My Stupid Hat is jammed on….

[Ruaidhri MurphyParticipant @ruaidhrimurphy46564]

OK, so I put on my stupid hat and it's stuck, so I need help.

Looking at the two tables for button tool sizes on pages 114 and 115 of Ivan Law's book "Gears and Gear Cutting" I find myself mystified.

The table shows the button diameter for a button for 20deg pressure angle No. 1 cutter as 51.30 Ins., and others similarly sized. Rather large button tool

There are a number of possibilities-

1. A whole series of misprints
2. Ivan Law knows nothing about gears
3. I am stupidly missing something.

1. Given that the same type of info appears on page 115 (for 30 deg) this seems unlikely
2. Can be dismissed out of hand
3. HELP!!!!

Can any of our mandarins shed some light please?

Regards,

Ruaidhrí

[Ruaidhri MurphyParticipant @ruaidhrimurphy46564]

Table in “Gears and Gear Cutting”

[JasonBModerator @jasonb]

Those sizes are for 1DP, you need to divide the sizes by your required DP so if making a 32DP cutter your 51.300" would be 1.603" Read the paragraph just above the 20PA table

As a No1 cutter is for a large number of teeth to a rack the button is still relatively large as the teeth have quite straight edges at those numbers

Edit, our old friend Ramon did a good write up on making this type of cutter, starts in this thread and continues over the page

Edited By JasonB on 24/09/2013 16:41:14

[BazyleParticipant @bazyle]

For larger diameters you don't have to use a whole button, rather you make just a sector as required by turning a bit of plate mounted on the lathe faceplate.

Also have a look for article(s) on using a screwfix cone drill down to a specific depth to get the required radious with built in relief from the cone shape.

[Ruaidhri MurphyParticipant @ruaidhrimurphy46564]

Thank you gentlemen.

Stupid hat is now off, and I am considering taking lessons in reading

My only excuse is that I'm Irish LOL

Regards,

Ruaidhrí

[Michael Cox 1Participant @michaelcox1]

If you are interested in the theory of the button method there is a write up on my website, see:

**LINK**

This explains how the size of buttons is calculated.

Mike

[John Stevenson 1Participant @johnstevenson1]

Posted by Ruaidhri Murphy on 24/09/2013 17:33:08:

My only excuse is that I'm Irish LOL

Regards,

Ruaidhrí

.

Another armpit of Europe

[Alan .204Participant @alan-204]

Bit harsh John,

Al.

[Sub MandrelParticipant @submandrel]

For the record I believe Ivan is overcautious about cutters for smaller gears. I made a successful No. 8 cutter for 13 tooth 20-degree PA gears using D=4.50 C=5.65 E=2.25 and W=4 (as always!).

Also, while you have your copy to hand the formulas on page 106 change SIN to COS in the top two formulas, but not the bottom two.

The calculations don't show an error as cos 45 = sin 45, but for non-symmetrical bevels…

Neil

P.S. John is based in Long Eaton – that could be a compliment

Edited By Stub Mandrel on 25/09/2013 11:57:50

[richardandtracyParticipant @richardandtracy]

Nice to see you Ruaidhri,

That'll be one hell of a pen. Or is it a toy for Fluffy?

All the best,

Richard.

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