What do you all use for making marks on metal that's going to be heated red hot or hotter that can seen? The question is I want to make precise layout marks on bars to be able to form and forge them. The parts are too long so setting stops off my hammer tooling won't work. I need some precision for uniformity of the product, lets say +/- 32nd of an inch.

I wish to mark a part and then put in the tool, register it to a witness mark on the tooling, and then hit it. I'm machining a lot of tools in mild and tool steel to forge parts and this issiue is giving me a problem. Everyone has been so helpful in sharing their tips and secrets, how about helping a new brother blacksmith wana be out again. Soap stone and little grind marks are too hard to see, is there anything better than that?

square center punch marks put in cold then enlarged at low red heat. The square marks show much better than round. On some of my punches I make a small point to feel the center punch mark. Got the idea from iron worker punches.

+1 to the square punch - then scrape some talc off a welder's chalk pencil (soap stone) into the mark. It will show dark when the metal is at heat.

I like a sharp cape chisel

I use a small fuller mark into the corner of the stock.

The square punch works suprisingly well. I made mine from a smallish ball peen hammer.

So for your square punches are you using something like a pritchel punch? Or is it more like a creaser?

For hot marking I like a center punch, but now will try a square point. I use a punch a little over two inches long with a handle of mild steel welded on. Keeps my hand away from heat and not in line of vision.

I sometimes use a chisel line across the part, kind of depends on how it will be forged. Square center punch is also nice. Thanks for the handle idea Rich I have a short one one that I only use on cold metal, I will have to add a handle to it.

Tippex resists pretty high heats. I believe in the US it is called "white-out" or similar; it is for correcting type-written mistakes.

i have always used a centre pop, but now i will try the square punch idea!

So for your square punches are you using something like a pritchel punch? Or is it more like a creaser?

I just regrind a round center punch to pyramid type point.

I dont make anything that precise.

But if I need a mark, I smack it cold with a center punch.

since steel expands with heat *very* precise markings will be imprecise in use...

They can be very precise if you make the necessary allowances, 1/64" per inch at a yellow/orange heat will get you pretty close.
I had to make up a U-shaped piece about 3' across once, the die was almost 3/4" wider than the finished(cooled off) piece in order to meet the +/- 1/16" tolerance.

I second the white out. Works well for some parts. Never knew about it until a month ago and a friend showed me. Make sure to place the white out on the metal when its cold and let it dry for a few minuets before you heat the bar.

A few minuets? Are we dancing at the forge now?

ooops auto correct strikes again. Well I have to keep limber some how......

Don't forget that the chisel or center punch marking can be a stress concentrator for certain items. We studied several pieces that had broken at such a marking or even a tooling mark in one of my Mat Sci classes.

since steel expands with heat *very* precise markings will be imprecise in use...

Whilst agreeing with your statement, In practice, I dont' see what you are getting at.

You mark it cold, heat it and it expands, work it, let it cool, metal goes back to original state,

The marks are datums to work from, and mark out calculated allowances to produce lengths required.

I would make forging allowances when marking out for whatever reason.

Often projects get more marks when hot based on previous marks after work has been done on it (why my measuring tape has singes along one side...and I have hook rules up to 2'...)

I'll try the white out and square punch marks with a little soap stone scrubbed in. And yes I lay it out cold, work with it hot and it goes right back to where it was Thanks guys

I do the square punch thing every now and then, but once the bar is heated I just scrape something with a sharp edge across the bar-the scale falls into the punch mark and show up that way pretty well-I'm just another illiterate smith too lazy to use the soapstone lol.

I've used Pentel PRESTO! brand correction pens for the past four years or so. It is a ball point and the plastic body is squeezable to start the flow, if necessary. It should not touch hot iron, or the ball mushes. In most cases, the mark lasts into an orange heat. I've tried other brands, but the ball feed failed after a short time.

Often projects get more marks when hot based on previous marks after work has been done on it (why my measuring tape has singes along one side...and I have hook rules up to 2'...)

Thanks Thomas, I agree in that situation, I tend to use dividers/calipers a lot to transfer measurements onto hot pieces, I also have scorched tapes.