I mentioned in my Parting tool upgrade post that I planned to upgrade the locking clamp for the tailstock too.
Like many locking clamps on the Unimat III the locking clamp for the tail stock is an M6 cap screw. It being tucked down the side of the tail stock body it isn’t always convenient to get to. Watching the videos from the GOG virtual shows done by the late David Smith (DLOS) on workshop practice I noted that he had done a similar upgrade and it prompted me to think about it. I finally go to it.
As luck would have it I have a small stock of 50mm stainless M6 cap screws. These are only threaded for part of their length so I started by threading one of them along it’s entire length. Not an easy task in stainless but I got there. Next I cut of the head and cut it approximately to length.
Then I drilled and tapped a short length of 16mm aluminium bar M6 and turned a 20% taper on the closed end. Having tried to fit it all together so that I could work out the handle length I realised that I had it too tall and it wouldn’t screw past the body of the tail stock. I parted off 5mm and that cured the problem. I screwed it on hand tight an marked where the handle was gong to be and had to change plans again.
My initial idea was to use another M6 screw for the handle and make a knob similar to the pinch boss to fit on the end. My test run proved that there just wasn’t enough room for any kind of knob so I was pondering what I might do when I remembered that I had a short length of steel bar in my tool box that I had had for years and it usually found use as a drift so was a little battered on the ends.
I faced one end off and turned it down to 5.85mm to thread M6 again it being stainless, made this a bit of fun but once I got it started it wasn’t as hard as threading the screw. Then I decided to taper the rest of it to make a handle shape so I centre drilled the threaded end and used a live centre to support it while I turned the taper. After initially completely forgetting that I needed to turn the topside feed not the carriage feed I ended up with the handle below which I was quite pleased with.
Having cross drilled the pinch boss I assembled it all and it looks like this
This is the unlocked position and a quarter turn locks it
Carried away by this success I have ordered some more 8mm stainless rod to make another to replace the cap screw on the quill lock.