On Mar 11, 1:19�pm, _
wrote:
Might be making some bespoke arrangements for a motorcycle project, and was
wondering if there is an available tool to cut the splines on bits to fit
these shafts.

If you fail to locate a ready-made broach, and have a near-death
experience when you see what a custom-made broach will cost, you may
consider making your own broach. You can probably make one on your
own if you have a milling machine and indexing fixture. Basically,
you make a splined shaft to match the hub you want to mate to, and cut
teeth in it. Many of the serration splines use a groove pattern which
can be cut with the edge of an ordinary end mill, cutting a 90-degree-
bottom groove in the shaft. You will need to make a splined section
several inches long. After cutting a facsimile of your shaft spline,
you proceed to turn it into a broach by these routine steps:

1. Turn the end of the splined shaft down to form a pilot at the
minor diameter of the spline.
2. Turn a long taper along the splined section of your shaft,
increasing the diameter from the pilot section to the major diameter
of the spline. It would be reasonable to figure on a tapered section
three or four inches long, so that each tooth in the finished broach
is required to cut only a couple of thousandths. You can see that to
cut spline teeth .050" deep, you will be needing 25 teeth.
3. At reasonable intervals along the tapered section, cut notches,
forming teeth with cutting edge toward the small end of the taper.
There should be little or no rake and relief on these teeth. Turn a
space between teeth to collect chips cut by the next tooth.

An article on how to make such broaches appeared in either Home Shop
Machinist or Machinist's Wrkshop a couple of years ago, and makes it
look quite doable by an inexperienced machinist. In selecting your
material, consider how many pieces you expect your broach to produce,
and the hardness of the hubs to be broached. For a few hubs of
aluminum, you could get away with a broach made of 4145 steel or other
popular shaft material. The 4145 can be oil hardend to make a very
durable broach for use in softer materials. If you want a real
production broach, select drill rod for your material and harden it to
full tool steel hardness.