help with a decision/ recomendations

[fishfinder401]

First of all, I'm not sure if this is the right section for this, but it seemed closest since it involves a gas forge. 

So, I was recently commisioned to make a knife for someone, the only issue is that my coal forge doesn't heat a large enough area to harden the while blade ( or at least not without some large risks)

This brings me to what I need advice on, to heat treat this I am looking at 3 main options, buying a propane forge or buying or making an electric heat treat oven. I would build the propane forge but I don't know much of the intricate details of how to get then working well and don't have the time right now to teach myself. Is there an inexpensive propane forge that will work for heating a 10 in blade to the correct temperatures, would I be better off just building a electric oven or is there an option I'm not seeing? Also my budget is at most 400 but preferably less. 

Thanks 

Noel

[Frosty]

Have you considered sending out to a heat treater? No matter what heat source you use heat treating it yourself always involves risk. Keeping the blade moving through the fire in your coal forge is how people have been doing it for a long long time, same for charcoal or most any solid fuel fire. Temper in an oven. If you use a cooking oil for hardening the wife might not kill you if you use the kitchen oven. I have a garage sale toaster oven and an oven thermometer in the shop that works a treat. It's a nicer toaster oven than the one in the kitchen and only cost $5.00.

If you're nervous about ruining the project, happens to everybody who heat treats in the shop, sending it out to heat treat is a good option but you'll have to either pass the cost along or eat it. It'll take time too, maybe weeks on the turn around.

If you only have ONE blade I certainly wouldn't build a propane forge unless you want a propane forge. If so they're not hard to build just don't fall into the trap of trying to build the PERFECT propane forge, there is no perfect anything. Just pick a set of plans and stick to ONE SET. Don't try mixing plans even the experienced guys don't mix and match. There are a few good burner plans available. If you pick the T burner plans I'll be happy to help you get it tuned. but its even more important to only use ONE set of plans and ignore all the helpful posts you see. Wayne Coe has a good web site with materials and good plans.

Frosty The Lucky.

 

[ianinsa]

While I think Frosty has given you sterling advice bear in mind that most businesses have minimum charge setups so a single blade may be a non-starter.

[jmccustomknives]

I built a single burner gas forge that can handle the HT on up to a 12" blade easily.  I probably have around $120 in it.  My double burner Diamondback Knifemakers Forge was pass through (like the one I built) and I was able to HT a 18" blade in it. 

A forge like this is an investment, you will use it for other things.  Dare I say, for knifemaking, you'll all but quit using the coal.

[fishfinder401]

9 hours ago, Frosty said:

Have you considered sending out to a heat treater? No matter what heat source you use heat treating it yourself always involves risk. Keeping the blade moving through the fire in your coal forge is how people have been doing it for a long long time, same for charcoal or most any solid fuel fire. Temper in an oven. If you use a cooking oil for hardening the wife might not kill you if you use the kitchen oven. I have a garage sale toaster oven and an oven thermometer in the shop that works a treat. It's a nicer toaster oven than the one in the kitchen and only cost $5.00.

If you're nervous about ruining the project, happens to everybody who heat treats in the shop, sending it out to heat treat is a good option but you'll have to either pass the cost along or eat it. It'll take time too, maybe weeks on the turn around.

If you only have ONE blade I certainly wouldn't build a propane forge unless you want a propane forge. If so they're not hard to build just don't fall into the trap of trying to build the PERFECT propane forge, there is no perfect anything. Just pick a set of plans and stick to ONE SET. Don't try mixing plans even the experienced guys don't mix and match. There are a few good burner plans available. If you pick the T burner plans I'll be happy to help you get it tuned. but its even more important to only use ONE set of plans and ignore all the helpful posts you see. Wayne Coe has a good web site with materials and good plans.

Frosty The Lucky.

 

I don't really want to send it out for someone else to heat treat, i have heated all my previous knives with my coal forge, and tempered with a toaster. 

i just had a thought though, although maybe this would be better suited to ask in the coal forge section, but what if i added another air source from the side, would that increase the size of the hot spot? i recently got a double squirrel cage blower for 2$at a yardsale, so if it would help i could rig them up to get more air spread over a larger area

[Frosty]

I'm not crazy about sending things out to a heat treater unless we're coffee shop buddies that is. A friend of mine picked up an old pottery kiln of a smallish size and changed out the temp sensors. He uses it to make Mokuma Gane and heat treat his blades. IIRC the new sensors and controls cost more than he spent on the kiln. It'll ramp up and down and hold a temp as long as you set it to. I'm thinking he's got the gear to heat treat some pretty exotic stuff for the garage shop.

Not knowing or maybe remembering what your forge looks like I can't make specific suggestions. However it isn't hard to redirect the air coming from an air grate into a long narrow blast. A piece of angle iron with holes drilled along it on both flanges, maybe alternated then laid over the existing air grate will make for a long air blast. Fire brick to shape the fire and you now have a long narrow fire ball. Fire Sausage? Hot links and eggs, Mmmmmmm.

It'd be as easy as just connecting a piece of pipe to your air supply with holes along it's length and laying it in the brick fire trench.

This isn't a difficult thing and you can test it out on cheap steel before committing your blade to it. Adapt,tweak and test is a blacksmith tradition you know.

Making or buying a propane forge is a good option as well, you can watch the temperature of your stock live. Just remember, do NOT stare into a propane forge! The IR can cause cataracts in time. Forget UV, the UV emitted by a propane forge is WAY less than emitted from your computer monitor, even LEDs emit more. Let' not talk about old, scratched up florescent tubes!

Frosty The Lucky.

[fishfinder401]

2 minutes ago, Frosty said:

I'm not crazy about sending things out to a heat treater unless we're coffee shop buddies that is. A friend of mine picked up an old pottery kiln of a smallish size and changed out the temp sensors. He uses it to make Mokuma Gane and heat treat his blades. IIRC the new sensors and controls cost more than he spent on the kiln. It'll ramp up and down and hold a temp as long as you set it to. I'm thinking he's got the gear to heat treat some pretty exotic stuff for the garage shop.

Not knowing or maybe remembering what your forge looks like I can't make specific suggestions. However it isn't hard to redirect the air coming from an air grate into a long narrow blast. A piece of angle iron with holes drilled along it on both flanges, maybe alternated then laid over the existing air grate will make for a long air blast. Fire brick to shape the fire and you now have a long narrow fire ball. Fire Sausage? Hot links and eggs, Mmmmmmm.

It'd be as easy as just connecting a piece of pipe to your air supply with holes along it's length and laying it in the brick fire trench.

This isn't a difficult thing and you can test it out on cheap steel before committing your blade to it. Adapt,tweak and test is a blacksmith tradition you know.

Making or buying a propane forge is a good option as well, you can watch the temperature of your stock live. Just remember, do NOT stare into a propane forge! The IR can cause cataracts in time. Forget UV, the UV emitted by a propane forge is WAY less than emitted from your computer monitor, even LEDs emit more. Let' not talk about old, scratched up florescent tubes!

Frosty The Lucky.

thanks, ill the something similar to what you mentioned with the angle iron. and if it helps, i am using an old riveters forge run off a leather belt, so i cant really modify the air system on it without possibly causing serious damage( wasn't in the best shape when i got it), but i can add another air source on the side if i need to. hows the IR and UV from a coal forge?

also, i do appreciate all the input everyone is giving me.

thanks

[EricJergensen]

Coal forge has IR problems as well, tho the coal on top of the fire makes it less intense generally than propane. I use #3 welding shades when I need to stare in either one and avoid staring when not protected. UV is negligible from coal.

[Buzzkill]

Another thing you can do to help a little is use a piece of pipe laid on your fire which you will pass the blade through when bringing the blade up to critical.  That will help even out the temperature a bit to reduce the likelihood of overheating the steel before quenching. Thin blades and small points are very easy to burn in a coal fire.  Try to keep the meatier parts of the blade closer to the center of the fire and save heating up the tip until just before you quench.

I'll echo jm here.  You probably won't have to burn many blades in coal before deciding that propane might be a better option.  Obviously people can and do make great blades with coal and charcoal, but a few seconds of inattention at the wrong time can destroy hours of work put into a blade.  It is a disheartening feeling.  Of course it's possible to destroy a blade with a propane forge as well, but once you get your temperature set where you want it, a minute or two of distraction is no longer disastrous.

[fishfinder401]

good to know about IR from coal, I'll be careful with that. And I'll have to try the pipe idea at some point. 

I've already learned about burning work up in coal, I've heat treated quite a few dozen blades with it, this one I was considering propane for is jsut larger than my normal blade