inch. Slow down the mill to about 100 to 150 rpm, as the tool steel tends to get hot.
Measure the drill rod on the flute end; in this case, it has not been turned so it is .312. Bring down the
cutter on the milling head while it is running and just touch the drill rod and stop.
Half of that size is .156; we do not want to cuts the flutes half way as the reamer would probably chatter.
The first flute should be cut .002 in front of center, the next should be cut .004 ahead of center, and the
third should be cut .006 ahead of center.
After the third flute is cut, the fourth should start back at .002, then .004 and the finish cut is .006 ahead
of center.
THE FLUTE THICKNESS
The flutes wall should have a thickness of about .060 to .080. This would be thinner on the smaller
reamers and thicker on the larger reamers. You do not want to make flute walls to thin as they tend to
break if the reamer gets to dull, and when this happens the barrel will more than likely be ruined.
DEPTH OF FLUTES
You want to use an ample supply of coolant when cutting the flutes. Depending on the reamer size you
will go in about 3/4 of the depth on the first cut and then finished to the correct depth the second pass.
Watch for bowing as you cut the flutes. If it is bowing, you are either taking to big a cut, the cutter is dull,