Hi. Hopefully this isn’t completely stupid but I’m just starting to get into knife making. Haven’t made one yet infact. Any way. I want to make a forge for cheap. I found three cinder blocks in my garage and wondering if it’ll work for forging small blades. I am hoping to use a blow torch as heating source   I have three blocks. I’m goinf to close out small gap at top with fire place brick and sneak the nozzle of blow torch through a whole in the top. Will this work for 6-8 inch blade forging. Please see photos attached. I just don’t want to burn down my house

Before you start, read the section on gas forges. There is much information there on how to build a for that WORKS. Look for the Frosty burner as a heat source.

Glenn was awfully nice there.  The answer to your proposal for a forge is an emphatic NO.  A typical blowtorch cannot put out near enough heat for any real forging and cinder blocks don't belong anywhere near a forge..unless you are just using them to set stuff on.

For a cheap solid fuel forge (since this seems to be posted under that subject though you are referencing a gas forge), look up JABOD forges.  One can be scabbed together in an hour for very little money, sometimes zero money if you scrounge well.  They're a great starter because you learn what you like and hate in a forge for pocket change, and can then move up to better if you choose to pursue the craft further.

You could use those three blocks to make a jabod and be forging today.

Pnut

Welcome to IFI... I'm going to advise you to read this thread. READ THIS FIRST

Cement will spalled and break down, so please do not use cement block or pavers in direct contact with high heat. A couple of inches of dirt or clay brick will protect it.( or a wooden table for that mater)

I second the simple sideblast forge as an inexpensive entery level multi fuel forge.  

Thank you. Much appreciated. I think I’m going to end up making a small coffee/paint can forge. Seems like it’s the best set up for me. 

I guess I shouldn't assume, but I'll lay odds you area planning on copying some YouTuber to make a coffee can forge using sand and Plaster of Paris as insulation  and a standard plumber's torch for heat.  This will not work well for your avowed goals.  Much better forge designs are available.

That’s an accurate assumption. My main concern is room that’s why I was going with that one and not wanting to get charcoal all the time. I do appreciate your advice. So I assume  u would recommend ajbod type set up. 

 

No condensention intended I do appreciate this advice 

Well there re several GOOD designs out there for micro/small forges---they just require using the CORRECT lining materials, Kaowool with a coating.  When folks say they can't afford the money on doing it right I usually ask them why they are willing to spend much more in wasted fuel costs than a good lining costs---how does that save money?  (And if you use a propane torch for a burner---get the adaptor to run it off a full sized tank---saves $$$$ big time!)

I've used a "one soft firebrick forge" that used a simple plumber's torch to forge the nails for my Mastermyr chest and a lot of hot forged silver jewelry---viking era hack silver designs.

Noting wrong with a small propane forge, if it is properly insulated.  The problem is the PP and sand don't insulate well and break down easily.  Also a standard propane torch puts out too little heat and the bottles run out too soon for a beginner to forge a 6-8" blade.

By all means start somewhere, but go with a better forge design.  It is actually more difficult to make a burner for a very small forge than a reasonably sized one.  There are a lot of resources on this site for the construction of a very good 300 cubic inch interior forge, but you will have to lay out some cash and do some research.  There are even fairly cheap gas forges available online these days.  I build my own, but you can get setup for around $200-$300 pretty easily.

The cheapest option is to make a JABOD or even a 55 gal drum or brake disc solid fuel forge.

My real suggestion is to take a bladesmithing class somewhere to be sure you really want to get involved. 

If you put your location in your profile, there is bound to be someone that can direct you to a place where you could take some classes, or get in some forging time before you invest more time and money.

With regards to the notion of forging using a small propane blowtorch:  Just give this test a try--take a piece of steel of appropriate size to forge a small knife and see how long it takes to get to a good forging heat.  Beyond red and toward a good yellow.  Even with an insulating box around it (like a coffee can forge), it would only heat up a little faster.

I think you'll find out what such a thing is a poor idea.  That is, unless you like waiting 15 minutes for your stock to heat up for 15 seconds of forging.  Lather, rinse, repeat a dozen or two times and you'll be wishing you never saw that youtube video.

Might be fine for something like small nail stock but it'll be awfully disappointing for someone intending to make knives or anything larger than that nail.

 

Plaster of Paris is ok for making lost wax molds for jewly casting but poor for gas forge lining. 

Other than space what are your requirements in a forge? 

So here’s the thing. I live in Milwaukee Northside. I don’t have a lot of space for a yard, in addition what I do have has a lot of ignitable things, weeds trees, etc. so I’m weary of a charcoal or camp fire burn because I don’t want to risk some of the embers flying on to other properties, as well as the smoke, because city ordinances with open flame etc. the reason I was thinking the coffee can forge is it can be done on a controlled environment in my garage, open the door if the insulation gives off fumes it’d be a nice controlled safe flame in my garage with little clean up or concern for surrounding environment. Also it seemed relatively cheap. Just trying to work with in my perceived restrictions. 

Look to make 3-8 inch knives 

Definitely look at the gas forges section of the forum. As noted above, one of the 300 cubic inch models will be just fine for bladesmithing, and while the initial investment isn't nothing, it will serve you quite well. I use one in my own garage shop, so I can personally vouch for their effectiveness. 

Please add your location to your profile settings. Have you read READ THIS FIRST!!! yet?

48 minutes ago, Ian6380 said:

I live in Milwaukee Northside.

We won't remember this once leaving this post, hence the suggestion to edit your profile to show your location.

The fumes from the insulation is the least of your worries, the controlled flame from a propane forge emits CO (carbon monoxide) which is known to be deadly. Adequate ventilation is an absolute must.