Replace Worn Collets

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Rcnewcomb
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Replace Worn Collets

Post by Rcnewcomb »

This is what happens when the v-bit slips out of the collet during the carving process.

I knew the collet was past its useful life, but I tried to get one more carving out of it. Nope.
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IMG_3710.jpg
IMG_3711.jpg
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Re: Replace Worn Collets

Post by garylmast »

Been there, done that.

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Re: Replace Worn Collets

Post by Phil »

Is there a way to tell if the collet is worn other than ruining a good piece of material?

Phil

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Re: Replace Worn Collets

Post by TomWS »

Good advice, thanks Randall!

It looks like the shank on the bit is pretty well worn. Maybe that's a result of this failure, but might also contribute to the problem.

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Re: Replace Worn Collets

Post by Adrian »

When the collet is worn the bit will spin in it so it's a chicken and egg situation. A failed collet will always come with a worn shank.

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Re: Replace Worn Collets

Post by TReischl »

This topic really interests me.

The whole idea of a collet "wearing" fascinates me. I completely understand a collet becoming damaged. But "worn"? How? And "worn" to the point of allowing the bit to be pulled out?

I have collets that have been running in my routers for almost 30 years now. Back to the hand held days, and the router table days. How come mine are not "worn" out? How come I have never had a bit pullout like is shown in the pictures above?

Frankly, I am not buying this whole "collets wear out" concept. How do they wear? The amount of metal to metal movement is extremely small during tightening. After that, there is no metal to metal movement to wear anything out.

I did a bit of a google search about how collets "wear". Interesting, all sorts of experts say they "wear", but I could not find one that explained HOW the collets wear. Just statements like " Like anything mechanical, collets will wear out over time."

Since I evidently have magical collets, here is what I think (yea, an opinion, we all know what that is like). . . .

Collets get "worn" when bits are not put in them properly. Most obvious is inserting bit too far, then when the nut is tightened the bit is not really locked in place and it can spin. I learned this early on in my experiences with a router. Bits rolling around knocking into each other can scar the shank on bits (the carbide is much harder than the shank), then when that bit is put in the collet, things cannot tighten up properly due to the dings on the shank. Running a bit with a slightly undersize shank also causes damage to a collet.

Lemme put it this way. A lot of us worked in machine shops during our careers. I do not know about the rest of you, but I never saw a shop just replace all the collets for a Bridgeport milling machine because they were "worn" out. I did see them replace ones that had been "sprung" and no longer ran true. But that was damage, not wear.

Not trying to start a big dust up here, but I am thinking this is one of those woodworking things that is not quite true, but everyone believes it, or else they are a heretic.
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Re: Replace Worn Collets

Post by garylmast »

Attached is a picture of a 'Wore Out' collet. Whether you call it wore out or damaged, the results are the same...your bit falls out. Another good way to damage a collet is to rub against the material causing it to burn the end, which damages the spring, which makes it 'wore out/damaged'. Anyway, it's time to throw it away. :roll: :roll: :roll:

Ok, I need to find something else to do now. :lol:

Gary
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Re: Replace Worn Collets

Post by TReischl »

WOW! Just WOW!

My 30 year old collets look way better than that. . . .

I guess repetitive damage could be filed in the "wear" category. . . . or maybe what we used to call "wear and tear".

I am just real careful with my tools, always have been. The Air Force originally sent me to aircraft mechanics school, one of the big things there was "use the right tool for the right job". None of that using a pliers to take a hex nut off, etc. They did not even like adjustable wrenches, those were considered a last resort tool. Too easy for them to loosen up and round over a bolt or nut. I think that training has saved me a lot of money over the years.
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Re: Replace Worn Collets

Post by Tailmaker »

I am still using the same collets after 11 years of CNC-ing. Some are a bit nicked from "wear" (multiple bit breakage or trying to bury in the wood) but they still have nominal runout and work fine. I am not super diligent with cleaning but blow the wood dust out once a while and lubricate with thin oil.
I did have trouble with long 1/2" bits that worked loose on long jobs especially when there was some chatter but even that was solved after switching to ball bearing collet nuts. They hold so much better.
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Re: Replace Worn Collets

Post by ZipperHead55 »

To piggyback somewhat on the "how the heck can that thing "wear" out?!" theme, I think that sometimes people go overboard on their cleaning of items.

An example of this is with weapons parts: I served 20 years in the Canadian Armour Corps (tanks, reconaissance vehicles), and we cleaned our weapons to the point that we wore the metal off getting them "perfectly" clean (no carbon buildup). We were provided with all the requisite tools, but sometimes they weren't "enough" and people used whatever they had on hand to clean them.... quickly, with little thought of the long term effects, such as taking dirty parts and grinding them in sand/dirt to remove the carbon (and likely a tiny bit of metal) or using grinders/wire-wheels, etc.

My unit did a week long stint with a British unit when I was on deployment in Bosnia, and I was surprised at how LITTLE they cleaned their weapons. After firing them, they knocked off the heavy carbon build up, but if there was a bit of carbon stuck in the grooves, they considered it "no harm, no foul" (a little bit of gunnery humour there, for those in the know). They also had way less "Gucci" kit in their weapons cleaning kits (we used CLP all the time, and they used basic gun oil, for example) and most of their tools were way less aggressive. We gave them a bunch of spare stuff we had (CLP, cleaning tools) to make their life easier, but I suspect that they weren't allowed to use it once the powers that be found out.

I rarely lubricate my CNC machine (I have a heated garage, so humidity isn't an issue), other than removing the dust buildup with a vacuum and compressed air and a cloth (I do the 500 hours lubrication maintenance though), and I only remove the dust from my collets/bits, and have never oiled them. I suspect that a lot of problems people have is due to their fascination with keeping their parts perfectly lubricated, not realizing that the oil will attract dust (or grit, depending on what you are machining) and cause more problems than if they just kept them clean/dry. I have 2 Axiom machines, and other than having a bit of binding issues (after the 500 hour lube, due to over-tightening the bolts after I did the steps), I have never had an issue with my rails/screws. 2 broken couplers (Z-axis) but that is probably due to cheap parts, not any failure to lube on my part.

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Re: Replace Worn Collets

Post by Adrian »

I guess a lot depends on how much the machine is run and how hard it's pushed. A hobby machine cutting in multiple passes for a couple of hours every week is a different beast to a large CNC running 60 hours plus a week at the top end of it's capabilities. Not to mention the number of times the bit itself is changed.

I have had issues with collets losing their grip despite always using a torque wrench and making sure the bits are properly seated etc. At the end of the day the cost of a collet over the time it lasts is miniscule compared to the cost of messing up a commercial job so I'll always err on the side of caution and change them every 2 to 3 months.

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Re: Replace Worn Collets

Post by sharkcutup »

TReischl wrote:
Mon May 23, 2022 4:10 pm
This topic really interests me.

The whole idea of a collet "wearing" fascinates me. I completely understand a collet becoming damaged. But "worn"? How? And "worn" to the point of allowing the bit to be pulled out?

I have collets that have been running in my routers for almost 30 years now. Back to the hand held days, and the router table days. How come mine are not "worn" out? How come I have never had a bit pullout like is shown in the pictures above?

Frankly, I am not buying this whole "collets wear out" concept. How do they wear? The amount of metal to metal movement is extremely small during tightening. After that, there is no metal to metal movement to wear anything out.

I did a bit of a google search about how collets "wear". Interesting, all sorts of experts say they "wear", but I could not find one that explained HOW the collets wear. Just statements like " Like anything mechanical, collets will wear out over time."

Since I evidently have magical collets, here is what I think (yea, an opinion, we all know what that is like). . . .

Collets get "worn" when bits are not put in them properly. Most obvious is inserting bit too far, then when the nut is tightened the bit is not really locked in place and it can spin. I learned this early on in my experiences with a router. Bits rolling around knocking into each other can scar the shank on bits (the carbide is much harder than the shank), then when that bit is put in the collet, things cannot tighten up properly due to the dings on the shank. Running a bit with a slightly undersize shank also causes damage to a collet.

Lemme put it this way. A lot of us worked in machine shops during our careers. I do not know about the rest of you, but I never saw a shop just replace all the collets for a Bridgeport milling machine because they were "worn" out. I did see them replace ones that had been "sprung" and no longer ran true. But that was damage, not wear.

Not trying to start a big dust up here, but I am thinking this is one of those woodworking things that is not quite true, but everyone believes it, or else they are a heretic.
Hey Ted,

Have you ever heard the term "Material Fatigue" In this particular case "Metal"?

https://en.wikipedia.org/wiki/Fatigue_(material)

Just Saying!!! :)

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Re: Replace Worn Collets

Post by Tex_Lawrence »

I've got a 1/8" collet that sometimes gets "stuck" in the machine. The collet/bit is otherwise smooth, not loose or with visible runout.

I'm thinking that if it happens again, I'm going to have to replace it since I won't be able to find it on the other side of my workshop! :wink: :wink:
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Re: Replace Worn Collets

Post by Rcnewcomb »

I won't be able to find it on the other side of my workshop!
Maybe a fun activity at the next Users Group Meeting, instead of a caber toss, we could have a collet toss competition.
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Re: Replace Worn Collets

Post by TReischl »

sharkcutup wrote:
Thu May 26, 2022 2:30 pm

Hey Ted,

Have you ever heard the term "Material Fatigue" In this particular case "Metal"?

https://en.wikipedia.org/wiki/Fatigue_(material)

Just Saying!!! :)

Sharkcutup
Certainly have, learned about it while getting a ME degree.

That is not what is going on with the collets. Now, if the router bit shanks were snapping or cracking. . .that would be a definite possibility. No one here has said their collets were falling apart, just getting worn.
"If you see a good fight, get in it." Dr. Vernon Johns

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