I have read with interest your notes from time to time in HOROLOGY on the making and use of fly cutters used in watch wheel cutting.
For a number of years I have used a type of fly or wheel cutter that has proven very satisfactory and during a recent chat with Major Paul M. Chamberlain he told me that others might be interested and suggested that I submit the idea for your approval.
I first cut a steel blank about 1/8" in thickness from a round piece of drill rod 5/8" diameter, using a cutting off tool in slide rest so as to leave the sides true and smooth.
Next drill and ream a hole through the blank the exact diameter of the wheel cutter arbor which you intend to use, place the round blank on the arbor and tighten the collars down hard, next put arbor with blank in lathe and form the outside with graver or tool in slide rest, making the disc or blank exact shape of wheel you wish to cut. In the case of a hardened steel winding gear I have used the old wheel as a form tool in the final finishing of the cutter, this is done, by clamping the old wheel with a small toolmaker's clamp on to a piece of steel that will fit in the tool post of your slide rest then run the old wheel up on the blank letting it scrape off any surplus material.
After the cutter is formed, remove same from arbor and enlarge hole .008 to .010 over arbor diameter. A portion of the cutter is then ground away making the cutting edge (see sketch for detail).
The cutter is then hardened and tempered and reground on the cutting edge mentioned in previous paragraph, same is now ready for use and is replaced on the arbor and while collars are tightened the cutter is held off center as far as it will go caused by looseness on arbor towards the cutting edge. This gives the cutter its proper clearance or backing off, on account of this type of construction the slight drag on back of cutter gives a nice burnishing action which really makes a smoother job than regular type relieved cutter. The cutter can be ground indefinitely, always replacing same on arbor so that cutting edge will be on high side.