Can I use a propane torch to heat up an area that needs a little shrinking, or should I stick with ace/oxy?
flame is to big and hard to control! heats sheet metal to slow! the flame contact is to broad to shrink a small dent. smaller hot spot and quick cooling will reduce the chance of chasing it!! and creating a bigger problem.
I have bee using a MAP gas torch to form metal on my gasser project. Inner fenders and outer fenders etc. I cat the patch close , grind and tach somewhere sort of central and the heat to dull red and work with the hammer. I am quite surprised how well it works. With the MAP gas no chance of overheating but enuf heat to do the job easily. Spend yesterday aft making and working an odd shaped patch for the inner front fenders of my Bug gasser project. Seems to me to beaboutperfect. Don
Yes you can. You could also a stainless shrinking disc. or for small jobs a heat gun. If it gets hot enough to turn water into steam you are moving metal.
I tried mapp to shrink a dent in a fairly flat hood and found it spread the heat too far, which made the shrink less effective. Perhaps with a narrower tip it would have been fine.
Propane's OK for stripping bondo, but propane is not as hot as MAP gas. Lots of plumbers use MAP now.
I use MAPP gas torch which I can hold single handedly. Its easy to heat area up and then work the stretched areas down with hammer taps
I use oxy/ propane to heat up fasteners and also to bend steel. I have a complete set of tips similar to ACE tips but a bit larger hole per tip.
In general, yes. Until you start having to heat very large objects or heavy cutting operations. Thing to remember about pro/oxy is that the flame has a different thermal profile than ace/oxy. Ace has more variance between inner & outer flame. Here are a few #'s for reference: pro/air = 3,630 °F pro/oxy = 4,530 °F ace/oxy = 6,330 °F
Wow! So 1800 degrees difference is quite a difference. I've never torch welded with gas other than acetylene. I imagine it would feel quite different. I've soldered radiators and copper tube with propane, but I've never done any body lead. I have the feeling a Bernz-O-Matic propane torch would be adequate, but perhaps just barely adequate, considering the quantity of lead I may wind up spreading on my Plymouth. I dunno. I'm going to have to test this out a bit. I did shrink some small spots with my propane torch though & it worked OK. Since I'm working outdoors under a tarp, wind is a big consideration sometimes, and that's what I'm thinking I'll have to deal with the most. I may get a MAP gas torch to do the body solder.
I use propane to shrink all the time, you just need to get it hot enough to make steam and the propane soldering torch does fine at that. I have also used a heat gun, sometimes I've even fired up the TIG and run a bead over the spot needing shrunk. Shrinking disc is still my favorite but the others have a use as well. Heat is all you need and it doesn't matter much on how you get it.
Agreed - more heat may allow you to work more quickly, but there's times when you don't want that. The key is to be able to heat a localized area while the surrounding metal remains (relatively) cool. On the TIG, I've used that too (often from being too lazy to drag the LPG/Oxy rig over) Start an arc but keep it moving around, with a little more distance, not allowing a puddle to form. Running a flipped over sanding disc gives you a flexible shrinking disc and lets you get onto a flat panel (metal shrinking disc will often run an edge if you don't have a convex one). It doesn't work quite as efficiently as a regular shrinking disc but it still gives results
Propane works for welding, but it is easy to add carbon (carborize) to the steel because the carbon doesn't all burn in the inner cone as cleanly as acetylene. Adding carbon to steel makes it more brittle, not good on body sheet metal