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SB 13 cutting 12tpi with tumblers set for 16tpi

Tennessee Tater

Plastic
Joined
May 10, 2016
I have a 70's vintage SB 13, just learning to run it. Today I attempted to cut a 16 tpi on a piece of 3/4" cold rolled bar stock. The thread looks good, but it cut 12tpi.
It has a double tumbler gearbox, & on the plate on it calls for the left tumbler to be in "b", with the right tumbler to be in the first (far left) position. I tried running on the bull great but the threads were really fine.
Any help greatly appreciated.
I also posted this in "gunsmithing"
Thanks
 
It does, 48 & 24 on the stud gear, have to figure out which is stud gear. Another gentleman replied with a link to a 13 with similar problem, going to take the iPad to the garage and try to figure it out. I looked at the thread and know that I have a 64 tooth on the tumbler input shaft that is being driven.

I'll post what I figure out.......or more questions.
Thanks
 
I think the 64tooth on the gearbox is right, looking at the thread johnoder posted. I took pictures, if i can figure out how to post them.20170616_195026.jpg
 

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Thanks for the link Johnoder, good read, going to clean up my gears and count teeth over the next few days, have to work tomorrow,
Many thanks, I'll get back to it in a day or two.
 

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Last edited:
You just need to replace that 34?? tooth gear with your 24 tooth gear.

You are fortunate as you have the compounded 127/100 metric gears in the idler position...no need to change that, the compounded idler only come into play when you are using the smaller outer 100t outer gear to drive the gearbox.

BTW- contact Ted about your carriage lock, he may also have the gearing instruction sheet for utilizing the metric capability you have.

[email protected]
 
Scan thanks to Mr. Wells

If you had one of these charts you could actually read, you could discern all the various stud gear tooth counts that are involved in cutting metric threads
 

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Thanks, I'm pretty sure i have that plate on the gear cover. I counted the teeth on the stud gear that's in use, it has 32 teeth
I counted the teeth on the other stud gear, don't remember off the top of my head, but I know it wasn't 48 tooth.

I don't think that i have a 24t gear, looked on ebay this morning, there is one listed, but the lister says it is for a single tumbler machine & wont work on a double tumbler.

I need to read a lot about this lathe to figure it out, what configuration it is etc.

Ken, i have no other gears other than what is on the machine.
I need to clean all of the old grease & gunk off of the gears & count the teeth,

Anyone have a 24t stud gear that will work on s double tumbler machine?
 
Hi Ted,
I'm new to machining, learning as I go. So google is my friend, I looked what DP is and it appears that just changing my stud gear wont work, I'll look up hot to measure dp.
Im at work right now, wont get home till 5.

Iwananew10, I'm watching it on ebsy, if it will fit my reversing lever & is a part of the puzzle ill get it.
I need to read up on this, research dp & how to determine if I need a complete set of gears. If I need a complete set, id rather buy them as a set than piecing the puzzle together with individual gears

Really appreciate the help from everyone.
 
The Metric transposing gears are 16 DP

Which says the stud gear installed, reported to be 32 teeth, is 16 DP - since it is engaged with the transposing set

Which also means that the usual every day (not part of metric rig) stud gear, stated to be 14DP, is not going to be able to use the metric transposing set as an idler
 








 
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