I see guys running countersunk bolts for skids xmembers etc but what I can't find is a grade for them? Do they make grade 8 countersunk bolts or what do guys run?

 

I believe you are looking for flat socket cap screws. Something like this:

https://www.fastenal.com/products/details/1124256?r=~|categoryl1:%22600000%20Fasteners%22|~% 20~|categoryl2:%22600039%20Sockets%22|~%20~|catego ryl3:%22600042%20Flat%20Socket%20Cap%20Screws%22|~


They are graded, sometimes differently than your typical hex cap screw (hex bolt). Refer to this chart to compare the strengths:

http://www.thruwayfasteners.com/docu...rs_Thruway.pdf

You can see the fastener I linked to has an ASTM F835 spec, quite close to a Grade 8 but actually has a higher hardness. I don't think you will have an issue with fastener strength in your application.

 

I would use grade 5 maybe grade 8 if you wanna go over kill.

 

Yep that's what I'm looking for. Now gotta decide if I want to countersink the holes or not. Prolly be easier than making bolt protectors.

 

I just use button head cap screws for simplicity on my skid plates.

 

Socket head cap screws?

 

No Button Head Cap screws.

Socket heads have tall shoulder heads. Button heads are shorter and tapered around

 

Ok I gotcha. Forgot about those. I might go that route then. Saves time and if I have problems I can always go back and countersink the holes.