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propane for shrinking?

Discussion in 'The Hokey Ass Message Board' started by gassersteve, Jun 18, 2013.

  1. Can I use a propane torch to heat up an area that needs a little shrinking, or should I stick with ace/oxy?
  2. christopher 78
    Joined: Jun 24, 2012
    Posts: 136

    christopher 78

    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.
    Last edited: Jun 18, 2013
  3. 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.
  4. 48 Chubby
    Joined: Apr 29, 2008
    Posts: 1,014

    48 Chubby
    Member Emeritus

    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.

  5. second_floor_loft
    Joined: Jul 23, 2008
    Posts: 93


    X2 on the MAP gas

  6. ArchangelKustom
    Joined: Nov 15, 2006
    Posts: 196

    from NR/OH

    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.
  7. I was thinking of using a hand held torch similar to what plumbers use to solder copper pipes.
  8. Ulu
    Joined: Feb 26, 2014
    Posts: 1,767

    from CenCal

    Propane's OK for stripping bondo, but propane is not as hot as MAP gas. Lots of plumbers use MAP now.
  9. dadseh
    Joined: May 13, 2001
    Posts: 526


    Ummm.... No!
  10. GRX
    Joined: Mar 28, 2014
    Posts: 68

    from MD

    Try oxy/propane. Cleaner than ace or mapp.
  11. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 26,430

    Jalopy Joker

    propane does shrink brain cells
  12. mink
    Joined: Oct 4, 2007
    Posts: 1,308

    from CT

    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
  13. Ulu
    Joined: Feb 26, 2014
    Posts: 1,767

    from CenCal

    Is it hot enough for normal torch welding?
  14. henry's57bbwagon
    Joined: Sep 12, 2008
    Posts: 677


    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.
  15. GRX
    Joined: Mar 28, 2014
    Posts: 68

    from MD

    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
  16. Ulu
    Joined: Feb 26, 2014
    Posts: 1,767

    from CenCal

    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.
  17. Da Tinman
    Joined: Dec 29, 2005
    Posts: 4,226

    Da Tinman

    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.
  18. BarryA
    Joined: Apr 22, 2007
    Posts: 643


    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
  19. 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

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