CafeenMan

I have a Fox conical spinner with adapter that I need to put on an O.S. .52 4-stroke. When this spinner was designed, engines tended to have shorter crankshafts. With this engine, I can only turn the cone retaining bolt in about 1/4". I could cut off the excess bolt, but it's not threaded and it's hardened steel.

I'm not sure how I can thread this bolt and it's a special shape that I'm sure I won't find anywhere else. I called Fox and they weren't much help. Any suggestions? All I need to do is figure out a way to thread this bolt. The attached photo should show the problem.

thanks

- Paul

Doug D.

Look for a die of the same pitch and diameter and cut the threads up to where you need them. If you've never done this before ask around. Local machine shops should be able to help. Make sure you explain carefully what you want done.
The only other alternative is a different spinner. [&:]

CafeenMan

Doug - I think the bolt is hardened. I'm afraid a die will bounce right off it. I don't mind ruining the die to cut the thread so a one time use is fine if it works. Somebody mentioned that maybe I should anneal the bolt. Not sure exactly how to do that. I don't even own a torch to heat it. Thanks for the suggestions.

dr_wogz

My Feedback: (3)

I guess teh pain is teh head of teh bolt.. No way in getting a shorter bolt? The spinner manufactuer can't make you one, shorter? And a regular socket head won't cut it?

No way to get a machininst to mill you a new shorter one, then have him / them 'dunk it' to harden it? or make it out of stainless?

Yeah, hardened steel bolts won't thread too well...

FlyingPilgrim

My Feedback: (26)

Why can't you simply buy a new bolt the length you need? If you have a Sears Hardware outlet near you, they are a good source for odd things like oval head screws etc. It should be available with a tapered seat (like a flat head screw), but with an oval head and probably phillips slot.

Pilgrim

CafeenMan

Pilgrim - Thanks. I guess I was unaware that this type bolt was common. I thought it was something specially made by Fox for their spinner. I live less than a mile from Home Depot and Lowes, so I'll check there. If no luck I'll venture on to Sears.

Thanks

- Paul

3DFanatic

My Feedback: (5)

Wildly unlikely that Fox would "invent a thread". Take the adapter to your nearest hardware superstore and find a bolt th at fits it.

CafeenMan

3D - Yeah, the thread is standard. I just didn't think the head shape was. I'm going hunting for one tomorrow.

Stick Jammer

Just a thought, but if you can't find a shorter bolt, would it be possible to get a shorter adapter for the prop shaft? It looks like that might work, even if you have to cut some of the threaded portion of the bolt off. 5 or 6 threads into the adapter should be enough to hold it.

MinnFlyer

My Feedback: (4)

Caffeen, if you heat the area you want to thread to a glowing red, then let it air cool, you should be able to run a die on it.

CafeenMan

OK, here's the situation:

The bolt that comes with the spinner is 10-32. I went to Home Depot and Lowes and they both carry oval head bolts but not 10-32. They have 10-24 and 8-32. I have some CB Associates spinners that are the right thread for the crankshaft, but I believe to be #8 for the spinner. So I bought both 10-24 and 8-32 oval heads to see what I could do with them. BTW - they had brass and stainless steel. I went with the stainless.

So, I figured either I could try to retap the Fox adapter from 10-32 to 10-24 and hope that it didn't come apart in use or use the CB adapter. I went with the second choice. The bolt is obviously too small for the hole in the spinner, but the head seats nicely and I don't think it will give me any problems. So for now the problem seems to be solved.

The nice thing about it is that I can't get any adapter on the shaft with the 2-part nut that came with the engine, so I used a regular 1/4-20 prop nut from a different engine. That allows me to use the spinner adapter as a lock nut against the prop nut. The adapter is aluminum though, so I can't crank it down as much as I like, but it still gives a little security against throwing the prop in a backfire. We'll see...

CafeenMan

OK, seems to work. Didn't get thrown and I'm not maimed any more than I usually am.

WilsonFlyer

My Feedback: (13)

FYI- A good die will thread that bolt if anybody still cares. Cheap dies will not.

_WIT_

Well, if it's Rockwell C 56 or harder, you won't machine it. What you could do is grind the OD of the screw down to the minor diameter of the threaded portion, to allow the screw to thread all the way down.

But, looks like you've got it working.