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Bevel gears (parallel depth method) - Sunset Machine - 03-28-2015
If you ever need to make a pair of bevel gears, here is one very simple method that uses standard spur gear form cutters. No fitting/filing needed.
Go to books.google.com and search for this ISBN number: 0-8311-1159-3
Open this book's online preview and find the section on "Parallel Depth Bevel Gears".
I've attached the excerpt here, handy-like. One caveat, they do not mesh with standard generated teeth. You'll have to make them in pairs.
EDIT: PDF attachment removed due to copyright issues.
RE: Bevel gears (parallel depth method) - Sunset Machine - 03-28-2015
Ed, there's a copyright preventing even parts of this book from being posted. Could you remove the PDF attachment, please?
RE: Bevel gears (parallel depth method) - EdK - 03-28-2015
(03-28-2015, 12:06 PM)Sunset Machine Wrote: Ed, there's a copyright preventing even parts of this book from being posted. Could you remove the PDF attachment, please?
Sunset,
Thanks for checking on the copyright status and being honest about it.
Ed
RE: Bevel gears (parallel depth method) - Sunset Machine - 03-28-2015
I lifted that PDF from another forum somewhere and found the instructions to work nicely on a 2 inch gear. Pleased with the results, I located the book for sale here: https://books.google.com/books?id=x2GThADLN-sC&lpg=PP8&dq=0-8311-1159-3&pg=PA68#v=onepage&q=0-8311-1159-3&f=false
It's a $100 book. Those four pages are a nice tease to buy the darn thing, but not now. Looks like the PrintScreen button comes to the rescue again.
RE: Bevel gears (parallel depth method) - Sunset Machine - 04-18-2015
Crummy thread, I really blew it here.
However, things have been slow in the shop and so encouraged by this simple method of cutting bevels, I thought I'd try taking it to the next level and try making an offset bevel. AKA skew bevel. No real need, just an exercise.
I mounted a dividing head on top of a rotary table. The DH was set to the face angle and a little trig produced a setting for the rotab. The first pass down the center looked okay and the offset appeared correct, so I continued.
Complete and utter failure! The problem is in the rotating/shifting the table for the second and third passes. The math is a tad over my head. Okay, a big tad..
Maybe someone here has a notion on how to do this..?
RE: Bevel gears (parallel depth method) - PixMan - 04-18-2015
I can't understand why you would need to rotate and shift for multiple passes. Wouldn't you just take multiple depth passes, or do those gears require that offsetting method?
I've only made spiral bevel skew gears once in my life, and that was in my 3rd year of vocational high school. Guess I made the one set and forgot the lesson. Sorry.
Nice complicated setup and cool dividing head you got there!
RE: Bevel gears (parallel depth method) - Sunset Machine - 04-18-2015
The cutter is a fixed form, yet the tooth space is tapered or wedge shaped. So it needs to be moved somehow. With the rotab at an angle like that, the simple rotate 8 holes and shift 1/4 of the circular pitch no longer works. I was hoping it would but kinda knew better. Needed to see it physically rather than as a cloud of numbers in my head. I can puzzle this out, but it will take months. Some people can see problems like this and know exactly what to do. I'm not blessed that way.
Oh, the DH there is too big. I have two smaller ones but didn't want to wrestle with that big thing. The little 2 inch gear blank barely fit under the cutter.
I *think* the setup would fit a vertical mill by mounting the rotab on its side.
RE: Bevel gears (parallel depth method) - Sunset Machine - 04-18-2015
Oh hey, that big DH was already on the table... I wasn't very clear. Heavy. Also wasn't clear that these aren't spiral teeth, they're just cut straight across at an offset that allows intersecting shafts to clear each other.. The best info on them has been Kozo Hirokoa's Climax, but so thorough and complex are his instructions. The regular bevels described in that gear book are no more complicated than making spur gears.
The big news here is that the missus informed me that she ordered the gear book and I was all wet about the price. $39.95 at Hastings.
Here is a drawing of the offset bevels from another book - Handbook for Machinists, 1915. The offset is only in the gear; the pinion has straight teeth.
RE: Bevel gears (parallel depth method) - PixMan - 04-19-2015
You've got me thinking now. I'll have to see if my 10" Yuasa H/V rotary table is big enough to mount my Walter HU-80 dividing head to try something like this. Of course I'd have to be 90º away because I only have the vertical spindle machine.
I do clearly see and understand the need to make at least two cuts now, and believe that's exactly what I did those 40 years ago when I last made such a gear set.
A very good friend of mine made gears like that when he built his Climax. I remember how he (justifiably) beamed with pride when he showed me the bevel skew gears he'd made.
RE: Bevel gears (parallel depth method) - Sunset Machine - 04-19-2015
A rotab makes setting easy, but now that I think about it you should be able to just set the head on the table at an angle matching the face angle of the blank. The formula for the angle to set the head itself to is 90-atan((2*offset)/(teeth/DP)). For example: .650" offset, 25 teeth, 20 DP, comes up 43.877 degrees. I may have these settings transposed. Apologies if so.
Centering the cutter itself was less scientific. A little blue and a square to make a mark, then the cutter eyeballed to it.
The rolling offset for a plain bevel goes something like 1/4 of the circ pitch, and 1/4 of the holes used for dividing. Somewhere was described "why this works", but it was a study in math all in itself. Therein lies the solution.
It starts on page 119 in this PDF.
https://ia700400.us.archive.org/3/items/handbookformachi00halsrich/handbookformachi00halsrich.pdf