Grade 5 or Grade 8 bolts?


Working on my 40 year old Huskey Bolens garden tractor I found a few broken bolts in the front end and mounting the engine, they were all grade 5 bolts, no idea if they had even been out before.
I drilled and removed the studs without too much problem, the one in a big cast steel piece took a few minutes with a MAPP torch.
So should I replace them with grade 8, hoping they wont break again? Or do I still use grade 5 so I am able to drill them again if they do break?
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I just routinely use 8 for almost everything, but certainly in an application where a 5 didn't hold up, I'd use 8. I also like to use nuts with nylon inserts. They never come loose, which leads to bolts shearing, but buying those is grade 8 is too expensive, so I generally use a lower grade nut
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RBM wrote:

Yes, the engine bolts often loosen up on this model, although they all have the good old kind of lock nut that is punched on each side. It's called a "tube frame" tractor and what happens is the tube starts to collapse and get oval looking making all the bolts loose.
I do have a fix for that, in a newer model I stripped for parts I found they put a steel plate inside the tube frame on each side of the bolts. Yesterday I bought some outrageously priced steel from Lows to do the same thing on this model. The tube frame will not crush again!
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On 07/05/2010 12:01 PM, Tony wrote:

Just as a point of order, I believe those are properly called Marsden nuts. I haven't seen one in years, though.
nate
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Nate Nagel wrote:

No,not quite. http://www.lok-mor.com/mar-loc.html
Now you have me curios what the name of the ones I like is? There is a mark, normally on two opposite sides where it was stamped or punched. It doesn't look like it would hold well but they really do. Maybe a regular nut on the anvil and smacked slightly out of round with a hammer?
I just remembered one time I needed a lock nut of any kind, no room for two nuts. I took my vise grips and distorted the threads on the bolt. It worked but not that great. It bought me time until I could return with something better.
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wrote:

Commonly referred to as "stover" nuts.

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snipped-for-privacy@snyder.on.ca wrote:

No, still not what I have. Stover nuts are slightly rounded at one end making them "one way" nuts. But while learning that, I scrolled down and found this:
Two Way Lock Nuts
Also Called: Centerlock Lock Nuts, Bi-Way Lock Nuts, Reversible Lock Nuts
Two Way LockSide indentations in Two Way Lock Nuts slightly distort their center threads to create a locking action when the distorted threads engage the threads of the mating part. An inexpensive, prevailing torque type of hex lock nut, assembly costs are reduced because the top and bottom of the nut are the same.
I found that with pictures here: http://www.fastenermart.com/html/encycnuts.html
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On 7/5/2010 11:01 AM, Tony wrote:

I often see tube spacers used in square box frames like that.
TDD
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wrote:

through with the ID the size of the bolt. Weld or braze it into the tube, and it will never crush again - and the bolts will stay tight.
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On 7/5/2010 10:18 AM, RBM wrote:

I thought the grade 8, although stronger, were more brittle than the grade 5 bolts.
TDD
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The Daring Dufas wrote:

That was also part of my question, the part I forgot to write!
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On Mon, 05 Jul 2010 15:19:44 -0500, The Daring Dufas

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I never get cheap with my nuts. My nuts are only the best top quality nuts that money can buy. After all, my nuts are what I use to create the future of this country.
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If your "#16 metric line wrench" post is any indicator of the quality of your nuts, our country is in deep do-do.
nb
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Try these: Aircraft bolts are commonly used by boy racers. They are sort of like Grade 8, but will tolerate some stretching under stress, so I have been told. Available on line at several aircraft supply houses. Probably something like the torque-to-yield rod and head bolts we find in automotive these days. Scary when you first use them, pull in steps to 80 lb-ft and then a quarter turn (!). Not reusable as aircraft types are.
Joe
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It depends on the application. Grade 8 bolts are hardened and therefor more brittle. While they are good for linear applications like head bolts, they suck for use in shear applications. I subbed a grade 8 bolt for a 5 as a alternator mounting bolt, where the alternator was hanging off the bolt, which was screwed into the engine block. It snapped off in a few days. Went back to grade 5 (less brittle) and had no further problem. I'd check with Husky Bolens to make sure. Are you the original owner? A previous owner may have subbed 5s for 8s in the past and that's why you're having problems now. Whatever, I've discovered they're not usually interchangeable.
nb
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notbob wrote:

I'm not the original owner, but being the second owner of a 40+ year old garden tractor isn't bad. Husky Bolens has changed owners a time or two and does not support the *good* ones made in the 60's and 70's. There is however a large group of collectors but I thought I'd get a quicker answer here. I'm still not sure which bolts I will use.
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Whichever grade you decide to use, get a can of antisieze compound to go along with them.
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plausible, and wrong." (H L Mencken)
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Larry W wrote:

Damn it! I was going to use that on the 4 bolts that screw into the casting but I forgot.
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