TEMPERING THE REAMERS
Turn off the furnace, close it up, and let it cool down to 350 degrees. We will then put the hardened
reamers into the furnace to draw the hardness, and remove internal stress. Leave the blanks in the
furnace until the furnace reaches 100 degrees, or better yet leave them in over night. The reamers will
be about 61 to 62 Rc in Hardness.
GRINDING THE REAMER
The reamer blanks are now ready to be ground to size. We will grind the flutes first. Set up the tool post
grinder on the lathe. Get everything lined up, put the small lathe dog on the reamer blank, on the pilot
end, and grind the flutes end first.
Clean out the centers on the blank, and set between the centers. Cover the bed of the lathe up to keep
the grinding dust off the ways. Set the lathe in back gear drives; turn on the lathe so it will run in reverse.
Then, turn on the tool post grinder, and starting at the tail stock end, just touch the grinder to the blank.
Move the grinder past the blank, then set it in about .005, and engage the feed. It will not clean up
completely, but it will start to clean up any part that is warped. Make one pass and if it is cleaned up
enough so you can get a measurement, check the size of both ends. There should be about .002 taper
from the pilot end to the end of the blank.
The tail stock end should be the smaller end. This is very important to have or you will get a rough bore.
We are grinding the rough reamer first, so you want to end up with the pilot end of the reamer .298.
When you get this size, remove the reamer blank from the lathe. While the lathe is set for the .002 taper,
we will do the other blank. It is done the same way except that the final size should be .3005. We will
allow the .0005 to hone in to size.
Now that the second reamer blank is ground, we will grind the leading edge taper. Set the compound on
the lathe to 1-1/2 degrees. This will be your cutting edge next to the pilot. Turn the lathe on in reverse
and the grinder and start feeding the wheel by hand on the cutting edge of the reamer. Grind this angle
down a few thousands into the recess. Do the other reamer also. It will take several passes to do this.
Take light passes not much over .005 so you will get a good finish.
GRINDING THE PILOT
When you have completed this on both reamers, take the blank from the lathe. Turn it around, put the
dog on the other end, and put it back in the lathe. Before doing this, make sure you bring the tail stock
back to center.
Square the grinding wheel up, and where the recess is grind this down to about .040 smaller than the
pull rod, which will be .250. When the recesses are completed, it is time to grind the pilots to correct
size. The roughing reamer which id .298 diameter, the pilot will be ground to .290.