Hi Paul,

          Well, I finally got the sun gear tapped out for the set screws. It
was not easy, but doable. I blunted three taps and broke one, but was able
to get broken piece out. The problem was that fact that the sun gear has
been nitrided. The outer nitriding was effectively removed when I ground off
the teeth, the inner hardening was bitch. After the holes were drilled and
opened up to 6.8mm for tapping 8x1.25mm for the set screws, I got in with a
ball ended diamond bit and ground back the hardening around the hole, this
made it easier on the taps. It took a while but came out OK. All ready now
to measure up and make the pattern for the housing.

                             Chris Hoskins NZ

Good work Chris.

It may be possible to normalize just the back half
of the sun gear. I have never done it. Those new hand held laser dot
temperature sensor guns could monitor the temperature of the sun gear
just near the teeth to keep them cool enough to be not affected.
The heat would be applied at the back part.

The sun gear would still be plenty strong enough.

Might make it easier to tap. I have never heard of it done.

I know Mazda induction hardens just the corners of the rotor.
Not the whole rotor.

This is bleeding edge tech :-)

Paul Lamar

I have heated round spots to take out the hardening before with no adverse effects. If a larger screen hole is to be drilled and tapped the cutting head works. Otherwise a welding tip does the trick.

Dale Davies


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