Helical Gear Cutting Lathe Attachment

[cfellows]

"Quite happy with it".

Chuck, if it was me, I would be ecstatic.

You've done a wonderful job of it, and given a lot of people something to think about. :bow: :bow:

Very well done indeed.

John

Thanks, John. I actually am pretty amazed that it came out the way it as supposed to. I've always wanted to cut helical gears and I guess if you want anything bad enough, you figure out a way.

Now I got to get back to work on my hot bulb engine to put these gears to work!

Chuck

 

[cfellows]

Chuck,

Good job!

Do you plan to post plans for your gear pitch fixture?

Thanks for sharing,

SAM

Thanks, Sam. Yeah, I have the drawings pretty much complete. Of course, for a fixture like this, there is a lot of flexiblity for design changes. And, some folks will have to figure out another way to mount it on their lathe if they don't have a milling attachment that mounts on the saddle.

Very nice, and enlightening. I very much appreciate your sharing the design and execution with us.

Thanks, Lee. I hope the design and forthcoming plans help out a few souls who were as befuddled about helical gears as I was.

Nice job Chuck!

Thanks, Bob... got a project in mind where these might be useful?

Chuck,
Very nice gears, please explain the math to the rest of us gear heads reading this and wondering how to work out the blank sizes.

Dan

Thanks, Dan. Hope you've seen what I posted and it is helpful.

Chuck; Great work.
Thats using the old head for something besides a hat rack. :bow: :bow: :bow: :bow: :bow:

Ron

Thanks, Ron.Spent a lot of hours thinking about this thing before I finally made something that worked!

Chuck, Great work, I, the videos are great, I really like this very much.thank you very much. larry

Thanks, Larry. Hope you can put it use at some point.

Thanks all for your continuing support. Most of the fun in building this stuff is sharing and the appreciation you give back to me. Always nice to show off a little bit!

Chuck

 

[Dan Rowe]

Chuck,
Many thanks for that explanation. I am trying to wrap my head around it, and I can see how you determined the blank diameters for the different angle settings of the lathe mill attachment.

Here is the part I am not getting.... how did you figure the angle of the sheet metal guide? I am assuming that you used the same guide for both gears but that might be wrong.

Many thanks for sharing your gear cutting experience now I have to invent a reason to need this type of gear.
Dan

 

[mklotz]

Chuck,

Great work and something for which I have a use.

In the interest of making your work more available to the math-shy, I've incorporated your calculations into a short computer program. With your permission, I intend to make that program available to all the forum members. Example output below...

===========================================
Chuck Fellows' Helical Gear Calculations

Number of teeth [6] ?
Diametral Pitch [40] ?
Helix angle [80 deg] ?

Diametral Pitch = 40.0000
Number of teeth = 6
Helix Angle = 80.0000 deg
Pitch Diameter = 0.8638 in
Helix Lead = 0.4785 in
===========================================

However, I think the program is missing (at least) two calculations that would be useful to anyone who wants to make such gears. One is the calculation of the blank diameter for the gear and the other is the whole depth calculation - how deep to cut the tooth. I know how to calculate these for spur gears but you may have done something different. If you supply those calculations I'll add them to the program.

If you email me (addy in my profile), I'll send you a beta copy of the program to evaluate.

 

[cfellows]

Chuck,

Great work and something for which I have a use.

In the interest of making your work more available to the math-shy, I've incorporated your calculations into a short computer program. With your permission, I intend to make that program available to all the forum members. Example output below...

===========================================
Chuck Fellows' Helical Gear Calculations

Number of teeth [6] ?
Diametral Pitch [40] ?
Helix angle [80 deg] ?

Diametral Pitch = 40.0000
Number of teeth = 6
Helix Angle = 80.0000 deg
Pitch Diameter = 0.8638 in
Helix Lead = 0.4785 in
===========================================

However, I think the program is missing (at least) two calculations that would be useful to anyone who wants to make such gears. One is the calculation of the blank diameter for the gear and the other is the whole depth calculation - how deep to cut the tooth. I know how to calculate these for spur gears but you may have done something different. If you supply those calculations I'll add them to the program.

If you email me (addy in my profile), I'll send you a beta copy of the program to evaluate.

Marv, I was going to ask if you'd be interested in writing a program such as this. The overall gear blank diameter and the tooth depth are calculated exactly the same for helix gears as for straight spur gears.

You might consider adding the calculations for cutting the aluminum template since there is only one additional parameter required... that's the diameter of the hub around which the template will be bent. The angle required for the template is determined from the circumference of the hub, calculated from the diameter + the thickness of template, to give you one leg of the right triangle. The other leg is the helix lead of the gear. The ratio of these two legs, of course, is the tangent of the angle required for the template.

Here's a diagram:

 

[mklotz]

With Chuck's help, I've put the program together. Below is a sample output. The example Chuck used in this thread is used as the default inputs to the program. (Of course, the user would supply the inputs relevant to his particular case.) As you can see, the program generates the same outputs that Chuck reported in this thread.

================================================
Chuck Fellows' Helical Gear Calculations

Number of teeth [6] ?
Diametral Pitch [40] ?
Helix angle [80 deg] ?
Mandrel hub diameter [1 in] ?
Template thickness [0.125 in] ?

Diametral Pitch = 40.0000
Number of teeth = 6
Helix Angle = 80.0000 deg
Gear Blank Diameter = 0.9138 in
Whole Depth = 0.0539 in
Pitch Diameter = 0.8638 in
Helix Lead = 0.4785 in
Template angle = 8.3337 deg
================================================

Chuck has given me permission to put the program on my webpage and I've done so. The archive name is HELIXCF. You can download it by simply clicking on its name on my site.

For those of you who are unfamiliar with my website, please take the time to read the Introduction. If you don't, you may get an opportunity to experience the Mr. Hyde side of my personality and you really, really don't want to do that.

 

[cfellows]

Marv, thanks for putting this program together. I just downloaded it and gave it a try using the parameters for the other gear I made which are 12 teeth, helix angle 10 deg and everything else stays the same. The results of your program match perfectly with what I had.

I would just like to add that the angle of the aluminum template is not terrible critical. One full degee either side of the calculation results will work fine. Plans should be forthcoming sometime this week, if I can manage to avoid the significant other and her infamous list of things to do!

Thx...
Chuck

 

[gbritnell]

First of all, thank you Chuck for the time and effort put into devising and chronicling this build and second thank you Marv for your program. I have already downloaded it and have a project in mind already.
George

 

[Deanofid]

Thanks very much, Chuck, for all this ground work, (and for sharing it!).
And, thank you Marv for the program work.

Makes me think mere mortals can actually do this!

One question, so I'm clear about this; The hub diameter, meaning the diameter for
the form used for bending the template can remain constant, is that right? I mean,
if I make the tool as Chuck shows, the hub that holds the template can stay the same
size for all gear sizes within the capacity of the tool?

Thanks again!

Dean

 

[ozzie46]

Chuck, Marv Thank you both.

It guys like you that make this the outstanding forum that it is.

Ron

 

[cfellows]

Thanks very much, Chuck, for all this ground work, (and for sharing it!).
And, thank you Marv for the program work.

Makes me think mere mortals can actually do this!

One question, so I'm clear about this; The hub diameter, meaning the diameter for
the form used for bending the template can remain constant, is that right? I mean,
if I make the tool as Chuck shows, the hub that holds the template can stay the same
size for all gear sizes within the capacity of the tool?

Thanks again!
Dean

Thanks Dean. Yes, the bending form and the hub of the fixture it fits on can stay the same. Using Marv's program, you can determine the angle needed on the template for different gears. Note that the angle on the template will change for different gear configurations and the angle of the template will not be the same as the helix angle of the gear except in the single case where the pitch diameter of the gear is the same as the template form.

 

[mklotz]

Marv, thanks for putting this program together. I just downloaded it and gave it a try using the parameters for the other gear I made which are 12 teeth, helix angle 10 deg and everything else stays the same. The results of your program match perfectly with what I had.

That's great. There's nothing better than a program that's been verified against actual, working hardware.

 

[kustomkb]

That's really smart Chuck. Outstanding and very well done!!

 

[Deanofid]

Thanks Chuck. It's nice to get something right once in a while, (for me, I mean!).


Dean

 

[tel]

if I can manage to avoid the significant other and her infamous list of things to do!

Run and hide Chuck - we need the info!

 

[cfellows]

OK, here are the drawings and information for my helical gear cutting fixture. Let me know if you find anything missing (huh... that doesn't sound right...) or if you have questions.

Thx...
Chuck

Edit: Updated corrected PDF file for helical gear fixture plans

View attachment HelicalAttachment.vsd

 

[tel]

;D Thank'ee Chuck - a beautifully presented article!

 

[ozzie46]

Thanks Chuck and karma for you.

Ron

 

[walnotr]

OK, here are the drawings and information for my helical gear cutting fixture. Let me know if you find anything missing (huh... that doesn't sound right...) or if you have questions.

Thx...
Chuck

I think there is a small error on page 2. When you give your example for a 40 degree - 40 PD gear the COS is shown as .786 instead of .766 that you listed everywhere else. Looks like the result is correct, just a miss-typed number.

Thanks for posting this. I have filed it away as something that might happen someday. Well done! :bow: :bow: :bow:

Steve C.