Next, the method of driving the machine had to be decided and I chose for it to be
mounted on the lathe's bed, taking its drive from the lathe itself using a belt and
pulley arrangement. The main advantage of this being that a range of low speeds was
available making it easy to experiment to find the best value for the work in hand.
I could have chosen to line up the input spindle with the lathes spindle and connect
them using a flexible coupling but felt that this would prevent me being able to
choose the input drive position as would be best for the design I eventually established.
With the design principles established I could perhaps revert to a direct drive if
it was found beneficial.
Another benefit of the belt drive arrangement would be that it could be driven from
an electric motor should the user wish. This I thought at the time would need a motor
with gear box as getting the reduction using just a single belt would be impractical
due to the ratio required. However, as I said above, the machine worked at speeds
higher than I had anticipate but even so a large reduction ratio would still be required,
only available with a single belt if a large pulley were acceptable on the filing
The basic design
With the design criteria established this was translated into a working design but
being complex it is difficult to get all the detail into a single assembly drawing
and I have therefore produced a basic assembly drawing plus additional sub assembly
drawings for each specific section of the machine. These are listed on the basic
Before I proceed with the sub assemblies some further background information is appropriate.
Where I call for holes to be counter bored for socket head cap screws I have not
quoted a diameter or depth. My reasoning for this is that readers counterbores are
likely to vary in size as I can find no quoted standard, the depth though should
be just larger than the thread diameter, typically 6.2mm for an M6 thread.
I have though quoted a clearance size hole that lines up with the pin diameter on
the counterbores that I have but as these may also vary the reader should check with
those he or she has just in case they are different.
I will be detailing the manufacturing method, where required, a part at a time but
the reader making the machine will find it very beneficial to organise manufacture
so that similar operations are carried out together. Typically, Photograph 2 shows
that I marked out all the flat components at the same time, having similarly cut
and machined them all to size previously. I then drilled them using one drill size
at a time to avoid the need to keep changing the drill in the drilling machine, similarly,
taps in my tapping stand.
Except were hole's need some special consideration I will not make any reference
to them being made, also cutting materials to size. To reduce the large amount of
offcuts of steel that I have, I have machined many of the smaller parts from larger
cross sections rather than purchase material to size. The Photographs may therefore
show machining marks where a normal drawn bar finish would be expected.
The Main Frame assembly starts on the next page.