I've been reading Ivan Law's book on making gear cutters and he described 
the design and build of a "button cutter" to generate an approimation of the 
involute profile.

Mr. Law sets out two tables of design information for the cutters,  one 
20deg pressure angle and the other is at 30deg pressure angle.   The design 
data is normalised at one diametrical pitch.

The puzzle I have is that the two buttons are of diameter "D" and the 
distance between the button centres is "C".

The thing I'm struggling with is that in both tables "C"  is less than "D". 
How can this be?

Too be honest it's a bit of an armchair question as I've had a kind offer 
from one of the guys on the group to cut the two gears I'm after,  but can't 
abide leaving things I don't understand to one side!

Steve

On 15 Jun, 11:30, "Steve"  wrote:
> I've been reading Ivan Law's book on making gear cutters and he described
> the design and build of a "button cutter" to generate an approimation of the
> involute profile.
>
> Mr. Law sets out two tables of design information for the cutters,  one
> 20deg pressure angle and the other is at 30deg pressure angle.   The design
> data is normalised at one diametrical pitch.
>
> The puzzle I have is that the two buttons are of diameter "D" and the
> distance between the button centres is "C".
>
> The thing I'm struggling with is that in both tables "C"  is less than "D".
> How can this be?
>
> Too be honest it's a bit of an armchair question as I've had a kind offer
> from one of the guys on the group to cut the two gears I'm after,  but can't
> abide leaving things I don't understand to one side!
>
> Steve

Yes !

C is less than D to make cutters to cut gears with the smaller number
of teeth.  In those cases, you have to grind flats on the buttons in
order to get the required distance apart.  It's all to do with the
geometry of involute gear teeth.

Andy

On Jun 15, 8:36 pm, houstonceng  wrote:
> On 15 Jun, 11:30, "Steve"  wrote:
>
>
>
>
>
> > I've been reading Ivan Law's book on making gear cutters and he described
> > the design and build of a "button cutter" to generate an approimation of the
> > involute profile.
>
> > Mr. Law sets out two tables of design information for the cutters,  one
> > 20deg pressure angle and the other is at 30deg pressure angle.   The design
> > data is normalised at one diametrical pitch.
>
> > The puzzle I have is that the two buttons are of diameter "D" and the
> > distance between the button centres is "C".
>
> > The thing I'm struggling with is that in both tables "C"  is less than "D".
> > How can this be?
>
> > Too be honest it's a bit of an armchair question as I've had a kind offer
> > from one of the guys on the group to cut the two gears I'm after,  but can't
> > abide leaving things I don't understand to one side!
>
> > Steve
>
> Yes !
>
> C is less than D to make cutters to cut gears with the smaller number
> of teeth.  In those cases, you have to grind flats on the buttons in
> order to get the required distance apart.  It's all to do with the
> geometry of involute gear teeth.
>
> Andy- Hide quoted text -
>
> - Show quoted text -

Sorry.  Got my "Cs" and "Ds" mixed up  Should have said "C is less
than D to make cutters to cut gears with the larger number
of teeth"

Andy

Steve wrote:
> I've been reading Ivan Law's book on making gear cutters and he 
> described the design and build of a "button cutter" to generate an 
> approimation of the involute profile.
> 
> Mr. Law sets out two tables of design information for the cutters,  one 
> 20deg pressure angle and the other is at 30deg pressure angle.   The 
> design data is normalised at one diametrical pitch.
> 
> The puzzle I have is that the two buttons are of diameter "D" and the 
> distance between the button centres is "C".
> 
> The thing I'm struggling with is that in both tables "C"  is less than 
> "D". How can this be?
> 
> Too be honest it's a bit of an armchair question as I've had a kind 
> offer from one of the guys on the group to cut the two gears I'm after,  
> but can't abide leaving things I don't understand to one side!
> 
> Steve
> 
> 
I have a pencilled note in my copy saying that there is an error in the 
table/tables on P114/5 and that there was an amendment published in 
Model Engineer, P744 15th June 1990.

I remember copying it and placing it carefully in the book - but damned 
if I can find it now. Maybe some kind soul has that issue handy?

John

On 15 Jun, 23:24, John Blakeley  wrote:
> Steve wrote:
> > I've been reading Ivan Law's book on making gear cutters and he
> > described the design and build of a "button cutter" to generate an
> > approimation of the involute profile.
>
> > Mr. Law sets out two tables of design information for the cutters,  one
> > 20deg pressure angle and the other is at 30deg pressure angle.   The
> > design data is normalised at one diametrical pitch.
>
> > The puzzle I have is that the two buttons are of diameter "D" and the
> > distance between the button centres is "C".
>
> > The thing I'm struggling with is that in both tables "C"  is less than
> > "D". How can this be?
>
> > Too be honest it's a bit of an armchair question as I've had a kind
> > offer from one of the guys on the group to cut the two gears I'm after,
> > but can't abide leaving things I don't understand to one side!
>
> > Steve
>
> I have a pencilled note in my copy saying that there is an error in the
> table/tables on P114/5 and that there was an amendment published in
> Model Engineer, P744 15th June 1990.
>
> I remember copying it and placing it carefully in the book - but damned
> if I can find it now. Maybe some kind soul has that issue handy?
>
> John

Search the newsgroup for "Ivan Laws" and you will find a couple of
threads on this topic and one contains a link to a spreadsheet written
by Duncan Munroe. I ended up concluding that there is an error in the
tables in my 2006 copy of this book, but as I was after 14.5 degree PA
then I had to resort to my own calculations anyway. It is a shame that
Ivan Law didn't spell out how he calculated the numbers in his tables
so we could check his workings - but on the other hand it is important
to realise that circular cutters are only an approximation to the
involute, and even pre-made cutters cover a range of gears. So there
is a fair bit of tolerance.

Steve (yes, another Steve)

Steve

"Lester Caine"  schreef in bericht 
news:pvOdnecduqxknsvVnZ2dneKdnZydnZ2d@bt.com...
> John Blakeley wrote:
>> Steve wrote:
>>> I've been reading Ivan Law's book on making gear cutters and he
>>> described the design and build of a "button cutter" to generate an
>>> approimation of the involute profile.
>>>
>>> Mr. Law sets out two tables of design information for the cutters,
>>> one 20deg pressure angle and the other is at 30deg pressure angle.
>>> The design data is normalised at one diametrical pitch.
>>>
>>> The puzzle I have is that the two buttons are of diameter "D" and the
>>> distance between the button centres is "C".
>>>
>>> The thing I'm struggling with is that in both tables "C"  is less than
>>> "D". How can this be?
>>>
>>> Too be honest it's a bit of an armchair question as I've had a kind
>>> offer from one of the guys on the group to cut the two gears I'm
>>> after,  but can't abide leaving things I don't understand to one side!
>>>
>>> Steve
>>>
>>>
>> I have a pencilled note in my copy saying that there is an error in the
>> table/tables on P114/5 and that there was an amendment published in
>> Model Engineer, P744 15th June 1990.
>>
>> I remember copying it and placing it carefully in the book - but damned
>> if I can find it now. Maybe some kind soul has that issue handy?
>
> -- 
> Lester Caine - G8HFL
> -----------------------------
> Contact - http://lsces.co.uk/lsces/wiki/?page=contact
> L.S.Caine Electronic Services - http://lsces.co.uk
> EnquirySolve - http://enquirysolve.com/
> Model Engineers Digital Workshop - http://medw.co.uk//
> Firebird - http://www.firebirdsql.org/index.php
>
If the attachment is the revised table, then THANKS...!!!
Best regards,
Dirk

On Mon, 16 Jun 2008 13:24:22 +0200, PG1D/PA-11Ø12 carved in stone:

> "Lester Caine"  schreef in bericht
> news:pvOdnecduqxknsvVnZ2dneKdnZydnZ2d@bt.com...
>> John Blakeley wrote:
>>> Steve wrote:
>>>> I've been reading Ivan Law's book on making gear cutters and he
>>>> described the design and build of a "button cutter" to generate an
>>>> approimation of the involute profile.
>>>>
>>>> Mr. Law sets out two tables of design information for the cutters,
>>>> one 20deg pressure angle and the other is at 30deg pressure angle.
>>>> The design data is normalised at one diametrical pitch.
>>>>
>>>> The puzzle I have is that the two buttons are of diameter "D" and the
>>>> distance between the button centres is "C".
>>>>
>>>> The thing I'm struggling with is that in both tables "C"  is less
>>>> than "D". How can this be?
>>>>
>>>> Too be honest it's a bit of an armchair question as I've had a kind
>>>> offer from one of the guys on the group to cut the two gears I'm
>>>> after,  but can't abide leaving things I don't understand to one
>>>> side!
>>>>
>>>> Steve
>>>>
>>>>
>>> I have a pencilled note in my copy saying that there is an error in
>>> the table/tables on P114/5 and that there was an amendment published
>>> in Model Engineer, P744 15th June 1990.
>>>
>>> I remember copying it and placing it carefully in the book - but
>>> damned if I can find it now. Maybe some kind soul has that issue
>>> handy?
>>
>> --
>> Lester Caine - G8HFL
>>
> If the attachment is the revised table, then THANKS...!!! Best regards,
> Dirk

I just tripped over this ref:

	http://ossmann.blogspot.com/2007_01_01_archive.html

and drop down to

	 Monday, Jan. 15th.2007

for a hot link to an XML spreadsheet called GearCreate8.  Has design 
parameters, G-code, PLT for HP plotters, a sheet for number of spokes, 
and a final G-code assembler.
It is designed for laser cutting of gears, but the data is valid for any 
method I'd think.
Mike in BC

Steve wrote:
> I've been reading Ivan Law's book on making gear cutters and he 
> described the design and build of a "button cutter" to generate an 
> approimation of the involute profile.
> 
> Mr. Law sets out two tables of design information for the cutters,  one 
> 20deg pressure angle and the other is at 30deg pressure angle.   The 
> design data is normalised at one diametrical pitch.
> 
> The puzzle I have is that the two buttons are of diameter "D" and the 
> distance between the button centres is "C".
> 
> The thing I'm struggling with is that in both tables "C"  is less than 
> "D". How can this be?
> 
> Too be honest it's a bit of an armchair question as I've had a kind 
> offer from one of the guys on the group to cut the two gears I'm after,  
> but can't abide leaving things I don't understand to one side!
> 
> Steve
> 
> 
I have a spreadsheet that will calculate these values. You can see it here:

http://www.helicron.net/files/involutecuttercalcs.xls

It calculates the button diameter, pitch and infeed for the form tool 
described by Ivan Law in his book "Gears and Gear Cutting". To obtain 
actual sizes then either divide by the DP of the actual gear to get 
sizes in inches or multiply by the module to get sizes in millimeters.

The table in the book is acknowledged as being in error and other tables 
exist on the 'net. One of these can be found here:
http://www.metalwebnews.com/howto/gear/gear1.html
(written by John Stevenson)

An article in Engineering in Miniature (Oct 1998) by D A G Brown 
describes the process and gives a set of formulae for calculating the 
relevant dimensions. I have used those calculations in this spreadsheet. 
The calculations are a bit scruffy but accurate in as much as they 
replicate the results of DAG Brown. Where those results differ from 
other published tables there are a couple of reasons. One is rounding 
errors. Another is that the tables often give dimensions for a cutter 
intended to cover a range of gears. The compiler of the table may have 
chosen any particular number of teeth for that cutter in the range quoted.

In general it seems that close enough will do. For example, take the No4 
cutter (26-34 teeth). For this, the range of button sizes is 8.89 to 
11.63. Any button size you pick will be an approximation for the other 
tooth numbers.

A related discussion I came across had the following suggestion from 
Jerry Kieffer: He makes single point form tool by using an end-mill to 
cut the profile out of a suitable blank. He says that for any given 
gear, there will probably be a standard size end mill of a diameter 
close enough for the task in hand. So for example, to make a 48 tooth, 
0.5module gear, the button diameter would be 16.42 * 0.5 = 8.21mm. An 
8mm end mill would be quite close enough using Jerry's  method.

Please note that I have never had to make my own cutters but expect to 
one day which is why have taken the trouble to keep track of these bits 
and pieces.

Peter Harrison

On Mon, 16 Jun 2008 20:34:20 +0100, Peter Harrison
 wrote:

>A related discussion I came across had the following suggestion from 
>Jerry Kieffer: He makes single point form tool by using an end-mill to 
>cut the profile out of a suitable blank. He says that for any given 
>gear, there will probably be a standard size end mill of a diameter 
>close enough for the task in hand. So for example, to make a 48 tooth, 
>0.5module gear, the button diameter would be 16.42 * 0.5 = 8.21mm. An 
>8mm end mill would be quite close enough using Jerry's  method.

Peter -

I described yet another approach in MEW #131 - ther article is also on
my website here:

http://www.jeffree.co.uk/Pages/multi-tooth-gear-cutter.htm

Regards,
Tony

Tony Jeffree wrote:
> On Mon, 16 Jun 2008 20:34:20 +0100, Peter Harrison
>  wrote:
> 
>> A related discussion I came across had the following suggestion from 
>> Jerry Kieffer: He makes single point form tool by using an end-mill to 
>> cut the profile out of a suitable blank. He says that for any given 
>> gear, there will probably be a standard size end mill of a diameter 
>> close enough for the task in hand. So for example, to make a 48 tooth, 
>> 0.5module gear, the button diameter would be 16.42 * 0.5 = 8.21mm. An 
>> 8mm end mill would be quite close enough using Jerry's  method.
> 
> Peter -
> 
> I described yet another approach in MEW #131 - ther article is also on
> my website here:
> 
> http://www.jeffree.co.uk/Pages/multi-tooth-gear-cutter.htm
> 
> Regards,
> Tony

So you did! I remember now. I have a similar, but less thorough, page here:

http://www.helicron.net/workshop/gearcutting/

But didn't you, or soeone, do a further piece about using CNC on the 
cutter position to get a much better generated shape?

As an aside, seeing your page prompts me to haul out my Peatol lathe and 
make it into a tool sharpener. It was going to go on Ebay but I don't 
think they fetch much.

Pete

On Mon, 16 Jun 2008 22:05:49 +0100, Peter Harrison
 wrote:

>> Peter -
>> 
>> I described yet another approach in MEW #131 - ther article is also on
>> my website here:
>> 
>> http://www.jeffree.co.uk/Pages/multi-tooth-gear-cutter.htm
>> 
>> Regards,
>> Tony
>
>So you did! I remember now. I have a similar, but less thorough, page here:
>
>http://www.helicron.net/workshop/gearcutting/
>
>But didn't you, or soeone, do a further piece about using CNC on the 
>cutter position to get a much better generated shape?

That would be a straightforward thing to do - I made a passing comment
in the article that it would be simple enough to do if you had a CNC
mill to hand, but haven't actually don it (yet).

The great thing about that technique is the simplicity of the cutters
- it doesn't get much simpler to make than a rack form cutter.
>
>As an aside, seeing your page prompts me to haul out my Peatol lathe and 
>make it into a tool sharpener. It was going to go on Ebay but I don't 
>think they fetch much.

Yep - good plan.

Regards,
Tony

On Mon, 16 Jun 2008 22:50:46 +0100, Tony Jeffree  wrote:


>
>The great thing about that technique is the simplicity of the cutters
>- it doesn't get much simpler to make than a rack form cutter.

Single tooth rack tool giving (almost) perfect involute result:-

http://www.youtube.com/watch?v=adRlGffXM5k


Now, where are John's pictures of his hobbing setup with a mill and your
DivisionMaster?

Mark Rand
RTFM

On Mon, 16 Jun 2008 23:03:16 +0100, Mark Rand
 wrote:

>>
>>The great thing about that technique is the simplicity of the cutters
>>- it doesn't get much simpler to make than a rack form cutter.
>
>Single tooth rack tool giving (almost) perfect involute result:-
>
>http://www.youtube.com/watch?v=adRlGffXM5k

Yep - thats the one! Would be simple enough to program with a rack
form fly cutter in a  mill instead of using a shaper.

Regards,
Tony