How do you choose the right bolt for the job?

[mp3deviant721]

I'm just wondering how one would go about choosing the correct bolt for replacing rivets. How the bolt should fit, what length, thread pitch, etc. More specifically, I'm going to replace the coil spring tower on my dad's 91 and was wondering what I should be getting at the hardware store.

 

[alwaysFlOoReD]

I'll tell you what I did in my case, which may be correct - or not. I usually ere on the side of caution so... I used 1/2' grade 8 bolts with the shortest unthreaded shank that I could find, thinking that would be stronger than the threaded portion. It ends up the unthreaded shank is about 1/2" long so I needed to add some washers for spacing, I used 3 washers meant for 7/16" bolts as they are a tighter fit to the shank - I don't like slop but that may be overkill. One flat washer under the head of the bolt and one flat + one lock washers under the nut. You have to make sure that the washers are stacked thick enough that the nut doesn't hit the non-threaded portion of the bolt. I used lock washers with regular nuts but you could also use ny-locks as long as your aren't close to any heat sources that could melt the nylon, or use the compressed nut, not sure of the correct term, but it's been squished slightly on 3 of the 6 sides - they are a grade 8 nut meant to be used once. I also think that a grade 5 would be sufficient as the rivets aren't grade 8 steel AFAIK. The drill bit that I used was a step bit that electrical contractors use, the one that steps up 1/8" at a time - from 1/8" to 1/2" worked great for me. Though you would get acceptable results from a regular 1/2" twist drill bit, just not as precise. And the step drill is easier to use IMO. I used course thread but fine is fine too I put the head of the bolt to the outside of the frame, so the spring had more clearance. There are a few threads on rivet removal in the tech section.
Good luck,

Richard

 

[Sasquatch_Ryda]

I use all Grade 8 1/2" UNC bolts with stover lock nuts on my trucks.

The holes will need to be enlarged to 1/2" for this to work.

If you don't want to drill 12mm metric will fit nice and snug.

 

[-Nathan-]

I use nothing but grade 8 bolts on my truck...on EVERYTHING...most times its completely unnecessary....but thats just in my nature

 

[Snoranger]

I agree with all of the above.

When I replaced the coil buckets on my old truck I used 1/2" grade 8. Never had a problem. Just be sure they arent going to loosen:
lock washer
nylock nut
stover nut
red lock-tite

Any of the above should be fine.

 

[strvger]

guess it depends on what i'm bolting together.
i use grade 8 for everything where there is little to no flexing or torquing and absolute strength is required. grade 8 bolts won't give and when they reach their limit, they will break off.
i use grade 5 bolts where good strength is needed but also where some minor flexing may occur. grade 5 bolts will "give" a little before reaching their breaking point. i like to replace the usual cheap bumper bolts with grade 5 bolts as an example.
but that's just me.

 

[Shran]

I use grade 8 on almost anything. Reason being - I can destroy the threads on a grade 2 very easily and once destroyed they can't be fixed. If they get rusted into something, a grade 2 always snaps off and you are drilling it out and re tapping the threads. I can also fix grade 8 threads with a hacksaw or sawzall blade easily. I rarely use grade 5 because the price difference is negligible.

 

[Mac]

Drilling the rivets out and using the grade 8's is what the Ford shop manual recommends.
Dave

 

[mp3deviant721]

I'll keep all your suggestions in mind. I will be doing the bucket swap in a few weeks.

 

[lil_Blue_Ford]

IIRC, the rivet holes are 7/16 and that's what is usually recommended for a bolt. I use nothing but 1/2" grade 8 on my suspension work though (except for replacing the long bolts for leaf springs, then I use what fits the sleeve). The reason why I use 1/2" instead of 7/16? Well, back a few years ago when I started messing with my suspension stuff I scored a good deal on a couple big boxes of 1/2" grade 8 bolts (worked out to something like $5 per 50 bolts), so since that's what I have on the shelf, that's what gets used.

The rivets work out to something like grade 5 though if memory serves me correctly. I've tried several methods to remove 'em though and what seems to work best is to use a torch and/or an air hammer. When I haven't had access to a big enough compressor to adequately run an air hammer with a sharp chisel bit and a blunt round bit (chisel the head off, switch bits and beat the rivet out), I've torched the heads of the rivets off and used a BFH and punch to knock the rivet out (I've seen them knocked out with a little ball peen hammer but there must be a knack to doing it right that I haven't got).

Where grade 8 bolts are not required on a truck, I use nothing but stainless because I hate rust. I buy 1/4" stainless bolts in packs of 100 at a time anymore, same goes for screws - I keep #8 x1/2" and x3/4" phillips pan heads on hand at all times along with the bolts.

 

[alwaysFlOoReD]

Another reason to use 1/2" is that the holes don't always line up, so you end up drilling them anyway. It's also the reason it's sometimes hard to remove the rivets.
Good luck,

Richard

 

[Sasquatch_Ryda]

IIRC, the rivet holes are 7/16 and that's what is usually recommended for a bolt.

7/16 is actually a bit sloppy in the holes. The holes are bang on 12mm.

 

[lil_Blue_Ford]

7/16 is actually a bit sloppy in the holes. The holes are bang on 12mm.

Figures they'd be metric.

I don't buy metric bolts unless I absolutely have no other choice. I'd rather drill/ream it out to put a standard size in. And I always have a handful of regular bolts in the truck (1/4" stainless, 3/8" stainless, 1/2 grade 8, and now that I have my plow on the truck 5/8" grade 8 and 3/4" grade 8).

FWIW, I have got a few replacement brackets - even factory Ford ones - that had one or more of the holes a lil larger than they were supposed to be since a 1/2" bolt fit easily without enlarging the hole.