The Threading Chart below is for an older Atlas lathe with a 32 tooth only gear on the reverse gear carrier.  It has been updated from the original chart, with information from the chart on a similar vintage lathe.  This information was provided by Pierre d'Entremont.  Thank you!
    Newer lathes have a combination 32 and 16 tooth wheel, and lack the two 96 tooth gears that came with the older models.

B = BACK POSITION (TOWARD HEADSTOCK)         F = FRONT POSITION (AWAY FROM HEADSTOCK)

I = IDLER GEAR                                                                S = SPACER GEAR

XXS = STEEL SPACER                                                      --- = BLANK
 

THREADS PER INCH		GEAR ON SCREW			POSITION A				POSITION B				POSITION C				COMPOUND TUMBLER GEAR			FIG.
						B	F			B	F			B	F
4			32F			64I	20S			32	64			-----	-----			32B			1
4.5			36F			64I	20S			32	64			-----	-----			32B			1
5			40F			64I	20S			32	64			-----	-----			32B			1
5.5			44F			64I	20S			32	64			-----	-----			32B			1
6			48F			64I	20S			32	64			-----	-----			32B			1
6.5			52F			64I	20S			32	64			-----	-----			32B			1
7			56F			64I	20S			32	64			-----	-----			32B			1
8**			32B			-----	-----			96I	20S			-----	-----			32B			2
9**			36B			-----	-----			96I	20S			-----	-----			32B			2
10**			40B			-----	-----			96I	20S			-----	-----			32B			2
11**			44B			-----	-----			96I	20S			-----	-----			32B			2
11.5**			46B			-----	-----			96I	20S			-----	-----			32B			2
12**			48B			-----	-----			96I	20S			-----	-----			32B			2
13**			52B			-----	-----			96I	20S			-----	-----			32B			2
14**			56B			-----	-----			96I	20S			-----	-----			32B			2
16**			64B			-----	-----			96I	20S			-----	-----			32B			2
18			36F			64	32			20S	64I			-----	-----			32B			3
20			40F			64	32			20S	64I			-----	-----			32B			3
22			44F			64	32			20S	64I			-----	-----			32B			3
23			46F			64	32			20S	64I			-----	-----			32B			3
24			48F			64	32			20S	64I			-----	-----			32B			3
26			52F			64	32			20S	64I			-----	-----			32B			3
27			54F			64	32			20S	64I			-----	-----			32B			3
28			56F			64	32			20S	64I			-----	-----			32B			3
32			64F			64	32			20S	56I			-----	-----			32B			3
36			96F			-----	-----			96	64			-----	-----			32B			4
40			96F			64I	20S			40	24			-----	-----			32B			5
44			96F			64I	20S			44	24			-----	-----			32B			5
48			96F			-----	-----			96	48			-----	-----			32B			4
56			96F			64I	20S			56	24			-----	-----			32B			5
64			96F			-----	-----			96	36			-----	-----			32B			4
72			96F			-----	-----			96	32			-----	-----			32B			4
80 *			96B			40	24			20S	64I			32	64			32B			6
96			96F			-----	-----			96	24			-----	-----			32B			4

        FEED ( in INCHES) PER REVOLUTION OF SPINDLE

0.0033		96B		64	24		-----	-----		20	96		32B		6
0.0043		96B		64	32		-----	-----		20	96		32B		6
0.0060		96B		52	36		-----	-----		20	96		32B		6
0.0087		96F		-----	-----		96	20		-----	-----		32B		4

* NOTE: USE 64 TOOTH IDLER GEAR IN "B" POSITION FOR THIS SETUP.
** NOTE: To save wear on the hard to find 96 tooth gears a 64 tooth gear can be subsituted in position B.

Formula Used

Gear Ratio = Driven Gear / Driving Gear

TPI = Gear Ratio 1 * Gear Ratio 2 * Gear Ratio 3 * Gear Ratio 4 * 8

Feed Per Revolution = 1 / TPI
 

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