Securing a square cable in a round hole?

[David Hodgkins]

I've finally finished my engine-turning jig and tried it out for the first time yesterday.

For a first panel, it came out quite good! I didn't clamp the work to the table and it shifted during the process so there are alignment issues but overall I like the results, which you can see in the pic below.

My biggest hiccup happened when the cable that I had glued to the end of the motor shaft with JB Weld gave way. Is there a stronger compound out there? What can I do to make the bond stronger? Will just sanding the end of the shaft make the adhesion that much better? should I cut striations into the end of the shaft with a grinder?

Here's the issue:




The cable is "clamped" to the front of the motor so that's not the issue. The issue is how to glue the cable into that little round hole so that it won't break loose as the motor turns.

Any tips you can give are greatly appreciated!

[David Hodgkins]

PS here's what the test panel looks like. I placed it in position as if it were the firewall. The idea is to get it straighter and more consistent before trying to do any actual panels...

[68GT500MAN]

David,
I was wondering Saturday as I was looking over the 33 when you were going to post some more information on this project. Nice use of Oak to make fixture. How much torque is there trying to turn the square shaft in the round hole? It seems to me that it will be difficult to keep the two pieces together as one, not knowing all of the pieces you are using, is it possible to drill and tap the shaft with the round hole and use two set screws? I would like to know the whole parts list needed to get started in engine turning.
Doug

[David Hodgkins]

Hi Doug,

A set screw sounds like a reasonable plan. Actually, now that you have me thinking about it, a set screw with an allen head sounds just about right. I assume it wouldn't throw the motor balance off?

re: the tools needed, I have all new parts in this jig and it's more expensive than I planned, by far! The motor alone lists for $800! (I got it for $450).

Would you be willing to let me turn your parts for you after I get the quality up?

[68GT500MAN]

Letting you do the work would be something I would be interested in. Use two small socket allen set screw (probably 8/32 x 3/16") to keep everything in balance.
Doug

[frankeeski]

X2 on the set screws Dave.

[David Hodgkins]

Guess who broke off a tap in not one, but TWO holes?!?!?!

AAAAAAAARRRRRRRRRRRRRRGGGGGGGGGGGGGGGGGGGGGGGGGGGG GGG!!!!!!!!!!!!!!

Fudge.

[David Hodgkins]

Well, I spoke with the guy I bought the motor from. I guess I'm going to cut off the top 1/3" of the motor shaft and try again...

One step forward, two steps back!

[68GT500MAN]

What size hole are you drilling for the tap?
Doug

[David Hodgkins]

the tap is a 6-32 and I was using a #5 for the hole. they came as a set.

[68GT500MAN]

Do you mean a #35 drill? Get a #32 (a little larger) and you will get 50% thread which will be easier to tap. Since you are trying to capture the square shaft the reduction in thread % will not cause a problem.
Doug

[David Hodgkins]

Success!

Unfortunately my DSLR was set to raw mode so I have to convert some images before posting them.

I ended up cutting about 3/8" off the shaft. I marked the center of the shaft with a sharpie while the motor was turning and drilled a new center hole, then drilled and tapped a hole from the side for the 6-32 X 3/8" set screw(Doug, I ended up using a #36 bit) . This time the operation was a success and the solution is a lot stronger than it was before.

Thanks guys!

[68GT500MAN]

Great news! Let me know when you are ready to start paying off the equipment.
Doug