I thought that this little device might be of use to someone.

I have made a start on the valves, guides and tappets for my model V8 and there are 32 of each of them, plus spares. To ensure repeatability, I decided to make a depth-stop system for 8mm watchmakers collets.

I started by making M4 tapped inserts for the back of the collets, in this case 2.6 and 3.0mm.

I then cut of the head of a long M4 screw and drilled 2.5mm holes at each end. In one end I "loctited" a M3 allen head screw turned down. The other hole accepts the actual depth stop.

I then made a couple of lock nuts from a scrap spur gear (hence the splines) turned down so they fit inside the drawbar. I then made a long and short depth stop for different purposes.

Here is the complete unit.

Some of the parts I have to make are very shallow so the long stop should be a great help.

The collets can be used normally when I don't require the stop as the clearance in the M4 insert is greater than the collet size so long stock will pass through.

Steve