View Full Version : Gear cutting

John S
30-09-2010, 11:53 PM
What I have been playing with.

Art Fenerty, the guy who originally wrote Mach3 before his retirement has come out of retirement to write a gear cutting program.

In typical Art fashion he's gone over the top doing eccentric gears 4 bar linkages etc, I have tried to get him back on the straight and narrow to do accurate spur gears.

the whole program was done to cut gears in the flat, router style and limited to thin gears that a vertical tool could reach and fit in.

Art has also added spur gears cut from a vertical cutter using a 4th axis.

Now he's the good bit, instead of using an expensive form cutter, of which you need 8 just to do one range of gears he has got the program to use a conventional off the shelf end mill costing, in my case, all of 2.99 [ less VAT ]

Watch this video of cutting a 45 degree helical gear with just a 3mm cutter.


It first off cuts a slot out equal to the root of the tooth then moves in Y, offsets the rotary table to match and planes a face, it does this 10 times on each face to form the involute face.
Watch the video at 2 minutes in to 3:10 minutes and you will see this step over.

Also does spur gears. I did two 14 teeth gears and put them on pins at the correct centre distance and they run fine.
I then did two more blanks, exactly the same size and modified the tooth shape to cut 13 on one and 15 on the other.


These gears will chop and change onto any pins and run in any order.

More later if there is any interest.
Oh the program, it's called Gearotic and can be found at http://www.gearotic.com (http://www.gearotic.com/)


01-10-2010, 01:06 AM
Love this John and if you want a go at practicing i could do with 24 tooth gear to mesh with an 8TPI leadscrew on my lathe for a thread gauge :-)

01-10-2010, 12:32 PM
GearCodit is a stand alone program for cutting gears,very simple to use.

01-10-2010, 12:44 PM
It would be even more fantastic if it run on Linux? This is a windoze free household......I watched the vids which are great and they explain very well. You up for having a go then?

John S
01-10-2010, 01:10 PM
GearCodit is a stand alone program for cutting gears,very simple to use.

Different animal. Uses hobs or involute cutters.

02-10-2010, 12:10 PM
This is a windoze free household...... yeah right better ask why am i going round there to instal some windoze....cos hes linux wont work thats why!!!!!!!!!!!!!!!!!!!!!1

John S
02-10-2010, 03:01 PM
Because everything is done in software you can play "what if ?" to your little hearts content.
Not quite what you want to fit in? How about a 18.5DP cutter or better still to get bang on a 18.67564 DP ?


I drew a 40 tooth XL series timing pulley up in CAD [ with the help of Mr SPI Industries http://bbs.homeshopmachinist.net/images/smilies/rolleyes.gif ] and got some measurements off it.

They went back to Gearotic [TM] and juggled some figures.


So if we use 16.25 DP we get an OD of 2.5240, we need 2.5240, OK so far

Then play with shift, stubbing and tooth width we get a total depth of 0.0571, we need 0.0550, 2 thou too deep, think I can live with this.

Tooth width is 0.1242 and we need 0.1240, even closer.

Now bung the dxf onto the original drawing and it's within a gnats left bollock.

It's still early days on this program but so was Mach3 at one stage and look where it is now.

Once saved all that is needed to make any XL pulley is to change the number of teeth.

03-10-2010, 07:55 PM
Hi John,

I watched your helical gear video on t'tube John, should sell quite a few licences on it's own I urge anyone at all interested in making gears to view it and download Gearotic Motion NOW!. I'm hoping the wife will buy my license for my birthday :)