TAPER PER INCH
To get the correct taper per inch, for the included 3 degrees taper per inch. We will use 1-1/2 degrees,
as the 3 degrees is included angle, or 1-1/2 degrees on both sides. Now look at the taper per inch
chart. In the left column go down to the 1 degree and then across to 30'. This is 1 1/2 degree, and you
will see a figure of 0.02618. This is taper per inch.
Now to set up the lathe for this taper, you will need 2 dial indicators; one will need to be at least a 1-inch
travel. You will need a piece of tool steel the exact length as the carbide and end pieces. So both have
to be the exact length, if not the angle will change. Make sure the tool steel is running true and center
both ends.
It would be wise to heat treat it, and grind it to exact size so there will be no run out. Be sure that is no
taper after grinding. Once this is ground and completed, leave it between the centers. Set the 1 dial
indicator on the carriage, and set tip on the tool steel.
Set the other so it will measure the travel of the carriage. Loosen up the setscrews on the tail stock, and
turn the one in that moves the center towards you. Move it over a bit, reclamp the tail stock, and reset the
center. Now zero both indicators, and move the carriage toward the head stock.
When it has traveled 1 inch, see how many thousands the other indicator reads. When you have set the
tail stock over so it reads .026 in a 1-inch travel, you have it set for 1-1/2 degrees, or 3 degrees included
angle.
Replace the piece of tool steel for the carbide, and then turn on the lathe. Be sure it is in back gear, turn
on the grinder and move it in so it is just touching the carbide at the tail stock end.
DO NOT TRY TO TAKE OFF OVER .005 PER EACH PASS.
The feed should be slow or you will wear out the diamond wheel to fast. When you have ground both
angles, to size, stop and check the O.D. of the work piece. You should leave about .0005 for final
finishing. Now you will have to grind the shank to fit the pull rod. You will grind this to the standard No. 5
taper reamer. No. 5 is the size that you want to use for the 30 calibers, and it will give you a diameter of
.2409 on the small end.
Reset the angle on the tail stock for the correct taper per inch of the taper pin reamer. Grind the shank