What is the correct grade bolt to use for mounting a prop? I "think" that grade 5 should be fine, but wonder if grade 8 would be better. I've seen conflicting advice on this.

Should the prop bolts be safety wired? I sounds like a good idea, but I wonder if it's really needed. Again, I've seen conflicting advise.

The prop came with 8 mm x 100 mm bolts, which were not only a little too long, but the wrong thread to fit my reduction drive adapter, which is threaded for 5/16-24 bolts.

There are only a few thousands of an inch difference between 8 mm and 5/16" bolts, so I don't think that's a problem, at least from a diameter perspective.

I was able to find 5/16-24 x 3-3/4" grade 5 bolts fairly easily from a local supplier. (That's what I needed to test fit my latest prop to my reduction drive's adapter) That's with a lock washer, and a flat washer.

What I've got fits up just fine, with almost full depth thread engagement, and they don't bottom out.

I've had no luck at all in finding either grade 5 or grade 8 drilled head bolts in this length.

So, I guess I have 3 questions.

1. Should we use grade 5 or grade 8 bolts?

2. Is safety wiring even needed?

3. Should I just quit worrying, and use what I've got?

Thanks,

Duane

Hey Duane, we use grade 8 bolts and no safety wire. The grade 5 would probably be OK but grade 8 is the standard in the industry. If you can't find them at the hardware stores, try to find a hardware supplier. Now you should not worry and go back to sleep. ;stir; :&&:
Thanks, Chuck

Chuck,

I was hoping that you'd pipe in on this. ;thumb;

The grade 5 bolts that I have are from a local industrial supplier. None of the usual hardware store variety places could come close. ;bawl;

This supplier told me that he "might" be able to find them in grade 8. I didn't pursue it at the time because I thought I'd just order some drilled head AN5 bolts from Aircraft Spruce. Problem is, they are not available in the length that I need.

At least you've assured me that I don't need to keep searching for a white elephant. (Drilled heads). I'll give my local industrial supplier a call tomorrow, and ask him if he can get this bolt in grade 8.

I'll sleep better tonight. :&&:

Thanks again,

Duane

Let me know if you can't find them and i will send you a set.
Chuck

Chuck,

Thank you for the offer. I "think" I've got the grade 8 bolts lined up. I'll go by Monday to see what he's got. If that doesn't work out, I'll give you a call.

Dropping the "drilled head" from my request has made the search so much simpler... :o

Thanks,

Duane