Cutting Gears. Diametral

Ray C said:
Part 3:

Why do gear cutters come in a set for a particular Modulus or Diametral Pitch?

To preserve (as much as possible) the Involute shape on a gear tooth, each cutter in a set has a slightly different profile shape to accommodate gears with small numbers of teeth vs large numbers of teeth. Each gear in the set can cut gears over a specified range with a given number of teeth. For this example, for the 32 tooth gear, a size #5 cutter will be used. The 80 tooth gear needs the size #7 cutter.

If someone wanted a perfectly matched set of gears for totally optimal operation, a special cutter with a unique involute profile would be needed for each gear with a given number of teeth. -Not practical... and thus, the cutter designers decided on the best trade-offs between performance and practicality and grouped standard cutters into a fixed set.

A typical breakdown for a Module 1 set (and most other metric and SAE styles) is shown here but, always look at the gear cutter itself. The range it can cut will be engraved in the side of the cutter.

Size 8: 135 - Rack
Size 7: 55 - 134 teeth
Size 6: 35 - 54 teeth
Size 5: 26 - 34 teeth
Size 4: 21 - 25 teeth
Size 3: 17 - 20 teeth
Size 2: 14 - 16 teeth
Size 1: 12 - 13 teeth

For size 8, it says Rack. That means a straight line of gears as in a Rack & Pinion setup.

Once again, when you're making gears that mesh, they need to be cut with cutters of the same Diametral pitch or metric modulus.

One thing I've always wondered (and don't know the answer to) is when designing a gear system with gears of different sizes, if it's best to try to chose the gears such that the teeth needed on the gear falls, for example, into the middle-range of the cutter's ability. I wonder if such parametric or (mathematically) transcendental logic has any benefit...

OK... next and final part will be setup and action shots... Stay tuned.

Ray
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In most of the cutter sets that I have, both diametral pitch and metric, the numbers of cutters are reverse of each other, that is, what is #1 in one set would be #8 in the other system, and vice versa.
 
benmychree said:
In most of the cutter sets that I have, both diametral pitch and metric, the numbers of cutters are reverse of each other, that is, what is #1 in one set would be #8 in the other system, and vice versa.
Click to expand...
I do know that import cutters are often numbered backwards from US made cutters.
 
Ray C said:
If there's interest, I will do another "tutorial" thread that outlines the bare basics to pull it off. .
Let me know you want to see a write-up like this.
Ray
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Sorry if I'm late but YES! It would be great to see it done.
 
Yes, imagine my surprise as I scrolled past a couple more posts and discovered how late I really was! LOL..

I am saddened to read that you won't be doing any more tutorials... You have a great "style" and format that makes it easy to read & learn.
But I also see there is an element that can take the "fun" out of it.
I just finished reading the miter / bevel gear thread and enjoyed it enough I'll be going back to re-read it! Minus the "banter".

So thanks for making the time for us all and sharing the knowledge. Well Done!
 
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