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Harold Hall

Workshop Projects

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Using a gloved hand I applied force directly to the cutter with a much greater result than that above. This made me realise that the strength of the spindle mount was of much greater significance. Whilst not totally a question of strength it is obvious that if the spindle mount deflects it will be greater the further the spindle is from the column so this also would have a bearing on the outcome.

 

Having made changes to all three items simultaneously the improvement was considerable but in retrospect I wish that I had only changed the thickness (6 mm to 10 mm) of the spindle mount. Having done that it would have then been easy to just drill 4 more holes to move the spindle nearer the column if considered worthwhile. Doing this as a stage two modification. With regard to the column height I think that my reduction of 75 mm probably made no worthwhile improvement.

 

For consistency with my final assembly and the photographs published I have, with the exception of a few very minor changes, kept the drawings in line with the prototype, stage two that is. Anyone deciding to make the milling head may like to consider the following additional changes that I offer in the light of experience.

 

A. Make the spindle mount say 50 mm longer and provide two sets of holes for mounting the spindle. This would of course need two belt lengths but the extended reach may be useful at times, even if this limited the cut that could be taken at this position. Do not under any circumstances be tempted to use thinner material, well, 3/8" (9.532 mm) may be OK but if you go imperial then 7/16" would be the much better way to go.

 

B. The spindle mount could be stiffened by increasing the length of the spindle mounting brackets (C4) to run virtually the whole length of the spindle mount,  giving it the strength of a channel rather than just a flat plate.

 

C. Make the pulley on the spindle out of steel rather than aluminium as the increased inertia would help to stabilise the speed when the four cutting edges on an end mill cut intermittently.

 

D. Add a larger steel flywheel to the pulley to increase the benefit of added inertia. This is frequently done by owners of even large Mill/Drills by attaching a steel flywheel to the stepped pulley.