I've spent a lot of time thinking about building a similar tool as this one I just found for sale online:

Marker

I noticed that the description says not to use cold rolled stock with this tool. Why not? I like working with cold rolled, and I know a lot of talented smiths that do as well. Why wouldn't it work with cold rolled?

Thanks,

Jim

Cold rolled is "harder" and so will wear the marker faster.

That was my first thought, too, but the chisel is made of S1. I would think it could be made hard enough for use on CR mild steel without sacrificing too much toughness. Maybe Grant will swing by and clarify this.

Yeah, I was hoping that Grant would pop in Isn't a lot of cold rolled 1018? I thought that mild hot rolled tended to run with a little more carbon in it...

I have no idea why it says that. No reason not to use it on CR. OBTW that's official!

I've spent a lot of time thinking about building a similar tool as this one I just found for sale online:
Marker

G'Day OOps!
Might be a dumb question but how does it work?

Very nicely thank you! (cue rimshot)

As I understand it---as you change thickness of stock, the angle of the marker changes keeping it aligned with the center----Very neat trick indeed!

Ah, thanks for the info Grant!

Very nicely thank you! (cue rimshot)

As I understand it---as you change thickness of stock, the angle of the marker changes keeping it aligned with the center----Very neat trick indeed!

Thanks for that

As I understand it---as you change thickness of stock, the angle of the marker changes keeping it aligned with the center----Very neat trick indeed!

Looks like our clever Mr. Sarver has once again been dabbling in the dark arts of Trigonometry and/or the Pythagorean Theorem.