Collet and Z slippage

[Simops]

Recently been noticing a very slight depth variation during cutting. I have big production run happening at the moment cutting numerous slots in 40 x 40 x 4mm aluminium angle......after a number of slots cut I notice that the slot is not being cut all the way through......

So ended up increasing my cut depth to compensate and thinking this should not be happening.

So next time it was occurring I re-zeroed the Z and this solved the problem. So I thought it must be that the bit is slipping up the collet because you shouldn't have to keep zeroing the Z......but I have already tightened as hard as I can (which always thought was not necessary to do).

So is this telling me that:
(A) I should be tightening the hell out of the collet more so then I have, OR
(B) is the collet worn and I should be replacing it????? I'm tending to think (B) but collet looks OK to me........is it time to replace it???

Cheers

[mark_stief]

Sounds like it's time to replace the collet and throw that bit away it will never stay tight now and will just ruin your new collet

[knight_toolworks]

can a collet really damage a solid carbide bit? I doubt it is a issue. the collet though sounds shot.

[Simops]

Sure I need to ditch the bit.....it's still going strong and is my favourite 3/16" spiral O single flute upcut that plows through the aluminium? Guess need to order a new collet.....the 1/4" one is used the most so guess not surprising? Thanks....

Cheers

[scottp55]

Is their any way to know when to replace collet BEFORE a problem like Michael's arises? I always visually inspect for burrs and galling and "feel" the fit of the bit. Heard a full time shop replaces every 3-4 months? We swap between 1/8-1/2" fairly often and nowhere near the hours of a full time shop. Anything in the software that keeps track of time on bits like the "Odometer"? Any sure visual indicator? Newbie question.

[knight_toolworks]

I have noticed it takes a bit ester turning when the wrench when the collet is getting there. you know after while how much you move the wrench to tighten the collet when the wrench travels extra then it is time. *

[scottp55]

Thanks Steve, I think I'm just starting to feel that on my 1/8". It feels different than the 1/4 and 1/2" recently. Probably explains why a .02" profile cut last week was an "air cut" instead-Thought I hadn't tightened it well enough.

[curtiss]

For small shank bits I use a little medium strength Lock-tight to coat the shank before placing it in the collet.

It dries and takes up any slack (I think / theory )

[Simops]

One of the bits I use is a 1/8" spiral 0 upcut with 1/4" shank ..... Decided to measure the shank and it's 6mm not 6.35mm (1/4")...... That probably doesn't help!!!

Cheers

[MogulTx]

I just recently had some trouble with a bit slipping in the collet. The collet it over a year old and has been my main 1/4" collet for all projects. I had a spare and immediately removed the old collet from service. Problem immediately went away. AFTER THAT, my guys also said they had recently lost a few bits due to breakage... and I said " Using the same feeds/speeds and no other variables?" Of course the response was int he affirmative. I asked them how many hours were on the collet, and neither could answer.

My fault. I should have just come in and pulled the collet at an interval that I thought was safe, and chunked it. Now, instead of $10-15, I probably have $150-200 in lost materials and bits... Good lesson.

I bought three new collets, and told them the first time a bit slips or breaks, throw the collet away. If it makes it to a year without slipping or breaking a bit: Throw it away. Collets are cheap. And they cause lots of difficulty when they get tired/loose.

[Simops]

All good info......mines now in the bin!
Question.....do I have replace the nut around the collet as well or can they continue to be used and just replace the collet within?

Cheers

[jerry_stanek]

The nut is fine as long as it isn't stripped.

[Simops]

Ok thanks that makes it cheaper......will buy a few 1/4" collets to have on hand....I think cutting aluminium is harder on the collet than I thought!!

Cheers

[curtiss]

If you use these for the 1/8 shank, you might not wear out a more expensive collet.

http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/bushing_ball_bearings.html

I like the #273's