SB 9 in Theoretical max spindle speed question.

Usfwood · Mar 3, 2019

Good afternoon. I was wondering if there was any information, or if any one has speed up the spindle speed on a 9 in lathe with the plain bearings. I don't really care about the limits (yet) of the gears or gearbox, just the spindle by itself. For example, if you want to use the lathe to mill something, you might want to speed up the spindle with a collet and an end Mill. Just a question for now.

Thanks and regards.

iwananew10K · Mar 3, 2019

This comes up all the time....sure you could speed one up without the gears in play...BUT it's still a horrible idea...unless you are trying for a Darwin Award.

Imagine what would happen if lubrication was insufficient and the spindle seized...feel lucky??

Hint- threaded spindle, not applicable to your end mill in a collet senario, but what can you not do with the speeds available?...personally I see no upside.

SteveBerry · Mar 3, 2019

South Bend made a 10k lathe with variable speed pulley drive and plain spindle bearings in 1967-68 that had a max spindle speed of 1800 rpms. If someone on here has that model and has removed the spindle for maintenance could describe the type of bearings in the headstock it would be nice to know if they are serated or solid cast iron or bronze bushings.

johnoder · Mar 3, 2019

Depends

You may realize there are 9" SBs with solid Bronze bearings

You may realize there are 9" SBs with the cast iron of the head stock for bearings

I fully expect that there are later 9" SBs with the thin Bronze shells

All different

Usfwood said:
Good afternoon. I was wondering if there was any information, or if any one has speed up the spindle speed on a 9 in lathe with the plain bearings. I don't really care about the limits (yet) of the gears or gearbox, just the spindle by itself. For example, if you want to use the lathe to mill something, you might want to speed up the spindle with a collet and an end Mill. Just a question for now.

Thanks and regards.

SBLatheman · Mar 3, 2019

SteveBerry said:
South Bend made a 10k lathe with variable speed pulley drive and plain spindle bearings in 1967-68 that had a max spindle speed of 1800 rpms. If someone on here has that model and has removed the spindle for maintenance could describe the type of bearings in the headstock it would be nice to know if they are serated or solid cast iron or bronze bushings.

All 10K’s had bronze spindle bearings.
Ted

SteveBerry · Mar 3, 2019

SBLatheman said:
All 10K’s had bronze spindle bearings.
Ted

Thanks Ted ,I figured you new the answer.

DMF_TomB · Mar 4, 2019

bearings get hot at high rpm for long periods of time. sometimes bearing clearance is adjusted on the loose side to prevent binding when hot.
.
many chucks have a rpm limit.that is too fast they can come apart throwing chunks of metal. and of course if things out of balance many a lathe will shake pretty bad. doesnt take much to make it out of balance.

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SB 9 in Theoretical max spindle speed question.

Usfwood

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iwananew10K

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SteveBerry

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johnoder

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SBLatheman

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SteveBerry

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DMF_TomB

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