collet

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Mark Taylor
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Joined: Sat, Feb 04 2006, 5:13PM
Location: Hilton Head / Bluffton SC

collet

Post by Mark Taylor »

We ran into an interesting situation today...while cutting 3/4 plywood our 3/8 compression bit slid out of the collet until it snapped and buried itself into the spoil board.

That bit has been in that collet for several months...so I don't understand how/why it would have come out.

Stupidly, I replaced the broken compression bit with a new bit (in the same collet - which I did clean and examine closely) and before finishing the sheet the new bit slid out of the collet and stuck into the plywood.

Obviously, I won't reuse that collet again...but I'm curious if others have run into this and have any explanation and/or find there is a \"life\" for the collets.

Mark
Forrest Chapman
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Post by Forrest Chapman »

Mark,

I don't know if this is an excepted practice but I've had my collets for 4 years now and do not have that problem. The one thing we did a few years ago was buy a torque wrench for the collets and that has improved the thread life. The tool is about $300 and well worth it. This may help your problem by being more consistant with the tension. If the collet does not have noticable wear or damage and has a clean cut I wouldn't trash it so quickly.

Forrest
Mark Taylor
Guru Member
Posts: 309
Joined: Sat, Feb 04 2006, 5:13PM
Location: Hilton Head / Bluffton SC

Post by Mark Taylor »

Forrest...

That makes sense to me...I have a hand router that I've had for more than 30 years and still use the same collets (1/4 & 1/2\") that it came with.

Tell me more about the torque wrench - is it similar to what I seen used on auto repairs?

Mark
Daniel Vonderheide
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Post by Daniel Vonderheide »

Mark,

The collets should periodically be changed and cleaned. As a rule of thumb, they should be changed every 1 to 2 years depending on the amount of use. If you have a tool slip or spin inside of a collet, the collet is ruined, even if it was new or it looks fine on the inside. Using a torque wrench is a great idea because it makes sure you do not stretch the threads on the toolholders. One other bit of advice is to make sure that the flutes of the tool are not inside the collet. If they are, the collet cannot apply pressure evenly around the tool and becomes oval in shape. You can find the torque wrenches at our online store http://www.woodworkerswholesale.com/ :wink:
Forrest Chapman
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Post by Forrest Chapman »

Mark,

I forgot to address one other thing you mentioned. You should maybe once a week take the tools out and blow out the collet and reset. Over time these tools can loosen if left to long.

The wrench is just like what you buy for auto use but has the special end on it. Its a little pricey but will save you lots in the long run.

Forrest
Mark Taylor
Guru Member
Posts: 309
Joined: Sat, Feb 04 2006, 5:13PM
Location: Hilton Head / Bluffton SC

Post by Mark Taylor »

Thanks Forest...

Cleaning and checking them on a regular basis makes perfect sense as well. However we have only had our machine since July 06 - and I know that that particular bit was replaced aproximately 2 months ago...so I find it hard to believe that it's damaged the collet (even though it obviously has).

So Daniel - your advise is to chuck the collet...which at this point I agree with, I'm not interested in seeing a 3/8\" bit coming flying out a 18,000 rmp again. The advise regarding flutes being outside the collett is something I'm already aware of and I know that wasn' the case on these incidents.

What is the pressure/torque recommended for tightening the collets down.

Thanks for your help

Mark
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