In a recent MEW Michael Cox had a tailstock turret. I had been meaning to make one for a long time, Michael's article kicked me along!!
The broad design criteria were,
1/ I had to be able to make it
2/ Max drill size 7.0mm, this allows comfortably for 1/4" drills, taps etc
3/ I reckoned that I needed 5 stations, centre drill, pilot drill, tap drill, taper tap, plug tap.
4/ The whole thing to be as small as possible
I have revised that a bit since and now believe a 4 station turret would be good, because two positions for taps is not necessary.
A friend of mine has a Schaublin 70 with a Schaublin tailstock turret, (not the dedicated 70TR turret Lathe). This as you would expect is a beautiful piece of kit. It has the stations parallel with the axis, not angled. This appealed to me not least because I would be less likely to leave bits of flesh dangling from the pointy bits. The Schaublin one was 60mm diameter and had 5 stations. Bingo, I could copy the basic layout of the Schaublin one, but with a simple spring loaded detent. Because space was a bit restricted ER11 collet chucks from CTC were used, instead of conventional chucks. All the sockets were reamed 10mm diameter, as was the central bore of the rotating part. As I had a bagful of M5 x 10mm long socket set screws left over from the QCTP project, they would be used for tool clamping, this explains the slightly unusual placing of the clamping screw holes.
I ordered enough material to make three complete turrets, as I expect some scrap. The machining is basically pretty easy, even for me. The hardest bits were getting the right fits between the rotating part and the fixed part, and a smooth yet positive detent mechanism, with no or minimal free play. The first fit (rotating to fixed bits) involved lapping the parts for a while on a surface plate with some oily 800 wet and dry. It now has a really nice smooth feel when indexing. The detent pin was a matter of very light lapping of the holes and polishing the pin.
So there we are it didn't take long and works a treat. What more could anyone want!!
cheers
Bill Pudney
ps the not very sharp centres are intended to be used with a tapping chuck, and don't need a sharp point. They are about to be replaced with a spring centre.
