Flame Cutting with Oxy Acetylene

Flame Cutting with Oxy Acetylene


I laid out a hexagon and I’m going to cut it by hand from ½ inch plate. The plate I’m using has kind of a pickled surface so it’s fairly clean. I wanted to do a couple of things with transferring the lines from my diagram or darkening them and one thing I want to get into real quick is that I like to use a sharpened soapstone. I can’t count the times that I’ve watched people do a layout with a dull soapstone piece. But let’s just say that I want to put a mark on a piece of steel, and I’ve seen people do this. They come over and they put a mark on and it looks like kind of big and so if I want to cut accurately, I’m guessing which side of that do I cut on and let’s just say that we came in and marked off 3 inches and I put another big fat mark on there. How am I going to work with that? So that’s kind of my point. That’s why I like to use sharpened soapstone that I bevel on a grinder, or you can do it with a file. In any event, if you want to make an accurate mark and let’s say I want to lay out a three inch piece, then I can get a very fine definition in line with the marks on the tape measure.


Frequently when you are using a torch to cut metal, especially C1018 steel, you need to mark where you are going to cut. There are lots of ways to make a mark or a line that range from using a magic marker or sharpie, or just scratching the metal with an awl. The best way to make the marks you need is to use soapstone, which is the solid form of the same talc that is used in talcum powder. The handiest way to do this is to use pre-cut rectangular (127 x 12.7 x 4.8mm) prismatic pieces of talc, which are held in a special pen shaped device with a pocket clip that allows the talc to be firmly held and advanced as the talc wears down. These soap stone holders are available from many companies such as: Forney, Ally Tools, Hobart, Firepower, and Tech Team®  https://www.techteamproducts.com/. We happen to like Tech Team’s model 759 the best https://www.amazon.com/Soapstone-Retractable-Oxy-Acetylene-Tech-Team/dp/B07NGJ4MB1/ref=sr_1_3?keywords=tech+soapstone+holder&qid=1565098360&s=gateway&sr=8-3 because it has a durable zinc finish and a positive locking and advancing mechanism for the soap stone. You can buy these from Lowe’s, Home Depot, Allied Welding Supply, or on Amazon.


Of course, you also need soap stone, aka talc, to feed the holder as you wear out the soap stone. Those refills are available from several companies such as: Homee, Anchor, VasTools, Uniweld, Hobart, and also Tech Team®  https://www.techteamproducts.com/. We like Tech Team’s 757 36 pc. of soap stone https://www.amazon.com/Tech-Team-Soapstone-Machining-Surfaces/dp/B07JMFBFW3/ref=sr_1_44?crid=13B5M9FVHOOXU&keywords=soap+stone+holder+welding&qid=1565097627&s=gateway&sprefix=soap+stone%2Caps%2C128&sr=8-44 the best because it is high quality, bright white soap stone that leaves clear and easy to erase marks on almost any metal surface. Ok and you can kind of tell the difference.


I already got a hexagon laid out and we were going to cut along the lines and sometimes I also like to use scribes when I’m doing precise work, like laying out bolt hole circles. If I want to transfer this a with a scribe to scratch into the steel the simple fact is that my soapstone mark goes away from the flame and we don’t want that.


Now, we mentioned cutting accurately with an oxy acetylene torch by hand. I need to get my dark shield on and I want to only use a couple of other items for my hand cutting. I’m gonna hand cut a hexagon out of a circle that we had laid out. I have a zero tip in here, 031, a long series, I’ve cleaned it, I did a Hey Siri search to get the correct pressure settings for the work I am going to do, and I’ve set my pressures according to the metal thicknesses and pressures I’m cutting and the size of tip and everything. It’s interesting to note the physics of a cut and the pressures and everything matter a whole lot. Years ago, I learned to cut with one hand using a guide. A lot of people use them. They make them commercially and some of them are magnetic. I had mine machine cut from a piece of angle iron, but I also have a piece of flat stock that I’ve tacked a handle on the backside. I had the machine shop flat cut it so it’s very smooth. And what’s interesting to note is I like to use superfine sharp marks because quite literally, you can line up one of the preheat flames right on top of your scribe and mark the edge. The oxygen flame allows you to cut within 1/32 inch very easily, 1/16 inch. If you want to oversize your cut and finish your grind with your sander, you can get some real accurate parts.


I’ve got my oxygen pressure set at 5 PSI acetylene and 20 PSI on my oxygen and I’ve cleaned my tip. Thank goodness for the burn bar, it’s a nice straight cut. It does need a little finish. It doesn’t have a super amount of slag hanging onto it. You’ll knock that off with a mill bastard file.


When I said I had a good clean tip and I know some of you can attest to this. When you preheat your material to start your cut and a piece of scale comes up, why does it always stick right in the oxygen hole and then disrupt your flame and causes turbulence? You’ll notice your flame comes back real short and that’s when you end up with the heavy slag, because of turbulence around your orifice. If you are cutting large diameter pipe or structural steel I beams you definitely do not want that. Remember keep your tip clean, get comfortable before you start, and concentrate on the cut while it’s happening. Good brands of tip cleaners include Victor, Irwin, US Forge, and Tech Team https://www.techteamproducts.com/. We like Tech Team’s 762 Tip Cleaner Set because it has all the correct size reamers, a file, and it comes in a handy storage case. https://www.amazon.com/Tech-Team-Long-Pattern-Cleaner-Oxy-Acetylene/dp/B07NGV9CS2/ref=sr_1_1?keywords=tech+team+tip+cleaner&qid=1553187220&s=gateway&sr=8-1. You can go right back to work and then sometimes you can cut for hours and it never happens. Sometimes that piece of scale comes up and hits you in the face or goes in your eye even when you’re wearing safety glasses and a dark shield.


I hope this helps that out. There’s been some questions on how to lay out panels. It doesn’t matter if it’s a Pentagon or a hexagon or an octagon. You can lay these out, use a little geometry. There are several methods. You hit Google for some layout methods. One gentleman came back with using trig. It all works. You know, it’s all math and crunching the numbers. So I hope this helps.