How Do I Make This Part?

[Harvey]

This is a plastic handle for a power disconnect cabinet that will be mounted outside and will be fully exposed to the sun and rain (i.e. not under a roof eve, etc). Therefore, I do not see it surviving very long, even if it IS intended for outdoor use. But more importantly, the disconnect box will be mounted to a restored 1932 airways beacon tower and the red & black plastic handle looks totally out of place. So I've decided to make a replacement handle out of aluminum.

The tricky part is going to be cutting the splined hole in the new handle to accept the splined shaft sticking out of the box. (The shaft rotates to open and close the disconnect switch.) Being that this is a low duty-cycle function (little use, limited rotation angle, and a very light force required), the fit of the new handle to the existing spline doesn't have to be to NASA specifications. I figure to make my new handle in two pieces: the splined end, and the handle itself (both, of which, can then be turned on my lathe) and then weld the two pieces together.

To create the seven splines, I plan to form them by simply drilling seven holes. (This piece is small, about 1.5" OD and the hole will be blind so broaching or filing them is out.) After drilling the splines, I'll then drill the larger center hole. Yes, I know it won't be perfect but I'm sure it'll suit my needs.

My question to y'all is how to lay out the splines (holes). If you'll look carefully at the pictures, you'll notice that six of the splines are a set width. However, there is one fat spline (at the 4 o'clock position in the pictures) that allows the handle to slide onto the shaft at only one azimuth. While the six smaller splines are equally spaced, this fatter indexing spline throws a curve into laying out all of the splines. In other words, the fat spline isn't conveniently twice the width of the smaller splines. (Is it clear what I'm trying to describe here?)

Sooooooo, any suggestions?

TIA

Harvey

 

[Ulma Doctor]

Hi Harvey,
i understood what you were trying to describe.
this is not answering your question at all, but rather another way of doing the operation.
the material you chose for the handle is aluminum.
with a little planning , you could make a rotary broach from basic elements and form the cutter from a piece of mild steel.
here's a link to a fairly recent post that gives the idea.
http://www.hobby-machinist.com/threads/rotary-broach.30404/

the cutter may be the hardest/most time consuming part to form.
mild steel should be sufficient for a 1 off in aluminum.
i hope the idea is useful.

 

[RJSakowski]

It looks like you will have to blueprint the feature. The splines in the socket appear to be uniform in thickness. That's a starter. Measure o.d. and i.d. If you can find someone with an optical comparator, you can build up a fairly accurate drawing of the spline. Once you have drawn your spline, make a full size pattern on paper. Glue it to some pasteboard and cut it out and check your fit on the shaft. Tweak the drawing as necessary and repeat. When yoou are satisfied with the fit, you can proceed to making the part.

+1 on the two pieces. The splined insert could be pressed in or threaded. In either case, I would use LocTite to help secure the insert. Rather than drill the spline pattern, I would mill it. A rotary table would be perfect for this job. I made a splined wrench for a Grizzly mill spindle that way.

Good luck!

 

[Dave Smith]

Harvey--without seeing more pictures of the handle and how far out the shaft extends out of the box is hard for me to help more---is it possible instead of making a whole new handle ---to just make an aluminum cover to give the existing handle a better look and keep the sun and weather off of it------what holds the handle on the shaft ?-----Dave

 

[MozamPete]

+1 on the two pieces. The splined insert could be pressed in or threaded. In either case, I would use LocTite to help secure the insert. Rather than drill the spline pattern, I would mill it. A rotary table would be perfect for this job. I made a splined wrench for a Grizzly mill spindle that way.

Good luck!

Or just machine the female spline section from the existing handle and fit/Loctite it into a new handle.

 

[mzayd3]

Would it be easier to remake both the handle and shaft with another configuration that is easier to machine?

 

[Billh50]

I would make the handle. Cut and turn the old handle so that I have the spline in a round piece. Drill a hole for the spline piece in the handle and then glue and pin the spline into the handle.

 

[brino]

Hi Harvey,

-can you simply steal the mating splined piece from the original handle? (cannot tell if it's plastic from photo)
-could you just mill the spline using a small end mill and rotary table?
-grind a flat on one side of the shaft stub for a grub screw
-is the shaft temporarily removable? Perhaps use it as a pattern and cast the mating piece in aluminum or even jb-weld
-can you drill and tap a hole in the end of the shaft? If it's low torque, loc-tite and a bolted handle might be enough
-with a threaded hole, perhaps a single toothed spline would suffice, it's easier to make....just like a key way
-can you turn down the shaft and either thread it(external) or grind a flat for a grub screw?
-what material is the shaft? Can you just weld a new handle on?

-brino

 

[Fabrickator]

I would make a new handle with a round hole big enough to fit over the spline shaft. Then I would drill a cross hole and pin it. Although, the mating surfaces look really short. Maybe instead, drill and tap a hole down the middle of the shaft and screw the handle on.

 

[Harvey]

Good Morning Guys, thanks for your inputs so far.

Note that I cannot modify the shaft itself. It is factory-assembled into a sealed $450.00 breaker assembly that I don't dare mess with for fear of damaging it and having to buy another.

Also, I'm not sure about making my new aluminum handle with the plastic splined section from the old one glued or pinned in. The old splined section (yes, it's plastic) seems strong but I doubt that it would still be strong after cutting it out of the rest of the handle. And since the original handle isn't available separately, a botched experiment would probably cost me another $450!

After sleeping on it last night, I'm considering laying a piece of balsa wood against the end of the shaft and lightly tapping it with a hammer to impress the spline pattern into it. That'll give me something to take to the workbench and measure.

I'm still open to suggestions though.

Harvey