Posted by Bob Nisbet on April 16, 2007 at 16:13:58:
In Reply to: Re: How Do I Make A Pinion gear for lathe chuck posted by BillS on April 09, 2007 at 13:08:27:
Bill, I decided to try something before starting.
I made a blank out of a piece of wood. I then drove the blank into the chuck so that it engaged the scroll gear. I then rotated the blank to get an impression of what the pinion should look like. To my surprise, it had 11 teeth.
The reason I did this was that calculating the number of required teeth could not be done by using the circumference, since there were two, one based on the minimum and one based on maximum pinion diameter. So, now I have that settled.
I then went about finding some 4140 steel. Got that. Then I designed the blank and included an integral arbor that would allow me to hold it while milling and would also hold a reference gear that I could use for indexing. I didn't have an 11 tooth gear, but did find a 44, so my indexing will use each 4th tooth to net an 11 tooth pinion.
Then I began designing a jig that would hold the blank at a 15 degree angle. This was fairly easy. I cut some flats on the mill and then orientated to bore a hole that would hold the arbor-blank.
My challenge is the cutter. I can grind a cutter blank to the correct tooth contour but don't have the expertise to flute it so that it would cut. Question: Is there anyplace that loans cutters or possibly someone that could sharpen my contoured cutter blank? Remember this has to be done in a very austere manner. I don't want to invest lots of cash into something that may only be worth $15 to $20.
Plan: Since the tooth depth will go from full depth to nil, I was thinking of doing the cutting in several stages. Stage 1 would be to set the blank arbor at 90 degrees to the cutter and start from the small end, progressing to the major dia. The first finished cut would give me full tooth depth only at the major dia. Then I planned to set the blank arbor at the proper 15 degrees, grind off a small portion of the cutter point, and cut again, beginning at the major dia, allowing me to progressively cut and achieve a uniform top to the teeth while the bottom would have steps. If I did this a few times, I can achieve the end game of a beveled tooth. Since the starting depth of the cutter will be deeper than mating tooth height, the steps at the tooth root will not be a problem.
What do you think of this plan?
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