Which Torch to buy

[1DaramG]

I am an amateur knife maker and am looking to get in to a little bit of forging. I have made a bucket forge at home but am having trouble finding the right torch for the job. The torch is to fit in to the base of the bucket which is about 25mm wide and 50mm deep. Any advise on which torches would give me the best heat for forging wold be greatly appreciated as so far i am seeing torches that can achieve 1200 c but from what I have read I need to go as high as 1700. 

Many Thanks

Duncan

[JHCC]

Welcome aboard, Duncan; glad to have you.

You don't say where you are in the world, although given your choice of metric units, I'm guessing somewhere outside the US. If you could give us a location, that can help us make recommendations based on what's available where you are.

Generally speaking, torches don't make good forge burners, but there are exceptions. If you could give us some photos of your forge along with details of its construction, we'll be happy to help with appropriatet advice.

[Frosty]

A forge 25mm , 1inch across by 50mm, 2inches deep is so small I don't know of a torch or burner that would heat it practically. Sure I could use the small brazing tip of my oxy propane torch but it would melt the liner out of your forge in a couple minutes and take a serious chance of damaging an expensive torch tip. 

For stock that would fit in such a tiny forge I'd have to recommend you look into induction forges / heaters. 

Of course if you miss-typed MM instead of CM it's a completely different story. There are lots of burners that'll heat a 25cm x 50cm forge to welding temperature.

Frosty The Lucky.

[Mikey98118]

A good place to begin your search for an appropriate air/fuel commercial torch would be English manufacturers; they have been making air/fuel torches and burners for a very long time. Otherwise, you'd best figure on building a burner.

[1DaramG]

Firstly thanks for getting in touch. As mentioned I am an amateur knife maker so am grateful for all the help you offer.  Im gonna try answer all in one hit.

JHCC. I am in the UK. Im finding it hard to get a torch that will burn 1700 degree c which is what I have read online wold be the best temp I might need for the task at hand which to start with will probably only be heating old files so I can experiment with those in regards to forging. I have attached a couple of pics to help you better understand my set up. 

Frosty. My apologies for not being a little more specific with the measurements I gave. Those are for the hole at the base of the forge which the torch goes in to. I put the hole at an angle also as my thinking was to create a vortex of heat inside the internal of the forge. I thought maybe this would spread the heat a little better rather than blasting the heat in one area. Id love to hear your thoughts on that BTW.

Mikey. I am looking to run this from a propane bottle (BBQ/Camping Bottle). MOst of what I can find here in the uk are either hand held burners which dont give me the correct connection or they have the correct connection but not a 1/4 inch male connection for the propane bottle. I was in a live chat with a you-tuber called Max Randolph who mentioned making his own burners. Dont know were I would begin with that. Any advise\links you could give me on that would be greatly appreciated.

 

Again many thanks for your input.

Duncan

[Goods]

I believe most file are W2 steel or close to that. W2’s forging temperature range is between 760C and 1038C. (If my google fu is any good…) If you’re reaching 1200C in your forge, you should be good, but it might take a little time for your steel to  reach temperature. (I’m used to running a coal fire where the fire is much hotter than the steel needs to be, and one of the challenges there is not to over heat thin sections. But it heat fast.)

What refractory did you use? This could end up being a pretty efficient little forge. 
 

Any pictures of it running just after lightning and when it’s reached temperature?

(If I’m off base, I’m sure someone will correct me!)

Keep it fun,

David

[Frosty]

Let's talk about how you built the forge, it can make a huge difference. Mikey has building little burners down pat and likes to help folk as much as I do.

Frosty The Lucky.

[Simian]

Hey duncan, Where in the UK are you?

 

You might want to have a look at Amal burners.

[swedefiddle]

Good Morning,

I have/am using the Amal Burner. Minimal adjustment, right out of the box. They do an excellent job and they aren't too dear either. A lot easier for someone starting out, to use a burner that works. Concentrate their time learning how to make the wooden stick work!!

Neil

 

[1DaramG]

Again thanks so much for your input. Ive been trying for a while to find a forum that actually helps. So in answer to your questions.

Goods. I used a 1700 degree castable refractory. The minimum thickness in the forge is about 50mm. I got the idea from a you-tuber called the art of craftsmanship and after doing a bit of homework saw a lot of people doing a plaster of paris mix but also saw a lot of negative in regards to longevity. So figured spend a little more and get something that can handle the heat. Proof will be in the pudding I guess. A huge thanks to for the info in regards to file heating temps. Maybe 1700 is too much for a starter and I can get lower temp torches easier than ones that will reach 1700.

Frosty. The build was simple. 50mm refractory in the bottom of the bucket, let that set then a drain pipe to create the void. A pre drilled hole for the burner which I blocked with an old broom handle to gain access and thats it really. I hope the two separate refractory stages dont create a weak point but then thats all in the learning curve I guess and also why ive not gone out and spent a lot of cash to start. Plus the experience of making my own is priceless. 

Simian and Swedefiddle. (Your name raises so many question). I will look into Amal burners. This is the exact reason I have been on these forums as you can offer information that I wouldnt even know to look for, so thank you for pointing me in the right direction. `Also Simian I live in Lincolnshire.

 

Thanks again for all your input. It really helps

Cheers

Duncan

[Mikey98118]

1DaramG,

Let's keep the confusion down by starting right where you are.

I can't be sure without you providing a close-up of the head of your present torch, but you can probably get away with sheathing its end in a tight fitting stainless steel tube or pipe. This is what you need to make sure it survives being mounted within the forge's burner portal (the hole it is laying in at present).

Properly mounting your present torch, or whatever torch or air/fuel burner you eventually choose, will increase internal temperature in that forge by about one-fifth.

It looks like you employed castable refractory to line your torch with. I have made several forges and furnaces, with nothing more than hard castable refractory; it isn't the best choice, but is also far from the worst. You can work with it. What you need more than a change in liner is to finish the forge, by providing an external baffle wall of firebrick, about an inch in front of the exhaust opening. Most people choose insulating or semi-insulating firebrick, but even plain firebricks will do a marvelous job of increasing forge temperature. This movable wall allows the hot gases to exit, while bouncing radiant heat back into the forge.

Next, you need to complete the refractory lining with a coat of re-missive material; there are several to choose from, but even plain kiln wash will do wonders. Why? Have you noted how rough the surfaces of your refractory is? All of the recommended coatings, including kiln wash, are SMOOTH. How well heat is reflected back from an incandescent surface depends on how small the particles that make up that surface is; this is why all these coatings rate their percentage of heat reflection as "up do."

The whole point of a forge is control of the heat that a burner or torch provides, So:

(A) Control the heat at its entrance (burner portal) by controlling the amount of secondary air that the flame can induce.

(B) Control the heat loss through its wall, with a finish coating, so that the forge interior will super-heat, causing it to radiate more. The hotter the internal surfaces the higher the percentage of heat transferred into your work. At yellow incandescent far more of the heat transferred into your work is from radiant energy; not directly from the flame.

(C) control heat loss through radiation at its exhaust, by bouncing that radiant energy back into the forge interior.

You will find these little tricks doing as much for you as a better torch or burner

[Latticino]

Looked a lot like a home-made plaster/sand mix refractory to me, glad you dodged that bullet.  As noted the hard cast refractory is not a particularly good insulator, so your forge may not be extremely efficient, but it is a small forge, so may not be a big deal.  Just be careful the galvanized can forge skin does not get heated to the point where it begins to smoke, particularly at the open end where there is no refractory.  I'm sure you are aware already of the poisonous gas that will be released.  Also, I would lean towards using a barbeque grille size tank and adjustable regulator if possible.  You will likely get tired of replacing the smaller propane cans, and the tanks are more cost effective. 

Aside from that, Mike and the rest of the group have laid it out pretty effectively, so I don't have a lot to add.  However, the one thing that you should consider is that the burner flame temperature isn't nearly as important as its heat output over time (typically rated in BTUH or MBH here in the states).  Flame temperatures are typically a bunch hotter than the temperature of the forge interior.  For the latter you should be aiming at least to get to a yellow orange color.  Yellow-white is even better if you plan on forge welding, but you certainly won't need that for basic forging of "simple" steels.

[timgunn1962]

Another vote for the Amal atmospheric Injector here. 

I tried to get the PC108 and PC109 Clarke torch sets to work as forge burners a number of years ago. By using the jet from the smallest of the 3 burners in the biggest of the 3 burners and increasing the air ingress area by drilling the holes bigger, I managed to get useful results. However, I work with burners and temperature control for a living, which means I probably have a better understanding than most smiths, and I have the equipment to measure temperatures up to the melting point of pure Iron and beyond. I couldn't get to the point where I could tell "anyone" precisely what to do with any expectation of repeatable results.

About the same time, I discovered that Burlen Fuel Systems were making the Amal injectors at a reasonable price (we'd used them at work for years, but they'd been hard to get hold of and more expensive during the time they were made by Grosvenor Works). I really couldn't/can't see any reason to use anything except the Amal injectors in the UK.

If you are anywhere near Lancashire, and want to try before you commit, I'm pretty sure I have a 1/2" Long-Venturi injector and the pipe, fittings, etc to get you set up and running.

[timgunn1962]

Sorry, got sidetracked and my reply sat on the computer before getting sent. 

1700 degC refractory seems likely to be pretty dense and a huge heat sink.

I'm guessing rather, and may be wrong, but if it's as big a heatsink as I suspect, it'll take a long time to reach temperature and there's a probability that the burner will need some sort of flame retention cup (or "flare"). With low thermal mass, the inside of the forge will usually get hot enough, quickly enough, that a straight-pipe burner is all that's needed. I light the forge with a blowtorch and keeping it there for the few seconds it takes to get to a temperature where the burner stays lit is no problem.

Do you have any of the refractory left? If so, a relatively thin coating as a hotface layer inside Ceramic Fibre Blanket should work. 

Here's one I made 4 years ago running at forging temperature, Austenitizing temperature and welding temperature. Temperatures shown are in degC above degF.

I think I have everything needed to make at least a couple more, except rigidizer and a hotface coating. 

[tinkertim]

If you're based in the UK, then the AMAL burners are a no-brainer!

Super adjustable and really hot. 

[Buzzkill]

On 7/6/2023 at 8:15 AM, 1DaramG said:

torches that can achieve 1200 c but from what I have read I need to go as high as 1700.

Unless you are planning to make crucible steel I don't think you need to reach temperatures anywhere near that hot.  One of the highest temperature tasks we do is forge welding, and that can be achieved around 1200 to 1250 degrees C in most cases.

[1DaramG]

Again this is just massively helpful. So thanks you all so much for you input.

I would say I have been focusing a little too much on the torch itself rather than retaining heat in the forge itself. I will be looking in to kiln wash and some fire bricks for sure. That has been a great mind set change so thanks Mikey98118 I will focus a lot more now on containing the heat.

Also thanks Latticino for the heads up on the safety tip. Im sure I was told about poisonous gases from Galvanised metal before but had totaly forgotten so my thanks. I am going to be running this from a 13kg gas bottle for the exact reason you stated. I also bought an adjustable regulator that will reach 60 psi so ive no worries there.

It looks as though the amal is getting the vote on the burner (tinkertim giving the third vote) so I guess ill go that way. timgunn1962 I was wondering if you could give me a bit more of a run down on the setup you have in the pictures you posted. Is that a fitting on the torch or just a bit of pipe? Does the length of the pipe matter and did you have that sealed to the furnace or was that just a tight fitting? Also you mention about the burner staying lit. Does the forge need to be at temp in order for the burner to pull the fuel?

I also agree now Buzzkill. I thing I have been wrongly assuming the 1700 degree mark. Having seen a few comments form other here I now think the lower temps will work fine. Trial and error but with all the advise for far im hoping less error.

 

Thanks again all for your input which has been such great help

Duncan

 

[timgunn1962]

The burner in my setup is just a length of pipe, cut square at the end. Length is not critical in my experience, though I've probably not tried less than ten or more than 25 nominal pipe diameters (5-12.5 inches on a half-inch burner or 10 inches to a couple of feet on a 1" burner). The burner fits "fairly closely" into the wall. I think I used a 22mm holesaw to cut the hole for the 1/2" pipe in the one in the pics. I don't want air getting in, or flame getting out, between the burner and the refractory, but I've not really tried to seal it.

A straight pipe burner running in open air will often (usually?) have the flame lift off the end of the pipe and go out. If you keep a torch next to the burner, this will keep the flame attached. The mixture exiting the burner will draw in the surrounding atmosphere and mix with it, exactly the same as the gas exiting the jet will draw in air at the Venturi. In open air, the atmosphere is air. In a forge, the atmosphere is flame, which, when drawn to the end of the burner, keeps the flame attached just like the torch in open air. 

When the forge is cold, it can rob enough heat from the burning gases that the stuff getting drawn to the burner is no longer flame and will not keep the flame attached to the burner. For brick kilns and similar industrial applications, 800 degC seems to be the temperature above which it is generally considered safe to inject gas/air mixture into a chamber without needing to expressly ensure it is burning. 

What we really don't want to do is fill the chamber with unburned Fuel/Air mixture and then ignite it.

I think the flame retention cup shown in the Amal injector leaflet https://amalcarb.co.uk/technical/amal-atmospheric-injectors essentially works like a little forge and keeps the flame attached by setting up a donut-shaped vortex (think smoke ring) on the step where the diameter doubles. 

I have built Heat-Treating drum "forges" for HT of Carbon Steel blades and I use a flame retention cup for these because they are intended to run quite close to 800 degC.

[1DaramG]

So one question that comes to mind is why the pipe. Would it be to do with the pressure from the burner pushing the flame away from the burner and therefore going out? Or is it more of a heat insulation thing? I spoke with Amal today but their guy in the know is on holiday so will talk with him next week in regards to which one I purchase.

Thanks again for your input. Has been such a help and will hopefully ensure that my eyebrows stay on my forehead.

Cheers

Duncan

Edited July 15, 2023 by Mod30
Remove excessive quote.

[tinkertim]

Hi Duncan,

The pipe length is a ratio related to the internal diameter of the pipe. I believe this ratio is to do with having enough length to give complete mixing of the gas and air before it reaches the flame at the end.  It makes quite a difference with single-jet burners, but no difference if you are feeding into the plenum chamber of a multi-jet burner (NARB).  It is something like 12:1.

Here's a link to some values from a previous chat.

As far as the size of the burner and diameter of the pipe, there is a rule-of-thumb that suggests a good 3/4" burner will bring a good 350cubic inch forge up to forge-welding temperature.  This is what I based my choice on.  I have used my AMAL 3/4" burner with ~8" pipe for single-jet use and multi-jet (NARB) use very successfully.  The turn-down range on my AMAL is pretty good, so I'm glad I went for a single 3/4" rather than 2 x 1/2" burners.

On the AMALCARB website, they sell propane injectors with a short-choke or long-venturi.  The short-choke is really intended to feed a multi-jet burner and so doesn't really need to worry about mixing the gas and air so much.  If you are going to use a single-jet burner, then chose the long-venturi version, as it has a correct-ratio expanding cone on it, that fits inside your length of malleable steel pipe nipple.  As the long-venturi version will wok with single-jet and multi-jet, I went with that option.  I also followed TimGunn's advice and got 2 sizes of jet for my 3/4" AMAL injector when ordering. From memory it was a 90 and a 110 sized jet, but it is cheaper to order an extra jet when you order your burner.  I have played around with both jets, and one worked better in a single-jet and the other size was better with my multi-jet setup.

You really need to work through the Burners-101 and Forges-101 threads to glean this info. It will take a while, but you will learn a lot from it.

Hope this helps.  Tink!

[Simian]

Looking at your forge, the 1/2" would be plenty. You'll need a few bits - 

A regulator, Gas hose, 3/8 BSP male gas pipe fitting (search Ebay for 3/8 male fulham Nozzle) plus  a 4" BSP threaded pipe.

That should be it, and is the same as I have. (although I'm currently building a small ribbon burner for it).

 

Or, you can make your own, small, frosty burner; 

 

[Mikey98118]

Good show! I don't know why more builders in the UK, mention what local fittings and parts they used to construct a burner. After all these years, you people should be able to find this information on our site, with a glance.

[Simian]

Very true Mikey. 

I guess for any one reading this in the UK, I built my Frosty burner with parts from 'Pipe Dream Fittings';

BLACK MILD STEEL PIPE / TUBE SELF COLOUR THREADED 1/2" 100mm; £1.57

REDUCING TEE BSP BLACK MALLEABLE IRON 3/4" x 1/2"; £1.94

FULL SOCKET BSPP STAINLESS STEEL 1/2"; £1.60

(Plus about £6 postage)

 

You'll also need (all from Ebay, prices including postage);

1/4 BSP FEMALE gas pipe fitting (search Ebay for 3/8 FEMALE fulham Nozzle); £5 each

1/8 BSP to 1/4 BSP HYDRAULIC ADAPTER (female/female; this is the bit I struggled to get right initially); £2.50 each

m5 thread 0.6mm mig tip; £2.80 for 5

 

That's around £13.00 per burner. 

 

You'll also need gas hose and regulator, and a 1/8" BSP taper tap.

 

 

[Mikey98118]

Thanks, Simian. This is the kind of information people there need.

[Mikey98118]

On 7/14/2023 at 8:00 AM, tinkertim said:

The pipe length is a ratio related to the internal diameter of the pipe. I believe this ratio is to do with having enough length to give complete mixing of the gas and air before it reaches the flame at the end.  It makes quite a difference with single-jet burners, but no difference if you are feeding into the plenum chamber of a multi-jet burner (NARB).  It is something like 12:1.

Well put. However, I have noticed that the "rule of thumb" concerning the length of a burner's mixing tube depends on the burner design