If you put the indicator on the taper on the inside of the collet chuck how does that read?

If thats good you are installing the collet into the nut before fitting?

I have seen some american sites where people have not done that and had run out

Rob,

Are you assembling the clap nut / collet correctly?

You must pre-mount the collet into the nut ensuring the groove in the collet is engaged with the crescent shaped extractor ring. Them put the collet complete with its nut into the chuck . If you simple put the collet in the chuck and do up the nut no collet however precise and/or expensive will run true.

Have a look at the Arc website catalogue which gives precise instructions.

As Ian has said, check Total Indicator Reading on the internal taper where the collet locates. And work either way from there.

Backwards to the backplate setup if you get TIR errors.

Forwards to the collet runout checks if the taper runs true.

Hi Rob

I would suggest you try to work out the cause a bit more before taking the location diameter down.

Like the other members I would be surprised if the chuck was that far out, but if it was I'm sure it could be exchanged.

Are you sure the spindle nose location is repeatable ? If the back plate register bore is not a good fit because of either the spindle nose being worn or skimmed at some point or the back plate accuracy, you won't ever get a repeatable run out and the 4 jaw would hide any such problem.

Perhaps clock the backplate location diameter or the outside diameter if you turned that at the same time.

If that's OK then are there any sillies such as location boss too high (ie chuck not sitting on the right area, which I assume, not having seen the chuck, is on the face with the largest diameter).

Do the holes have any burrs that touch the mating surface.

Good luck – Will

The loose register trick is exactly what I did with the er25 adaptor on a lathe backplate. Only a small ammount is required, about 0.004", 0.1mm and the normal screw clearance will allow exact lining up if it is necessary. I have bought a small quantity of higher quality collets in the most used sizes, Cutwel and Vertex. Remember, if the collet is not perfect, the fine adjustment may have to be carried out each time the workpiece is changed, as there is no way of indexing the collets in this system.

The wobble that you got is very large, did you face off the backplate at the same time as producing the register? Is the depth of the register less than the depth of the recess in the collet plate? Have you checked the running of the taper inside the collet plate, you will need a lever indicator to do so, the plunger dti's will have difficulty reaching inside. Poor quality collets may have up to 0.003" runout which is bad.

Edited By old mart on 03/06/2020 17:33:47

Check the inside of the collet, there's another thread on here last week, turned out to be burrs from cutting the slits

I can’t find a reply from you regarding checking the internal taper of the chuck…don’t be fooled into thinking that if the external body runout is ok, that the rest will be ok too…not so….I’m having the same problem with a MT4-ER32 chuck on my Warco lathe…measuring the morse taper of the chuck where it sticks out from the lathe spindle it’s fine, but measuring the internal chuck taper it’s 3 thou out…and the rest of the body is too..

considering collet chucks are designed for accurate work, you’d think they’ve made with some sort of accuracy in the first place…

if you’re not getting a good reading at the chuck taper there’s no point checking the nut or collets, as it can only get worse not better..you need to work forwards from the beginning, starting at the lathe spindle, …backplate face…etc….Good luck

It would be worth taking the collet plate off the backplate and check the running of the backplate.