"Tang" on the end of a male Morse taper?

.

Not necessarily an idiotic reason ... Maybe a recollection of seeing a Jacot Tool.

**LINK**

https://goo.gl/images/wollIo

MichaelG.

For non-capstan lathes it seems to depend upon the whim of the designer, and on tool clearance. A bed mounted capstan with the turret at an angle has more clearance as the tools index round. For clarity this is an example of a capstan unit with the turret at right-angles to the bed:

Andrew

I wouldn't worry about it; I'm an expert at making mistakes.

Andrew

Errr, I don't follow?

The capstan and indexing mechanism are mounted on a 'solid' collet. The grooves in the large diameter are the indexing grooves and index each tool location axially in line with the mounting collet. The mounting collet has a keyway, but this is a loose fit on the corresponding internal pin in the tailstock shaft. The capstan mechanism and shaft can be rotated several degrees before the collet is tightened. The collet is held in place with a drawbar similar to the R8 system. This may help illustrate the arrangement:

There is no external keyway in the mounting shaft. The only thing that stops the whole shebang rotating is the lever operating mechanism that mates with a pair of the series of holes to the right. As shown here:

The mechanism is pretty loose, so the capstan unit can rotate several degrees either way. Indeed it does so when operating, depending upon the direction of cut. However, alignment is not lost. I have never done anything special as regards alignment when fitting the capstan unit.

As an aside indexing is done when the capstan is pulled back against the tailstock casting. This pushes on a spring loaded lever which disengages the indexing pin allowing the capstan to be spun by hand to the wanted position.

Andrew

Hello Tim,

My sentiments entirely!

Andrew.