I made two rotary tables from castings that were commercially available but found
that the T-slots called for did not line up with standard that were available. I
have though realised since that possibly it was the intention that Woodruff cutters
should be used as these were available with dimensions that were quite close. However,
I chose to make my own and were very pleased with the results. Having made the cutters
and hardened them and then finding that they worked perfectly was very satisfying.
By so doing I had raised my confidence level regarding hardening cutting tools and
if nothing else it had been a worthwhile exercise.
To minimise material wastage, carry out the turning operations between centres, as
this will avoid a small stub that would be destined for the scrap bin, if held in
the chuck. This would not be ideal even if only mild steel but with silver steel
being more expensive, definitely the way to proceed.
If though your lathe spindle is bored large enough to take the material being used
then you can consider using the chuck. Even so, I still would recommend producing
the cutter between centres as this is the only way of achieving total concentricity
between the cutter head and its shank.
Cut a length of material and face and centre drill each end whilst mounted in the
three-jaw chuck. Use a small centre drill and then only made a very small tapered
portion, as I consider that the pilot portion of the drill may weaken the waist behind
the cutter when hardened.
If a threaded shank cutter is being made it is imperative that the driving dog does
not slip so a small flat should be filed on the head end for the driving dog screw
to bear. This flat will eventually be removed by the action of cutting the teeth.
Now reduce the material to the shank diameter required and produced the thread. Photograph
1. Of course, if you use milling cutters with plain shanks then the thread is not
Next, with the cutter removed, reversed, and between centres, turn the waist, also
the cutter head to the diameter and width required, Photograph 2. You must at least,
skim the outer diameter to ensure that it is concentric with the shank. Commercially
available cutters are made slightly oversize in terms of diameter to allow for sharpening
a number of times whilst still producing a slot large enough to take the width of
the tee nut.
Not now having the photographs used in the original article those on these pages
have been scanned from the magazine and are now of poor quality. Because of this
there are no large size pictures provided.