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Rigging together an improvised Oxy-Mapp torch

I need an oxy-fuel torch for heating and bending metal. I had an old rig but it was beyond it's certification age. So I bought a new (and larger) oxygen tank and planned to use the acetylene in the old tank until it ran out. Unfortunately it ran out an hour into use! Not being in the position to immediately buy a new acetylene tank I decided to rig a disposable map gas canister to do the job. Observe below how it went. -- May/21/2008

The oxy-mapp assembly

Here is the 80cuft oxygen tank with the disposable Mapp gas. The one drawback of this system is that the Mapp gas (and propane, when propane tanks are used) dissolve some of the rubber in the fuel hose since it's an acetylene hose and propane is damaging to it.

the torch head

I began with a typical propane or Mapp gas torch head. These are meant to be screwed onto the small disposable gas tanks.

Torch head cut

First I unscrewed the "neck" part of the torch assembly from the valve body. It was very tight and I think it had "Locktight" adhesive on it. After it was unscrewed I cut the torch tip off leaving only about 1" of the bottom portion of the neck (the part with the threads). The torch tip can be discarded (or tossed into the brass scrap bin).

Torch to hose adaptor

The short section of the neck that I cut was soldered to a section of a brass fitting that has threads that match the acetylene hose. This formed the adapter so the Mapp gas tank can be connected to the acetylene hose.

A crude adapter

Here is a crude version of an adapter. Instead of soldering the brass fittings directly together like in the adapter above I soldered them to a piece of copper tube with caps on the ends. This was the first version I made. The valve body was from a very old torch and had a bad leak so I discarded it for the newer one detailed on this page.

The adapter on the tank

Here the adapter fitting is screwed back into the valve body and all is screwed onto the Mapp gas tank. At this point it is ready for the hose to be installed.

The mapp gas flame

Here is the flame from the Mapp gas conversion. It is not as intense as an acetylene flame but it is plenty hot enough to heat steel.

With this conversion I can also use propane for a oxy-propane torch if I want. But with propane the torch is harder to adjust to a stable flame. The propane flame tends to blow out when adjusting it until the torch tip is warmed up a bit.

Page contents copyright © 2008 by L. Oliver II - www.BackyardMetalcasting.com
mini oxy-mapp torch

Here is a store-bought miniature oxy-Mapp torch set. The small flame is very hot but the disposable oxygen tanks only last about 15 minutes.

mini oxy-mapp torch

For those interested here is a photo of the cart I built for the tank. Welded together from various pieces of steel, mostly rebar.

Converted to oxy-propane

After about 1.5 years of good use the valve for the disposable Mapp gas tank failed and I couldn't use the torch with Mapp gas anymore. So here's the modified cart making it officially an oxy-propane rig. It looks bizarre but works great. This bigger propane tank works better than the disposable ones.

I intend to stay with this system since replacing those disposable gas tanks gets expensive. Unfortunately I can't find a supplier of large tanks of Mapp gas and I don't want to use acetylene so oxy-propane it'll be. Now I plan to replace the cutting torch with a heating tip and use this just as a heating torch since I have something else for cutting.

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This website was created Sept. 28, 2000