By James Stamper
For the next few segments, we’re going to talk about hardware (i.e. nuts, bolts, washers and other fasteners). When I worked in the parts department, I would cringe every time a customer would say, “I’ve got a bolt/nut but I don’t know the part number”; or even worse, when they would pull one out of their pocket! It took some time and some wisdom from my elders, but I have gained the knowledge to help my customers. Now it is my time to pass on that knowledge to you. So, without further ado, here is a segment I call All Screwed Up!
The first step in our fastener education is learning about the different grades and how they are used. Here is an outline of the where, what, and why:
U.S. Bolts (Standard)
Grade 2: Medium to low Carbon Steel
- These are for non-critical joinery and applications.
Grade 5: Medium grade Carbon steel, quenched and tempered.
- The most commonly used grade in automotive applications.
Grade 8: Medium Carbon alloy steel, quenched and tempered.
- These are stronger and better suited for mechanically straining applications, like vehicle suspension systems.
18-8 Stainless Steel: Alloy with 17-19% Chromium, & 8-13% Nickel (Mostly 18% Chromium and 8% Nickel, hence 18-8)
- Generally nonmagnetic, and is hardened only by cold working. Stainless steel is highly corrosion resistant for the price and is commonly used as turbo mounting bolts.
Metric Bolts (MM)
Class 8.8: Medium Carbon Steel, quenched and tempered.
Class 10.9: Alloy steel, quenched and tempered.
Class 12.9: Alloy Steel, quenched and tempered.
A-2 Stainless: Steel alloy with 17-19% Chromium and 8-13% Nickel.