The back gears are the two gears on in this case the back of the headstock. The Direct Drive pin, which is located on the right-hand face of the larger spindle gear (commonly referred to as the Bull Gear) must be pushed in for Direct Drive. This locks the spindle cone pulley to the bull gear which is in turn keyed to the spindle and the spindle turns at the same speed as the cone pulley. With the pin pulled out, and the two back gears engaged with the two spindle gears, the pulley turns at the same speed as it did in direct drive but the spindle turns at about 1/6th of the speed of the pulley. How fast the cone pulley turns is selected by which of the four grooves that the spindle belt is in and which of the two motor and countershaft pulley grooves the motor belt is in. So that is how you get 8 different spindle speeds. The other 8 speeds are accessed by engaging Back Gear. Each MOLO (Manual Of Lathe Operation) has a speed chart plus lathe models with QCGB have a chart on the headstock.
Over the decades that the Atlas and Craftsman lathes were in production, Atlas supplied three different types of parts lists. Until 1945, there was a section view drawing of the machine or a photograph of all of the individual parts spread out on a table, and a list of part numbers. Beginning in 1945, Atlas changed to the "Exploded View" or "Illustrated" parts list.
Unfortunately, they did not go back and do an Illustrated version of the parts lists for any of the older machines. So the Illustrated parts lists done by Atlas begin with the 10F, 101.07403, 101.21400, M1B/MFB/MHB, and S7B. And everything newer.
Mostly by the technique of cut/copy/edit and paste, I have created illustrated parts lists on the 101.07383 and just finished one on the 101.07402. PDF's of these plus of most of the parts or owners manuals produced since 1945 are available for download in Downloads (CAUTION: Access to Downloads requires that the member have Donor status [any level]). Some of these have been cleaned up. Also in Downloads are a few PDF scans of Atlas and Craftsman catalogs, the Atlas MOLO, and quite a few cleaned up scans of the original Atlas parts drawings. The drawings are mostly limited to those parts that Clausing no longer stocks.
Downloads also has mostly PDF scans of manuals and parts lists for many other makes/brands of machines. Instructions for using Downloads will be found in the Sticky area at the top of this forum (only) and in the general instructions for using this Site at the top of the list of Fora under the Forums tab in the site's main toolbar.
