View Full Version : How is this done?

10-23-2008, 02:29 PM
I am in the process of attempting to make some control pedals for a motorcycle. Making the lever isn't the problem, however, how are the splines cut in the center of this hole? Broaching? EDM maybe?

This is the one part of the project that I think I'll need help on. Anyone here have experience with these and be willing to cut the splines for me (for a fee , of course).


Hole is .375" ID, 1.00" thick


10-23-2008, 02:54 PM
Internal splines are a pain unless you have a shaper or slotting head.

They're probably pull-broached in mass production, but you'll be amazed how much a 24-tooth spline broach will run you :)

Assuming you don't have any special equipment, you can set-up the part in an indexer on a mill table, chuck a spline-tooth form tool in the mill's spindle, and use the quill feed to methodically cut each spline tooth, a little bit at a time.

Not great for your quill sleeve, but if it's a one-off...

You can do a similar manual-slotting setup on the lathe: mount the piece in the lathe spindle, lock the spindle with the back gear, and rack the carriage back and forth to slot the spline teeth.

If you're planning to make a bunch of these, you might look into getting a quote for a spline broach.

10-23-2008, 03:22 PM
This year I made 2 of these, for a Honda motorcycle.
Determined angle (90 degree) and number of tooth.
Ground a broach (for one tooth) out of round toolbit and shaped the tooth on the mill by holding the toolbit in a chuck and move up and down. For one off's easy.

Made a round back side, which is already removed here, to hold it in soft jaws on the rotary table. Not much to measure, so I tried it every now and then on the gearshift shaft, which was on the motorcycle.


10-23-2008, 03:37 PM
Nice work!
I would do some test holes, drilled to various sizes, and use a junk splined shaft to cold form the splines. If its aluminum, use alot of lube and press the shaft through.

10-23-2008, 03:54 PM
Nice work!
I would do some test holes, drilled to various sizes, and use a junk splined shaft to cold form the splines. If its aluminum, use alot of lube and press the shaft through.

Thought about that, but put the idea aside, because you need a center and stages, just like a broach, so an original splined shaft would just be too short. The fit and finish needs to be really good.

Note the wide saw slit, that is where Honda removes the teeth, so the clamping brings the sides together, instead of trying to slide the teeth off on that spot.

As with all things, once you start these seemingly simple things, you learn a few things on the way, and it's still in one peace. And yes, I use it.

10-23-2008, 04:13 PM
Since this is a One-Off repair... how about just cutting a keyway in the shaft, and then one in the pedal and insert a piece of keystock?

10-23-2008, 04:45 PM
Many bike engines require a full strip-down of the engine to remove the gearchange shaft. Also (and more importantly) that kind of gear lever is adjustable only by moving it round on the splines, so a keyway will offer no adjustment.

EDIT: looking at the pic again it appears to be a brake lever, which would lend itself more reaily to a keyway-fixing, but still not ideal.

10-23-2008, 06:28 PM
metal filled epoxy with release agent on on the splines of the gear box

10-23-2008, 07:11 PM
Find a wrecked donor and grind for a rotary broach? I don't think tolerances would be that critical on this one...

10-23-2008, 09:45 PM
If you have access to a milling machine with a rotary table, I think you should be able to improvise a single point broaching tool. Hand grind an old drill bit so that it has the profile of the spline and mount it on the milling machine (chuck is fine). You'll be using the milling machine like a vertical shaper. It will take a while but making series of light cuts, you should be able to create the profile.

10-24-2008, 10:31 AM
Thanks to all for their suggestions - lots of good ideas!

10-29-2008, 04:40 PM
I saw one suggestion for rotary broaching (http://www.rotarybroaching.com). If you were thinking about rotary broaching, the main cost is in the broach holder. It's around 800 bucks, and a custom broach like that one would probably be around 300. Of course, after you had the broach holder, you could broach squares and hexes too. However, there is an issue with rotary broaching, and it has to do with tooth height. Rotary broaching has some tooth height limitations depending on the material, so you would really need to call a rotary broach manufacturer first and see if it's pracitical.
Rotary Broaching Tools