Grade and State of Stainless Steel Rulers

[pawilkes]

I am a mechanical engineer and entrepreneur working on a new product. I've used stainless steel rulers (with the cork backing removed) that are 0.020" thick for my prototypes and need to figure out what grade and state the stainless used in these rulers are so that I can order material for production.

One website (

https://secure.mycart.net/catalogs/store.asp?pid=177300)

states that they use 301 stainless but I do not know what hardness they use. The materials are pretty springy so I assume it is fully hardened but it could be half hardened, I'm not sure. I'm hoping someone who deals with stainless sheet could give me their expert advice on what hardened state these rulers are typically made of. Thanks for the help

phil

 

[mcguire]

The strain at yield equals half the thickness divided by the radius of curvature, when bent just to he point of yield. It sounds as if you didn't note the radius of curvature or the angle at which yielding occurred. Since you produced 20% more strain in the 301 1/4 hard (same bending, different thickness)they seemed to have yielded at about the same strain (1.20x19 approximately equals 26 within the presumed accuracy of measurement). Therefore they have the same yield strength and the ruler is probably 301 1/4 hard. Your test tells you nothing about the tensile strength, but if it is 301 1/4 hard, the minimum yield is 75 KSI and the minimum tensile is 125 KSI.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[pawilkes]

I had some analysis done and the rulers are either 410 or 420 and have hardness of 28.8 to 32.1 Rockwell and a tensile strength of 137,000 to 150,000 psi. Not precise numbers but good enough for me. The strength numbers are equivalent to 1/2 hardened 301 which is what I'm going to use. Thanks for the help everyone.