Harold Hall

The Drive

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 machine itself.


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 drawing.


Before I proceed with the sub assemblies some further background information is appropriate.


Workshop Projects

Brief notes.

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.


All small pictures can be clicked on to provide a larger view