Michael Kellough

Man, that picture makes my eyes hurt.
Please put the camera on the anvil next time

Good job getting up to speed for little cost!

Maybe I don't need a forge for this?

I ground out two test blades. I heated one using an ordinary propane torch and it got to bright orange. Even though the blade is very small it was still difficult to get the whole business end of the blank to maintain the same brightness but I quenched it in oil and tested the hardness with a couple of tools. A good sharp screwdriver blade skated across but the corner of a file scratched the surface a little. At first I thought it might only be scratching the scale but I cleaned the scale off and the scratch remained.

One problem I noticed is that the blade warps away from the side I ground. I ground only one side so that one side is coplanar with the center of the handle and one side is a long flat bevel. If I can't keep it from warping I'll have to do a different grind/shape I guess.

Since the blade was warped I decided to test the hardness a little farther and bent the blade back towards flat and a half inch snapped off.

I have no idea how hard the blade needs to be prior to tempering. Is bright orange hot enough? I suppose yellow is the next hotter color. Do I need to go there? Is there a minimum time for the heat to be held at a certain temp/color?

To treat the second blade I used two identical propane torches (in air like the first blade) and they created a larger hot spot so it was easy to get the whole blade section of the blank to bright orange very quickly, like under ten seconds. I kept it at that color for about twenty seconds and immediately quenched in oil as before.

The blades are now cooling in the oven after baking at 375F for an hour. I hope I wasn't supposed to quench them

Any comments are welcome, even virtual dope slaps as long as they're accompanied by explanation :)

Thanks for the extra notes on heat treating.

I agree about trying to just harden the business end and I have been worried about the thin edge of the blade getting too hot to fast.

I wonder about putting another piece of stock in close to the thin edge as a sink to slow the heating of the edge? Another thought, what about heating a piece of angle and letting the blade draw heat from the inside of the angle with the thick edge close to the inside corner and the thin edge much farther from the hot angle. Had a similar thought using pipe instead of angle. Finally, I wonder if I can just use a propane torch (or two from opposite sides) directly on the thick edge of the blade? A slot in some sheet metal could shield the thin edge from the flame.

You may know the answer to these speculative questions but I know I have to just try it to learn. Still, it's great to hear what experienced people have to say.

I'm new so this may be a little off topic. I've been reading....

Kaowool insulates and ITC-100 consolidates and protects the Koawool.
But ITC-100 is prized for it's thermal reflectivity, so, what stores the heat?

Is this why many forges have a floor of firebrick?

I'm planning to make a bean can forge for heat treating very small knives.
Would I need to leave room for some kind of heat sink or would the air and
insulation retain enough heat to soak a small blade?

Yes they have Michael, Rob Gunter's recuperative forge made while he was at Sandia labs is probably the best known and I think you can still get plans for it.

There are other recuperative schemes as well including the recuperative wall furnace. This is a situation where there is a gap between an inner liner and an outer insulating liner. The hot gasses in the forge are encouraged to exit the main chamber into the gap before being exhausted from the furnace all together.

A couple years ago while doing one of my semi-regular web surfs for new burner info I ran across a British firm who were getting much beter performance by preheating the propane instead of the intake air. There were charts and diagrams showing how they got their results and what those were. I was very intrigued but haven't gotten around to rigging a propane preheater.

One of these days I'm just going to have to do some serious experimenting, there are all these tantalizing ideas out there I'd just love to mix and match.

Frosty

In a direct-fired forge with a +2000F exhaust temperature, the insulating value of the walls is a pretty small component of "efficiency". Sure, in a totally enclosed electric oven, the biggest loss is through the walls. Hold your hand two inches from the shell of your forge. Now hold your hand two inches from the front opening. Where is the greatest loss of heat? The exhaust temperature has to be pretty close to the forge temperature or how could colder gases be coming out from a hotter chamber? 90% of the heat is going out the front door! How much of the remaining 10% are you willing to fight for?

Too many people get hung up on "thermal efficiency". The only "efficiency" I care about is how many dollars of fuel does it take to make a given dollar value of product. Once you have an adequate amount of insulation (say 2") adding more will gain you very little. Far more "economy" can be gained by having a smaller forge for the smaller work.

There are areas where you can gain efficiency. Good mixing helps. I always inject my gas into the intake of my blower. No, I don't have any more problem with "flashback" than any other design. Only if I try to turn the fire down unreasonably low. Multi-port burners or concentric ring burners have a much shorter flame front. They're like a bunch of small burners. Combustion is complete in a much shorter distance.

In industry, they understand that it works best to use the flame to heat the walls and let the incandescent walls heat the work. Turn on your forge from cold and try to heat a piece in the flame. Doesn't work very well, does it? In fact, after the forge is fully up to speed, you can turn it off, put in a small piece and heat it up with no fire at all! Why does it work so much better after the forge is warmed up? RADIANT energy from the walls! Some texts claim as much as 80% of the heat transfer is due to radiation. It's also much better for welding because the flame is incomplete combustion and contains hot oxygen, unburned fuel and all sorts of nasties.

After exhaust gases, radiation is the next biggest loss. Keep openings as small as possible. If it dazzles your eyes, that's radiant energy escaping.

There is very little difference in efficiency between insulating refractories and hard fire brick. Brick just has a much higher "thermal mass". It takes longer to heat up, but all that stored energy keeps the temperature up when you put a big piece in the forge. Brick maintains a much more stable, constant temperature for the same reason. While bricks and hard castables don't insulate that well, it still takes a long time for a BTU to travel from the hot side to the cold side. Iv'e seen brick forges that were still dull red inside the next morning! Now that makes a nice "turn off the forge, brick it up and leave over night" anneal.

Other than the above, the only way to gain significant efficiency is by using the exhaust to heat the incoming air. Preheating also can yield significantly higher forge temperatures.

well mousehole is a maker of anvil and anvil tools/accessories. now rathole im not familiar with that term... unless someone was bashing mousehole products which i dont believe for a min. they make quality stuff.

Of course! :rolleyes:

Very interesting! Thanks for posting.

One of the comments about third world craftsmen reminds me of a carver I met in Belize. He had an old refrigerator in his outdoor shed workshop but he had no electricity to run it. I asked about it and he opened the door so I could see that it was full of tools and work in progress.

Mousehole is an english brand of anvils made for a couple hundred years, wrought iron body, hard steel plate fire welded to the wrought iron body. High quality anvils.

Rathole is an american brand of anvils, presently in production, cast ductile iron, if I remember correctly, also very high quality.

That sounds like a good plan. Although with that small of a blade you could harden the end and grind the entire blade afterwards, then temper it.

Watch your heat while hardening, as the thinner edges, and point will heat faster than the other parts.

I tried the glossary at anvilfire and found nothing so what is the meaning of the terms mousehole and rathole? I saw them reading posts about anvil stands.

11342 - 1894, they made 7000 anvils that year.

Thanks for the ideas and sugestions for further search guys. So the goal is to conduct/absorb vibration away from the anvil? (lead sheet, silicone, chain, soft wood, etc.) In the case of the magnet it seems to be a more complex mechanism, it rebounds against the anvil's vibrations slightly out of phase?

So I should do this in order,

1. Cut stock to length
2. Grind to form (slightly oversized)
3. Harden (in bean can forge)
4. Temper (in toaster oven)
5. Fine grind and polish to final form

Is that about right? Any corrections or additional details will be greatly appreciated.

Search didn't bring anything up but I've seen mention of muting anvils that really ring, such as my good old HD. How do you mute an anvil?

I get it Junker, thanks.

Frosty, that sounds just right for this little project, thank you.

11342 - 1894, they made 7000 anvils that year.

"Do not grind to size,"

Do you mean don't grind the edge sharp? Surely I should grind the drop point and bevel to the approximate edge. ?

That looks very cool! How long have you been smithing?

I'm totally new to this craft but I want to make some small marking/utility knives for some of my woodworking friends. The form will be similar to the German chip carving knives. Like this

The blades will be about 3 inches long including 2" of tang. I've ordered some annealed 0.1 steel, 1/32" thick x 1/2" wide, from McMaster-Carr and I plan to simply grind the shape, drill holes for pins, and then try to heat treat. Heat treating is the part I'm worried about. Since these blades are so small do you think I could simply use an ordinary propane torch? I've been pondering making a tiny "forge" from a plumbing Tee fitting and feed the flame in the side. Is that stupid?

I have a 200# HB bought at least 20 years ago for $100. At that time I didn't know to look for the number signifying weight and I was so excited about finding it and getting a great price that I just picked it up and set it in the trunk of my Volkswagon Rabbitt. When I got home I couldn't get it out for the life of me. I'd lift as high as I could and the car just kept on following it up. Finally went and got my neighbor to help.

I've been accumulating stuff ever since and I'm finally getting ready to set up a forge. If there are any other guys in the SI area lets get in touch.

The number on my HB seems to be 11342. Anyone know it's age?