Longer '65 Seatbelt Attaching Bolt?

[Greg Madden]

My '65 had damaged fiberglass around the drivers side seatbelt attachment point. It looked like perhaps a previous owner let the seatbelt hang out the door and it got caught under the wheel. It had been repaired by drilling a hole *through* the frame and running a bolt through the seatbelt, what was left of the fiberglass & reinforcement plate, and the frame! (Lots of fun when I pulled the body & couldn't figure out *why* the body wouldn't lift at that point!) Years ago I repaired the fiberglass damage and rivited in a replacement reinforcement plate. However, my fiberglass repair is now thicker than the original fiberglass, and the stock (repro) bolt only engages a few threads. I don't really want to go back and grind the fiberglass down further since it is a repair. Anyone know of a similar, but longer bolt, possibly for another application? Otherwise I'm thinking of having a machine shop make one.

Regards,

- Greg

[Joe L.]

Re: Longer '65 Seatbelt Attaching Bolt?

Geg----

I don't know that I'd recommend that you go the route of having bolts made for this application. First off, I think that you'll find it quite expensive to have this done. Just getting set-up to machine the bolts will take considerable time(which machine shops charge for by the hour)and then to make just two such bolts will probably result in the cost per unit to be incredible.

Second, but most important, is the fact that non-hardened bolts with cut threads such as a machine shop will likely make for you, will not be as strong as the hardened, alloy steel, rolled thread bolts that were originally used. These bolts are a SAFETY related item. Given the fact that 60s Corvettes have few enough occupant protection safety features, I wouldn't consider it wise to compromise the integrity of the few that you have going for you.

I don't know off-hand what other seat belt bolts might be of similar configuration, but longer. However, I'd guess that if you went down to your local "self-service" type wrecking yard and perused their stock of 60s-era GM cars, you might very well find similar, but longer, bolts. In fact, you might even find some intersting and valuable seat belt buckles in the process.

Otherwise, I think that I'd probably carefully grind away a little of your fiberglass repair area. This can readily be done with a fiberglass-type repair and should not significantly weaken it. Especially since, based upon your description of where you're at, the amount of material to be removed would be minimal.

[Greg Madden]

Re: Longer '65 Seatbelt Attaching Bolt?

Thanks for the suggestions. I've looked around my local Vette dismantler but haven't found anything, and vehicles get stripped and crushed quickly at the local wrecking yards (LA area) so there aren't any 60's vehicle to look through.

True, any manufactured bolt would have to be made of the correct material, hardened, etc. I don't know about the significance of cut vs rolled threads but I think the fiberglass would fail long before a cut thread bolt would pull out in that application since the force is tangential to the bolt.

Grinding down the fiberglass is not so easy since the reinforcement plate is riveted to the fiberglass and there are three rivet heads which are in the way of any grinding. I'd have to lift the body, remove the rivets, grind the area, and re-rivet the plate. Lifting the body has all the usual attendant risk of damage to my nice lacquer paint etc. so I'm not looking forward to it. If I can't find a suitable substitute, and can't convince myself a manufactured one would be acceptable, I'll lift the body.

Regards,

- Greg

[Duke W.]

Re: Longer '65 Seatbelt Attaching Bolt?

Measure the length of the OEM bolt, then determine what length you need to have at have least two threads extend through the nut plate. If you're lucky it might be a standard length bolt. You can always use too long a bolt, then search for a the proper length later. Most hardware stores sell quarter inch lengths up to 1 1/2 inch, then half-inch increments above that, but there are zillions of standard bolts out there, and a good hardware store might have quarter inch lengths out to a longer shank length. Be sure you match the SAE grade to the original bolt. If it has three radial lines in the head it is grade 5. Five radial lines is grade 8, which is a higher tensile strength steel. I'm assuming the bolt has a standard hex head, but I don't recall. I believe later GM cars use Torx head bolts for the seat belt anchors. Once you find a proper bolt be sure to torque it to the proper value as this is a critical safety application.

Duke

[Terry M.]

Re: Grade 8 head mark?

Duke,

I am going to shoot for the hip here - and I do so knowing that usually getts me in trouble:

Isn't grade 8 mark 6 lines on the head? I thought it was -2 on all of them.

I know I could look, but in a rush.

Terry

[Wayne W.]

Re: Grade 8 head mark?

You got it Terry grade 8 is six marks.

[Joe L.]

Re: Longer '65 Seatbelt Attaching Bolt?

Greg-----

If it means lifting the body to grind the fiberglass, I DEFINITELY would't go that far. In that case, I'd use a standard grade 8 bolt as the others have suggested and forsake the correct heads. Or, take a standard bolt and have the head machined to match the originals; that way you'll have all of the properties of the high strenth bolt. To obtain a standard grade 8 bolt with the unthreaded shank like the original bolts, select a longer bolt with equivalent unthreaded shank length. Then, cut off the threaded portion to match the lenth of the threads that you require.

I really do think, though, that getting a machinest to machine these heads to match is going to be prohibitively expensive. But, if you at least start with a bolt as I've described it will be cheaper than from scratch.

If you end up having the bolts made from scratch, I'd recommend using H-11 or H-12 tool steel. Material cost here is inconsequential.

[Duke W.]

Yeah...

sometines I screw up and get in trouble, too - six radials lines, not five is grade 8.

Duke