Some parts resembling a casting were obtained with parallel pieces that were machined, assembled and bolted together to the required shape and dimension before being glued into a single piece and finished with metal epoxy, as can be seen in the tailstock and 3-arm fixed steady
For the milling unit head I could not find a suitable second hand or spare part, so its components were designed and machined - just for aesthetic reasons - as a smaller version of the headstock with both having their spindle running in conical roller bearings. Driven by its own small motor, the swivelling vertical is fitted with a 3-jaw chuck from an Emco Unimat 3 lathe and it's final vertical setting made with the help of a micrometer barrel.
For hand feeding of the carriage a very fine-pitch leadscrew is used, this being supported on a pair of home-made brackets and turned with a 'balanced' handle. The assembly allowing a very slow and steady feed to be applied that makes accurate work very much easier - as well as giving a good surface finish.
A threading system was added to the lathe by using a precision tempered screw from a 50 mm micrometer as a "master", to form a kind of "chase screwcutting" unit. The principal metric and imperial pitches that interest me ( 0,5, 0,75 and 1 mm or the RMS microscope standard) are obtained by changing the proper wheels. In this mode, the micrometer screw simply translates according to the chuck rotation, driving the carriage via the brass rod through a Cardan shaft. To engage the mechanism, the carriage has to be disengaged from the hand-feed screw at its right-hand end and, while this might seem complicated, it works well.
The modified cross slide and the collets are from a small Mentor lathe, an Italian machine that was on the market many years ago. The rectified and tempered inner ring of a ball bearing is used to hold the collets, it being concentric to a brass-flanged element secured in the chuck with centering checked by a dial indicator.
Taken from a big computer tape-drive unit of the 1970s, the powerful 24V DC motor is carried on two steel bars at the back of the headstock, so allowing the drive to be used when the headstock is swivelled. Speed-reduction gears for screwing are also provided and I feed the motor with two 12V car batteries, so half or full speeds can be selected in forward or reverse, by just operating the multiple-switch selector at the left. Recently, a power supply has been fitted of the type that gives infinitely-variable speed control.
The Rohm 4-jaw self-centring chuck is 140 mm in diameter and its central hole 40 mm, the same as the generously-sized home through the headstock spindle. Hence, most usefully, parts up to that diameter can than be worked regardless of their length. A 100 mm, 3-jaw chuck from the former USSR can also be mounted on the same (cast iron) backplate.
To allow for more working space, and for a closer positioning as well, the tailstock can be slid axially on its mount and fixed in position by two bolts. The spindle is a No.2 Morse taper that, as it runs in cast-iron that contains free graphite, is not hardened but with proper care and lubrication should last well and run smoothly.
60 holes for an indexing circle were added only recently; a precision master was obtained and the holes copied onto an aluminum ring that was then precisely glued to the pulley. The brass stop is visible at the left, with its wooden handle, near to the chase screwcutting unit.
The lathe (thanks to the DC motor) is very quiet and, due to its compact dimensions and modular construction, has proved to be the ideal precision machine for my opto-- mechanical components.
I hope the images tell about my long-time passion and love for this machine and for lathe working in general. Thank you again so much for your kind attention.
With Best Regards
Pierino Delv˛, Italy.