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Yea, no need for the compound with CNC and that also adds slack unless you just bind up the ways. A spacer block for your tool mount will work fine.

John

OK, scratching around I found some rather thick C channel, wide enough to take the compound, the vice is a bit big for the compound, but it fits fine on my 10mm plate. My only concern becomes strength. If I use only existing holes in the compound I will be bolting it down with 2 6mm bolts, I do think I will duplicate the 25mm centre pin, probably bolting that down with a 10mm bolt. There is currently one hole to mount the tool holder, though I can add more holes, there is also a raised platform for the tool holder, so a logical place for another hole would require a wide shim. I hopefully attach a picture of what I have in mind. I am not looking forward to cutting the channel iron though, I think it may take a while.
Regards
Peet

Soundreflections wrote:You just need something that can screw onto the spindle nose. It need not be terribly precise at first. (though will be an interesting excercise in internal threading).
You then mount it on the spindle, and machine OD and register in-situ to take the chuck. Then it _has_ to be true.

If you want to then clean up the back face, re-mount the three-jaw, mount a bar in that then mount the4-jaw on the bar.

As JT says, a bit of sturdy angle would work (possibly with a welded gusset).
Bolt it to the cross-slide (I am not sure how, this is the hardest part) and face it off with a lathe tool held in the 4-jaw chuck (crosswise, like a big fly-cutter).
Then bore a hole to suit the compound-slide pivot pin. Probably with a drill mounted in the chuck, followed by a lathe boring-bar mounted eccentrically in a 4-jaw chuck (an adjustable boring bar would be better, of course). Maybe this one:-)
global.ebay.com/Wohlhaupter-UPA2-5702/261069311985/item (actually I was going to post a joke link to a $2000 tool, but that one is a significant bargain at the current price)

Drill more holes at the correct centres for the hold-down bolts, then mount it properly.

Then face it off with the scary fly-cutter again, and drill a second hole. The size of this one doesn't matter, but needs to be smaller than the compound slide register.

Then put the lathe back together, and turn a spigot to fit in the second hole snugly, and to suit the recess in the compound slide base.

OK, Only one pic survived - I must still figure quite how pictures work in this forum.

Soundreflections wrote:
You can only insert one pic using the button, but you can link to several usingtags. There is a button above the edit window that you can use to not really help with the tags.

andypugh wrote:
My machine has a face as the end of the spindle - it cannot be removed. So I have a 125mm 4 jaw chuck (100mm 3 jaw), so that I can have an adaptor plate that fits the 3 jaw's profile, then has the 4 jaw bolted on. I hope this makes sense?

My biggest problem here is I don't think I will have the desired vertical travel for the hole. I see what you mean by the bit in a 4 jaw, with an offset to whatever size one wants.

I do not follow hundred percent about where I need to face, though I realise the importance thereof. I will only have vertical adjustment once the compound is mounted. I could possibly face the 10mm steel plate, depending on travel, and then mount the vice - or how feasible would it be to have T slots? I suppose 10mm is getting a bit thin here!
Regards
Peet