The VersaMil (which is in current production) is an interesting accessory designed to be both attached to a lathe, or almost any other machine tool, to increase its versatility - and also as a stand-alone unit which can, for example, be mounted onto a compound slide rest and then attached to very large components and machining operations carried out directly on the workpiece.
The device started life in 1952, built by the Dumore Grinders in Wisconsin, and quickly found a home in the US Military for use both in ships and maintenance trucks and trailers - the VersaMil set is still installed in every small ship and submarine in the US Navy. Dumore sold their tool line to the Phillips Corporation in 1978 and the Versamil part of the business was acquired by the present owners in 1999.
The basic design is simple but ingenious; a hardened and ground spindle with a No. 2 Morse taper is contained within a head holding an oil-bath right-angle drive. The head is arranged to be driven, by a precision feed-screw, up and down four hardened and ground columns arranged in a square pattern and sandwiched between a base plate and top cap. The 1725 rpm drive motor is mounted on a platform at the rear and drives to the gearbox via a single V belt; the mounting is designed so that should motor get in the way of a job on one side it can be removed and replaced on the other.
Although the unit is perfectly usable on its own, a range of attachments is marketed to extend its versatility; these include internal, external and deep-hole grinding units, a high-speed milling head, a shaper attachment, a "universal" head, two sizes of feed table to adapt the unit for self-contained operation and a dividing head designed specifically to attach to a lathe and allow the accurate indexing of the spindle when machining gears or drilling holes in a flange.
If any reader has photographs of their versa-mill in action, the author would be pleased to hear from you.