ER32 Collet Thread Problem

[FulmenParticipant @fulmen]

Well done. I would probably just single point them with power, it’s not as hard as many imagine.

[Howard LewisParticipant @howardlewis46836]

Glad that you have managed to overcome the problem.

It is puzzling that the problem should gradually arise, part way along the thread.

But hopefully, those days are behind you!

Howard

[Nigel Graham 2Participant @nigelgraham2]

I did not manage to identify where the fault actually was, but as I cleared the thread the remaining tight spots only appeared when the nut was about half-way on or a bit more. Once past that, the threads were fine.

It’s as if the male thread was either distorted somewhere in the middle section, perhaps by my straining it, or had somehow been cut shallow in the first place.

 

Fulmen –

I didn’t want to use power even on lowest belt setting, back-gear and low motor speed, as I was holding the tool in my hand!

[Neil LickfoldParticipant @neillickfold44316]

I have seen this before. There will be a piece of swarf that has bruised the nut. I used a 1.5mm pitched tap, and used it like an internal thread file. Set up the nut, ran the spindle on lowest lathe speed, in my case was 70rpm. Hand held the tap as it ran through the thread. Then try the body until it fits. Just make sure that there is no bruised area on the body at all. It takes very little to cause trouble with the close fitting threads.

[FulmenParticipant @fulmen]

@ Nigel: No, you shouldn’t try that under power unless you have a supplier for new fingers.

As for the cause of this I guess some things will always remain a mystery. Could be that the leading edge of the female thread got distorted, snagging on a small imperfection on the male. But who cares as long as it works?

[Martin ConnellyParticipant @martinconnelly55370]

The best guide to the question of “Is the collet in the nut correctly?” is that the collet face should be close to the nut face as you can see in Jason’s video.

Martin C

[Diogenes]

 

 

On Diogenes Said:

Not all nuts ‘snap’ the collets in – the Bison ones are a ‘drop-in’ fit – you can easily swap collets in and out with the tools ‘pre-loaded’..

I don’t know about the current models of Bison ER collet nuts or any design changes that may have been made. Mine are probably about 15 yrs old now. But I can definitely say they require the same method of hooking the collets extraction groove under the nut extraction lip and rotating the collet over to snap them into place like any other ER collet nut. If there’s been a design change and it still works just as well, that would be something very nice to have.

While Nigel seems to have now found and solved the problem. As far as his question about, “I don’t know if I’d been a bit too heavy-handed at some point and distorted the thread – is that possible?” Highly doubtful with any properly manufactured collet chuck and nut. His ER 32 series have a recommended tightening torque of up to 100 ft. lbs. Even reaching that upper number for the larger bore sizes of collets is probably impossible for most with the wrench length the larger ER series of chucks are supplied with. Even my Bison collet wrench is too short. Those fancy torque wrenches made for tightening ER collet nuts to repeatable numbers are a lot longer for good reason.

Technically and depending on the collets features such as though bored or when counter bored for the smaller sizes, and certainly with those ball bearing nuts. Those can all change the recommended torque numbers. I think a very worthwhile 5 minute video explaining the differences and how collet damage can happen with over tightening. https://www.youtube.com/watch?v=7Jbhep1PzuI

I can’t say for sure what the actual cause of Nigel’s problem was. But his description of the repair sounds exactly like thread galling on the chuck threads. Without any apparent damage on the nuts internal threads, then likely the chuck is a slightly different alloy or different level of heat treatment and hardness. By his description, then without question the flanks of the chuck threads were somehow torn and damaged. How he did the repair seems to rule out any thread distortion at all. I’d very closely re-inspect the nut threads for any embedded contamination and use a bit of lubrication on the threads from now on just to be sure the same issue doesn’t happen again. I’d also check all of the collets for any burrs still left from when the slots were originally cut. For some collet manufacturers and lower priced collets, and forum posts mentioning it, that could certainly be possible. One of those small hardened burrs finally breaking off and getting into the threads would definitely do that exact type of damage.

 

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for the video link, Pete

It makes very good sense !

MichaelG.

[PeteParticipant @pete41194]

Your welcome Michael. There’s quite a bit to learn on that channel about ER chucks, nut’s and collets. For something as simple looking as they seem, there’s a bit more to them than I first thought.

[Author]

Posts