New to board and I have a problem

[Mike]

This is a part of a planetary gear and I have had several of these wipe out like shown in jpg's from the manufacturer @700 a pop >:(.
I have not made gears but I have a CNC mill with 4th axis. I should be able to make this.
I just don't know  ??? the cutter I should get to cut the form.
I made a dxf with measurements, the form is free hand .
I count 12 teeth OD .437 Root dia. .29

Thanks for any help.
Mike

[JustinO]

I'd probably grind a form tool to fit the gap -- that makes it a brainless hand/eye coordination thing.

What is this from? What sort of torque and speed does it handle?

If you grind a clean cross section where there is no wear, you could compare that to what Gearotic produces with various parameters. Your gear may have some shifting out of its root and outside diameters to avoid undercutting.

You'll also want to analyze the mating gear -- some of the parameters are the same and more easily seen on the bigger gear.

[BobL]

Mike;

Thank you Justin for your input.

Mike I'm no expert to give you any advise on structural data, torque or speed properties, but I agree that you should be able to make a similar part using Gearotic. if you create this gear using your collected parameters, then export it as a dxf,  the tool cutter profile should be present on the top right side, inside the dxf.  Once you cut this shape as your tool, then it should be just a matter of using Gearotic 4th axis milling to cut it out. Art is usually the expert with this stuff,  but he's vacationing at the moment and won't be back for another 2 weeks.  I should have paid closer attention...lol

 

Cheers
Bob

[Mike]

I can wait  8) I think I need a cutter like this with a 1.75 OD .038 wide tip.

[Nate]

I can wait  8) I think I need a cutter like this with a 1.75 OD .038 wide tip.

Full disclosuse: I have next to no experience with machining, less with CNC, and no experience cutting gears.

That said, you should be able to cut the gear with any cutter that will fit between the teeth.  If you have a cutter with a taper that matches the pressure angle of the gear (and the gear is an involute gear) it makes pathing much easier.

(Basically, it would work like this guy's tool: http://www.jeffree.co.uk/pages/multi-to ... cutter.htm)

Measuring the pressure angles of gears can apparently be a little tricky.  Most gears are 14.5 or 20 degree pressure angle these days.

I've seen a suggestion to roll the gear in clay to make a rack and then to measure the rack. Here's a fancier approach:

http://www.brighthubengineering.com/mac ... d=noscript

...

I'm curious, what does that part do?

[John S]

If you are going to use a form cutter you need a 32DP, 20 degree PA, No#8 cutter

[BobL]

Thanks for all your input guys..


Cheers
Bob
:D

[Mike]

Thanks to all who replied. Doing some reading http://www.bostongear.com/pdf/gear_theory.pdf and math I too figured I need a 32 pitch, 20 deg PA. Now I need to find a cutter. #8 cutters I've seen all are > than 1.75".  I was able to download the gear profile from http://www.rushgears.com. If I can not buy a cutter at a reasonable price I'll make it myself. Anyone know of a supplier?

With CAD I was able to see the cutter Diameter must be 1.25" or smaller, based on the depth of cut and point the cutter leaves the work I would say a .625" diameter cutter is needed.

This is the 2[sup]nd[/sup] of 3 reduction gear sets and used in a 1hp pneumatic drive.
Thanks,
Mike

[Mike]

I talked with Ash Gear. They said;
"A cutter that you are looking for does not exist :o. I suppose you could have a small single cutter made?  But given the delivery and expense you would be better of having Rush gears cut the gear with a hobbing machine."

Looks like I'm making a [glow=SILVER,3,100][font=Verdana][font=Verdana]CUTTER[/font][/font][/glow] ;D.

[Nate]

I talked with Ash Gear. They said;
"A cutter that you are looking for does not exist :o. I suppose you could have a small single cutter made?  But given the delivery and expense you would be better of having Rush gears cut the gear with a hobbing machine."

Looks like I'm making a [glow=SILVER,3,100][font=Verdana][font=Verdana]CUTTER[/font][/font][/glow]

On a 4-axis CNC set-up, you could also cut the gear with a slitting saw.

[Mike]

I see what you mean  :). I had not thought of that.
https://youtu.be/SJQtx80euGM?t=3m11s
I was thinking of buying the 2.25 diameter 32P 20PA #8 cutter and slicing a single tooth out.
Make a fly cutter to hold the single tooth. 8)
I just scored   ;D a Boston Gear pitch gauge on EBAY.

Boston Gear
Gear tooth gauge set
nice compact set including

no 4 - 14 1/2 degree
no 4 - 20 degree
no 5 - 14 1/2 degree
no 5 - 20 degree
no 6 - 14 1/2 degree
no 6 - 20 degree
no 8 - 14 1/2 degree
no 8 - 20 degree
no 10 - 20 degree - no 10 - 14 1/2 degree
no 12 - 20 degree - no 12 - 14 1/2 degree
no 16 - 14 1/2 degree - no 16 - 20 degree
no 20 - 14 1/2 degree - no 20 - 20 degree
no 24 - 14 12/ degree - no 24 - 20 degree
no 32 - 14 1/2 degree - no 32 - 20 degree
no 48 - 14 1/2 degree- no 40 - 20 degree
no 64 - 14 1/2 degree - no 64 - 20 degree

[Nate]

I see what you mean  :). I had not thought of that.
https://youtu.be/SJQtx80euGM?t=3m11s
...

You have the Y axis automated too, you can use an even simpler tool.

https://www.youtube.com/watch?v=AN99dDm ... e=youtu.be

Obviously the most important part is getting a working part, if you can get a slitting saw that will fit the dimensions of your gear, that should be significantly faster than the single tooth tool.

[Mike]

get a slitting saw that will fit the dimensions of your gear
I wish :( 1.25" Nope, any bigger and it will hit the squirrel cage.

[Nate]

get a slitting saw that will fit the dimensions of your gear
I wish :( 1.25" Nope, any bigger and it will hit the squirrel cage.

Again, I have no personal experience, but McMaster-Carr sells slitting saws down to 3/4 of an inch diameter.

[Mike]

:o So they do.

I downloaded a couple of programs to generate a tool path here.

• http://gearotic.com/ESW/FavIcons/index.php?topic=131.0
• http://gearotic.com/ESW/FavIcons/index.php?topic=130.0