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metric vs sae ?


racsan

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anyone know offhand how close 14mm is to a 9/16" bolt? changed my rear springs yesterday & had to cut 3 of the 4 9/16 bolts that hold the leaf springs to the bushings/hangers. cannot find 9/16 bolts locally, have found some 14mm though, only 2 things, 1-not sure if its close enough to work, and 2- has a hardness of 8.8, idont know what that translates to, is 8.8 metric hardness compareable to a grade 5 or 8? i know where i can get the correct bolts, but if i can get it back on the road today vs 2days from now, it would be better, my loaner vehicle from dad is the '96 bronco, needless to say the 351 likes its fule alot more than my 4.0, even if it is a much nicer ride.
 
The 14mm is a tad smaller. You may experience some clunking noise due to the slight size difference. They will be a little bit weaker as well, but will still be plenty of strength for you. I just went through something quite similar helping my buddy with his 99 Cobra. I will try and find a very helpful forum I found.


EDIT: Here you go, that didn't take long (I love Gmail search). This isn't exactly what you are doing, but will show you some technical data on the bolts.

http://www.svtperformance.com/forums/suspension-modifications-211/331799-12mm-vs-14mm-vs-9-16-a.html
 
Last edited:
Metric grade 8.8 is about equal to SAE grade 5. Metric grade 10.9 is about equal to SAE grade 8.
 
I'd use the 14mm to get by if you need your truck. I'd order the 9/16 though.

That kind of stuff eats at me. A couple weeks ago I made my brother go to 4 different stores before we found the right bolt for his ball joint.
 
I have both metric and sae tools. You should always have both if you work on cars, motorcycles and boats and lawn mowers as I have for years. Allen sets as well.
 
I have both metric and sae tools. You should always have both if you work on cars, motorcycles and boats and lawn mowers as I have for years. Allen sets as well.

That's really neat.




Did you read his question Stray? LOL
 
I have both metric and sae tools. You should always have both if you work on cars, motorcycles and boats and lawn mowers as I have for years. Allen sets as well.

He is talking about the shaft, not the head.

The problem you are more likely to encounter is that the thread pitch is going to be off because of the difference in shaft sizes and the way metric and SAE threading is determined. They might go in part way before you notice it start to get hard, but you stand a chance of boogering up your threads.

What I have noticed with sizes that are that close is that you usually can get 2 or 3 threads in before you really start to notice the difference.
 
I'd look for the strength, particularly sheer strength, in a bolt for this application. that is, essentially what the ratings are all about...from what I've been told...same for seat bolts...it's actually illegal to use less than grade 8 when bolting a seat in your truck in Canada...or so I've been told...

Accident investigators may find you used an incorrect bolt and that could nullify your insurance...

This all came to me when I was building my truck...but may have changed in the last five years...

Brafasco is a Canadian company but they they manufacture and carry every bolt in both metric and SAE...didn't see any listings for US stores...but probably something similar around you...if not...try the dealership or NAPA...I bought OEM exhaust studs from them and they were very much more expensive than other places...
 
That's really neat.


Did you read his question Stray? LOL



Yes, I did...lol...and he does not have the right tools to do a job he needs to do. That is why I said what I did. So...he needs to go get some tools from Tim the Tool Man....lol
 
Can you point out where he mentions tools? Because apparently I'm blind.

Sent from a Commodore 64 using a 300 baud modem
 
That makes two of us.I took it as the bolt size.
 
Stock leaf spring bolts should be metric bolts with a 10.9 hardness (Grade 8 is the standard/US rating). Since metric bolts were hard to come by locally until they put in a new Fastenal store, I usually just went with a similar sized US bolt. I'd just replace the bolt and nut with new when I did it. Never really had any problems doing that either.

If you ever need a place to order oddball stuff from, check out http://www.mcmastercarr.com
 
Fastenal should have it, or be able to get it.

I need to get some bushings that Fastenal didn't have. We use McMaster Carr all the time at work. I will have to try them for these bushings.

Sent from a Commodore 64 using a 300 baud modem
 
Stock leaf spring bolts should be metric bolts with a 10.9 hardness (Grade 8 is the standard/US rating). Since metric bolts were hard to come by locally until they put in a new Fastenal store, I usually just went with a similar sized US bolt. I'd just replace the bolt and nut with new when I did it. Never really had any problems doing that either.

If you ever need a place to order oddball stuff from, check out http://www.mcmastercarr.com

This. OEM spring bolts are 14mm x 120 mm. I always put 9/16" in their place. Replacement spring eye bushings are made with a 9/16" hole in them.
 
ended up going with the 14mm, theres a little bit of play between the bolt & bushing, but very little, i dont think you could wrap a .010 shim around the bolt then get it through the sleeve. and yes i do have both sae & metric tools, the hex head size was the least of my concern, id have used a allen head if the dimentions were correct. i thought long & hard about the hardness issue, and for being a 19 y/o truck that rarely sees more than 500# in the bed i think im good. the bolts are probly harder than the brackets they go through anyways. the "new" springs did help a couple of things, as well as confirmed my bent frame, had to not use the factory lift block on the right side due to the wheelwell measurement being almost 3" more on the right side vs the left, took the block out & right side is only 1" higher. what really surprized me was that the steering wheel is now pretty much straight when before it was almost a 1/4 turn to the right when driving straight. theres no doubt theres less days ahead of this truck than are behind it, but with a 12 mile daily (round trip) commute, i think it will do me a while longer. there is a local fastenal store, very pricey & they arent open on the weekends. of all places i got my hardware at a local farm store (rural king) wish they would have had the 10.7 instead of the 8.8, but for some reason they only came in that hardness for that size. if it was a 3/4 ton that really saw a regualr load, then i would have worried more about the bolt hardness
 

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