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on request
For some time now I have been regularly sharpening end mills on the Stent Tool Cutter Grinder but when it came to lathe tools I revert to free hand grinding on a bench grinder. What is needed is an adjustable tool rest to allow the variety of compound angles to be set and the lathe tool be guided either by hand or fixed using the Stent Grinder. Whilst this seems like a simple task to design the problem is fitting the various hinges and locking levers in the space available to allow all the angles possibly required. In the case of the Stent there was limited vertical room for the rest so all the tilting and rotating mechanism would have to be fairly compact, preferably using a single locking handle.
I had just finished making
some ball handles for locking the mill gibs and the thought occurred that maybe
a ball type arrangement could be used to give the necessary tilting and
rotational movement in a tool rest. Making the ball would be no problem but
making an exact ball recess is another matter! As a challenge and not expecting
much success I decided to experiment and make a 1" diameter ball from mild
steel and then try and make the matching half ball recess in a 2" diameter
x 9/16" thick mild steel bar. I used the Ball Turning Jig I had made some
years ago and after a 5/32" diameter pilot hole was drilled the jig
generated the ball hemisphere. By using marking blue on the finished ball and
testing it for fit so that marking blue transferred evenly the job was soon
finished. Rather pleased that all seemed well I then made the other half. The
two halves plus the ball were now assembled and clamped with a small amount of
grinding paste to bed in the ball. After a few minutes manipulation of the ball
stem the whole lot was taken apart and I was very pleasantly surprised to see a
perfect match with 100% witness marks! The grinding paste was cleaned off and
this formed the major part of the tilting and rotation mechanism. The addition
of ancillary bits, the table and locking base unit plus a setting gauge and
tool clamps and the job was finished.
Whilst this is probably not the only method or the best for a tool rest design it worked out very well. The method proved the accuracy of the ball turning jig being capable of developing accurate balls and matching hemispheres plus a great deal of personal satisfaction completing a job which I did not think possible using this method.
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