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Craftsman spindle bore question
- Thread starter Oldwing76
- Start date
- Joined
- Nov 14, 2016
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- 3,006
It seems like a lot of lathes set the spindle bore with the use of MT collets in mind rather than maximum size physically possible.
Using Sherline as an example the stock lathe with a 3/4"-16 spindle thread is set up with an MT1 taper, and a stock spindle bore of 10mm (0.405"), but because there was interest in a larger spindle bore they now offer a replacement headstock with a 14.28mm (9/16") bore using the same 3/4"-16 spindle just bored out larger, but of course losing the ability to use MT1 tooling. This larger bore is bigger than the large end of the MT1 taper @ 12.065mm so they took more material than simply boring the taper straight.
Atlas / Craftsman 6" is of course larger using an MT2 taper, the large end of which is 17.78mm. Of course materials and spindle design will impact the ultimate strength of the spindle, but presumably you could go to as much as 18 or 19mm using what Sherline did as an example, and you are only talking 16mm +/- so not even fully removing the taper from the bore.
I personally wouldn't do it, because A, I'd screw it up, and B I'm loathe to make irreversible modifications to my machines, but that is just me. From a purely technical perspective boring it out as you wish is probably no issue to the lathes performance. Worst case you buy a new spindle, which I believe are still available from Clausing.
Using Sherline as an example the stock lathe with a 3/4"-16 spindle thread is set up with an MT1 taper, and a stock spindle bore of 10mm (0.405"), but because there was interest in a larger spindle bore they now offer a replacement headstock with a 14.28mm (9/16") bore using the same 3/4"-16 spindle just bored out larger, but of course losing the ability to use MT1 tooling. This larger bore is bigger than the large end of the MT1 taper @ 12.065mm so they took more material than simply boring the taper straight.
Atlas / Craftsman 6" is of course larger using an MT2 taper, the large end of which is 17.78mm. Of course materials and spindle design will impact the ultimate strength of the spindle, but presumably you could go to as much as 18 or 19mm using what Sherline did as an example, and you are only talking 16mm +/- so not even fully removing the taper from the bore.
I personally wouldn't do it, because A, I'd screw it up, and B I'm loathe to make irreversible modifications to my machines, but that is just me. From a purely technical perspective boring it out as you wish is probably no issue to the lathes performance. Worst case you buy a new spindle, which I believe are still available from Clausing.
- Joined
- Dec 25, 2011
- Messages
- 10,513
I thought that I had responded to jwmay's reply last night but now I don't see my reply. But at age 80 I guess that I shall have to quit depending on memory alone for critical dimensions like through-bore. In any case, jwmay is correct and my memory was incorrect. Fortunately, Oldwing76 didn't rush out and buy one of the larger Atlas or Craftsman machines.