NTM 9"C Change Gears

Andrew R Stewart

Andrew R Stewart

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My New To Me lathe (SB 1952 9" C) came with change gears but the gear train was not set up as the feed and thread chart showed. I’ve sourced one compound gear and will use it for the initial arrangement. In trying to figure this out I have a few questions, any help, comments are appreciated.

First to put some of this in perspective I don’t turn threads. Haven’t with my toy Atlas 6” Mk2 for 40 years and have no plans to do so in the future (but you never know). My use of the feed screw is for general material removal and having a nice finish when done.

Is there a list of the OEM change gear “set” when these lathes were sold new? A list of the range of tooth count made?

Then there’s the various positions the gears have. Feed screw end, banjo or tumbler. Why would one want a bigger feed screw gear VS a smaller one if the feed rate could be otherwise be the same?

I’ve read that a C version came with a 56/18 compound gear and the B came with a 72/18 one. Reasons other to effect the feed rate?

I’m trying to both understand best set up for a feed rate and explore what OEM and future threading options I might have. I suspect I will want to get a handful more gears as I learn more. Andy
 
Thanks, While not what I wanted to hear your reply made me do more work and list the chart's gear locations and sizes mentioned. Then I, again, reviewed what I have. The result is that I have two gears not shown on the chart. (A 10/108 compound gear and a 116 screw gear). Si I know the chart's mentioned gears are not the only ones offered. I thought that this was the case and am not surprised.

Still I am interested in knowing the full selection that SB offered. Perhaps in time I will research the old catalogs on line and see if more are listed.

My question about gear size and if two different gearing set ups that result in the same feed rate and if one would be better then the other is likely of minor issue. I suspect that set up lash, lube and wear make for greater differences then gear size do in this case. As would having a gear train with fewer gears likely mean less noise/roughness make a bigger difference then any one gear's tooth count. Still I like to think about this kind of stuff.

So perhaps the unasked question is that of feed rate, and the gearing needs will follow to suit. Andy
 
If it were me, I'd want the full set so I'd figure out which gears I was missing and scour eBay for them.
 
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