help on alchin drawings

HI

everyone had some information from colleagues on the site about gear cutting.as i never cut gears before.

I am in the process of cutting the gears ( using d/head and an ajax M/machine) cut the 100 tooth gear (16DP using correct cutter but the teeth look thin, even though i took them to the correct depth( 0.1348".

Will they look thin?.

Also when i come ot cut the bevel gears will spur gear cutters work or do thy have to be special bevel cutters.

thanks

Joe

At the midpoint of the tooth the width of the tooth, and of the space, should be the same. If the teeth look thinner then something is wrong. What diameter was the OD of the blank?

If you want to cut "proper" bevel gears, which are designed using the DP at the outer face, then you will need special 'bevel' involute cutters. As far as I know these are obsolete and unobtainable. If you cut bevel gears using the parallel depth method, where the design is done using the DP at the inner face, then normal imvolute cutters are fine.

Andrew

Andrew

Thank you for taking the timeto reply and help.

The OD was 6.375" with depth of cut 0.134" for 100 teeth on 16DP.

The D/head was 40:1 and i used 8 holes on a 20 holes plate.

Thanks for the clarification on the bevel gearsI do really appreciate your help.

joe

Sounds right provided you had 9 holes between the fingers. Eight for the 100 spacing and another hole for the pin.

If you are going to use the parallel depth method from Ivan Law's book then you use ordinary cutters but of different value to spur gears.

I have a spreadsheet that calculates all the parameters without straining your brain! PM me your email address and I will email it to you.

Les

The OD is correct. Total depth is correct for the standard depth of 2.157/DP. But tooth depth can vary; typically 2.25/DP for low tooth counts and 2.125/DP for large tooth counts. The total depth should be marked on the cutter, often as D+f.

A face on picture would be helpful.

Andrew

Thanks to both Les and Andrew.

The gear cutter had the words D+f .1348.

Less my email is

[email protected]

once again so grateful for the help you guys have given and the time.

Joe

Joseph, I've just sent it to you.

Les

If we assume that the OD and depth of cut are correct then the next question is: are all the teeth the same width, but too narrow, or does the tooth width vary around the periphery?

Out of idle curiosity which number involute cutter did you use?

Andrew

Andrew

they seem to vary a little but not a great deal i would say they seem a little narrow.

I used a DRO to put the cut on ( but using mm equivalent to ).1348 which was 3.425mm) I did notice that sometime the DRO readout exceded the 3.420mm by around0.02 going between 3.420 to 3.440.

The cutter i used was the 55 to 134 tnink thats No 2.

Thank for trying to solve this puzzle.

I have all the gears to cut for the Alchin.

joe

Joseph, what pressure angle are you cutting? If 14.5pa then they will look narrower than 20pa which is what most modern gears are cut to these days and could be what you are making comparrisons with.

yes its 14.5 PA so that will be the issue maybe

This shows the difference, the upper one is 100T 20pa and the lower 14.5pa

thats helpful thanks

The width of the tooth at the pitch circle diameter is not dependent upon pressure angle. But larger pressure angles gives a tooth that is more triangular in shape.

Andrew