# Cutting threads on a early Craftsman 12" am I missing anything?



## nwarcade (Mar 26, 2017)

Hi All,
I posted about this old Craftsman lathe a couple of months back.  I've been using the time since to read and learn as much as I can about these machines.  I would like to start cutting some threads but my machine seems to differ from the other 12 inch craftsman/atlas lathes I've found.

The biggest difference is that my banjo bracket has one less slot than the others I've seen.  It also has a standard 32t gear on the tumbler spindle where other 12 inch lathes I've seen have a compound gear.  I can't find anything stating the 32t gear is correct or if it should have a compound gear like the other 10/12 inch lathes.

Before I get too deep I was hoping someone could take a look at my gear inventory and chime in if I'm missing anything.   For change gears here's what I have...
96t x 2
64t x 2
56t
54t
48t
46t
44t
40t
36t (mis-read as 35t)
32t
24t
20t

I think I'm missing at least one gear stud.  Would something like this work or do the 6" parts not cross over.

LATHE-CHANGE-GEAR-BUSHING-SLEEVE-BOLT-and-NUT











Thanks in advance All,
J


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## wa5cab (Mar 26, 2017)

J,

You have an early 12", of which there aren't that many around.  The 3-slot banjos are on the 19F and the later 12" from 101.07362 on.  There is also one error on your threading chart.  The word "SPINDLE" shown next to the 32T gear at the top of each drawing should be "TUMBLER".  The actual 32T spindle gear and the 20T and 24T tumbler gears are not shown in the drawings on this chart.  This has been corrected on the early 12" threading chart in DOWNLOADS.

The 16T/32T Tumbler gear is only used on the 10F and the later 12" machines that have a 3-slot banjo and don't use a 

If you download the 101.07381 parts list from DOWNLOADS, it shows all of the gears that you should have.  Note that the list of gears on the parts list includes the three tumbler gears, which on the early machines were the same gears as the rest of the change gears.  So for example, where it shows 2 24T gears, one of them is the tumbler 24T.  On your list, besides the 36T, you are missing an additional 32T gear and a 52T gear.

Off hand, the only 6" parts I recall that will fit/are the same as those on the 10" or 12" are the two tailstock lock cylinders.


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## mikey (Mar 26, 2017)

Robert, I've been meaning to tell you for a long time how impressive your fund of knowledge is regarding these Altas lathes. If there is an "expert" on these lathes, it has to be you. Even a non-Atlas owning rube like me can see this so THANK YOU for all you do.

Mike


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## nwarcade (Mar 26, 2017)

Well said Mike, I couldn't agree more.  Thanks for the info Robert.  I went though my gears again and I actually have a 36t (looked like a 35 in the poor light) so I guess I'm just missing the additional 32t, 52t and the gear stud assembly.  Before I hit eBay looking for the wrong item should I just duplicate the gear stud assembly I have or will it be different for the second position on the banjo?  And just to double check all of the gears in my reverse tumbler are correct and in the right locations?
Thanks Again,
J


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## T Bredehoft (Mar 26, 2017)

Did I miss something, or should the two tumbler gears be the same tooth count? Should not the feed be the same in both directions?


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## markba633csi (Mar 26, 2017)

No they are different- they are just idlers and they are different sizes to get one "out of the way" so to speak.
Right Robert?
Mark S.
ps as you can see though, the little one wears fast.


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## wa5cab (Mar 27, 2017)

Thanks for the kind words.  Some might say that I spend too much time chasing the supporting documentation and not enough making chips.  

Mark,

Yes, that's correct.  If the two gears were the same tooth count, because of where the tumbler pivot is relative to the spindle and to the three index holes, they wouldn't engage properly when the pin on the S8-45 Reverse Tumbler Plunger Knob was in the index hole (or you wouldn't be able to get the pin into one of the holes).  On the later 12" machines, the relative positions of everything is slightly different and both gears are 24T.  One of the hardest things to get comfortable with is the fact that in a spur-gear train of several consecutive gears, the tooth counts of the first and last are the only thing that matters so far as ratio is concerned.  Only if you have a compound gear (two gears stacked on a single keyed bushing and input to one and output from the other) does the tooth count matter.

J, yes, your tumbler appears to be assembled correctly.  And both gear stud assemblies are the same.


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