Mating fire box to propane tank

[red12]

Gentlemen,

I apologize if this is the wrong place to post this so please direct me to the appropriate thread if I have erred. I need to cut the "birds mouth" out of the domed end of my propane tank to mate the firebox I just built to it. I have a plasma cutter, cutting wheels, levels, and squares. I just want to make sure that my cuts are even, level, and square. I need advice on how to lay this out properly and also maybe a few hints on how to put a makeshift guide so that when I cut it with the plasma that my cuts are as straight as possible. I'm a newbie to metal fabrication and have tried to do as much and learn as much on my own as possible. Any help would be greatly appreciated.

 

[red12]

Done a bit of measuring today but the layout doesn't look right.

 

[daveomak]

Did you use this calculating tutorial...

http://www.smokingmeatforums.com/t/...ak-and-others-ready-to-use-rev-4#post_1264161

 

[red12]

I know this is an old thread but if it helps anyone I came up with my own solution.  I leveled the tank and used a transit (laser level) to mark the lines on the tank to make an accurate cut so that the curved surface of the tank fit the flat surfaces of the firebox.  The lateral line was drawn around the domed end first, then a 90 degree line was drawn and if fit right the first time.  Hope this helps another person out there like me who is not skilled in such matters.

image.jpg

• red12
• Mar 2, 2015

 

[seattlepitboss]

Did one of these recently. The first step is to know where the top of your tank is. Most tanks are rolled and welded where the edges meet. I generally lay out and centerpunch a line down the center of that longitudinal weld, and call that the top of the smoker. Next step is to orient the tank so the top line is truly at the top.

Now make a flat level surface going sideways to the tank. I put a sawhorse across one end at the right height. Next, set a laser on the flat level surface. Adjust things until the beam is just at the height of your firebox cut line. Sharpen up a piece of soapstone or get out your sharpie. Aim the laser all the way to one side and draw a dot where the laser dot is. Then rotate the laser a little so the dot moves sideways a couple inches, and draw another dot. Continue to turn the laser without sliding it sideways, marking points every couple inches until you've gone all the way across. Now connect the dots and you have your firebox top cut line.

The laser can be a cheap laser pointer, or a sophisticated surveying instrument, or anything in between.

To lay out a cut around the circumference of the tank, I cut an old 2x72" sanding belt and wrapped it around overlapping some. When the overlaps are all tidy and straight, an edge will be perpendicular to the tank. But to cut in a firebox, you can just cut along the edge of the end cap weld seam.

Your cuts don't need to be perfect. Don't be afraid - just make your cuts and if there's a little gap, fill it up when you weld in the firebox.

seattlepitboss