Involute Gear Cutter Marked 24DP “Bevel”

[Barry Smith 4Participant @barrysmith4]

Hi, I have a involute gear cutter marked:

20 PA 24 DP Bevel on one side

WALKERS TV .853

Bore 1″ Dia 2.25″ 16 teeth

Anyway of telling what the gear cutter is ?

The total depth of cut smaller than the number 4, so does this suggest the cutter number is between 5 and 8?

Thanks Barry

[Anonymous]

That’s a rare beast! It is intended to cut a 24DP, 20 degree PA, straight tooth bevel gear. It should have number on it to determine the number of teeth for which it can be used. Any DOC value will not match that for a spur gear as the DOC varies along the length of a bevel gear.

The BEVEL marking indicates that the cutter is narrower than a standard 24DP involute cutter so it will fit though the small end of the bevel gear while having the correct flank shape for the outer end of the tooth. The bevel gear is cut in two passes, offset one way and then the other. This will lead to a tooth shape that is correct at the outer edge, and is of the correct width but not curved enough at the inner edge.

Andrew

[Brian WoodParticipant @brianwood45127]

Thank you Andrew for your explanation. I have a couple of bevel cutters in my box, without trecking across the yard to check the details I don’t remember the markings, but now I can understand them.

Regards   Brian

[Barry Smith 4Participant @barrysmith4]

Thanks for the answers.  I need to cut a spur gear for my 1024 so it wont be of any use in this undertaking.  I have a 1, 3 and 6 so I need to be on the look out for a No 2 with 20 PA.   Is there some reason whilst the 14.5PA seem to be more popular?

Cheers

Barry

[Anonymous]

The 14.5 degree pressure angle is largely obsolete in industry. The 20 degree value is preferred, partly because it results in a stronger tooth, albeit at the expense of increased bearing load.

A number of the budget involute cutters are made in China where older standards are still common. My original far east boring head used BSW set screws for locking the slide and tool.

Andrew

[Author]

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