Quote Originally Posted by cropwell View Post

My comment (sent as a PM) is that you should remove the chuck and measure run-out on the face and periphery of the back plate. If this is within limits then you should be able to set up the workpiece in a 4jaw chuck using a dti (plenty of vids on Youtube).
Thank you for the comment and the PM. I was too busy so I had no time to answer earlier. Don't know what happened to this post or the forum, why replying was not working before. Anyway, yes, the is a self centring 4-jaw 100mm chuck. Maybe it's a bit too large for my tiny CNC, but I thought it's better to buy a bigger one than a too small one, and also got it what I regarded a good price, 280USD including EU taxes and three days shipping from Spain. Now with some refund the price I paid was only 250USD, so that's even better.

Anyway, I did what you suggested (after I agreed with the seller) and the chuck plate seems fime apart from what I mentioned before about the flange, which I think is a bit too large. I will see if I will continue improving it, though grinding is not my favourite first choice, since I don't have anything which is good and reliable enough for this sort of precision grinding. The Dremel seems very rude and inaccurate, but maybe that doesn't matter. Anyway, I will see later on if I will continue or not, and in which order.

One thing I discovered was that the jaws for the ID clamping (not the ones which are in the video) are definitely something wrong with because one of the jaw is not closing completely, but maybe that's normal, maybe you not supposed to clamp in it like if it was OD jaw. I will need to check how well it grips on a pipe before I conclude that there is something wrong with it, but in any case those jaws are not as important as these OD ones for me.