Surface roughness

Date 07-26-2001 23:53

Can anyone help me with this? We are starting a job which has many RBS ("dogbone") areas on
W14X22 and W14X26 rolled shapes. The engineer of record has specified FEMA-353 for tolerances.
They state Flame cut to 500 micro-inches and say use AWS sample #3 to verify. I have an AWS
Surface roughness guide. We are doing a better finish than Sample #3. My question is: Can some-
one define a micro-inch. The Project Manager insists that it is 1/1000000th of an inch. Or that 500
micro-inches is .000050. The AWS Sample #3 looks a lot rougher than that......Thanks.

By Jorge Giraldo (**)

Date 07-27-2001 13:52

Effectively, as your Project Manager says, a micro-inch is 1/1000000 of an inch (the meaning of the prefix micro is 10^(-6) wich is the same as 1/1000000). In such way, 500 micro-inches are 0.000500 inches (not 0.000050 inches as you posted), wich is a tipical value that you can obtain with flame cutting. The tipical range of this manufacturing process by common production methods is 500-1000 micro-inches. If you have the correct AWS sample you can visually (and easily) determine if your surface preparation is correct, I meant if it is cumplying with the required roughness.
I hope this help you.

Jorge Giraldo
Medellín, Colombia