Author Topic: Gear tooth generator program for Don  (Read 1020 times)

Offline gbritnell

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Gear tooth generator program for Don
« on: March 20, 2019, 11:24:48 PM »
Many years ago I taught Patternmaking apprenticeship classes. One of the classes was mechanical drawing. You know boards, triangles, compasses and pencils. The teaching book, which seemed to get updated every couple of years was Technical Drawing 8th Edition. In the section on gearing there was a chart (attached) labeled Wellman's Involute Odontograph.  By doing the layout and using the supplied factors one could develop an involute tooth form. Now where this was derived from or what the accuracy is I can't say, I just know that I have been using it for many years to machine my tooth form cutters.
When I posted the information about making helical gears in my thread about the Maudslay Marine Engine Don had asked a question about how I developed my gear tooth cutters so I did a step by step picture layout to illustrate how I do it. When I got through I used Don's spur gear spread sheet to see how close my numbers came to the ones generated by the program.
As can be seen by the last sketch at the bottom center of the page (blown up 10x size) the only difference between what I created and what the spread sheet provides is .001 difference at the tip and root of the tooth form. I dare say we can't machine it that close with a form cutter into drill rod so I would say that either one would be satisfactory.

Talent unshared is talent wasted.

Offline Don1966

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Re: Gear tooth generator program for Don
« Reply #1 on: March 20, 2019, 11:38:10 PM »
Thanks George much appreciated, I am always curious how people go about getting the results they want. With your help I have a way better understanding.
I am attaching a link to how to draw a gear profile...

« Last Edit: March 20, 2019, 11:44:34 PM by Don1966 »

Offline jadge

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Re: Gear tooth generator program for Don
« Reply #2 on: March 22, 2019, 09:04:09 PM »
When I made my internal gear and matching pinion I took a slightly different approach. For the involute shape I used the parametric equations for the involute of a circle in a spreadsheet to generate sufficient points. I then imported those into my CAD program to generate a 3D model. To cut the internal gear I simply used the same points to create the shape I needed for the slotting tool and used the CNC mill to cut the shape on the end of a piece of HSS. I made the pinion by using the 4th axis of the CNC mill and a ballnose cutter. If I was going to make an involute cutter I'd create a model of the cutter using the spreadsheet data and CAD, and machine it on the CNC mill. I've not made an involute cutter, but it's the same principle as I used to make this spline cutter: