That's basically correct. Instructions for adjusting the Timken bearings (including the warm-up period before doing so) are given in all of the Atlas MOLO's (Manual Of Lathe Operation). They are on pages 12 and 13 in all versions showing Copyright 1937 on the Copyright page and on pages 9 and 10 on versions printed in 1954 through 1988. All of the instructions begin with the 30 minute run to warm up the spindle and bearings.. Not mentioned is that if possible, the zero end float position should be determined with a dial indicator set up to measure spindle axial movement. Basically, after the warm up, which should be done with the tumbler or gear box in the neutral or OFF position (there is no need to also warm up the change gears or QCGB), the threaded collar is tightened an additional amount equal to two teeth on the 32T spindle gear..
In the later MOLO's printed in 1960 and later the instructions are repeated on pages 14 and 15 as part of the headstock re-assembly instructions.
Atlas also produced some headstock technical bulletins in the 1960's and 1970's that give essentially the same instructions.
All of the instructions give essentially the same steps - run the headstock in neutral for about half an hour to warm it up, and then preload the Timken bearings by tightening the threaded collar on the left end of the spindle to the zero end-float position and then further tightening by the amount of two teeth on the 32T spindle output gear. This applies to all Timken bearing equipped headstocks on 6", 10" and 12" Atlas and Atlas-Craftsman lathes.
Similar instructions are given in the MOLO for babbit bearing headstocks. Although not actually mentioned, the Babbit bearing instructions also generally apply to the sleeve (bronze) bearing 6" sold by Sears as their model 101.07301 up until mid-1957.
