to tap into the airline with a line from your gas supply.
The basic tools for heat-treating are the gas torch. The torch is a simple apparatus consisting of a
mixing tube into which fuel gas and a blast of air are introduced to be mixed and burned at the end of
the tube. An old vacuum cleaner can be used for the air blast.
The hose used for the various attachments for the cleaner can be used to deliver the blast of air to the
torch. You will have to make a fitting for attaching the hose at the dust-bag outlet and arrange the cleaner
so that air can enter at the suction end.
At the torch, a gate of sheet metal is arranged to regulate the amount of air entering the mixing tube. You
can also reduce the airflow by reducing the speed of the blower. A simple light dimmer found at any
hardware store would do the job very well, if you have a DC blower motor.
The fuel is supplied through a rubber tube of a size to fit the supply pipe and the fitting on the torch. You
should have a 1/4 inch needle valve to adjust the gas to air mixture. Using Butane or Propane from a
5-gallon bottle works better as there may not be enough pressure from natural gas. If you use butane,
make sure all your fittings, and hose are for high pressure.
It has rubber ends that will fit on the gas nipples at each end. Any other good rubber tube can be used,
such as a 3/8-inch garden hose. The mixing tube must be long enough so that the gas and air are
thoroughly mixed by the time it gets to the burner end.
Artificial gas will burn at the end of a plain mixing tube, but for natural gas there must be a special tip on
the burner end to maintain the flame, or else the air blast will snuff it out. This special tip consists of a
jacket fitted around the end of the mixing tube with several small holes drilled into the mixing tube. This
gives a low-velocity supply of gas and air to the jacket.
This will maintain a small circular flame around the end of the mixing tube, which will keep the mixture
ignited as it comes out of the end of the main burner tube.