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I Forge Iron

Forge, Bolts and heat

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Just a quick question.. I've bolted part of my forge together with regular grade 5 bolts, but I was told I should use grade 8 instead. Would this make any difference? As far as I understand, the increase in grades only increases the yield and tensile strength of the bolt, not heat resistance. Am I correct?

Should I be worried about the bolt heads melting and my forge falling apart?

Think I should clay it to make the fire area a bit smaller? I'll be burning coal, although I would like to try charcoal at some point. (If I recall that requires more area for a fire.)

The only things left on my list are a clinker breaker/grate and the ash dump then my forge is ready to go! (finally)


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You probably shouldn't use THOSE bolts simply because of the plating. You can find unplated carriage bolts that'll do two things for you:

First you won't have to breath unknown metal vapors from burning plating.

Second, carriage bolts will have less exposure to the fire and will absorb less heat so they won't be melting off.

I know I just recently made a case that zinc smoke is nowhere near as dangerous as it's reputed to be. This does not mean I believe in exposing myself unnecessarily. Then there's the difference between hot dip galvanizing and electroplated zinc.

The electroplated variety usually has other metals in the alloy, most notably cadmium which is very toxic. Lastly not all "silver" colored plating metals on bolts are zinc and breathing any of them is bad for you.

A layer of clay over all of it will take care of all of these concerns though.


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I started using the cheapest stainless bolts I could find just so I could take stuff apart later. Any carbon steel bolt/nut combo (even with zinc) will rust up tighter'n Dick's hatband after a few sessions of heat, coal and water and you'll probably have to cut them if you ever need to disassemble the forge. As the others stated, strength of the bolt is not an issue and plain old Home Depot fasteners will work.

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Note that for charcoal you want *LESS* surface area but a deeper fire. All charcoal in the forge will start to burn throwing off extra heat on you---grilled smith anyone?---but not helping heat the piece in the center of the forge.

So when using charcoal I add firebricks around the tuyere making a deeper fire that doesn't spread out where it's not helping. For small pieces it is a box or C around the tuyere for long pieces a wall on either side. Note that charcoal takes less air than coal and be sure to use *real* charcoal and not briquettes.

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keller those will work fine. Keep in mind that the bottom of the forge isn't in the actual fire, just under it, so the heat won't get to it as much. I'm glad you're looking for a clinker breaker, those make a nice easy to clean/clear fire, much better than a peice of steel with slots/holes drilled.

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