Collet nut problem

[Chuck Keysor]

HONEST, this is NOT an April Fool's joke! I don't want to wait until tomorrow to post my new question problem!

Something seems wrong with my collet nut. There is what looks like a flat washer inside, which is not concentrically positioned with the rest of the collet nut! Please see the attached photos!!!

Is this part that looks like a washer supposed to be loose so it can relocate correctly when this gets tightened down on the collet? IF so, I have a problem, as this part that is eccentric will not move, or if it will move, it is really locked in. How can I persuade this to move without damaging something else in the collet nut? Should I grind away (last resort) the part that seems to interfere with the correct seating of the collet????? HELP! Chuck

Details:
An hour ago, I re-installed my CMT "Laser" V-bit, to put some layout reference points onto some stock (for my 16 foot rail cap). I gave a manual spin to the collet nut, and noticed that the tip of my v-bit was NOT rotating concentric to its axis! As a guess, it was maybe eccentric by .010. I removed the collet nut, and cleaned it, remounted and tightened it, and still no good..... I removed the collet nut, and the collet and bit stayed in place, I spun the spindle shaft and noted that the tip of the Laser bit was in fact now rotating without any tip eccentricity.

Then I looked in my collet nut, and said, gee, this thing has always looked wrong on the inside (as shown in the second picture) for as long as I have had my Bot up and running. When I noticed it originally, I just guessed it slid around, and would position itself correctly when the collet nut was tightened. But I never actually saw it move. So, I tried now to move this eccentric part, that looks like a washer, and said, this thing is stuck!

I thought, maybe this is a fringe interference problem, and with this collet for 1/2 bits, maybe the eccentricity only happens when I really tighten things down. Because I have used this same collet and CMT laser bit to do some amazingly detailed/fine lines that would not have been possible with the newly observed eccentricity.

Then I thought, gee,,,,, I have bought a hand full of other bits for my precise lines, and they have all failed terribly. But they were using a 1/4 or a 1/8" collet! (Maybe the 1/4 and 1/8" collets interfere just a little bit more with this thing that looks like an eccentrically located washer. All my collets I bought new a year ago.) And the other bits using the smaller collets all produced terrible results. Can this eccentric washer looking issue be the cause for all these problems?


Can I hope to move this part into position since it seems jammed, or do I have to grind it away, or buy a new collet nut????

Thanks, Chuck!!!! PS: Again, this is NOT a joke!!!

[twelchPTM]

i use a PC router on my bot so i can't claim to have the answer but the hole in the "mystery piece" appears to be ovaled which i don't think would be right in any case.
I would suggest buying a new one and then when the new one arrives you can compare the two and if it turns out that the one is infact just "stuck", you will have a spare and it never hurts to have a back up for something as critical as a collet nut.

[twelchPTM]

by the way if it is a washer it somehow getting ovaled would explain it getting stuck!

[Brady Watson]

There are 2 styles of that nut. What you have there, and another style that looks 'concentric' all the way around. The one you have just has a relief in it so you can more easily 'side step' the spring collet out.

Nuts & collets are consumables. If you have problems with tools slipping, replace them. I recommend one of 3 places ONLY: ShopBot, PDS Colombo (http://www.pdscolombo.com/) or Techniks (http://www.techniksusa.com/)

-B

[Chuck Keysor]

Thanks Brady. I'll order a new collet from SB tomorrow, as they were already closed by the time I read your post.

I did grind away the area where I could see some contact had occurred on the eccentric part of the collet nut. Then I was able to mount my bit without any problem.

Thanks, Chuck

[Ajcoholic]

Chuck,
If you research the way the ER series of collets is designed, the "offset" bore/lip is an integral part of the collet nut, and as Brady said, designed so the collet is easy to snap into and out of the nut.

By design, these nuts need to engage the rebate in the collet nose, to make them "self extracting".

I have collets and nuts from three various suppliers and they all have been working fine, and they are all the same design.

Just by coincidence - about the time I bought my machine last year, an article in "Home Shop Machinist" was about making up a collet nut for the ER style collets, and it explained things very well, and how they are turned/made.

AJC

[Ajcoholic]

here is something I found on the net that describes it well:

http://www.arceurotrade.co.uk/Catalogue/Collets/ER-Collets-Collet-Chucks/ER25-Collets-Collet-Chucks

[Chuck Keysor]

Hello Andrew. Thanks for your follow-up. I guess I'll find out what improvement the offset design offers when I order the non-off-set version of collet nut.

And, while I earlier reported that after grinding away the little bit of the eccentric ledge where the collet had left a wear mark, that the bit mounted fine..... well, I was only lucky, as I tried dismounting and remounting the bit, and was not able to always get the bit to spin true on axis. Mind you, it is only off by maybe 10 or 20 thousands by eye, but for much of what I have been playing with, that is a big problem.

I did clean out the spindle inside where the collet fits, and the collet. And with the collet pressed in place, without the nut, the bit spins true. So I hope the new collet nut fixes this.

Thanks, Chuck

[gene]

that is the same way my collet nut has been since it was brand new. It makes it easier to remove the collet . I wouldnt buy another one , it will b just like the one you have. justt make sure that the collet snaps into the nut before you put it back on the spindle

[Chuck Keysor]

Andrew, thanks for the write-up on the collet and collet nut design! I had no idea. I had never followed the shown installation sequence. I wonder if my random eccentric bit problems would have been eliminated had I followed the correct collet installation procedure............... Sigh,,,,, as noted, I already ground out some of the eccentricity, so it is too late. Well, as noted, I'll order a new collet nut tomorrow. If I still have my problem after getting the new nut, I'll repost asking what else to replace. My collets are new.

Thanks, Chuck