calstar 

Brazing torch tips seem to have recommended regulator pressure such as 5lbs+-propane/5lbs+-oxy(using oxy tank) for a Victor TEN #2 , but is this the max pressure avaiilable? If I fully open up the propane control on the torch handle(for the full pressure available from the regulator) it's pretty much a full on "blow torch", not suitable for brazing in most cases. Seems like all the control is done with the torch to dial in pressure/heat once the lowest pressure needed is reached. Am I seeing this correctly?

thanks, Brian

calstar 

OK, let me ask a different way: does anyone completely open the torch control to utilize the full regulator pressure setting when brazing?

thanks

Doug Fattic 

Brian, I'm having a hard time wrapping my mind around your question. I suppose because I don't see why anyone would want to open up the torch control knob all the way - especially if using propane. You wrote "Seems like all the control is done with the torch to dial in pressure/heat once the lowest pressure needed is reached. Am I seeing this correctly?" And I would say yes you are seeing it correctly. In other words to begin I find the lowest fuel pressure that will run the tip I am using. With my setup that is around 4 PSI but there is nothing sacred in that setting. Then I open up the oxygen regulator enough so that it will provide enough oxygen to get a neural flame at the highest fuel setting I will be using for that application. Is there some reason you see why anyone would open the torch control completely to utilize the full regulator pressure setting when brazing?

calstar 

No, I am/was curious how the pressure set at the reg relates to the control pressure on the torch. For example 4lb is set at the reg but then the torch is only partially opened, the pressure must be less than the 4 available. I searched the net but did't find anything regarding this, it's only an "academic" question, I'm not interested in running the torch wide open, just curious, I don't mean to waste anyones time.

thanks

vintage cellar

There is an old-time way to set your regulator pressures that DOES initially use wide-open torch valves. I learned about it when researching torch-welding for 4130 airframes and aluminum.

You (slowly) open your tanks with the regulator adjuster-screws turned out (so the regulator is closed) and no gas should be flowing through the hoses.
Torch valves should both be open 1- 1.5 full turns.
Hold the tip next to your cheek and slowly turn in the fuel regulator screw until you feel a faint flow of gas, and at that point lower and light the torch (not pointed towards your cheek !).
Turn the fuel regulator key inwards to increase the flame until it stops smoking and then "jumps" off the end of the tip.Slightly lessen the fuel gas flow at the regulator to lightly re-attach the flame to the tip.
You now have the fuel gas regulator pressure setting correct for the actual tip / mixer / hoses / flashbacks / hose couplers / whatever set up YOU are actually using.

At this point you slowly turn the Oxygen regulator key until you achieve a neutral flame. When you have that established you now have the correct and safe pressure settings on both regulators, again - for YOUR
particular set-up. You can then slightly alter the flame at the torch valves for caburizing vs. neutral vs. oxidizing. Larger and smaller flame sizes should be based on changing the tip SIZE, not "starving" the tip of pressure and potentially causing a backfire by closing down the torch valves.

You should record the pressures to save time the next time you use that particular tip.

The idea behind this method is mostly safety related WRT making SURE there is adequate gas flow through the tip in order to prevent backfires and flashbacks.
Manufacturers pressure settings are approximations and might not be adequate in some cases, and too high in others. Things like hose couplings, long hose lengths, small hose diameters, all act to
constrict the flow of the gasses and could lead to inadequate flow. The pressure you set at the regulator is not the same pressure you get at the torch.
Likewise, regulator gauges can be old, cheap (especially current ones), and not particularly accurate at all in the lower 2 - 10 PSI pressures used by bike builders.

The old-time method I just described might be a little too complicated for beginners, but like all tools, it might come in handy for some.

I'm wondering if it might be useful for using propane and an oxygen concentrator with a flow-meter instead of a pressure gauge ?

Regards,
Michael / Vintage Cellar

calstar 

Interesting, thanks Vintage Cellar.

​​​​​​"Turn the fuel regulator key inwards to increase the flame until it stops smoking and then "jumps" off the end of the tip.Slightly lessen the fuel gas flow at the regulator to lightly re-attach the flame to the tip. You now have the fuel gas regulator pressure setting correct for the actual tip / mixer / hoses / flashbacks / hose couplers / whatever set up YOU are actually using.

Although using propane(no smoke) and with the regulator set at a "suggested" pressure I open the torch a little and light the torch, turn it up until the flame leaves the tip, then reduce at the torch to reattach it, next open oxy torch control slowly and aim for a nuetral flame, fine tune as needed, so sorta/kinda along the same line.

"Likewise, regulator gauges can be old, cheap (especially current ones), and not particularly accurate at all in the lower 2 - 10 PSI pressures used by bike builders."

I agree, apples and oranges, same as tire/pump pressure gauges, they are only accurate relative to themselves, one guys/gals pump may easily differ substantially from another's.

"Manufacturers pressure settings are approximations and might not be adequate in some cases, and too high in others. Things like hose couplings, long hose lengths, small hose diameters, all act to constrict the flow of the gasses and could lead to inadequate flow. The pressure you set at the regulator is not the same pressure you get at the torch.​​​​​"

This is pretty much what I was trying to get at when I first asked(evidently unclearly) my question.

regards, Brian