I took out a couple rivets today to prepare for shortening my wheel base. The hole was about .405-.415" or so, and the same with the rivets (though they possibly did get messed up due to having to be hammered out)

My question is, I'm going to have to drill everything out to 1/2" aren't I? It's a little under 7/16" (.43), but I can't find any grade 8 bolts in town that size, 3/8" is at .375. Am I correct in thinking that if I use 3/8" bolts that I will have too much play? Granite thats about .02" around the bolt. Anyone know?

Thanks

 

7/16' or 1/2' - 3/8 will allow too much slop - try Granger or MacMasters and Carr for bolts
and Lock Nuts in grade 8

 

I'm replacing the front crossmember in my '37 Buick, I'm going to 1/2" button head bolts and locking flange nuts. The button heads will look pretty close to the rivets I drilled out. The button bolts I have I got from the local well stocked hardware store and the nuts from Fastenal. You can get the same from McMaster but you have to buy in larger quantities than what I needed. I was told the button heads are grade 8, at least they are better than standard.

1/2-13 Large Flange Top Locknut Grade F (GR 5) Steel Zinc | Fastenal



I searched the HAMB forum and posted a question about rivets vs. bolts. As usual the HAMB replied with a lot of information. When using rivets you can get away with some slop in the holes because as the rivets are mashed down they will fill voids. Using bolts aren't as forgiving. It was suggested to me to ream the holes to 1/2", I just going to use a 1/2" drill. I plan to insert a couple of tapered pins in the holes before drilling and then install the bolts one at a time as I drill out the next hole to help keep everything aligned.

 

im surprised your not putting rivets back in if someone wouldn't of walked off with my forge thats the way i would a gone

 

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One thing I forgot, some big truck guys chimed in on the HAMB and said they used bolt type rivets, called Huck rivets:



The big problem with using these is you have to buy a $1500 tool to install them.

 

Scott, the problem with a step drill, at least the ones I have, they probably won't go deep enough before you engage the next step. You'd have to attack the hole from bot sides. I might work if you can easily get at both sides but the holes I am doing are accessable from top a lot easier than the bottom. I would go with a good 1/2" with a side handle.

 

Thanks guys. I found some 7/16" in town, I'll just drill out the holes a little bit more. Had to get a little longer bolt than I'd probably normally use, but I thought it be a wise idea to have the part actually in the hole, where all the stress would be, thread free. Seems like it would defeat the purpose if crushable threads where in the hole.


I suppose I could use rivets, but they loose their heads when removed so I'd have to forge a new set and right now thats just one more thing, especially with 32+ of them...

Also, I'm planning on swapping axles later on in the build, and if I don't use the same suspension I may be cursing up a storm when I have to do all that again... thus the bolts.


Bob, do you already have all the holes in the frame as well? I had planned to move the axle up and once aligned just bore out and drill the frame hole at the same time. Sorta do one on each side, bolt it down, then do another. Make it easier to keep it all where it should be I'd think.

 

you can buy 3/8ths rivets from centaur forge but if its coming apart again bolting is good

 

I think that's a great idea, Stephen. Just be 100% sure that the nut doesn't bottom out on the bolt shank, where it wouldn't get tight against the frame, but be very tight while turning, if you know what I mean.

 

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Yep I checked that quite a bit. Had to measure how much of the shackle and frame there was (about 1/2"), then after washers and lock washers it's plenty in the clear. They're 2" bolt, I'm sure 1 1/4" would have done the trick but I wanted that unthreaded part. Besides they can be cut if I feel the need. The fits probably going to be tight enough I'll have to hammer them in, least a little tap-tap-tappa-roo.


Think I should use washers on the shackle side as well? lol it's not going to look as clean as the rivets did, but eh.

 

A tap-tap fit in your application is a good thing. I wouldn't use a washer on the bolt head side. The shackle casting is plenty heavy to distribute the load. Adding a washer there would create more problems than help, imo.

 

Yeah I think you're right on that, but I figured I'd ask, keeps me from wondering about it every time I look at it. I'm just use to using washers everywhere on everything, ha.

 

Here's a good discussion on the subject from Practical Machinist.com. Stu

OT: Strength differences between bolt and rivet - Practical Machinist - Largest Manufacturing Technology Forum on the Web