I've got to replace some bolts and they have a 9 (*could* be a 6) marked on the top. I tried to google it but came up dry. Anybody know what kind/grade of bolt this is?

 

Uhh, for the RX-7, it's 10mm Grade, no idea!

 

I think its a 6. I think its the grade. not sure.

 

Yes most important bolts are graded from 1 to 8 or something like that, look up bolt grades. They are bascially quality guarentee's (sp?) make sure to never go down in number...

 

Well, being a mechanic most of my life..... would lead me to belive you probably have a Grade 2 bolt. You didnt mention any hash markings on the bolt head. In most cases, you count the number of hash marks and if there is a center a marking of some sort or a an actual number you can ussually add two the the grade strength. I will post a link for you. There are losts of bunk bolts out there now. You can read the web page I post and see what I mean. If you want more info I will be more than happy to post some more links.

SAE Standards for bolts

Doug

 

http://www.boltdepot.com/fastener-in...ade-Chart.aspx

 

http://home.jtan.com/~joe/KIAT/kiat_2.htm

 

Here is the friend of anyone dealing in metric hardware:
http://www.metricmcc.com/

Here is the page for 'markings':
http://www.metricmcc.com/catalog/Ch10/10-1022.pdf#search='boltsproperty%20classes'

Unfortunately, this covers European and US metric products, not Japanese. The Japanese standards are JIC, same as ours are SAE.

Upon rereading this I realised the last line can be confusing. The JIC standards are not the same as SAE, just that they use the JIC standards in the same way we use SAE, but they are not interchangeable.

 

IamWedge, this is a bolt from my RX-7, so it's not SAE and therefore, no hash marks.

The bolts I'm referring to where from the transmission front cover, but I just replaced those with grade 8.8 (all I could find). Just noticed though that the bell housing bolts are also maked with a '9'.