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created 28/07/15 - updated 29/07/15

Shop-made Micro-Precision Grinder and Thickness Sander

Grinding certainly is an operation that does not contribute to the longevity of a lathe. I therefore avoided this as far as possible. On the other hand, I always missed a maschine with which one can grind sub-millimetre thick materials and small, short workpieces. In addition my small PROXXON table saw, notwithstanding some improvements, is not really suitable for sawing on parts that small. A watchmakers lathe is a good basis for the development of a suitable machine. A short while ago, I was able to obtain a ball-bearing headstock at a good price, which will form the heart of the machine. In the past some manufacturers of small bench lathes actually offered grinding and sawing machines on the basis of their headstocks, but this is long ago.
There are, of course, two main types of watchmakers lathes, those with the round, so-called D-bed and those with the prismatic WW-bed. The WW-bed would be more solid and heavier, but the D-bed gives more geometric flexibility for the envisaged attachments. In addition, D-bed parts are easier to come by in Europe than WW-compatible parts. Over the years I had already collected a number of useful parts inter alia with a view to construct such machine.
I first made an adjustable motor bracket from a couple of recycled parts. This bracket mounts to the lathe bed, so that motor and grinding machine form a self-contained unit. There are feet to which such lathes can be mounted and that allow their orientation in various direction, which will come handy. A common practice amoung the watchmakers of old was to hold the lathe in the bench-vice, which is even better, when the vice can be rotated. In this way the workplace is kept free.

Boley grinding
maschine on the basis of
a lathe headstock

Micro-grinder assembly with motor bracket
Mounted in
a bench vice

In use with an
original watchmakers
lathe saw table

Small shop-made
filing table
with fixed
90° fence

Filing table
with adjustable fence
So-called 'utility' set
for grinding
and sawing
made by Waltham

Utility set in use

Grinding Tables
All these attachments are held in the T-rest holder of the lathe, which allows to position e.g. the saw table in a particular height and distance from the grinding disc.
Later I will also make an inclining table that allows to grind composite angles onto parts. Of course, one table may have been sufficient, but I found that fixed angles reduce the tool mounting times and are more solid.

Micro-grinding rest for
generating mitres

Speciality holder for
very small parts, such as wires
parts of the
thickness sander
in use

Micro-Thickness sander
Staying with the idea of providing tools for working on really small and delicate parts, I also designed a micro-thickness sander attachment. The brief was that parts with a maximum width of 10 mm and minimal thickness of 0.1 mm should be able to be worked on.
The main body was fashioned from a block of aluminium.  I prefer actually to use steel for machine parts, but choose aluminium here in order to speed up the machining process. The main body houses two small threaded spindles that allow to raise and lower the sanding table. A variety of zylindrical tools can used, such as expanding mandrels for sanding paper tubes and corundum, rubber-bound, or diamond grinding bits. The attachment could also be used like a planer by employing small milling bits.
The main body was designed to be clamped to the lathe bed in the same way as the T-rest holders. In my spare-parts box I found a suitable tightening bolt and the associated hardware.
The spindles were threaded 6 mm x 0.5 mm on the lathe. This thread provides for a very sensitive height adjustment and was possible, as I had by chance a matching tap for the thumb-screws. The knurling on them was not cut with knurling wheels, but milled in using a 60° cutter and the dividing head in the milling machines. This is kind to the lathe.
The sanding table was fashioned from a piece of flat steel for greater wear-resistance. In order to prevent the lateral movement of the parts being sanded, I milled into the surface a schallow channel. The sides of the channel were undercut using a dove-tail cutter in order to keep the workpieces down on the table. I have provided the table with two M2-threaded holes that will allow to attach a fence or a down-holder. With this fence the thickness sander table can also be used as a micro-router e.g. for shaping longer strips of wood or plastic.
Considering the smallness of the parts to be worked and the consequently small amounts of dust I have not foreseen any dust control.

Bench mounting

To be continued ...

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