The original Miter Gears in Jr's Axles were store bought and made from a relatively soft stainless steel. It would have cost me way too much to have some made and the gear shops I talked to could not cut the gears after they were heat treated. I decided to give it a shot and this is what I came up with...

I had a friend Robert Cole turn the blanks for me out of 17-4PH stainless steel on this CNC Lathe. CNC ensures all the blanks are exactly the same and perfectly sized. I then drilled and tapped a #6-32 hole through to the bore and sent the blanks out to be heat treated to H1100 or about 45Rc.

Not only did I have to build gears but since this has never been done before, I had to build custom indexing and inspection tools too. I had tried to cut 4 teeth at a time indexing 6 times first and it was not possible, after another failed attempt I realized I would have to cut 1 tooth at a time indexing 24 times.

Tooling ready to go I needed a 4 axis program for the Wire EDM. I started by using my solid model of the Gear that I previously created in AutoDesks Mechanical Desktop software. I then imported the model into AutoCAD where I rotated it 45 degrees and sliced it twice to create an upper and lower path. The last step was to import the upper and lower paths into Exprit-X CAD CAM and generate the XYUV program for the EDM machine.

This picture shows the toolpath on the screen of the machine that cut the teeth, a Mitsubishi FX-10 Wire EDM.

Each tooth took 3 minutes and 10 seconds to cut or about 1 hour and 16 minutes a gear. This picture shows a partially finished gear.

This is to the best of my knowledge the first and only Miter Bevel Gear ever cut on a Wire EDM Machine in the world (If you know otherwise, please email me)

This view shows the fixture well, the brass setscrew on the top holds the shaft that the gear blank and index ring are attached to in place. The index ring is pinned to the shaft and locates on a dowel pin in the base of the fixture. To index the blank you have to loosen the setscrew, lift and index, lower, and tighten the setscrew (very simple).

There they are, the finished Gears on my custom inpection tool! I passivated them to clean them up and to help prevent rust (even though its stainless steel). I made the inspection tool just for this job and it is designed to have a .2000" gap with a perfect mesh. The Jo block you see under the lower gear is exactly .2000". The top gap measured .2010"! There is only .0010" clearance in these gears!

Here's another look at the finished Gears on my inspection tool. The true tapered involute teeth mesh perfectly. The original gears were 48 pitch 30 teeth with a 3/16" face and the new gears are 32 pitch 24 teeth with a 1/4" face. Bigger teeth and harder material equals a much much stronger gear!

While I had the Axles apart I drilled and tapped inpection holes on the pumpkin housings. They will allow me to check and lube the gears from time to time without having to disassemble the entire Axles.

The main Axle shaft is the original made from titanium but the Pinion shaft is new and made from a hardened gage pin. The other change is that the gears are pinned to the shafts with 3/32" diameter dowel pins.

This picture shows the Gears in place inside the pumpkin housing. I had to enlarge the opening in the pumpkin housings to fit these larger gears but they still only have .010" clearance inside the housing! To see the rest of the Axle assembly check out the previous page.