ER32 Collet Nuts - heads up

[picclock]

My small 4 jaw lathe chuck wasn't holding some 3mm steel very well so I thought I would use the ER32 collet chuck from the mill, held in my 4" 4 jaw. So I align it central using the outside of the chuck as a guide. Insert collet and 3mm steel rod and check the runout. Its hopeless so I adjust the 4 jaw to centre and think thats that. Turn the required groove, loosen the ER32 chuck, advance the rod, tighten the collet nut, turn on lathe and the work is visibly off centre. Rins and repeat with 4 jaw. Advance rod, check with indicator, 21 thou runout ???

After lots of mucking about looking for invisible bits of swarf and trying to pin down the source of the eccentricity it appears to be a function of the ball raced collet nut. Problem pretty much disappears with non ball raced part around (0.4 thou variation).

So if you use one of the ball bearing type ER32 collet nuts, it may be worth checking it once in a while

Best Regards

picclock

 

[Blogwitch]

What you are trying to achieve is really not the way to treat a precision tool like a collet chuck. Three or four points of heavy contact around a hollow part is bound to deform it in one way or another.

Because of how you have abused it, it is now most probably ruined.

I have been using those ball raced collet nuts for a few years now, and have never had any trouble with any of the three I have, all run perfectly true. But I don't go around clamping them up in chucks.


Bogs

 

[picclock]

I doubt that it is damaged as it performs flawlessly with a non ball raced nut. I have another ball raced nut I may try with if I ever do this again, but either way the nut caused the repeatability issue. The 4 jaw only grips the thickest part of the ER32 Adapter and I think it unlikely to have caused any damage. Will check it out when back in the mill.

Best Regards

picclock

 

[velocette]

This is what I do when using ER 32 Collet Chuck in the lathe Take off the chuck and slap it into the Morse Taper
in the spindle.
Hold it in the spindle with a "Threaded Rod" and a large washer and nut
Works fine for me

Eric

 

[Davo J]

I don't think you have done any damage, they are pretty thick in that part of the collet chuck.
You might have got a bad nut, did you check it when you first bought it? I so it seems something has gone wrong along the way.

Dave

 

[mu38&Bg#]

I would have to think you have a bad collet nut.

Greg

 

[picclock]

I've put the collet back on the mill and the runout is exactly the same as before, around 0.4 thou, and that seems true over the length of the internal taper. The chuck jaws grip the outside affects the last 5mm of the internal taper only, and otherwise its solid metal which I think would be hard to damage. Either way its not ruined and seems to have suffered not a bit of harm.

I will do the runout tests on the mill with some more 3mm silver steel, and use all three of the nuts I have. Will post the results when I'm done. It will be interesting to see how well the other ball raced nut I have performs. Would never have thought to check it before I had the problem on the lathe.

Best regards

picclock

 

[Blogwitch]

I think you are completely missing the point here.

You can't just go around clamping up precision tooling in a non precision tool like a lathe chuck, they give too much pressure onto small contact areas. Would you clamp up a micrometer or a digivern up in a bench vice to hold it? Same sort of thing.

Items that you require to be accurate should be treated with at least a little respect.

I make lathe and mill tooling out of big lumps of scrap, but once the precision tool is then made, it is treated as though I had spent hundreds of bucks on buying it in.

You may get away with it once or twice, but one day you will be decrying the retailer for selling you something that doesn't run true, when all along it is most probably the way you have treated the tooling in the first place.

I am very sorry to get on my high horse over this, but I absolutely hate to see perfectly good tooling being abused.


Bogs

 

[picclock]

@ Bogstandard
>>You can't just go around clamping up precision tooling in a non precision tool like a lathe chuck,

Well I'm sorry, but not only can I, I did, and no harm was caused ;D

However I have tracked down the cause of the error which this thread was about anyway. On the ball raced nut is a lower rotating taper section, and on this particular nut it appears that a final looks like a final deburring operation was missed on the end of the taper. Its quite difficult to take a picture of although the burr is very sharp and protrudes out from the taper.

is the best I can do with my camera.

I would have thought that the force from the collet being tightened would have caused it to bend/break/ straighten, but it seems very hard. I might have a go at disassembling it and removing it with a stone but I'm not too bothered now that I have found the cause of the error.

The other ball raced nut has the edge ground around 1/3 mm and feels very good in comparison.

Ho Hum - another annoying puzzle dealt with.

Thanks for your interest

Best regards

picclock

 

[Omnimill]

Glad you've found the fault, it can be a bit frustrating not knowing what's going on sometimes!

Vic.