Stainless or Grade 8

[kylev]

What would you do for bolts on the radiator. I am replacing all the bolts on my cub as I restore and am going with the same grade 8 bolts everywhere. What about the bolts that hold the radiatior on? Would you use stainless on those?

To me it looks better but I want to make sure I get the right kind so that they dont break on me.

Thanks

[Eugene]

This is more of a personal choice than anything else.

I wouldn't go to the expense of stainless steel. For some applications grade 8 is over kill. Unless the bolt is damaged, I clean up the threads and reuse. Replacing bolts gets expensive in a hurry.

As far as the radiator bolts. The original were not stainles steel. I replaced the radiator on my Cub over a year ago. I didn't have a problem removing 50 year old bolts.

Eugene

[Buzzard Wing]

Kyle, I used a lot of stainless on Rufus, but other than the ones that attach the hood (were not painted on a yellow/white Cub) I primed and painted the heads of all of them.

I am only replacing the 'bad' fastners on the 50, mostly because it is getting expensive. I did buy boxes of common lockwashers.

The bolts that caused trouble seem to always be in a casting and it may not be a good idea to use grade 8. I was told that when I was proudly showing off the grade 8 bolts that were holding on the mower bracket and hitch. The reason was you don't want a bolt 'stronger' than the casting, better to break the bolt than the casting. Makes sense.

I did put nev-r-seize on the bolts on the platform (battery box, seat post etc).

A pretty good habit I have gotten into is to chase every hole with a tap. Especially a good idea if you have painted. But it is tedious in places like the radiator and the final drive pans.

[Jim Becker]

Stainless steel bolts are about equivalent strength to a grade 2. I wouldn't use them anyplace structural that started out with a better grade of bolt.

Higher grade bolts have higher quality threads that consequently are slightly larger than the lower grades. Thus they will hold better in castings where there is probably accumulated wear. The main factors to keep from breaking a casting are 1) Keep all the bolts tight, and 2) don't abuse the tractor. Most broken castings will be broken across part of a joint (where the bolts were tight) and unbroken across the rest (where the bolts were loose).

[Paul B]

As far as I know, on a Cub, most (key word being most) original bolts were only grade 5, as they are in most automotive uses, and using grade 8 replacements is overkill and an un-needed expense. But then, it is your tractor as the saying goes.

I am sure it can be found other places too, but the McMaster-Carr site list the strength comparsion of different grades and materials of bolts. It can be found on the pages with the bolts.

[Donny M]

Here's a handy dandy chart: http://www.boltdepot.com/fastener-information/Bolt-Grade-Chart.htm

[brichter]

Stainless steel is great in corrosive atmospheres but you had better be careful. If you should happen to crossthread a nut and it "galls" you are in major trouble. We used a lot of stainless in the mill where I worked and always had trouble with newbies using stainless carelessly. I use grade 5 on Andy.

[bald]

Donny M, thanks for that chart. I just printed it off on photo paper and posted it in my shop. It will function as a memory aid..of which I am sometimes in need.
bald

[Patbretagne]

Donny, Thanks for the chart.
The site
http://www.boltdepot.com/
from where the chart comes from is well worth bookmarking for reference, for buying all sorts of fastners, impressive, thanks
Pat

[dracer398]

If you use stainless bolts with stainless nuts, be sure that you use anti-seize or like mentioned above it will gall. (Murphys Law)

Also, for the lower radiator mounting, I would use grade 5 steel bolts (zinc or cad plated) with either sealer or anti-seize to protect the threads. Most likely these bolts will be painted anyway.

Brian

[Donny M]

Generally, the reason that stainless galls is, over tightening. Stainless will stretch somewhat when over tightened, this deforms the threads and results in galling.
Many a 3/8 stainless bolt has been rung off (broken) after the bolt has galled. Not such a bad job with a long breaker bar. Larger bolts are a different story, good job for a sawsall
Some manufactures that use a lot of stainless have started using graphite coated nuts to minimize the problem. I used many graphite coated nuts when putting Ralph back together.