Replace Worn Collets

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Leo
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Re: Replace Worn Collets

Post by Leo »

I was going to NOT post to this thread, because it is very controversial.

I am also in the camp of scratching my head about "WORN OUT" collets.

I do not want to even try to imagine in 9 companies and 40 years and perhaps hundreds of machines and so many machinists and so on how many collets - mostly ER style - I have encountered. I can assure you, cutting metals, cast iron, steel, aluminum, brass, bronze - and year wood. Our little world of hobby, or light commercial CNC routing is absolutely ZERO as compared to heavy industrial manufacturing. Normal wear on well cared for collets to the point of failure, I dunno about that one. I guess after many thousands of REALLY heavy use - maybe, but not that I have seen.

One of my very best machinists used to break down his setup and then wash all his tooling in a hot parts cleaner which was always kept clean, not like a safety clean tank. This included all his collets. No such thing as over cleaning. I have a small ultrasonic cleaner that I use to clean stuff like that.

I have seen and used collets that were 20 - 30 years old and WELL used, but well cared for.

I have also seen hoards of damaged collets and thrown them out. I have tried reaming, ID grinding, filing and so on. It's not worth trying to fix them, just toss them. Damaged collets are damaged - but not necessarily worn.

Some things to consider.

1) Dust can get impacted inside collets. (Clean your collets - with more than just air blast)
2) Dust CAN get impacted inside the taper in the spindle. (Clean your inside spindle taper - with more than just air blast)
https://www.penntoolco.com/big-kaiser-e ... 7-815-093/
3) Keep the shank of the cutter clean. (I use a green 3M pad - and NO - you are not going to remove material from carbide because it is abrasive, also not from the HSS that is hardened.)
4) Keep the inside of the collet nut clean.
5) DO NOT overtighten. ( The nut can also get damaged)(I can't tell you how many times I have seen overtightened nuts - the top cracks and looses its integrity.)
6) If you bury your spindle and burn the end of the collet, there is a good chance you damaged the NUT as well as the collet.
7) Cheap collets are simply - CHEAP.
Good collets may cost $30 - $50 EACH. Parlec, Techniks, Rego-fix = good brands
Ultra Precision - Exact size = good features for a little extra money
8) Good collets will last for many years if cared for properly.

** 9) NEVER push a cutter into a collet that is a tiny bit too small. (good fit is when cutter slides easily smoothly into collet)
**10) NEVER over tighten a collet that is too small for the cutter.
**11) ALWAYS use the CORRECT collet for the cutter.

**12) 6mm is .236 - it is to be used for a 6mm cutter - DO NOT push a 1/4" (.250) cutter into it.
**13) 1/4" (.250) collet is for a 1/4 (.250) cutter - DO NOT tighten the nut down to a 6mm (.238) cutter
**14) These two things WILL cause metal fatigue and damage the collet. (that is NOT wear)
**15) Using the correct collets will not cause any significant fatigue as there is not enough stress induced. (especially with exact size collets)

There are lots of people that don't "really" know about collets. Why would someone know? Who teaches about collets? It is not just common knowledge. Why would anyone know? For me, that was part of my job. I learned by being instructed by the manufacturers of collets as well as many other things, but collets was one of the things. I passed on what I learned throughout my career in manufacturing. So, I can try to pass on some of that knowledge here as well.

I am sorry if this is offensive to some, it is not meant to be so, but it is my personal experience in teaching and mentoring throughout my career with many many thousands of collets.

I do hope you look on the 15 points and maybe - perhaps learn a little about collets.

I hope there is an Ace in here that you can keep.
Imagine the Possibilities of a Creative mind, combined with the functionality of CNC

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Rcnewcomb
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Re: Replace Worn Collets

Post by Rcnewcomb »

Thank you Leo for this great perspective. This is good stuff.

Perhaps I should have titled this post "Replace DAMAGED Collets" since the collet in question was damaged by crashing into a wood clamp.

The upshot was that, because the collet was damaged, it no longer held the bit adequately.
- Randall Newcomb
10 fingers in, 10 fingers out, another good day in the shop

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Leo
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Re: Replace Worn Collets

Post by Leo »

Randall, I really didn't want to disrespect you. I have a great deal of respect for you.

I do hope that some members can gain some insight into collets from the info I posted.

Collets can be damaged as they are made from high strength steel and hardened to a high hardness. As such, they are brittle and crack easily.
Imagine the Possibilities of a Creative mind, combined with the functionality of CNC

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Rcnewcomb
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Re: Replace Worn Collets

Post by Rcnewcomb »

Randall, I really didn't want to disrespect you. I have a great deal of respect for you.
No worries. My wife of 42 years has no problem telling me whenever I am wrong. :wink:
- Randall Newcomb
10 fingers in, 10 fingers out, another good day in the shop

garylmast
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Re: Replace Worn Collets

Post by garylmast »

No worries. My wife of 42 years has no problem telling me whenever I am wrong. :wink:]


You only have been wrong 42-years? My 53rd Anniversary is next week.

Gary

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Phil
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Re: Replace Worn Collets

Post by Phil »

I have only had a problem with a bit slipping when I was using a down spiral bit. I suspected the collet so I replaced the collet with a new one. The bit slipped even though I am certain that I had tightened the collet adequately. I haven't used down spiral bits since and have not had a bit slipping problem since.

Phil

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