Quote Originally Posted by Web Goblin View Post
I see. Are the jaws on your 4 jaw chuck long enough to hold both pieces at the same time or did you do them seperately?
The jaws on my chuck a long enough to hold a few mounts... I thought the same to start with then realised it wasn't going to hold them securely enough due to the uneven clamping pressure. I think when you tighten the chuck up it grabs the one nearest the face of the chuck (since that's closest to where the scroll applies the force) which causes the jaws to be at a slight angle and therefore not put much force on the next part out. It would have held both with the chuck done up pretty tight ... but that would make 4 horrible marks on the part from the jaws, and I doubt it would actually be any more accurate than doing them separately as long as your centre mark is good.

To make things quicker (for the spindle mount pictured fixed to the spindle) I made it so around the 80mm hole there is a 100mm square. That enabled me to put it straight into the 200mm 4-jaw self centring chuck (the main one I use on the lathe). I used the normal jaws as the external jaws would get in the way of the boring bar.

On a related topic ... I wonder how many tram the spindle on their CNC router? I've had to do it with mine as aluminium highlights the error.