Steel size when beginning a knife

[MikeTausig]

Hello all. 

I have read through every word of all the knife making classes, searched the forum using the actual search function, and gone through every page & thread in the knifemaking topic only to come up empty handed. The only discussions I found regarding steel type and choice do not involve SIZE of the initial bar in relationship to the  end product, only using weight - which doesn’t make sense to me until after the project is finished. 

The question I am trying to answer is one I’m hoping their might be a rule of thumb for, or some other derivative means in order to “know” what size steel to start with. Before I go on, yes...I absolutely realize that design and desired size will help determine what size (and/or size & shape) to use...just to be clear. Also, I don’t want projects to be done only on abrasives...I want to actually forge a blade out of larger steal, I’m just not sure how to pick the right SIZE stock. 

For the purposes of this conversation, I’d like to offer two specific scenarios, as having read this forum long enough I know that very little insight can be offered without details. 

For both scenarios, let’s say the steel is 108X, and each blade will have approximately the same function, diverging really only in size, and simple imperfections in design reproduction. 

Scenario A] The finished product will be a clip point Bowie w/ full tang, likely 3/16 thick at its thickest, with a blade between 4-6” long x 2-2.75” wide (or thereabouts). All proportions of the clip point design are “normal,” with no major prounounced recurve. Guard will be assembled of secondary metal. 

Scenario B] Basically the same knife in the earlier scenario but with the following dimensions: thickness will be a full 1/4” - 5/16”, blade length will be between 8-10”.

These are just examples that I’m hoping to get a better idea how to “know” what i need without running volumetric calculations to determine need, and learning how to recall that knowledge and apply it to different sizes and designs.

Another issue I’m curious about when thinking about what steel to start with, is there a consensus among bladesmiths about initial thickness ratio to finished result thickness, as it pertains to what the initial steal thickness is? And by that I mean, if I want a blade that is 3/16” thick upon completion, do some folks recommend buying a 3/16” bar and forging only the edge, tip, point, ricasso, choil, tang, etc, then just heating to temp, and quenching? To me this doesn’t “feel” like fully forging a blade, but that’s an opinion NOT for this thread. 

I hope this long-winded missive is clear and concise as to what I’m asking & hoping to learn, and again, please know that I do recognize the numerous variables...just asking if there is a “bladesmith trick” to knowing size. 

Thank you,

Mike

[DuEulear]

Personally i start with 1/4 flat bar and forge to shape this is only because it is the thinnest barstock sold by my employer on the grades of toolsteel i work in. ( that i putchase at a discount) forging dose allow us to make our parent bar out of almost anything. Some toolsteel only comes in rounds from my supplier so i will forge to a size i need from round.

 

i caint offer any ruel or math on the subject other than start size should probably be around 110-120% of your desired finished size ( forged ) by volume. This should give plenty allowence for grinding. 

Du

[ThomasPowers]

Some people start with ball bearings and forge knifeblades from them, good steel,  as steel is a plastic material; weight is a good indicator of what you can forge from it once you factor in grinding losses and scaling losses.

I would suggest you get some mild steel blanks of various sizes and see what YOU can forge from them.

[swedefiddle]

Good Morning Mike,

The simplest way to figure out how much material you start with, requires that you have an idea of what you want before you start. I use Play-Doh, Modeling Clay, Plasticene or something similar to make the finished size blade(?) you want. Scrunch it up and roll the Play-Doh out to the size of material you wish to start from. Add probably 15-25% for scale loss and/or grinding loss, or OOPS loss. Play-Doh, Plasticene or modeling clay can be worked by hand or by Hammer & Anvil. It works identical to hot Steel.

Pay attention to which way you shape the tip of the Blade. If you initially make the tip shape opposite of what you want as a finished shape (from the spine down to the tip), as you forge the cutting edges it stretches the blade side and brings the tip back up to the side of the spine, with minimal straightening.

Don't expect to find written answers to all your questions. You will learn and adjust your thinking, by making. Don't look at a mistake (or what you think MAY be a mistake) as a waste of time. Pay attention to how the metal moves or wants to move and work with it, not against it (unless you need to).

Enjoy the Journey, Neil

 

[Jclonts82]

Another thing to consider is your skill level and accuracy and depth of hammer blows. When I first started about 1.5 years ago, I forged really thick and ground it thin, because I had a few errant hammer blows that I would have to grind down everything else around it to erase the divot from that blow. NOW I hand forge my bevels all the way to about a nickel thickness in the cutting edge without having to grind much to get the steel flat. All that is better hammer control.

If I wanted a blade that was 3/16th thick, I would probably start at 1/4. If I wanted a knife 2" wide, I could easily pull a bevel down to meet that width from 1.5" x 1/4" bar. I could probably, If i was careful do it from 1.25" stock, and it would be a REAL stretch for ME to pull it from 1" stock. I'm sure others could do that easily, I'm also sure there are those that absolutely would NOT be able to cleanly and evenly pull that edge down. 

Also consider distal tapers, you need less length in your starting bar if you are capable enough to forge in the distal taper, if you're wanting one. 

 

Probably not the exact answer you wanted, but the answer to this particular question is unique for every smith. 

[Buzzkill]

9 hours ago, MikeTausig said:

And by that I mean, if I want a blade that is 3/16” thick upon completion, do some folks recommend buying a 3/16” bar and forging only the edge, tip, point, ricasso, choil, tang, etc, then just heating to temp, and quenching? To me this doesn’t “feel” like fully forging a blade

Your experience/skill level is probably the biggest determining factor here.  The amount of material that you lose due to scale is largely dependent on how many times you have to heat the stock at forging temperatures.  How much you will lose to grinding is largely dependent on your hammer control and how closely you can accurately forge to final dimensions.  Personally if I want to end up with a maximum thickness of 3/16" and I'm using flat stock I'll use 1/4" or thicker.  I still make too many mistakes at the anvil to try for anything thinner.  If you can accurately forge in your bevels and tip without decreasing your overall thickness by more than a couple layers of scale then I'd say go for it.  If you are trying to go for efficient production you want the least amount of material loss and the least amount of time spent to create your final product.  The less material you have to move, the better you should fare in both of those categories.

The bottom line is I don't think anyone can reasonably give you a good rule of thumb because so much of that depends on you.  I'd ballpark it by suggesting 25% more than you need if you're just starting and as you get better you can shrink that down to maybe 10% more.  You'll always lose a little to scale and rough grinding unless you want the "brut de forge" finish.

[MikeTausig]

Thank you all for the responses. As noted, I recognize the variables on this are largely contingent on ME, but figured I would at least ask about a “rule of thumb.”  

As mother always used to say, “if you don’t ask, you won’t know.”

mike

 

[MikeTausig]

But seriously...I was able to extract good ideas from every single one of your responses. For a six sigma guy,  those are great numbers! 

I’m appreciative to each of you for taking the time to respond, and offer your thoughts freely. I’m nearly 50, so starting something new (bladesmithing, not metal work) is daunting, but in a positive way. 

Be well. 

Mike “Little Mountain” Tausig

[lyuv]

I"m an engineer in my 50's. Over analizing is my thing (too?), so I have been where you"re now, and I can only advise you to pick a hammer and go forge a blade. The short experience will teach you WAY more that reading and analizing. At least regarding this issue.

You already recognized the wide range of parameters and values (and interactions) involved. Formulating it, to a remotely reasonable accuracy, is futile.

[ThomasPowers]

One of the fundamental tenets of engineering is: "If at first you don't succeed; try a bigger hammer!"  Works surprisingly well in blacksmithing too, except for the times it's "try a *smaller* hammer!"

Overthinking it doesn't work real well when you don't have the solid background of experience to let you assign real world values to the myriad of variables in the problem.

Blacksmithing is definitely not a "In a vacuum assuming, a perfectly elastic collision of two spherical objects..." type of thing.

BS Geology/Geophysics; BS CIS; 37 years smithing and in my 60's...

 

[Frosty]

Well, it's been said already. <sigh> Blacksmithing is a tactile eyeball craft. By time you can put numbers and rules of thumb to a project you don't need them and they don't apply to other folks. 

I don't forge blades but I have the experience and knowledge to make an educated guess if I were to take a lash at it. For me and my set up. Believe me I'd guess about a 100% margin of error too. I know for a fact I'd take it to the fire way more than an experienced bladesmith and while I wouldn't leave too many hammer marks, I'd leave more than I should. I'd forge it thick and grind it thin before I cut the extra off. Well, I'd cut the extra off before I did more than rough grinding. 

Weigh the blade you want to make, double or triple it and cut that much stock. It'll get you close.

We LOVE pics you know. Keep us in the loop please. 

Frosty The Lucky.

[jlpservicesinc]

Ideally you have to have a place you want to start at.. 

This means having a known blade with a known weight.. 

Or using math to figure out volumes of metal and then figuring out what this leads to.. 

There is a huge difference between someone starting out and an old crow like myself.. I can get as much metal out of an object as possible.. 

As an example here is a knife made from a bicycle chain and there was no loss (cutoffs or wasted materials) I used every inch of chain..  it is also just 1 fold as I wanted to keep the pattern as clear as possible..   The reason I am using this as an example is you can see there is little loss.. 

Basically all I did was remove the air spaces in the chain.. 
 

There is a post about a wrought iron hook and in the thread there is a book that will show you how to figure out what size stock you need for a given size..  

[lyuv]

Jilpserviceinc - I love this knife. Those clean and utilitarian lines are what I strive for.

Can you please weight the knife and the chain? This will give us an idea of the upper limit of metal "efficiency" in this type of knife and proccess.

[jlpservicesinc]

It started out at 14oz.. when done it was about4,oz..  I weighed them today but all I have is one of the vintage beam scales (not the right name for it)

 

 

[SLAG]

Balance beam scale?  also a steelyard?  as opposed to a spring balance scale. (or even a geared balance scale.)

Such weighing devices come in many types and some types have been around well over three thousand years.

SLAG.

[ThomasPowers]

I have a triple beam scale like I used to use back in Chemistry class; very handy when trying out various recipes that have stated amounts rather than "grab a handful of Borax and...")

[jlpservicesinc]

steelyard.. Thats it.. Thanks Slag..  Thomas.. Way back in the day I used to own. 2 different scales for weighing of horse shoes and associated filler metals.. The steelyards are handy though this one is off about 4 oz but I just account for it in the measurement..  Not sure how accurate it is but for what I do it makes little difference.. 

The small one i use I'm not even sure i'm using it right as it's a go/ no go.. Type..  vs the type with a lubber line (arrows to line up)..

Lyuv..   It's funny but when I start with a knife I always have a design in mind (everything I forge)..  I then pick the metal based on this idea.. 

I never account for the losses starting out as every blade is forged to as near a shape as it can be with only a little filing to get it ready for heat treat.. I completely remove all scale and divets/hammer marks before hardening as I don't use a belt grinder and once hardened it just ruins files.. 

The reason why I am pointing this out is i was shocked at how much lighter the blade was.. The chain has grit and rust and such but to go from basically 1lb to 4oz is a reduction of 4/1..

I never have measured for the losses.. I just account for them automatically based on experience.. 

[lyuv]

Jlpservicesinc - Thank you.

I was VERY unhappy with my metal loss ratio. But seeing that even a well seasoned "old crow" has to deal with loss, is a significant confidence boost.

Me and my bladesmithing buddy, started logging our works, including material going in, and final weight. The purpose is to help us better plan. So far, the data is just embarrassing.

[jlpservicesinc]

Lyuv, it's just a matter of fact..  Welding uses up a lot of metal.. and I have found that the first few heats are ok, Then by heat 3 or 4 the losses start to account..  

Regular forge work seems to be pretty negligible.. But once the welding comes in it changes the whole ball game.. 

1 other thing.. A weld that does not take and is heated again to welding temperature will have higher losses than a piece that is welded that first time without the extra reheat.. 

Forging out Damascus billets from vintage materials needing rehab the losses are very high.. I bet upwards of 10% or more per welding heat..  I never stopped to measure them.

Lots of people doing Damascus will start with the smallest/thinnest strips possible in the stack.. This will allow for a higher layer count without all the associated losses and pattern changes.. 

 

[ThomasPowers]

The more surface area the more scale losses.