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Making a Sub Miniature Live Centre

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Was the problem being without? I thought it was because the one shown in the first photo had a larger diameter body than the newly made one?

I was looking at the finish that has been achieved in the last photo on the taper turned using the centre and the finish on the taper on the rotating Centre which would have by necessity been done without it  :).


Charles Lamont:
Jasonb, the main problem is the amount of tool overhang needed to clear between the toolpost and the body of the centre. I have often found this a problem, even with an extended toolholder. Wanting a hollow centre for some valve stems, I came up with this. It is a revolving centre with a bearing ball rather than a ball bearing.
The unhardened silver steel centres run in a bronze bush bored in situ. The little radial hole is needed to be able to get the ball out, if necessary.

Fair point on larger machines but this is the Cowells so work is likely to be small and tooling not of a large cross section, 6 x 6 or 1/4" square would be in keeping for the machine so maybe only 12mm / 1/2" tool overhang at the most and not taking any heavy cuts. length of that DCGT insert is more than that projection and you would not want your toolpost clamp screw on the insert

Jo Why by necessity, a cowels live ctr is shown in the first photo and can be seen in the images of what came with the lathe so that could have been used. I think the MT shown in the chuck is a bought in taper and the one with the rougher finish what was on the home made mini one where a live ctr was available.

FYI (at least in England)

Live centre: goes in the spindle end, revolves with the spindle and is soft so can be trued before use.
Dead centre: goes in tail stock end, usually hardened so it doesn't wear.
Revolving or low friction centre : goes in tailstock end revolves with work piece.


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