I'm looking for ideas on how to cut R/C servo spline grooves into a hole in
aluminum.OR even on how to build a tool to
do this for small production runs, say 5 to 10 at a time or so - by hand is
fine. Maybe some kind of lever operated
OR - maybe if there is a way to just press the spline grooves onto a shaft of
steel and then harden it I can fabricate a
punch that way.
I just got a Sherline mill machine with a few of the basic accessories, if that
Any ideas are welcome !
I would drill the hole in your gear the size od. of the largest dia of
your shaft you need to press it on...
Then I would rub some never seaze on the PTO shaft... Then I would mix
some J-B weld up and press on the gear and squese in the J-B weld
around the splines... After it drys you can press the gear off and you
will have what you want....
Is this a through hole, or a blind hole? The suggestions below
are assuming a through hole. For a blind hole, you will probably want
something like a wobble broach -- and I have no idea how you would find
one in the right size. You might have to make one. Look them up on the
Hmm ... I would suggest finding out what gear that duplicates,
and buy some gear wire of the proper size. Turn a series of steps into
it like a broach, then harden it (it is probably annealed so it can be
machined to fit into hubs of larger gears), and you have a broach for
Have you ever seen a broach? There are two fairly common
styles -- the ones used with bushings to cut keys in hubs, and square or
hex ones for making appropriate sized and shaped holes in workpieces.
Look them up on the Dumont web page (just search on "Dumont broach"
(without the quotes) to see what they look like.
All need a press. I don't know the size of your needed spline, but I
suspect that the little 1/2 ton presses would do for that. For some
things, the three ton which I have is marginal.
It sounds a bit minimal for this task. A sherline lathe could
be used in cutting the steps and clearances in the gear wire to make the
punch -- or any other small lathe.
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Servo output splines are only about 3/16" some much smaller. A few
slightly larger. In the old days most servos had square output shafts. I
still have a few.The introduction of splines was a real breakthru. Most
servos come with about 5 different output arms/wheels. Computerized
radios have sorta negated the need for some of these. Mostly hey have
always been molded nylon but you can get metal ones anodized in pretty
colors for showing off your wallet.
I would suppose that there are many folks here that make holes in metal
parts frequently, that don't know what type of hole you're referring
to, and I'm one of 'em.
As far as internal splines go, they're one of the more difficult types
of holes to make, depending on hole depth/metal thickness, accuracy and
load characteristics. A relatively easy way to make a hole with
serrations (not exactly splines)is to drill small holes in a circle.
Changing the circle size and drill size will obtain different results,
maybe a certain combination will work for your parts.
Your application isn't extremely critical, and I assume the reason that
the shaft is splined is to permit installation of an accessory at
various positions. I have no idea if another fastener (shaft nut) is
utilized to keep the parts (you're wanting to make) in place.
A followup reply suggests that the hole is about 3/16". If you would
care to be more descriptive, you might get more help.
When I first saw the question, I though that the servo shaft could have
many really fine splines.
If there were only 6 splines (for example), I might try pushing a Torx
(Tor-X) driver thru a hole in aluminum. This method would involve
distorting/displacing the hole in the aluminum part (instead of trying
to punch a precisely splined hole).
You'd need to experiment with various sized holes in small increments,
as a slightly different sized hole might produce better results.
Polishing and/or slightly tapering the driver splines and using a heavy
duty lubricant may improve the results.
The method you use to push it thru will depend upon what
tools/equipment you have, or might be inclined to get. A small
mechanical (Panapress) press would very likely improve your chances of
being able to attain repeatable results.
If it turns out that you determine that matching the splines of the
shaft isn't going to be cost effective for you to do, then you might
pursue other ways to accomplish your task. Maybe you could locate small
splined hubs that fit the shaft (in brass, maybe), that you could then
solder extensions to.
Modifying available servo arms/cranks? might be easier, depending upon
the method used. I've used the "magical, miraclulous" aluminum repair
rod for fabricating and repairing many small aluminum parts. If you're
comfortable using a propane torch, it might be an option for you. Don't
have great expectations of great looking results.
If you aren't experienced in using a torch, experiment with a lot of
small scrap aluminum pieces, as it's fairly easy to completely
melt/liquify small parts.
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