The "Rigidmil" dates back to 1917 when Charlie "CB" DeVlieg was employed as a works manager at the machine-tool builders Kearney & Trecker. His experience there leading him to design a novel bed-type milling machine and when, in the mid 1920's he left K&T, he offered his design to the Sundstrand Machine Tool Co.. Liking the idea, Sundstrand gave him a job and put into production the "Rigidmil" - its very name, of course, indicating its particular appeal. Of course, DeVlieg did go on to considerable success with his own commonly and millers, that in many cases, followed the layout of a Rigidmil.
Eventually to be built as the Models No.00, No.0, No.1, 3-A, 3-C, No.4, Model 33 Fluid Screw, C-Type, and in Vertical, Duplex and Triplex types, the No.0 was intended for production work. It could be had as a simple, hand-operated model or when hydraulically driven, equipped for automatic cycle work of the simpler kind. For the hydraulic model, a choice of two table sizes was offered, these having working surfaces of 8" x 34" and 8" x 46". The smaller table had a longitudinal travel of 12" and the larger 18". The hand-feed model was limited to just one table, this having a working surface of 8" x 30" and a longitudinal travel of 14". All tables had just one 11/16" wide central T-slot. Under hydraulic control, the table's feed rate could be infinitely adjusted between 1/2" to 28" per minute with a rapid feed of 325" per minute. Unusually for a machine tool company, all the hydraulic equipment was manufactured by Sundstrand themselves, the firm also running a Hydraulic equipment division.
Like most millers designed to be as rigid as possible, the No.0 Rigidmil had a non-elevating table, vertical feeds being by the cutter-arbor holding overarm being arranged to move up and down through a range of 10.5" under the control of a handwheel.
All versions were fitted with the same 1.h.p., 3-phase, 3600 r.p.m. main-drive motor. Instead of an expensive, built-in gearbox with the necessary selectors and speed-change handles, the Rigidmil made do with hand-installed, pick-off gears, these being arranged in pairs on fixed-centre studs. The maker's offered two speed ranges, 25 to 1200 r.p.m. and 50 to 2400 r.p.m., the appropriate set of gears being supplied with each to give a total of 16 different speeds. In case a particular speed within the range offered was not to a customer's requirements, extra gears could be supplied to meet that need. While pick-off gears need time for the operator to select and fit, as this was a production machine intended for long runs, the disadvantage over a much more expensive, quick-to-operate general-purpose miller was marginal.
Of the same general arrangement as the No.0, the No.00 Rigidmil was intended for the production of small parts for such items as locks, typewrites, mechanical calculators and guns, etc. Like the No.0, the No.00 could be had as either a manual or hydraulically-controlled model, the latter with an automatic table cycle facility that allowed one operator to attend to several machines. A single size of table was offered, 7.5" x 25", with two 9/16" T-slots spaced 2.25" apart. While the standard travel was just 8", as a special order this could be increased to 12". The infinitely-variable table travel ran from 1/2" to 37" per minute with a rapid facility set at 400" per minute.
Spindle speeds were set using pick-off gears, the speed range "A" varying from 57 to 2416 r.p.m. and the range "B" from 85 to 2814 r.p.m. with, as on the No.0 model, extra gears available to produce any speed required by the customer.
The full specification of the Sundstrand No.00, the No.0 and No.1  Rigidmils and their various features can be found below and on the following page