From: MMEAGHER To: "'7x10minilathe@egroups.com'" <7x10minilathe@egroups.com> Subject: [7x10minilathe] Change Gear Measurements Well, I checked some of the 7x10 change gears on an optical comparator this morning, and here is what I have found: Circular pitch = 0.1245 in Pressure angle = 20° Bore = 0.4735 in Face Width = 0.3070 in Keyway Width = 0.1151 in Keyway Length (above bore) = 0.0563 in I measured the 50-tooth and 60-tooth gears at several points to verify the dimensions. At 100x magnification, the involute profile was, to put it mildly, terrible. No clearly defined lines on the tooth form made it difficult to get a true reading, particularly for the pressure angle. But that is to be expected with a molded gear as opposed to a gear which has been machined. Calculating diametral pitch (Pd) from circular pitch (Pc): Pd = pi/Pc = pi/0.1245 = 25.23 Not a nice even number, so it's probably metric. Determining the module: module = m = 25.4/Pd = 25.4/25.23 = 1.0067 Definitely metric, IMHO. If I were ordering gears from a catalog, here's what I would look for: module = 1.0 pressure angle = 20° bore = 12 mm face width = 8 mm keyway width = 3 mm keyway length (above bore) = 1.4 mm minimum If there is anyone else in this group who also has the ability to measure these characteristics on the change gears, that would be greatly appreciated. That way, what I have measured and reported here can either be verified of thrown out the window. Mike Carrollton, TX (at work)

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