Lynn, what are some of the tricks for closing up
   rotor slots to compensate for wear?

   Paul Lamar

I have added material to rotors in the form of brazing holes shut at the
base of balancing holes. Also building up corner seal edges that have
been broken off in mishandling or shipping accidents. Also for filling
in dents.

I made a mandrel for inserting into corner seal holes so I could heat up
imperfect corner seal holes and form it around the mandrel with small
hammer blows.

For poor apex seal slots I used hammer blows on a pin punch with a 3/8"
flat tip. Go at it in rows, back and forth. Stay away from the groove
edges. When the groove starts to close up Install an old steel apex seal
and a .003" feeler gage covered in Nickel anti-seize. Carry on until the
seal is trapped in the groove. Be very careful around the corner seal
holes. Drive out the seal with a pin punch. Finnish to dead flat sides
with a small file run flat against each side with old feeler gages piled
up against the file to fill the groove and give just a hint of pressure.
Oiled liberally during the file operation. It goes fast. Measure often.

I have often thought of a repair method to save old rotors. Perhaps a
groove of 3/8" by 3/8" to take out the stock groove, and a like sized
piece of mild or even a heat treatable steel Furnace brazed in place.
Then machine new stock grooves. You could keep going until the side seal
grooves get too big. Then even over sized side seals?

I have also TIG welded dents and holes with no failures. Use mild steel
filler rod.

Having the unwashed doing this for aircraft use might not be a great
idea. But anyone who TIGs once a week or likes to braze projects could
pick it up quickly. Good for saving blown up motors for street cars.

You can also lap irons against each other to a great finish. Even irons
that have been hot spotted by a bearing death can be saved. If the hot
spot is high you can hit it with a DA and dry 80 grit before lapping.

Lap a bit and check for high spots then grind them a bit and lap some
more. An offset bearing in a slow turning drill press or a mill just
makes it too easy not to do. Just run the bearing against the inside of
the center hole. A pan under the work saves the lapping compound to be
poured on over and over. Or, painted on with a brush. Wash the irons at
the car wash several times. I used valve grinding compound. Since you
are doing two irons at once, it goes quickly.

Lynn E. Hanover