# How Do I Make This Part?



## Harvey (May 11, 2015)

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


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## Ulma Doctor (May 11, 2015)

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.


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## RJSakowski (May 11, 2015)

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!


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## Dave Smith (May 12, 2015)

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


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## MozamPete (May 12, 2015)

RJSakowski said:


> +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.


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## mzayd3 (May 12, 2015)

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


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## Billh50 (May 12, 2015)

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.


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## brino (May 12, 2015)

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


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## Fabrickator (May 12, 2015)

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.


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## Harvey (May 12, 2015)

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


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## T Bredehoft (May 12, 2015)

You might try, instead of bruising balsa, casting some plastic on the shaft, spray it with Pam, or other suitable vegetable non-stick spray,  (temporary mold release compound) packing JB weld around it with an embedded flat head screw for a handle.  This would give you an exact copy of what  you're trying to fabricate.


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## SkyKen (May 12, 2015)

Hi! You may be able to use low temperature fixturing alloy, I get mine from enco model# MH505-3877 in the last flyer I got.
This one melts at 180 deg. Others melt at lower or higher temperatures. Just make a plug and measure it to your hearts content.
I would also look at a torqe (spelling) type screw and see if it would fit with a little tlc.
Looks like you are on the right track. I hate plastic out side.


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## brino (May 12, 2015)

SkyKen said:


> I would also look at a torqe (spelling) type screw and see if it would fit with a little tlc.



Hey SkyKen, I like that idea; start with a torx-head bolt and modify it......however, a torx is 6-point and this beast is 7, with one odd-ball sized one....so it may not work out being low "tlc".

The more I think about it, I'd just find a nut that goes over the spline and jb-weld it in place, then make a handle for the hex nut...

-brino


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## SkyKen (May 12, 2015)

Sorry  Brino I did not count the splines, my bad. Hey I did not count the splines on a torx either.
Got to go wash the plane and get the condition inspection done before the weekend.
Ken


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## Bill C. (May 12, 2015)

Sounds like a proprietary design, a pain in the neck.  I like JB weld just make sure there are no air bubbles.


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## randyc (May 12, 2015)

Ulma Doctor said:


> 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.
> ...




I like Mike's (Ulma Doctor) suggestion - a rotary broach is exactly what I would use.

One could argue that it would be WAY overkill for a one-off part - but once the tool is made, it's there for future use, all that's required is to make a new broach for each new application and that's a comparatively simple task once the entire tool has been made.

Here's one that I made, it's not any better than the broach that Mike posted but I did include a drawing for it:

http://www.hobby-machinist.com/threads/a-simple-compact-rotary-broach.33032/

Another thought - plastic might not be a good first choice for continuous outdoor exposure.  UV radiation breaks down the characteristics of most plastic compositions fairly quickly, as I recall.  Unless the material is specifically specified to be resistant to UV, aluminum might be a better solution


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## Mark_f (May 12, 2015)

Fabrickator said:


> 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.



Fabrickator's idea sounds like the best idea I have read so far. and drill two or three set screw holes to lock into the shaft splines.


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## jim18655 (May 12, 2015)

Paint to match the switch box? A rain-tight switch handle would be UV resistant and last a long time. 
You could mold, drill and file to fit. I think you could file to shape faster than making a special cutter. A rotary table will help with the layout. Measure the turns or degrees between splines as you move the proper size bit into the spline notch and repeat on the new handle. File the drilled holes square after you drill the center hole out.


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## cvairwerks (May 15, 2015)

Harvey: Order youi a 2 pound kit of DMR503 from Dynamold and make a copy of the shaft head, You can then use that to make a plug for the head and create a silicone mold for the handle and cast your own using UV stabilized resin.


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## Round in circles (May 15, 2015)

JB weld a simple UVv resistant pipe sleeve over the handle or machine out a dedicated channel & fix it with JB weld  .

 Those handles are long so you can easily open the cabinet or turn things off & made of electrical grade  plastic to reduce the chances of you getting electrocuted .

Don't use aluminium handles on power kill switches for you may get far more of a shock that you bargained for .


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## Harvey (May 15, 2015)

David,

The disconnect switch is for a 24 volt control circuit so I doubt that electrocution will be a threat.

But thanks for throwing in a warning flag.

Harvey


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## tomw (May 16, 2015)

If 24V AC, it can kill, and it will definitely hurt. The heart circuitry does very poorly with stray ac current. So, if you are planning on using this while standing in a shallow tropical bay overlooking the breakers on the reef, I would recommend a plastic handle. Not that I have done this. Oh....


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## John Hasler (May 16, 2015)

tomw said:


> If 24V AC, it can kill,



UL disagrees.


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## tomw (May 16, 2015)

That was meant as a joke. Sorry. I got a hell of shock from a 24V AC motor I was using to help me sample in a mangrove. I have a feeling it was more than 24V!


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## drom68 (May 17, 2015)

Harvey, from the pictures it looks like it is an 8 spline piece with two splines combined to make the one large spline/keyway.  Not sure if you have a dividing head or rotary table but you could use one of them to make what is needed to broach the splines.  You could broach all 8 splines and then remove the section between two of the splines to make your one large one.  There a couple of thoughts I have on this, but have to leave right now. I'll get back and try explain a little better later tonight.


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## John Hasler (May 17, 2015)

tomw said:


> That was meant as a joke. Sorry. I got a hell of shock from a 24V AC motor I was using to help me sample in a mangrove. I have a feeling it was more than 24V!


Yes, if you interrupt the current through a big inductor such as the armature of a motor you can get a pretty good high voltage spike.


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## Harvey (May 17, 2015)

Drom68,

If you'll take a close look at the picture, you'll see that an evenly-spaced 8-spline pattern won't work.  An 8-spline layout will have four pairs of splines with mirror images on their opposite sides.  On my splined shaft, no two splines are opposite each other.  You has a good thought and I appreciate your input.

Harvey


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## Harvey (May 17, 2015)

Posted by Drom68
"Harvey, from the pictures it looks like it is an 8 spline piece with two splines combined to make the one large spline/keyway. Not sure if you have a dividing head or rotary table but you could use one of them to make what is needed to broach the splines. You could broach all 8 splines and then remove the section between two of the splines to make your one large one."


Drom,
An evenly-spaced 8-spline pattern won't work. Each spline in an even-numbered pattern will have another spline exactly across from it on the other side of the circle. If you'll take a close look at the picture, you'll see that on my splined shaft, no two splines are opposite each other. You had a good thought though and I appreciate your input.

Harvey


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## Harvey (May 17, 2015)

Posted by John Hasler
"Yes, if you interrupt the current through a big inductor such as the armature of a motor you can get a pretty good high voltage spike."

John,
My 24VAC  is fused at 5A.  It's control voltage to activate a couple of remote relays and a panel lamp.  There are no motors or other spike-inducing devices.  Thanks for looking out for my safety though.

Harvey


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