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The Delv˛ Home-made Lathe

The builder writes:
Dear Tony,
I'm fond of photography and, as an amateur astronomer, I love making most of the equipment needed. Consequently, I also love lathes - so I'm frequently visiting your useful and inspiring website. I now write about my own home-built lathe and hope this will be of some interest to you and others. All the images were taken recently, following a thorough cleaning.
Looking for a lathe, I found that commercially available ones were either unsuited to my needs, or too expensive, so I turned to a do-it-yourself project. Over many years I built my precision lathe by collecting spare parts, single components and some custom-made items. It started more than 30 years ago with the finding of a transverse slide from an old, dismantled lathe. This piece appeared ideal as it offered a very stable base and a graduated plane for the headstock and precision slides. The length of the part was not an issue as my main need was to make small items such as adapter rings for the photographic instruments and telescopes that are my pastime. Now retired, I once worked in the field of Technical Optics.
During the long time through which the initial project evolved  - the idea of building a small but precise and versatile machine - much invaluable assistance was given by many friends who contributed important suggestions, together with the careful machining of the most essential and critical parts.
At first, the inner Ts in the base casting were milled to provide a guide for the main carriage and a solid base was also added at the back to hold a column on which to mount a milling or drilling head. Plain surfaces to hold the main screw supports were also machined along the front face.
Most of the components derive from disassembled instrumentation, machine shop discarded pieces that I could modify and adapt according to my needs - and long walks at the flea markets. I was told the headstock was the discarded part of an experimental glass lathe; other parts, like the tailstock, were of my own design. Some other lucky finds can be seen in the images: the main handle for example is a Schaublin piece. Precision slides from various machinery were adapted according to their intended use. At first, the components and assembly of the lathe were both quite basic, but the essential parts now allowed it to work - and so, occasionally, turn its own simpler pieces.
Continued below:

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.

The lathe with its swivel-head milling attachment in place

The headstock can be swivelled for special jobs

The screwcutting toothed-belt pulleys in place

The components for chase screwcutting

The Delv˛ lathe with its fixed steady in position

The casting for the bed with, at the back, a heavy bracket to hold the milling and drilling unit

The carriage T-slotted assembly with a bracket to hold the Cardan-shaft drive on its left-hand side

The very fine-pitch carriage feedscrew and its custom-made support brackets

Mentor compound slide assembly with a home-made 4-way toolpost

Headstock with a pair of steel bars to support the drive motor

Collets and custom-made accessories

Fabricated tailstock

Tailstock components

DC motor and speed-reduction gearing

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The Delvo Home-made Lathe