Calculate start size of stock

[jsurgeson]

This is probably a very blond question, but I am a stock removal maker who has just started out in the forging world.

Example:
I want to forge a blade whose overall final dimensions will be 5 x 50 x 300 (blade + tang)
My stock material is 8mm thick plate.

Question:
What starting size blank would I start with?

I suppose I could just start with those same overall dimensions, but that would waste. Is there a simple way to
fairly accurately calculate the minimum size blank required to end up with a particular end size? or is this just a thumb suck?

I hope this questions makes some sort of sense, if not sorry

Jeff

[Timothy Miller]

Start with a bar made out of clay of the size steel you have. Shape the blade you want out of this clay bar. Take all of the clay you removed and reform it into the same section you started with only it will be shorter now. Subtract the remaining clay from the original length of clay bar and you have how much steel you need. Make sure to make the clay blade a bit thicker than the finished blade you will be making to allow for grinding. After a wile you will just know how much steel you need for a forging in most cases it comes with experience.

[Toreus]

You can't just do a straight volume comparison, though, right? Don't you have to take scaling into account?

[Timothy Miller]

Yes your right 10% to 20 % depending on the amount of times you heat. Most beginners in my experience tend to start with too much steel. But I'm a blacksmith not a knife maker.

[jsurgeson]

I like it, the clay trick makes sense, I am sure after a few times playing with clay it will
become obvious how much steel is required for a given blade, thanks guys.

[maddog]

I use the clay method too for shapes that are difficult to estimate. I make the piece out of clay and then either form it into the shape of the stock I plan to use and measure the length or sometimes, drop it in a measuring jug half full of water and note the change in volume.

But this trick works because in forging you dont usually remove much material, you push it around. For a stock removal project I'm not sure how to use clay for this.

[arftist]

Since this subject is on the table I will mention that clay is good for practicing forging in general, not just figuring out the volume needed, but also how the metal will flow under the hammer or press.

[jsurgeson]

maddag:

Cheers, thanks for the volume tip. Coming from a stock removal background I dont think it would be
necessary to use the clay method, you would start with flat bar stock the correct overall thickness
and width, bandsaw or grind out profile and then finish grind.

arftist:

makes sense, thanks for that.

[Timothy Miller]

maddag:

Cheers, thanks for the volume tip. Coming from a stock removal background I dont think it would be
necessary to use the clay method, you would start with flat bar stock the correct overall thickness
and width, bandsaw or grind out profile and then finish grind.

arftist:

makes sense, thanks for that.

Well then your back to stock removal and not forging.

[jsurgeson]

southshoresmith:

Sorry dont follow, was just replying to maddog that "if" you were using the "stock removal" method then
there would probably be no need to use the clay method to establish volume of steel needed, at least in my
experience it has never been necessary.

My original questions asks how to "calculate start size of stock" when forging a blade from an irregular
piece of stock, for which the clay method was suggested. :)

[Timothy Miller]

I misunderstood, sorry I speak New York English, we talk first and sometimes we listen.

[jsurgeson]

I misunderstood, sorry I speak New York English, we talk first and sometimes we listen.

Dont feel lonely I too suffer the same ailment
Thanks for taking the time to get involved