The following is from Mert Baker and is related to a discussion on the 9x20Lathe site in Yahoo Groups. 
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 I assume you have a 9x20.  This will work on any lathe with a #2 MT TS ram.

What I will describe is how to make one just like the one I bought.

You will need a 5" long piece of easy to machine steel bar 1.5" in dia. You will need to know how to turn a #2MT, and have your lathe set up so you can do this.  I have instructions for this, too, if you need 'em.
  1.  Chuck the blank piece in the lathe carefully, and face & C-drill the   end.
  2.  Turn the end in the TS to 7/8" dia. for 1/2.
  3.  Set your compound to 45°, and chamfer the end for 1/16" or so, and then turn the shoulder to a cone.  (This last is merely cosmetic)
  4.  Drill the end to a depth of 1-1/4", mine is 7/16" to fit most of the reamers I use, and for smaller ones I use split bushings.  Suit yourself.
  5.  Reverse it in the chuck, holding it on the small dia., and face & C-drill the end.
  6.  Make a truing cut the full length, just enough to clean up any wobble effect.
  7. Measure out 1-3/16" along the full dia. from the HS end, and cut a shallow groove.
  8. Turn to .710 Dia. from the TS end up to the groove.  Face the shoulder.
  9.  Cut a shallow groove (just a scratch) in the face 1/4" in form the edge.
  10.  Turn a notch, 1/4" wide, right next to the shoulder.  The bottom of the notch wants to be finished with a round nose toolbit so as to leave radii in the corners.  You want to leave the dia of the piece a little over 1/2" in the bottom of the notch.  Cone the side of the notch away from the HS at 45° or so.  This notch is for clearance for the heads of screws you will be installing later on.
  11.  Now turn a #2MT on the shank.  The shank is too long for a 7x machine, & maybe for a 9x, be very careful in the final stages of the finishing cuts, as a few thou too small, and you have to start over.  A very little off the dia, makes for a big difference in how far the taper will go into the ram socket.  You have been alerted.
  12.  Taper finished & checked for size, remove from the lathe, first making a c-punch mark nest to the #1 chuck jaw, and drill 2 holes, 7/8" deep, with a #21 drill.  These are parallel with the axis of the part you are making, and start in that groove you cut in the shoulder 1/4" in from the edge.  They should be 180° apart.
  13.  Chuck it back in the lathe, with the mark next to the #1 jaw, & the taper end supported in the TS.  Start parting off.  The parting toolbit should be in the center of the large dia.  When you have cut down to 5/8" dia or so, remove the TS support & finish parting, either with the toolbit or a hacksaw.  Carefully face the two parted surfaces. They want to be nice & smooth.  You can do this whole cut with a saw, if you can cut it at 90° true.
  14.  Notice that the 2 #21 holes in the small piece are not very deep.  Deepen 'em to 3/8" & tap 10-32.  Drill out the ones in the large piece with a 1/4" clearance drill.  Drill & tap the radial hole for the 1/4-20 setscrew to hold the reamer shank in the short piece, and assemble with 2 10-32x3/4" button head Allen screws. NOTE: They are not tightened; the 2 pieces are supposed to be free to slide (or float!).  Some grease in there will help.
  Mert