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I Forge Iron

Is plaster of Paris mixed with sand a good liner for a forge?


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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. 

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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.)

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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. 

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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. 

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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. 

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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...

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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?

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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:

 

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  • 1 year later...
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?

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