Welcome to IFI... I suggest reading this. READ THIS FIRST

I suppose I should have added that I’m a woodworking tool maker and the steel I buy (particularly for prototyping, in which I can go through dozens of blanks) is becoming prohibitively expensive. 

Is there a particular reason you want to case harden steel rather than just use a steel that hardens thoroughly when quenched? Case hardening seems like significantly more time and effort involved to get it right.

You’re absolutely right; it is significantly more time and energy. But I enjoy this stuff so sometimes I choose to do it myself rather than buy it. In addition, for prototyping tools, I still need the functionality of the finished tool even though I wouldn’t use that particular iron. As I said, I sometimes go through a dozen or more irons on a prototype, and at $40 a pop or more (that’s a minimum) it can get pretty expensive. 

Frog50, what sort of tools are you making? And what size stock are you using for these blanks? $40 each seems pretty darn expensive.

Traditional side escapement planes for the most part, though I’m branching out to other wooden planes. The best source for real quality iron blanks is Lie Neilson in Maine. Best stuff I’ve ever seen but you’re right, pricey. 

Lie-Nielsen makes their blades out of O-1 steel. You could get a three-foot length of O-1 bar at 1/8" thick x 1-1/2" wide for about $30 and make a pretty fair number of blades. If you want to prototype, find your local steel supplier and get a stick of A36; a 20' length of 1/8" x 1-1/2" would probably run you even less than the 0-1. You wouldn't even have to case-harden it if you were testing it on something soft, like basswood.

(Also, just to avoid confusion for the non-woodworkers here, an "iron" for a plane refers to its blade, not to what the blade is made of.)

Yup. Did that. Ever try and cut a blank and get the taper correct out of O-1 steel without CNC? Or maybe I should say with only hand tools. It’s a ....

on the other hand, I can cut everything I want out of mild steel and not break my wrist or my wallet. 

No reason to put a taper on the blade other than period-correctness. Doesn't affect performance. The only reason the old blades were tapered was to save material, back when steel was scarce. If you make the entire blade 1/8" thick, you'll be fine.

If you really want to have the taper, then I'd suggest annealing the blank and drawfiling it. 

Oh yeah, thanks for the clarification on the word iron. I’m used to woodworking forums and didn’t even consider that might be confusing. 

No worries. Clarification = good.

Sorry, but the taper does effect performance. It wasn’t for conserving iron. (Did you forget my prototyping?). Roubo has straight irons in the 16th century. Everybody after him had tapered irons. Roubo had more reason to conserve material than most. 

Believe me, I wanted to make planes with straight irons. It would’ve made my life so much easier! But, alas, they simply didn’t work as well. 

I defer to your experience, and would therefore suggest making yourself a jig for drawfiling consistent tapers. 

Okay. I’ll defer to your experience now and beg you to tell me what is drawfiling? I have an idea, but it’s probably wrong. 

Edited November 23, 20196 yr by Mod34
Edited for inappropriate language

Drawfiling is a filing method that uses a file rather like a drawknife. In other words, you hold the handle of the file in one hand and the far end of the file in the other and pull it towards you along the length of the workpiece.  You can also reverse the file in your hands and push it away from you, if you like. In both cases, the file moves perpendicular to its length, unlike the more usual "cross filing", where it moves along its length.

This is a very accurate method of filing and can remove a lot of material fairly quickly. It's used quite a lot in bladesmithing, especially by those who do not have belt grinders.

As for the filing jig suggestion, think of the steel jigs that are used to plane the tapered segments of a bamboo fly rod. If you make something similar out of hardened steel (that is, hardened to the point that a file will not cut it), you can plop your annealed O-1 or mild steel blank in it and file it down to its finished taper with relative ease. 

Thank you. That’s pretty much what I thought it was. Considering materials and size, what type of file would be best for my uses? I can envision a jig. 

Hard to go wrong with a decent-sized mill bastard.

You could also make a rough out jig and hog most of the steel to be removed with an angle grinder and then drawfile to perfection.

The problem with case hardening is that you can't sharpen them without going through the case.

I picked up an old school textbook on metalworking once for US$1 as it covered things like drawfiling and basic speeds and feeds; things I knew I had in Middle School shop classes around 1970...

Hi,

Thank you all for your responses. Inadvertently I’ve learned much except of course for my initial question: What can I use for a liner besides Plaster of Paris, sand, and steel wool? I’ve already built my foundry with the aforementioned materials  and will use it until it falls apart (perhaps very quickly). Anybody like to hazard a guess about what might be better next time?

The materials for lining a forge and a foundry are quite similar.  We have an extensive gas forge section which covers in detail the construction materials, layers sequence, etc.  Rather than type all of that information out again I'd prefer to point you to the Forges 101 thread.   It is quite lengthy though, so you may want a comfy chair, some snacks, and a cold beverage for that one.  If you'd like the condensed version then this one should have most of your answers:

 

What did they suggest over at alloyavenue.com a website dedicated to foundry work? (Used to be Backyard Metal casting.com.)

Thank you, Buzzkill 

On 3/16/2018 at 10:38 PM, Johnny Chesser said:

I’ve ran about 250-300 lbs of L.P through it with very little flaking and zero spalling, my meter only goes up to 1400 degrees and it maxed out in less than a minute?

You've run a liquid petroleum furnace that got to the temperature of 1400 degrees celcius in a minute?

Welcome to IFI, Oliver! 

Johnny was last here May 18 2018 so it's unlikely that he will reply to your question. (If you hover the cursor over the person's name it will show the last time they visited---handy when dealing with dormant threads to see if the OP is still around.)