# Re: How Do I Make A Pinion gear for lathe chuck

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Posted by BillS on April 09, 2007 at 13:08:27:

In Reply to: How Do I Make A Pinion gear for lathe chuck posted by Bob Nisbet on April 05, 2007 at 20:23:36:

This can be tricky, but let's take a stab at it.

First is pressure angle. This is going to be difficult without seeing the scroll gear or without a 20 deg plus 14.5 degree gear pitch gage set. I think you will need a gearshop to look at the scroll gear and the assembly if you can't determine the pressure angle.

Let's assume you know the pressure angle. Next we need the tooth count of the scroll gear (large member of the bevel set).

Is the pinion missing or is it there but without teeth?

Is the chuck metric in its measurements? Screw threads, bore dimensions, or anything that might indicate it is metric, hence the gear set might be metric.

Then we need the pitch. If you have a set of gear pitch gages, measure the pitch at the OD of the scroll gear. If not, send me the OD and we'll see if we can approx. the pitch.

Then we need the pitch angle of scroll gear. This is the angle of teeth on an imaginary line approx. half way up the tooth. If you want, measure two angles: Face Angle: angle between the face (or top) of the tooth and the bore.
Root Angle: Angle between the root (bottom) of the tooth and the bore. These angles are going to be larger than 45 Deg.

If the scroll angles are not 90 degrees (or very close to 90), then you will need to get with a gearshop that has a Gleason spur bevel gear machine. This is not something that can be easily generated on a milling machine. Maybe someone can share a similar experience here.

If the scroll angle is 90 degrees (or within 1-2 degrees of 90), indicating a face gear, then you might be able to cut the pinion as a modified spur cylindrical gear with a short face, and you might get a good approx. to the ideal pinion on a milling machine. You'll still need a cutter with an involute profile (again matching the desired pressure angle).

I should be able get an idea of what you're up against once you send the measurements.

You can fax data and sketches to me if you prefer.
1 866 861 5808

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