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Help with figuring out what size stock to use.


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Hey is there a formula I can use to help me figure out any size stock to use to make specific dimension item. For example if I'm make a 6 inch wide 13 inch long and 1/8 inch thick plate but all I have is round and square stock. What size round or square stock will I need to do so. Thanks for the help.

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Volume of a rectangular solid = l x w x h,  where l = length, w = width, and h = height.

Volume of a cylinder: πr² x l, where l = length and r = the radius of the round end.

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Volume = Volume  (subject to scale losses which depend a lot on your skills and equipment.)

Now don't fall into the trap that "free" heavy stock can be used to make small items as the time involved in changing it's dimensions may way out cost sourcing stuff closer to the wanted size.

I often pick up scrap I find where it has a lot of my work already done for me---long tapers, knobs on the end, etc for items I make on a regular basis.

Have you checked for an ABANA Affiliate out your way?  Fastest way to accelerate through the learning curve is to get some hands on teaching!

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24 minutes ago, ThomasPowers said:

Volume = Volume  (subject to scale losses which depend a lot on your skills and equipment.)

Now don't fall into the trap that "free" heavy stock can be used to make small items as the time involved in changing it's dimensions may way out cost sourcing stuff closer to the wanted size.

I often pick up scrap I find where it has a lot of my work already done for me---long tapers, knobs on the end, etc for items I make on a regular basis.

Have you checked for an ABANA Affiliate out your way?  Fastest way to accelerate through the learning curve is to get some hands on teaching!

Well online I found a piece of 4140 stock that is 12"L x 3"W x 1/4"H for $20 plus shipping. I was thinking I could make that the dimensions I needed. 

Yes I have a mentor close to me. Dave Edwards he lets me work out of his shop and give him a hand on some of his projects.

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1/4 X 3 X 12 will not make 1/8 X 6 X 13. Close, but you'd have to cheat one of the dimensions, and as mentioned above, factor for scale loss.

Personally, I wouldn't want to try to stretch the width (/reduce the thickness) that much, especially with 4140, but if you really like hammering....

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24 minutes ago, scottyp74 said:

Well online I found a piece of 4140 stock that is 12"L x 3"W x 1/4"H

Quick tip: if you halve one dimension, you can double another and still keep the volume the same. Thus, if you took your piece of 12" x 3" x 1/4" and hammered it to twice as wide and half as thick, that gives you 12" x 6" x 1/8", which is smaller than your target dimension. Add is scale loss, and you're looking at a finished piece that's even smaller.

A piece that size is going to weigh about two and a half pounds. Whatever you're paying for the steel itself, you're adding another eight bucks a pound for shipping. Is it worth it? You're going to be putting a lot of time into drawing out the metal -- is that time well spent, or could you spend it on something else that isn't just brute hammering? You're going to have to pay for the fuel to heat the metal enough to draw it out -- is it worth the fuel cost?

Have you contacted local steel suppliers? Or fabrications shops? My local steel supplier has a drop bin with all manner of plate, channel, bar, round, tube, etc for 75¢ a pound; you might well be able to pick up a piece of plate in the right size for less than the cost of a happy meal (especially if 4140 isn't critical).

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1 hour ago, ThomasPowers said:

Volume = Volume  (subject to scale losses ...)

 

18 minutes ago, JME1149 said:

and as mentioned above, factor for scale loss

 

14 minutes ago, JHCC said:

Add in scale loss, and you're looking at a finished piece that's even smaller.

Would I be wrong in assuming that you cannot really estimate a scale loss % (by volume) due to the fact that it depends (in no small part) on the number of heats?

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Just now, Eli Taylor said:

Would I be wrong in assuming that you cannot really estimate a scale loss % (by volume) due to the fact that it depends (in no small part) on the number of heats?

Scale loss is a function of the heat of the metal and its exposure to oxygen. A heavily oxidizing fire will cause scale to form more rapidly, as will multiple heats and heating the piece to high temperatures.

However, if you are making multiples of a particular piece and you've gotten a handle on how much you typically lose to scale, you can estimate the loss rate and include that in your stock calculations. For example, if you routinely make hammers from 3 lb chunks of steel and those hammers typically come out at 2.7 lbs, you know that you're losing 10% to scale loss.

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New smiths tend to have much larger scale losses than experienced smiths.  This is probably because they know how to set their forges to heat with less scaling, they don't leave stuff in the fire scaling up, they use fewer heats.   With experience you get to know your personal values---and can look at a piece and say "time to fiddle with the choke, looks like it's running a bit lean"

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I buy a 20' stick of 1/8"x6" for the same money you're getting that 4140 for.  Unless you need the high carbon content for a blade, I can't see any reason to use HC steel.  If you are making a blade (and who isn't trying to make swords these days!?!), you'd be far better off shelling out the bucks for new steel in the size you need.  

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