I just added 50 mm of daylight…

[old martParticipant @oldmart]

But you are using the drawbar to tighten the collet, and if it wants to rotate in the spindle, holding the spindle won't help, or am I missing the point?

With the R8 in the Tom Senior without a pin I can lock the spindle, but if one of the R8 collets decides to turn when being tightened there is some bother, especially as none of them project from the spindle. I may drill axial holes in the end of some of the most used ones some time.

An advantage of not having the pin in the R8 spindle is that I can use a 30 size taper cleaner as the tapers are similar (not identical). The upper part of the spindle can't be cleaned with the 30 cleaner, but there is much less chance of contamination. I can recommend you getting one of those cleaners, they certainly do pick up some muck.

Edited By old mart on 21/12/2020 21:44:55

[John HaineParticipant @johnhaine32865]

The problem is getting enough torque on the drawbar nut to fully tighten the collet into the taper and lock the tool. There is no way to get a firm grip on the spindle to hold it still while you tighten the nut. There's no tendency for the collet to rotate relative to the taper that I have discovered yet. Where the spindle emerges from the mill head there is a plain steel collar machined on the end of the spindle, a radial hole in that to take a tommy bar would be all that's needed.

The R8 spindle in my VMB does have a pin and I've had no bother with the collets not entering the taper though a few of them did need a little work with a file to clean up the keyway. Why doesn't yours have a pin?

[old martParticipant @oldmart]

I was hoping that the end of the collets would project from the spindle when they were in use., allowing a flat to be milled at the collet end od.

Last year the museum inherited an Atlas 12 x24 lathe and a Tom Senior light vertical. The TS needed a lot of work and as we already had a drill mill with R8 and lots of tooling, I decided to convert the TS to R8 from MT2. This required a lot of work, but it has been well worth it. I bought a new R8 spindle from ARC to convert. The new spindle is much shorter than the TS one and the top half of the TS spindle has been grafted to the Chinese one. I had my doubts about the Chinese spindle at first, but after extensive testing, it was found to be running perfectly true. The pin hole was not drilled through to the bore, so I decided to leave the pin out. A lot of people seem to prefer not having a pin and I am now a convert.

[JasonBModerator @jasonb]

John, the KX3 has an 8MM hole like you mention on the widest part of the spindle where it sticks out the bottom of the head, works well for both doing up or undoing the drawbar as well as stopping the spindle turning when using a spanner on collet nuts. The SX2.7 has a pair of holes in the end of the spindle but they are not as easy to use.

[old martParticipant @oldmart]

This picture shows the flat I put on the end of the TS R8 spindle. The flat is as close as possible to the oil seal as the wall thickness is greater further up the taper. As you have another mill to use (isn't it wonderful having two), you could remove the spindle from the Nova Mill and either produce a flat, or a hole for a C spanner on the end. I modified a spanner to fit the flats exactly for holding the spindle.

 

Edited By old mart on 22/12/2020 16:09:08

[Nick HughesParticipant @nickhughes97026]

I've seen a spanner made for R8 collets, that has 3 small protruding vertical "Petals", that fit into the end slots of the collet, to hold them and the spindle when tightening.

Possibly a similar, but larger version could be devised for the INT30 collet?

[Author]

Posts