Pratt & Whitney 7" x 16" Precision Bench Lathe
Prior to World War 2, this particular pattern of lathe was greatly favoured by professional tool, watch, clock and instrument makers for their critically-dimensioned work.
The spindle was made from tool steel, hardened and ground and running in a plain bearings of the same material with a double taper at the chuck end and a plain cylindrical bearing at the other. In order to achieve the necessary accuracy and long life associated with type of set-up in 1899 the American Machinist reported that P & W had built a set of specialised grinding machines that employed diamond laps to finish both the bearings and the spindles. As an interesting aside (although other companies had also developed successful models) P & W were also responsible for the design, again in 1899, of what was to become almost the standard machine for the manufacture of bicycle ball bearing cups and cones; it was capable of running up to 28,500 rpm working to within .00025".
Equipped with a two-speed countershaft unit and a 3/4 H.P. motor the lathe had 6 spindle speeds from 144 to 1208 rpm. The left-hand face of the headstock cone pulley was supplied with a ring of 48 indexing holes with the option of a 60 hole ring to special order. Both headstock and tailstock tapers were listed as No. 4 Jarno, but examples have been found with both 2 Morse Taper and 3C (or 3AT) collet fittings in the headstock - and tailstocks with a No. 1 Morse Taper.
On other pages are illustrations of the many special accessories made for this beautiful little lathe including: screwcutting, grinding, milling,  power filing,  special tailstocks, a "Complete Workshop" Unit, a Double Lathe Mounting and a Geared Countershaft Drive Unit.

If any reader has a good quality picture of a late-model Pratt & Whitney lathe the author would be delighted to hear from you.
Please email:
Tony@lathes.co.uk