GEARS AND GEAR SCALES


| September/October 1967



18 West Washington Street, Newnan, Georgia

I was born and raised in a machine shop and we were around some complicated and nice jobs, including making a blank for gears and getting the boys at the cotton mill to cut the teeth for us; once in a while, making gears.

Back in my early days the mills must have made hundreds of gears a month as it took a different set of gears to make every kind of thread. They had different machines by the dozens, besides all of the ones that stripped and wore out so we never did think we were ever a match for any of the mill boys where gears were concerned.

My folks usually had gear scales and pattern rules that had lines of 10, 12, 14,, and 16, but we were never able to get a scale that 18ths and all of the other lines up to 32 like the mills had. Some said the Cotton Mill Machinery people had the rules made by the hundred and then resold them to people who bought the mills. I never saw but 3 in my whole life like I always wanted and now you cannot even buy one that has 18ths on it anywhere. This small one used to have a lot of useful information about a circle and figuring gears.

My Dad left me a 301 Starrett 10, 12, 14, 16ths and all subdivided, but no 18th and a South Bend lathe has 18 pitch gears. We use a 5/16 tap if we do not use a mike when on 18ths.I knew a Mr. Brasch, a master mechanic of a large mill at Grantville, who was a graduate of the Brown and Sharpe Trade School. Mr. Brasch was noted for his secret trick gears, a gear that could go behind or replace another gear with a smaller or larger number of teeth and keep the same adjustment. This would save the company lots when a minor change was necessary on the finished product. Mr. Brasch carried his dozens of secrets to his grave but I believe he used the same method that Ford did in the Model T rear end. He had 2 different pinions to fit the same set-up. No doubt Mr. Brasch studied under the same men who helped Ford with his gears.

More about the Marsh valve gear -replacing worn gears. Some of the early Advances were equipped with a casted cast iron gear with 21 teeth and the circular pitch was 2/3 of an inch. This is the measurement taken at the pitch line from the center of one tooth to the center of the next tooth. This way and style for measuring gears was the most practical way to make gears prior to 1900 or so because gears were casted in a foundry and this was the easiest way to make the wooden patterns.