# Why some SB lathes have graduated dial 0-120



## tbone8 (Jun 21, 2021)

Curious, are the 0-120 dials metric or something?


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## MrWhoopee (Jun 21, 2021)

tbone8 said:


> Curious, are the 0-120 dials metric or something?


120 or 125? How many marks between 120 and 0? Picture?
125 would be 8-tpi lead-screw.


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## tbone8 (Jun 21, 2021)

MrWhoopee said:


> 120 or 125? How many marks between 120 and 0? Picture?
> 125 would be 8-tpi lead-screw.


Will double check tomorrow but after looking at one on the ebay, like you say, it is probably 0-125. So each hash mark would still be .001 with that 8 tpi screw then? Why was that done, seems confusing...


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## MrWhoopee (Jun 21, 2021)

tbone8 said:


> Will double check tomorrow but after looking at one on the ebay, like you say, it is probably 0-125. So each hash mark would still be .001 with that 8 tpi screw then? Why was that done, seems confusing...


Yes, still .001. I believe early machines had 8-tpi cross-feed lead-screws, back when it was common to think and design in fractions.


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## benmychree (Jun 21, 2021)

That was before direct reading dials, which had to be larger in diameter, so we knew that .125 on the dial meant .250 on the diameter for the crossfeed.


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## tbone8 (Jun 21, 2021)

MrWhoopee said:


> Yes, still .001. I believe early machines had 8-tpi cross-feed lead-screws, back when it was common to think and design in fractions.


Thanks Mr Whoopee and gee, your the greatest!
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