn't be able to do my job with .0015 TIR.

I clean everything with isopropyl alcohol and blow it off real well.

Is your collet brand new? If someone broke off a cutter at one time, the collet may be damaged and not noticeable to the naked eye. Check it with a loupe or microscope if you have one.

Throw everything in an ultrasonic cleaning tank if you have one.

You don't need to tighten the nut down all that much. No need to kill it.

The shank of the endmill can look clean to the naked eye but actually have quite a bit of dust and what not stuck to it. Isopropyl and a lint free cloth to clean and then check with optics.

That's all I can think of. Good luck. Buy a good lyndex/nikken holder for future use.

[diecutter]

Is the ER-16 collet you are using one of those ones that covers a small range of diameters above and below the nominal size? These are common in inexpensive sets that cover a large range of diameters with few collets. The collet style that fits one exact diameter is much more accurate since it is not a compromised "one size fits all style."

I use the exact size (dedicated) collets for engraving in die steel with carbide end mills and split points smaller than 0.030" dia. and they only snap if I push them too hard or past when they lose their cutting edges. Hope this helps.

[HuFlungDung]

Make sure that the collet is assembled into the collet nut before you put the tool into the collet. The collet will otherwise be deflected by the eccentric withdrawal ring in the collet, as well as the fact that the nut would not pull the collet out of the toolholder.

That may be obvious to you, but I've heard tales of guys who don't know how to use ER collets properly, so it does happen