First time bevel gear cutting

[davidyat]

I could use some help. I've cut spur gears before but now I want to tackle bevel gears. If there are any threads on HMEM for this, please point me in the right direction. Any help will be appreciated so I don't end up with a box full of scrap bevel gears.
Grasshopper

 

[ShopShoe]

I know some members here have made bevel gears, but a search on this forum did not turn up anygood threads.

I do, however, believe that this video by Keith Rucker provides a good overview of the process and problems:



Good Luck. and please post your experiences.

--ShopShoe

 

[Drawfiler]

I would be ready to make scrap! Making these on a miller is a compromise but you can get acceptable results, have a look at Machinery’s handbook and Ivan Laws book on gear cutting.
Basically you turn a cone to the angle of the top of the teeth, set the dividing head to the angle of the root of the teeth and mill round once then what I do is to engage the cutter with a tooth gullet at the small end and slacken the blank in the dividing head chuck and wind the table over by half the difference in the width of the gullet at the large end,
Go round again and repeat the process with the other side of the tooth.
There is more to it than this but this will make a reasonable gear.

 

[davidyat]

Well, took the plunge and cut the blanks I had made for the bevel gears. My machining mentor showed me how I had to make 3 passes and the offsets needed for proper bevel gears. I practiced on some Delrin and you can see how I completely botched it up with the 3 passes. The diameters at the large end of the bevel is 0.834 in. These are rather small. I was using Vederstein's 0.8 mm module spur gear cutter for 25 teeth. Yes, I know there are bevel gear module cutters, but for 1 operation, let's see if this works. I am attempting to make Vederstein's Dancer Engine. He only made one pass on each gear and his engine runs. So that's what I did. For what these gears are made for, I believe mine will work. I am making some blank flat plates with holes for the axles and mounting them at 90 degrees on a flat plate to see if I am close enough before I go any further. If they run somewhat OK on the flat plate, I'll be very lucky.
Grasshopper

 

[GreenTwin]

My dad made beveled gears for his steam auto differential, but unfortunately he did not document how he did it.

Your gears look good !

.

 

[GailInNM]

We had a nice discussion on cutting bevel gears about a dozen years aghttps://www.homemodelenginemachinist.com/threads/new-guy-from-wis.35856/#post-406954o. If one is interested the thread is well worth reading.
Here is a link to the thread:
https://www.homemodelenginemachinist.com/threads/new-guy-from-wis.35856/#post-406954

 

[kiwi2]

Hi Grasshopper,
Be careful when consulting Ivan Law's book on gear cutting. He only covers two same tooth gears where the pitch cone angle is 45 degrees. I didn't realise that this is not true for the 30tooth/60tooth bevel gear combination I was trying to make. I wasted a lot of time before I found my mistake.
There is apparently an error in his maths as well concerning the OD of the small end. He has:
OD small end = PD + 2xAddendum x Sin pitch cone angle. Apparently it should be the Cos of the pitch cone angle. It doesn't matter when the angle is 45 degrees (both sin and cos are .707) but it does matter if the number of teeth on the two gears are not equal and the pitch cone angle is not 45 degrees.
I finally sussed out how to proceed after reading an article called "Bob's Better Bevels" in the June 2022 issue of the UK magazine "Model Engineer's Workshop". Very well written and easy to understand.
Cutting the 60 tooth gear was an exercise in stamina as the number of passes was 60 x 3 = 180. I had to do it in 3 sessions.
Regards,
Alan C.

 

[L98fiero]

Hi Grasshopper,
Be careful when consulting Ivan Law's book on gear cutting. He only covers two same tooth gears where the pitch cone angle is 45 degrees. I didn't realise that this is not true for the 30tooth/60tooth bevel gear combination I was trying to make. I wasted a lot of time before I found my mistake.
There is apparently an error in his maths as well concerning the OD of the small end. He has:
OD small end = PD + 2xAddendum x Sin pitch cone angle. Apparently it should be the Cos of the pitch cone angle. It doesn't matter when the angle is 45 degrees (both sin and cos are .707) but it does matter if the number of teeth on the two gears are not equal and the pitch cone angle is not 45 degrees.
I finally sussed out how to proceed after reading an article called "Bob's Better Bevels" in the June 2022 issue of the UK magazine "Model Engineer's Workshop". Very well written and easy to understand.
Cutting the 60 tooth gear was an exercise in stamina as the number of passes was 60 x 3 = 180. I had to do it in 3 sessions.
Regards,
Alan C.

FWIW, you can do bevel gears with only a straight cut, but you have to use a tooth form cutter suitable for the outer diameter and that means it will contact only at the outside end of the teeth, the two/three cut method is better as it provides better/more contact.

There is complete instructions on bevel gear cutting in 'Gear Cutting Practice' (1937) by Colvin and Stanley, chapter 6, there is a Lindsay reproduction, but it's also online as a pdf at archive.org. I have the book but found the Lindsay pdf at archive.org and have no idea if Lindsay authorized it on that site. A copy of the original is also available https://archive.org/details/in.ernet.dli.2015.238742/mode/2up so you need not worry about a Lindsay copyright infringement though I don't know if reprints are even subject to copyrights.

There's also 'Gear Cutting in Theory and Practice' (1914), by Joseph Gregory Horner and 'Practical Treatise on Gearing'(1902) by Brown and Sharpe

​

 

[GreenTwin]

To the best of my knowledge, Linday books basically published old books that were out of copyright, verbatim.
When you republish a book that is out of copyright verbatim, you cannot re-copyright it.
If the book is in the public domain, then anyone can use it regardless.

The old book scans made by Google that were published before 1929 have some interesting language posted by Google at the beginning, and a naive person may think that Google has some sort of rights to a book that is out of copyright just because they scanned it, but that would be false.

One way that you can copyright old material is if you mix and match material, and come up with a totally unique arrangement of old material, perhaps with your own narritive added. Then you can copyright that unique arrangement.

I don't recall ever seeing a Lindsay book that had a copyright on it, or if it did, it was a verbatim copy of a book that was out of copyright, and so the Linday copyright was invalid.
(Edit: Apparently you can add a newly created cover to an old book, and then add your copyright? which may have been what Lindsay did on some of the old books.)
https://gatekeeperpress.com/reprinting-and-selling-public-domain-books/

I think this is correct (found online).
In the United States, works published before January 1, 1929, are in the public domain.

And I am sure that there must be some method to transfer books into the public domain even if they are published after 1929, but I am not positive of that.

.

 

[Richard Hed]

To the best of my knowledge, Linday books basically published old books that were out of copyright, verbatim.
When you republish a book that is out of copyright verbatim, you cannot re-copyright it.
If the book is in the public domain, then anyone can use it regardless.

The old book scans made by Google that were published before 1929 have some interesting language posted by Google at the beginning, and a naive person may think that Google has some sort of rights to a book that is out of copyright just because they scanned it, but that would be false.

One way that you can copyright old material is if you mix and match material, and come up with a totally unique arrangement of old material, perhaps with your own narritive added. Then you can copyright that unique arrangement.

I don't recall ever seeing a Lindsay book that had a copyright on it, or if it did, it was a verbatim copy of a book that was out of copyright, and so the Linday copyright was invalid.
(Edit: Apparently you can add a newly created cover to an old book, and then add your copyright? which may have been what Lindsay did on some of the old books.)
https://gatekeeperpress.com/reprinting-and-selling-public-domain-books/

I think this is correct (found online).
In the United States, works published before January 1, 1929, are in the public domain.

And I am sure that there must be some method to transfer books into the public domain even if they are published after 1929, but I am not positive of that.

.

Lindsay was doing us a large favor publishing all those books. Remember that he did it in the DARK AGES, before cruise control and before the internet. I bot several of his books.

 

[GreenTwin]

I have a lot of Lindsay books too.
It was an inexpensive way to get old books in print.

And Lindsay dug up some old material that I doubt would ever have seen the light of day otherwise.

Tom Lindsay always use to tell me "When I retire, I may build a steam engine".
So when he retired, I sent him an email "No more excuses, get busy now and BUILD that Steam Engine".

.

 

[davidyat]

First off, thank you everyone for your input. I'm just an amateur machinist. I just want to make a steam engine, make it run, then put it on a shelf and look for another project. My machining mentor showed me where I made my mistake and botched the Delrin practice piece. I zigged when I should have zagged on passes 2 and 3. Next I finished the second bevel, made a jig to see if it would work and it does. I only made one pass on each gear. At least in the video they do what I want them to do.
Grasshopper

 

[ajoeiam]

First off, thank you everyone for your input. I'm just an amateur machinist. I just want to make a steam engine, make it run, then put it on a shelf and look for another project. My machining mentor showed me where I made my mistake and botched the Delrin practice piece. I zigged when I should have zagged on passes 2 and 3. Next I finished the second bevel, made a jig to see if it would work and it does. I only made one pass on each gear. At least in the video they do what I want them to do.
Grasshopper

(totally tongue in cheek) now if only you would do a spiral bevel gear set (grinning - - - the fact that you even made your set is a real big deal - - - good on you).)

More seriously - - - good on you!
Learning is most always a good thing!!!

 

[ajoeiam]

FWIW, you can do bevel gears with only a straight cut, but you have to use a tooth form cutter suitable for the outer diameter and that means it will contact only at the outside end of the teeth, the two/three cut method is better as it provides better/more contact.

There is complete instructions on bevel gear cutting in 'Gear Cutting Practice' (1937) by Colvin and Stanley, chapter 6, there is a Lindsay reproduction, but it's also online as a pdf at archive.org. I have the book but found the Lindsay pdf at archive.org and have no idea if Lindsay authorized it on that site. A copy of the original is also available https://archive.org/details/in.ernet.dli.2015.238742/mode/2up so you need not worry about a Lindsay copyright infringement though I don't know if reprints are even subject to copyrights.

There's also 'Gear Cutting in Theory and Practice' (1914), by Joseph Gregory Horner and 'Practical Treatise on Gearing'(1902) by Brown and Sharpe

​

Thank you ever so much for the list of references!!!

Do you happen to know of anything for spiral bevel gearing?

(Tried looking in archive - - - I don't find their search engine 'wonderful' though!)

TIA

 

[Jager]

I would be ready to make scrap! Making these on a miller is a compromise but you can get acceptable results, have a look at Machinery’s handbook and Ivan Laws book on gear cutting.
Basically you turn a cone to the angle of the top of the teeth, set the dividing head to the angle of the root of the teeth and mill round once then what I do is to engage the cutter with a tooth gullet at the small end and slacken the blank in the dividing head chuck and wind the table over by half the difference in the width of the gullet at the large end,
Go round again and repeat the process with the other side of the tooth.
There is more to it than this but this will make a reasonable gear.

I second the suggestion to consult Ivan Laws book, it is very informative and readily understood.
I followed it when making a pair of bevel gears to drive the governor on my ME beam engine and am delighted at the result.

David

 

[Richard Hed]

There is also a war time book "Gear Cutting Practice" that has great info. You should be able to find a copy on Archive.org

 

[ccolby]

I used the procedure given in Machinery's Handbook and got excellent results. On the down side, you have to obtain a copy that is around the 11th edition or earlier as the bevel gear procedure is deleted from later editions. I quickly found an inexpensive early handbook on eBay, which is where I also purchased a used Starrett gear tooth vernier caliper that you will also need to ensure properly dimensioned teeth.

I made the cast iron bevel gears using a Powermatic-Burke vertical mill and an Ellis dividing head.

I needed the gears for the restoration of my 1883 non-compression Continental Gas Engine made in New York City by Charles Gaume, a French immigrant. The engine is one of the first internal combustion engines both designed and manufactured in the USA.

 

[TSutrina]

This approach will work for both spur and bevel gears. For bevel gears the mod changes along the gear cone. So calculate the mode at the small end of the cone. Pitch Diameter_small end / number of teeth = mod_small end. and Pitch Diameter_large end / number of teeth = mod_large end.

The slitter saw will be determined by the small end. The above procedure will work for where you choose on the cone. The angle of the axis of the gear is when the line at the radius of the Pitch Circle minus one mod which is different at the two ends. This line is parallel to the travel of the cut. Typically the table. Video is available at the site in the attached files.

Note can use a trapezoidal cutter for cutting the smallest mod but tall enough to cut the largest mod tooth. Still have to cut both sides of the tooth and make multiple cuts as one would do with a slitter saw. The reason to do this is stiffness of the cutter. The hobbing a gearhighlite file shows how to apply the same approach as the slitter with less cuts but cutting more material off.

 

[peterl95124]

congratulations on a successful pair of bevel gears, yeah !!!
next up try a pair of 45-deg helical gears !!!

I tip my hat to anyone that has the patience, persistence, and
above all the ability to keep focus and not make any mistakes
during a very long and error prone process.

now that you've "been there, done that" you might consider what I do,
my motto is I don't make my own screws, ball-bearings, or gears [life is
too short for the number of engines I'm hoping to build] !!!

Peter.

ps, I've made only three gears so far, a starter ring gear cut into a flywheel,
an involute spline on the end of a propellor shaft, and a propellor hub with
corresponding internal involute spline, in other words only when I'm forced to.