ER25 closing nuts

Clocked both types of my ER25 chucks in the lathe and they're all with 1/10th of a thou. ........But if I mix the closing nuts (I have 4) and use another nut to that I used to turn something then I have up to 2thou runout. Did think that they would be interchangeable. What's the general thought on this?

Cheers

Graham W

As it's the taper of the collet and the corresponding taper in the chuck that locates the workpiece, I'm inclined to think the extra runout is determined by something other than the closing nut. Check both for tiny bits of swarf or other detritus that may give rise to the wobbles.

John

First thing I checked, both in the nut and the collet, cleaned anything I found out but still the same.

Graham W

I think every time you disassemble and reassemble you will get a different reading. Consistent results may be achieved to within a tolerance if everything in the assembly is consistent.

Check the collet is going back in exactly the same position each time as any runout in that will affect readings if it is rotated. Are you applying the same force? you don't say if they are plain or bearing nuts which will need different torque and affect tightness.

Perhaps some of the nuts have a thread that is too close fitting. I think that there should be some slack in the thread so that the closing nut doesn't push the outer taper of the collet out of alignment.

Russell

Just be thankful you have some combinations that work, and mark the matching pairs to keep them together.

Have 3 plain nuts and one ball bearing type tightened as much as I can using standard spanner. Scenario 1 is when I make a holding 'jig' to lap a piston. I turn 1 end to usually 15mm perhaps in a 3 jaw, then that end into, usually 15mm collet/chuck, and turn to suit piston and finish for pull rod. Next time I use it perhaps using another chuck and nut there is a degree of run-out, not to much of a problem with a hand held lap. Scenario 2 today was with the liner for a Holly Buddy engine. Turned 1 end down to 16mm this time in 3 jaw then that into collet chuck and turned the diameters leaving extra length for parting off. Put that onto a ER25Stephenson square block held on an angle plate and drilled for transfer ports and cut the exhausts. Back to the lathe and run-out was 1 thou, not as bad as seen previously, so bored the liner at that, came to part off and the run-out clearly showed when blade presented to the liner. Think I'll do some tests as suggested then and keep 1 nut to each chuck which can sometimes be difficult if using mill to drill holes working way up the sizes on multiples of same item but the devil drives.

Cheers

Graham W

Try this

silver steel stub in chuck. Clock run out. Loosen rotate the collet in the holder 45 degrees. Remeasure runout

repeat at the next 6 settings. Chances are you will find the runout is in the collet. They vary tremendously in quality and runout is only good with ones which are sold with an actually detailed number some I have been looking at are quoted at 0.0006” from amazon but not yet convinced this is the best without going to a silly price. I need to look further.

HSEAMALL 19PCS ER32 Precision Spring Collet Set,2mm-20mm ER32 Collet Chuck for CNC Workholding Engraving & Milling Lathe Tool

Putting a short stub of 15mm into a collet may be a problem, it is possible to have the part at a slight angle. You should not assume the part will be pushed into the perfect position by closing the collet down on it. This is the type of part where soft jaws help. You can machine the jaws to hold the diameter correctly and also a rear step to tap the part down on to.

Martin C

You don't say what grade of collets you are using, Typical general quality will be something like 0.015mm, cheapies could be worse, Precision and super precision ones better but at a price. So just like a 3 jaw if the collet is not in exactly the same position in it's holder and the work not in exactly the same position in the collet then you will not repeat the setting.

Add to that your nuts may be of differing qualities so may be pushing the collet off. Larger the collet the less tightening force you need to apply and less force if a bearing nut so may be too much which can be as bad as too little.

Bought the set complete and spare nuts from my favorite Leicesteshirer supplier a few years back and haven't been disappointed with anything they've supplied me. Recently bought a 16mm collet Swiss made (Sets seem to go to 15mm max) but have the same variability with that. Always make the stub at around 3/4" long so not overly short I would have thought. Perhaps the point that Jason is making about tightening is worth looking at as I try to get them as tight as I can.

Graham W

Checking the collet closing nuts is good advice. I have experienced excessive runout problems with an ER 32 collet system and blamed the collets as the taper clocked true. Eventually, I tried each of my 3 collet closing nuts and found the two plain ones 'off' but the ballbearing one gave consistent acceptable results. The plain ones have binned!