I want to make gears in small scale with a cnc desktop mill. What is the minimum axis I need to cut gears? Will a 3 or 4-axis mill do the job?

Thanks
Ray
rcjetpilot@rcmodeler.net

Hi Ray,

There are different methods for cutting gears. The only one that I am familiar with on a milling machine is to use an involute cutter. Using an involute cutter is a quick and relatively painless way of making gears - the only drawback is that you will need about 8 different cutters to cover all the number of teeth for a particular gear size (for example if you wanted to cut a 15 tooth module 1 gear and a 30 tooth module 1 gear, you'd have to use different cutters. The same would go for a 30 tooth and, say a 70 tooth). For this reason, you often find involute cutter sets that come with all the cutters for a particular 'size' gear.

You would probably then need 4 axes to cut the gears under full CNC. Once the z-axis has been lined up with the centre of the gear, it can be left alone (but make sure it is properly centred!). The a-axis would be used to index the gear and the x and y axes would be used to do the actual cutting.

Very often with small gears, you can cut the teeth in one pass which makes the process very quick. I have found the finish of gears very good when done using this method.

I hope this helps.

Regards
Warren

Ray,
I don't know what controller you are using but there are some add on wizards to go with mach3 that can go gears.
Go to
http://www.newfangledsolutions.com/
and work down Products to seee the different wizards, here's the gear wizard.
http://www.newfangledsolutions.com/images/products/cut_gear.jpg

You fill in the boxes and it automatically writes the code.

John S.

Depends how small the gear is (Diam. & Thickness) I think you could get by with a minimum of "2-axis" If you had "Z" Fixed. Like mentioned before "Z" shouldn't move once its in position. So all you would need is "X-axis" & "A-axis" All your doing is rotating "A-axis", slide "X-axis across the part, Repeat process, 360 deg.

Why would you spend $200.00 to buy software just to cut a gear? Write the G-code yourself using Notepad or something free! I'm thinking your probably cutting parts for some type of RC model (from your email).

Don't get me wrong about the Mach software, that control is worth every penny!

A gear is simple to program yourself, If I want "20-teeth" (360 / 20 = 18) So rotate "A-axis" (18 deg.), Then Feed "X-axis into the gear, Retract "X-axis", Rotate "A-axis" etc. etc.

Just get some scrap material practice, till it looks good.

Don't waste your money on more software, This is DIY (or is it)?

If you can't write code this place has 18,628 members and I'm sure most will help :)

If you have CAD software with a gear generator (Bobcad has one, or geargen plugin for Rhino), you can use it to draw the gear. Then contour around the profile of the gear with an endmill small enough to get in between the gear teeth. This generally limits you to relatively thin gears (due to the dia/length ratio of the endmill). If you don't have a CAD package that generates gear teeth, you can use math to generate the involute and make the gear yourself. (do a google search for "gear polar involute" and you will see the formulas. I wrote an article on an simple graphical method for HSM but they haven't published it yet so I can't put it up on the web.

Bad link - Removed by Wayne

Bobcads gear generator is not geometrically correct.
It fudges everything below the pitch circle line.
can't comment on the Rhino one as I haven't tried it but many of the CAD programs that draw gears only do an approximation of a gear.

John S.

RE: bad gear drawings generated in BC.

I downloaded DXF drawings of gears from Boston Gear or maybe it was Spi? Then used offsets and cut gears from delrin with .0625 end mills. The smallest gears I could make with that size cutter were 16 pitch.

I've been bitten by the gear bug now too! Been looking for a simple way to cut them, simple(?) spur gear to put on a 1 inch s/s shaft. About 4 inches in diameter - 64 minimum teeth, 2 of them same size, etc. After endless hours of googling ('vista and others) I came across a couple of programs:

http://www.realhamradio.com/gearhome.htm

Does anyone have experience with this program? Heck - for about 50 bucks I just might try it out - ought be easier than drawing it up and all the steps between "I want it, I needit and I have it!".
:cheers: Jim
Note - I see this is in Benchtop Mills - I'd be using my router :D

What type of gear do you want to make?
There are different types.
A spur gear ( a "normal" gear)
A helical gear.
a worm gear.

Hello. For simple, straight gears, I use the free Geargen plugin for Rhino. I used Visual Mill profile machining to cut it. This is the latest one I cut: http://www.cnczone.com/forums/showpost.php?p=125196&postcount=5

I used two endmills; an 1/8" to rough out most material and then a 1/16" to finish. While it's true these gears were only 1/8" high, I don't see a problem using the same method to cut thicker ones.

JR

Looking to do a couple of spur grears - JR your lead looks promising too Thanks!
Here's a shot of the gears for the steering vane. 2 1:1 spur gears on shafts.
:cheers: Jim