# double tumbler/single tumbler



## porthos (Jan 30, 2014)

i have yet to visit the heavy 10 that who's owner i made contact with a few weeks ago. last weekend it was a lot of snow. maybe this weekend. with all this time to think, i come up with questions.#1 what is the advantage of a double tumbler over a single tumbler?  #2 if there are no "tumblers, is it not a quick change? this is a 1942 govt surplus. #3 are there any disadvantages to the 1942 heavy 10L vs. a 1954 10R (all things being equal as far as general condition)? whenever and whatever i get, i won't be happy until it runs and looks like new. my experience with a metal lathe is an ENCO 9x20 bought in 1985. just to "tinker" with. never made anything fancy. a few cast bullet sizing dies and some gun related stuff.. this past fall i went to vo-tech. class for  a 60 hour course. made a indicator base using a mill and lathe. now i know enough to get in trouble

thanks
porthos


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## OldMachinist (Jan 30, 2014)

South Bend switched to double tumbler quick change gearboxes sometime in the early 50's. So if the lathe you're looking at is from 1942 it will be a single tumbler. For reference there were two different double tumbler boxes with different ranges of threads they would cut.

A 10L has a spindle thru hole of 1-3/8" and 10R is 1-1/16".


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## fastback (Jan 30, 2014)

The double tumbler actually came out in the late 40's, I think it was 47.  The single tumbler was not built by SB (I don't remember the builder) the double tumbler was built by SB.  


I have a 1942 single tumbler that will do something like 48 pitches.  The single tumbler has a sliding gear at the end of the gear box and also an arm above the gear box that has 3 settings, they can be changed while the lathe is running. The sliding gear can only be moved when the lathe is at stop or you will destroy the gear.  The nice thing about these lathes both single and double tumbler you don't need to change gears all that is need is to engage the gear and/or reset levers.  Either one works fine.  I think that the early double tumblers needed some change gears to be able to do all of the pitches.  

I like mine and would not want the double upgrade.  I doubt that you would go wrong with either one.  The real issue is the spindle size.  The 10L has the 1 3/8 spindle hole.  Bigger is better.

Paul


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