Helical Stub Gear

[vintagengineerParticipant @vintagengineer]

I need to make a helical stub gear. I am struggling to find any data on cutting these. Has anyone got any data on cutting them?

[vintagengineerParticipant @vintagengineer]

[Neil WyattModerator @neilwyatt]

I suggest you rush out and buy a copy of MEW 243 and then wait for 244. This article explores cutting them on a Jacobs machine in no little detail.

[John Stevenson 1Participant @johnstevenson1]

Loads of date.

Look up Fellows stub tooth.

 

They have two numbers something like 10/12 where the first number is the size of the tooth and the second number is the depth of the tooth. All values based on DP.

 

You can get form cutters for them but they are like cows testicles. Hobs are far easier to get but then you need a hobbing machine and usually , being commercial they tend to be big, 3" plus in diameter.

 

It is possible to fudge the numbers or make a button cutter given more detail. Helical gears are not the same as spur gears in that you take the number of teeth, add 2 teeth and divide by the OD.

Helical gears also take into account the helix angle. a 20 tooth helical gear will be bigger than a 20 tooth spur gear and one with the teeth at 45 degrees will be far bigger still.

 

It's a well used quirk in gear cutting to get two ratios into a given fixed centre distance by just altering the helix angle.

 

Or you can cut them on a CNC using just an off the shelf end mill or slot drill.

 

Edited By John Stevenson on 24/03/2017 00:53:17

[John HinkleyParticipant @johnhinkley26699]

I think Neil means issues 253 and 254!

John

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