The Threading Chart below is for newer Atlas lathes with a combination 16 & 32 tooth gear on the reverse gear carrier.  It has been made from information from Pierre d'Entremont, and Stephen F. Blancard.  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.

A-B-C-D ARE GEAR STUD POSITIONS

I = IDLER GEAR                                                                S = SPACER GEAR

XXS = STEEL SPACER                                                      --- = BLANK
 

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

                           Figure 1 (4 to 7 TPI)                                           Figure 2 (8 to 16 TPI)

                          Figure 3 (18 to 32 TPI)                                         Figure 4 (36 to 64 TPI)

                            Figure 5 (72 TPI)                                               Figure 6 (80 & 96 TPI)

                            Figure 7 (0.0087 inch)                                        Figure 8 (0.0071 inch)

                            Figure 9 (0.0050 inch)                                      Figure 10 (0.0035 inch)

                            Figure 11 (0.0024 inch)

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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