Forge Question

D

docmott

Joined
Dec 10, 2022
Messages
82
Aloha, I've been forging my knives in a wood burning forge. My wood supply has been cut down so im looking into a single burner propane forge. So the question is does anyone know about how many knives you would get out of a 5gal bottle of propane? im sure it would be easier and they might come out better but propane is pretty high here on the island of Molokai, HI. thanks!
 
The forge I use is a two burner, but I’m usually only using 1 burner, and when I‘m running a small 5gal tank it lasts about 4 (roughly) hours. now how many Blade can you make in that amount of time? That’s entirely up to your equipment, skill and what you are making.
 
Bunker Hill Blades said:
The forge I use is a two burner, but I’m usually only using 1 burner, and when I‘m running a small 5gal tank it lasts about 4 (roughly) hours. now how many Blade can you make in that amount of time? That’s entirely up to your equipment, skill and what you are making.
Click to expand...
Ok thats what I need to know. with the wood burner I can do around 10 an hour. I spend more time getting the quinch oil to the right temp.
 
To add, every forge is different, some sip, some use more. (I know, a btu is a btu, but!). Some designs/builds are just more efficient so go in with both eyes open knowing you may get more or less.
Good luck!
 
From what I see online, you are only paying about a dollar more per gallon that we do in Virginia.

I usually get 5-10 hours forge time from a tank on a single burner forge like the Atlas. I can usually forge out a knife in 30 minutes or less, so 10-20 knives easily. It varies depending on how large your blank is and your skill level. As a rule of thumb, a single burner Atlas type forge uses about $1 per hour of gas. For you that might be $1.50 an hour. If what you are trying to figure out is the cost in gas per blade, just call it $1 per blade.

Some fuel saving tips:
Make a simple two-stage burner control. It is just a needle valve by-pass line going parallel to a gate valve main line valve somewhere before the needle valve at the forge. Open the main line gate valve with the by-pass shut off. Open the valve at the forge and adjust to the flame you want. Open the needle vale on the by-pass side and when you see the flame getting bigger, shut off the main line valve. Adjust the by-pass for the lowest flame that won't blow out. In use, once you are forging and the valves are set you shut off the main line valve when you pull the steel out of the forge. This puts it on a very low stand-by mode. When you stick the steel back in, open the main valve again. A setup like this can save 30% of the fuel use.

Another method is super simple. Just shut off the gas when you pull the steel and turn it back on when you put it back in. If you are forging at full heat, the forge will relight automatically from the red-hot chamber. It will make a nice WHOOF when it relights, but that won't be a problem as long as you are out of the way. Keep a long flex neck BBQ lighter handy for the times it doesn't light right away.

Other ways are making a simple pilot light from scrap parts from a junked water heater or BBQ. It works pretty much like the by-pass setup.

Building a good forge with a proper blown burner and plenty of insulation is the way to get the most bang for your buck from the propane.

A big help in forging time and cost is getting a 100-pound tank (23 gallons in comparison to 4 gallons for a 20# tank). The tanks are less than $200 and the cost of filling them can be a lot lower per gallon than exchanging a cylinder. I run a three-burner Whisper Lowboy forge most of the time and a tank lasts all summer of regular forging. The main plus is the tank won't freeze up when forging in the summertime.
 
Last edited:
Stacy E. Apelt - Bladesmith said:
From what I see online, you are only paying about a dollar more per gallon that we do in Virginia.

I usually get 5-10 hours forge time from a tank on a single burner forge like the Atlas. I can usually forge out a knife in 30 minutes or less, so 10-20 knives easily. It varies depending on how large your blank is and your skill level. As a rule of thumb, a single burner Atlas type forge uses about $1 per hour of gas. For you that might be $1.50 an hour. If what you are trying to figure out is the cost in gas per blade, just call it $1 per blade.

Some fuel saving tips:
Make a simple two-stage burner control. It is just a needle valve by-pass line going parallel to a gate valve main line valve somewhere before the needle valve at the forge. Open the main line valve with the by-pass shut off. Open the valve at the forge and adjust to the flame you want. Open the by-pass and when you see the flame getting bigger, shut off the main line valve. Adjust the by-pass for the lowest flame that won't blow out. In use, once you are forging and the valves are set you shut off the main line valve when you pull the steel out of the forge. This puts it on a very low stand-by mode. When you stick the steel back in, open the main valve again. A setup like this can save 30% of the fuel use.

Another method is super simple. Just shut off the gas when you pull the steel and turn it back on when you put it back in. If you are forging at full heat, the forge will relight automatically from the red-hot chamber. It will make a nice WHOOF when it relights, but that won't be a problem as long as you are out of the way.

Other ways are making a simple pilot light from scrap parts from a water heater or BBQ. It works pretty much like the by-pass setup.

Building a good forge with a proper blown burner and plenty of insulation is the way to get the most bang for your buck from the propane.

A big help in forging time and cost is getting a 100-pound tank (23 gallons in comparison to 4 gallons for a 20# tank). The tanks are less than $200 and the cost of filling them can be a lot lower per gallon than exchanging a cylinder. I run a three burner forge most of the time and a tank lasts all summer of regular forging.
Click to expand...
I pay $36 for a 5gal tank. I just need the forge for heat treating now. I do want to sometime start forging to make some things but first things first. im enjoying making knives and still figuring things out. half of the problem is the equipment, 2x42 belt sander, things aren't square so im playing all the time trying to get thing set. ive made my own bevel plate for it and it works. my 1x30 works great. thanks, for the tips
 
If just doing HT figure around 30 minutes run time to soak the forge then do the HT, so somewhere around10-20 blades if done at separate times. If done in batches, it would obviously be much cheaper.

Just an FYI, it is a 20# tank. They don't rate them in gallons. it holds just a tad under 4 gallons of propane.
 
Stacy E. Apelt - Bladesmith said:
If just doing HT figure around 30 minutes run time to soak the forge then do the HT, so somewhere around10-20 blades if done at separate times. If done in batches, it would obviously be much cheaper.

Just an FYI, it is a 20# tank. They don't rate them in gallons. it holds just a tad under 4 gallons of propane.
Click to expand...
yes you're right, if I told them I want to fill my #20 tank, they wouldn't have a clue what im talking about.

I would try to do 8 to 10 at a time. my wood forge will heat one in about 5min and I can preheat one too?
 
docmott said:
I spend more time getting the quinch oil to the right temp.
Click to expand...
Lots of ways to skin that cat my friend without using wood nor propane. If you have power, a outdoor rated pet heating pad could warm it for you, heck if you were off grid you could buy a few extra large air activated emergency heat packs if you have no other choice ;)
 
I need to cool it off. I quench for 4-5min. but the the oil is 180+ . I just bought more oil and dilute it back to 120-140.. ready for the the next blade.
 
An Atlas knifemakers forge, runs about 15 hours at 20 PSI. A friend runs his at about 10 PSI and he gets 24 hours out of a 20 lbs. tank.

Get a piece of wool and partially block the front and you can run it at about 3 PSI and get almost 36 hours at 2300°. Do not completely block off the front, nor run it at full pressure if you block off the front. It will melt the refractory if you do.
 
Thank you! I might be going this way. is that a 20lb tank or #20 tank. I pay $36 for a #20 tank
 
For cooling the oil tank, freeze some bottles of water and have them in a cooler by the quench tank.. Tie a string on each bottle neck. Take a bottle out and dry it off quickly, then lower it in the tank and pull it up and down. It will drop the oil temp fast.

How much oil are you using? A sufficient volume will not rise to 180° from 120° unless you are quenching many HUGE blades. 2-3 gallons is the minimum for multiple blade quenching. 5 gallons is even better. If your setup really requires cooling the oil, you can make a circulating oil cooler out of a transmission oil cooler and pump.
 
$29.87 for a swap and go at the big hardware chain store.

Given the exchange rate that is a 30%+ discount to US prices quoted here.

Larger size works out cheaper but here they are a booked refill or swap and the cylinders are rented from most companies.
 
Stacy E. Apelt - Bladesmith said:
For cooling the oil tank, freeze some bottles of water and have them in a cooler by the quench tank.. Tie a string on each bottle neck. Take a bottle out and dry it off quickly, then lower it in the tank and pull it up and down. It will drop the oil temp fast.

How much oil are you using? A sufficient volume will not rise to 180° from 120° unless you are quenching many HUGE blades. 2-3 gallons is the minimum for multiple blade quenching. 5 gallons is even better. If your setup really requires cooling the oil, you can make a circulating oil cooler out of a transmission oil cooler and pump.
Click to expand...
ok good idea. my blades are 8in or less. the oil is in a container thats a little bit more than a quart. I have about an extra gallon that I use to cool the hot one down. I'll look for a larger container I thinking a tin 1gal paint container ?
 
Brad Martin said:
$29.87 for a swap and go at the big hardware chain store.

Given the exchange rate that is a 30%+ discount to US prices quoted here.

Larger size works out cheaper but here they are a booked refill or swap and the cylinders are rented from most companies.
Click to expand...
no big box store here. no fast-food. theres not even a stoplight on my island
 
A quart of oil for an 8" blade will not properly harden the blade. It may not harden it much at all. You need at least one gallon of oil. The tank should be at least 4" wide and 4" deeper than the blade. a 12" deep tank that is 5" wide holds 1 gallon. 18" by 4" is also a gallon.
 
You must log in or register to reply here.
Back
Top