In woodworking we have marking gauges which are an adjustable rod with a pin and a fence. And we also have center line scribes.

Neither of them work very well for small pieces of metal such as that used in knife making.

Are there comparable tools in metal working?

Oddleg calipers (sometimes called hermaphrodite calipers)

or angle backmarkers

or dividers used carefully

Here is the scribe i use for marking the center of blades it's simple and works well.
It is 1 1/2" x 1/38" x 1/4" and the brass rod is 1/4".
Bob

Edited August 4, 200817 yr by Robert Mayo

For center scribing blades I use an engine valve with the edge beveled. Chuck it into a drillpress and run it along the edge of the blade for the centerline.

Bruce, how do you find the center to start with?

I don't. Pick an arbitrary spot somewhere close to center and make a line. Flip it over and repeat. That will give a corresponding line and I grind to them. Usually they are 1/32 or so apart. I like to leave a little meat on for heat treating.

Oddleg calipers (sometimes called hermaphrodite calipers)

or angle backmarkers

or dividers used carefully

John, thank you, those oddleg calipers are the berries. I'll have to buy a pair. Never seen such a thing before, but can immediately see all kinds of uses for them.

Glad you found the information useful, you may be able to pick some up from any old engineers, or yard sales,

You can always make a pair for yourself, or modify a pair of dividers, one way to do this is to weld or braze a small piece of metal to one leg to form a shoulder stop, about 1/8" to 1/4" up from the end, to allow it to sit on the edge of the metal being marked, the other point can be then made to be level with this shoulder

If you make your own, a tig tungsten can be used as the scribing point

Edited August 5, 200817 yr by John B
Extra information for point

I have a set of scribes like Robert Mayo has and works great. I have also in an emeergency used the next section size drill bit to scribe a line . On 1/8 inch use 3/16 drill bit and flip and mark both sides.

hey i use a utility knife for scribing. most of my steel is annealed when i mark it out, so it is soft enough to carve a nice deep line in. also with the knife, you can tape your pattern to the steel and then cut the tape around the edges, at the same time scribing the steel! if you make templates out of thick paper you can also cut through the pattern in places to show bevel lines engraving etc.
i certainly prefer it to an actual scriber.