differance between 14.5 and 20 degree Pressure angle gear cutters

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differance between 14.5 and 20 degree Pressure angle gear cutters SDL 01-20-2008
Posted by SDL on January 20, 2008, 6:33 pm
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Any one know how to tell the differance between 14.5 and 20 degree
Pressure
angle gear cutters, of the brown and sharpe pattern.
I have some that are marked 14.5 PA some 20 and some no marks (all Mod
4)

Steve larner


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Posted by Anonymous. on January 21, 2008, 3:40 am
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> Any one know how to tell the differance between 14.5 and 20 degree
> Pressure angle gear cutters, of the brown and sharpe pattern.
> I have some that are marked 14.5 PA some 20 and some no marks (all Mod
> 4)

Rather like the difference between metric and BA screw threads, in that
the principles are the same, but not the measurements.

If you could get them to work together (and I don't know the answer
'cos they might bind) then you'd have increased wear and noise because
you'd get sliding and not rolling contact.

What is the pressure angle?

Imagine two gear wheels in mesh.

Draw a line joining the two centres.

Imagine two of the teeth in contact exactly at the point of crossing the
line.

Then the tangent of the point of contact is at that angle to the line
joining the centres.



Posted by Anonymous. on January 21, 2008, 3:42 am
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OOPS! SORRY! I was talking about gear wheels and not their cutters, but
the principles discussed below would apply to any gears you tried to cut
with
the cutters

>> Any one know how to tell the differance between 14.5 and 20 degree
>> Pressure angle gear cutters, of the brown and sharpe pattern.
>> I have some that are marked 14.5 PA some 20 and some no marks (all Mod
>> 4)
>
> Rather like the difference between metric and BA screw threads, in that
> the principles are the same, but not the measurements.
>
> If you could get them to work together (and I don't know the answer
> 'cos they might bind) then you'd have increased wear and noise because
> you'd get sliding and not rolling contact.
>
> What is the pressure angle?
>
> Imagine two gear wheels in mesh.
>
> Draw a line joining the two centres.
>
> Imagine two of the teeth in contact exactly at the point of crossing the
> line.
>
> Then the tangent of the point of contact is at that angle to the line
> joining the centres.
>
>



Posted by SDL on January 21, 2008, 3:38 pm
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Anonymous. Wrote:
> OOPS! SORRY! I was talking about gear wheels and not their
cutters, but
> the principles discussed below would apply to any gears you tried to
> cut
> with
> the cutters
>
> I agree but I have some cutters marked 14.5 some 20 deg and some with
> no
angle so i want to determine which set they belong to.
>
> Steve Larner


--
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Posted by on January 22, 2008, 2:19 pm
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> Anonymous. Wrote:
>
> > OOPS! SORRY! I was talking about gear wheels and not their cutters, but
> > the principles discussed below would apply to any gears you tried to
> > cut
> > with
> > the cutters
>
> > I agree but I have some cutters marked 14.5 some 20 deg and some with
> > no angle so i want to determine which set they belong to.
>
> > Steve Larner
>
> --
> SDL
> ------------------------------------------------------------------------
> SDL's Profile:http://www.rcgroups.com/forums/member.php?u=3D177565
> View this thread:http://www.rcgroups.com/forums/showthread.php?t=3D805112

Why not try the old trick of rolling each gear through a pit of
plastiscine and then measuring the angle of the teeth in the plastic
rack you have created,
Peter

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