Bevel and pinion gear cutting

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JohnR
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Bevel and pinion gear cutting

Post by JohnR » Tue Apr 06, 2021 9:49 am

I am the point of cutting my gears for my 1 1/2" Shay.
My question is with regards to the three cuts with the cutter. The first being down the
middle and the second and third cut offset both sides of the first cut.
How do I determine the offset amount ?
I will be making 25 and 50 tooth gears at 16 DP.
I have Ivan Laws book but cannot read the formulas as the printing is blurred ( also trifocals
do not help).
Any help would be appreciated.

John

Russ Hanscom
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Re: Bevel and pinion gear cutting

Post by Russ Hanscom » Tue Apr 06, 2021 1:55 pm

I have the Law book, and if what you want is on page 106, mine is clear.

Give me an email address and I will send you a pdf of the page.

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Rich_Carlstedt
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Re: Bevel and pinion gear cutting

Post by Rich_Carlstedt » Tue Apr 06, 2021 3:53 pm

John
I addressed some of that in a earlier Chaski Post
viewtopic.php?f=4&t=108880&p=417280&hil ... ng#p417280

Hope that helps as well
Rich

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JohnR
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Re: Bevel and pinion gear cutting

Post by JohnR » Mon Apr 19, 2021 2:04 pm

Gentleman
My apologies for not responding back until now.
I have a question with regards to cutter selection.
The angle is approximately 26.5 deg.
Applying the formula found in Ivan Laws book I come up
with the use of a #2 cutter ( 55 tooth ) for a 25 tooth
tooth bevel gear.
Is this right?
Again thank you for your help.

JohnR

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Rich_Carlstedt
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Re: Bevel and pinion gear cutting

Post by Rich_Carlstedt » Mon Apr 19, 2021 9:47 pm

John
I can understand why the formulas are not clear, as Ivan Laws used numbers that confuse the reader,
He should NOT have used the same number of teeth as he does pitch (20 and 20) in his examples - this is confusing
when the formulas do not designate which is to be used but instead just have the number 20 listed.

John, Really should have more info , but using what you posted, I get this data,
You are right, the angles are 26.56 for the Pinion ( small) gear and 63,44 for the large

Cutter size is 1/.447= 2.23 x 25 teeth= 55.9 , so use a #2 cutter for the small gear and the large gear is 1/.8944 x 50 = 55.9 , so the same cutter for it
Pitch diameter (PD) , Small end of small Gear is 1.562 and small end of large gear is 3.125
Diameter of small end of small gear is 1.6179 and the large gear is 3.2368
Your Chordal Thickness is .0981, so the offset you will use is .049 for both gears
When you offset , you want 1/4 of the Pitch or 1/4 x 360 x 25 = 3.6 Degrees for the small gear
and 1.8 Degrees for the large gear
Hope this helps

Rich

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