Leadscrew Reversing Gearbox
This potentially troublesome mechanism is clamped to the bed at the headstock end of the leadscrew. The sliding sleeve, together with its engagement "dogs", is clearly visible.

General arrangement of the original 10" Atlas (circa 1934 - 1960) headstock. The 60 indexing holes are visible on the front face of the bull wheel whilst the locating pin can be seen protruding through the front of the headstock casting. This headstock is fitted with "babbit" plain bearings, an option that had disappeared from the catalogs by 1952, and a separate "bolt-on" backgear assembly.

Atlas 10" Saddle, apron and compound slide assembly as used on early versions of the Model F with power cross feed.
The cross slide was rather short - a feature that tended to wear just the middle section of the wayside - and had no T slots.   In the UK several owners have taken the optional-extra "long" cross slide from a Myford ML7 and fitted that instead. The conversion does require some machining with the dovetail on the thicker side of the slide being cut back for around 1/4-inch and the saddle likewise narrowed by taking little from each side of the cross-slide ways.

Early through to late-type power cross feed apron. Of very light, single-sided cast-iron construction, and using ZAMAK for almost all other parts, the apron was remarkable for providing power cross feed with a minimum of components. The leadscrew on the power-feed Model F was increased in diameter to 3/4" from the 5/8" of the original Model D. Note the use of square nuts to retain the rack-feed unit.

Swing over bed: 101/4"
Swing over carriage: 65/8"
Threading range: 4 to 240 standard, right or left-hand threads
Collet capacity:  1/2"
No. of Spindle Speeds: 16 (8 Direct, 8 Backgeared )
8 Direct spindle speeds RPM: 164, 266, 418, 500, 685, 805, 1270, 2072
8 Backgeared  spindle speeds RPM:  28, 45, 70, 83, 112, 134, 211, 345
Feeds (Left or Right) per revolution of spindle:  0.0078",  0.0069",  0.0063",  0.0057",  0.0055",  0.0052",  0.0048",  0.0044",  0.0042"
Leadscrew: 3/4" diam., 8 Acme threads per inch
Spindle nose: 1.5" diameter, 8 pitch, National Form thread
Spindle nose taper:  bored for No. 3 Morse taper with reducing sleeve to take No. 2 Morse taper
Clearance through spindle: 25/32"
Back gears: 12 pitch, 7/8" wide
Backgear shaft bearings: Oilite bronze
Backgear ratio (approximate): 6 to 1
Spindle gear: 16 pitch, 32 teeth, 7/8" wide
Tailstock ram: 11/8" diameter
Tailstock ram travel: 23/4"
Tailstock Ram Graduations: O to 3" by 1/16ths
Tailstock set-over, forward or back: 3/4"
Cross feed travel: 61/2"
Cross feed screw:  1/2"  Diameter with Acme threads
Feed screw collar graduations:  O to 0.1" by 0,001"
Top slide (tool post) travel:  21/4"
Tool post:  3/8" x  7/8" slot to take 3/8" tool bits or a tool holder for 1/4" tool bits
Tool post swivel:  Graduated 0 to 90 degrees, right and left
Motor Recommended:  1/3 or 1/2 HP, 1725 RPM
Motor mounting: adjustable base-plate
Hole through motor pulley: 5/8" Diameter
Built-in motor control switch: 10 Ampere for single-phase current only - 3-phase switch extra.
Countershaft spindle: roller bearings
V-Belts for complete drive: 1/2" Wide
Motor pulley to countershaft pulley: each 2-step, 2-speed
Drive pulleys: countershaft to headstock: 4-step
Indexing circle on headstock pulley: 60 hole
Standard specification: automatic, reversible power cross and longitudinal feeds.

Supplied with the lathe: