I think it was there specifically for machines with no auto-eject, no draw bar and a cross-slot in the quill where a taper wedge is driven in to release the tool,

– Nick

Yep, that's right, it's named a drill drift, one of the first things I made.

Michael W

Andrew, fit a 25mm long false tool in the turret and grip lightly in the 3j sc chuck or collet, with the turret release knob in the operating position move the tailstock onto the MT shank to seat the MT into the tailstock, release from the chuck and set the turret finally with a copper or lead hammer. This will ensure concentricity of the turret in your chosen position. Most turrets are built on a MT shank with tang which aligns the tool as built.

Emgee

The only tools with a tang are axial thrust types, so the morse taper tightens (if anything) as the pressure is applied. The tang is not there to impart any drive, but only to effect ejection with the aid of a wedge.

Drawbars are required for non-axial thrust duties, such as side milling, to avoid the tool loosening in the holder.

Drawbar versions can be converted by screwing in a tang, while many threaded male tapers need a bolt, or similar, fitted to enable them to eject from a tailstock, per eg.

Your morse taper is both your alignment and grip for the tool, so it is of the utmost importance to keep both male and female surfaces scrupulously clean.

I've often found this necessary but wondered if what I was doing was correct. Glad to now know it is the right method.

Roger

Andrew is correct in stating that toolholder positions should align with the tailstock socket. In practice not having tang location and being able to rotate the assembly could be an advantage. The tang on the MT mount of the hefty, professional, one I have for my Smart & Brown 1024 and Pratt & Whitney B locates it with the unused tools to the back of the bed. A decent idea in must cases but swinging things round by 45° to put them more or less upwards would make it far easier to tool clashing with the coolant pipe mount on the 1024. Plenty of room on the bigger P & W model B. As is I have to carefully set the cross-slide position before using the capstan and there are limitations when using longer drills. Sometimes I'm tempted to dig out the smaller cheap import I got in SouthBend 9" driving days which doesn't have a tang, just a round button, but it always looks silly flimsy to me. Works but care needed.

The 1024 tailstock barrel has both drift slot and self eject which, I think, is unusual.

Clive.

Assuming the unit is made correctly, even with the capstan at an angle how will rotating it about the lathe axis change anything other than moving the error from say, the top to the side? I stand by my assertion that if it doesn't align then the problem is the registration of the turret or maybe the tail stock is not set true to the lathe axis?

Mike

Edited By Mike Poole on 07/01/2017 13:03:56

Just read your post Andrew, sometimes clarity of thought evades us, glad it has all fallen into place now.

Edited By Mike Poole on 07/01/2017 13:09:29

Sorry to learn about the problems which Andrew ascribes to his medicine.

My medicine says in big letters: KEEP AWAY FROM CHILDREN

So I do.

Cheers, Tim

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

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