Made from 50x20x70mm mild steel, the standoff increases the cross slide travel forward by 25mm over standard. Made using the four jaw independant chuck, this part puts the heaviest loads on the machine as there is a fair bit of metal to be removed through interupted cuts. This piece would be much easier on a mill.
The unusual length (62mm) is a carry over from this parts past life in V2 of the cross slide drive. It use to be longer and have little bearings in it.
First the ends were squared up by facing in the four jaw. You will need extra length to have something to grip while turning the outer radius.
Then the inner holes can be marked out. The two 4mm holes which mount the standoff to the saddle (the inner ones with the long counterbores) should be drilled from the saddle end, as a drill will wander a fair way over the full depth. Best to use a new or well ground bit for these.
Center drill the central bore. Support this end with a the live center while you turn the 16.5mm radius. It could also be milled square to 33mm wide. Once this is finshed you can drill and bore the 12mm center hole as it then gives you a good reference for marking out the outer end.
Hacksaw the length down to near 62mm removing the unturned end, turn the peice around and can face it to it's final length.
To drill the long counterbores I dialed in on the outer ends of the long 4mm hole already done. It really doesn't matter that the outer end will have wandered. I just used a 7mm drill, the socket head screws want seat perfectly, but the loads are light.
Finally the motor mount fastening holes can be drilled 3.2mm and tapped M4.