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Projects Need some help with metal shrinking

Discussion in 'The Hokey Ass Message Board' started by Automotive Stud, Oct 26, 2010.

  1. Automotive Stud
    Joined: Sep 26, 2004
    Posts: 4,304

    Automotive Stud
    Member

    I'm working on restoring this old gas pump for my dad. I have this one panel that's really warped at the bottom where it looks like there were holes that were brazed shut with too much heat once upon a time. Well I tried watching a video on youtube about shrinking metal with heat and tried that. It's hard to say if it really worked or not, this is some heavy steel. Should I try it with heat again or just cut this portion out, mig in a new piece, and bondo up the seam?

    If I use heat again is there any technique I should use? I tried getting it really hot in one spot and then putting the wet sponge on or get the whole area hot and hit it? I tried both ways with limited success. The hot in one spot seemed to work better, but I was afraid of just warping it worse.

    Thanks!
     

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  2. yekoms
    Joined: Jan 21, 2007
    Posts: 1,088

    yekoms
    Member

  3. oldgoaly
    Joined: Oct 22, 2004
    Posts: 562

    oldgoaly
    Member

    if it has shrunk from heat a hammer on dolly with fairly hard hits will cause the metal to stretch. You will need to hit the right spots. go slow and bring it slowly til it just right. One thing I might add is there could be more than one "repair" made, which makes the your repair a little harder. What model/brand of pump do you have? tt
     
  4. pimpin paint
    Joined: May 31, 2005
    Posts: 4,937

    pimpin paint
    Member
    from so cal

    Hey,

    Is your intent to leave the brass repair, or remove it and reweld the area? If you're going to remove it, I'd suggest you finish all your welding before you atempt any shrinking.
    On the plus side, thick metal is easier to shrink than very thin overworked metal. I would try and straighten the panel as best you can, prior to the use of any heat. Once you've straightened as much as possible look for areas that are raised above the panel's normal level. As you push down on these watch just how the panel flexes. Start with the largest area of flex and land your first shrink there. Sometimes, several small shrinks in a small area are necessary to tighten up a panel. Remember, small shrinks, the size of a dime or smaller, are much better than large ones. It's shrink, cool with water, feel the panel, straighten with a hammer & dolly or spoon, shrink again, as necessary, until the stretched areas come under control with the straightening process.
    Flat panels are tough to shrink for a beginner, but if you go slow with small shrinks, and use control with the hammer/dolly you'll get this.

    Good luck,

    " Life ain't no Disney movie "
     

  5. Automotive Stud
    Joined: Sep 26, 2004
    Posts: 4,304

    Automotive Stud
    Member

    The pump is an Erie 753. I didn't intend to remove the brass as long as I can get the panel flat, but if I have to cut it out i'd probably cut that part out too. I'll try shrinking again gettin smaller areas hotter. I figured this would be a good piece to learn on as I can't really hurt it, worst case I cut it out.

    Should I hammer with it hot or hammer than heat than cool than hammer repeat?
     
  6. get a small spot red hot, use hammer on dolly , on red spot then douse w cold water on sponge, should have assistant to hold torch, if large area do more spots on highest areas

    that small spot can be close to a 1/2 in,
    a friend did large fabrications and told of straightening large heavy steel parts with heat

    worst case scenario cut and replace metal, controll warpage and heat!!@!:p
     
  7. Automotive Stud
    Joined: Sep 26, 2004
    Posts: 4,304

    Automotive Stud
    Member

    Cool I'll try it that way. Don't worry I can weld a piece in no problem I had to do that on another panel that had some pin holes. I figured it would be nice to keep as many original panels as I can and learn a new skill in the process.
     
  8. robleticia
    Joined: Oct 15, 2007
    Posts: 2,496

    robleticia
    Member

    What about those shrinking disks? do those work or has anyone ever used them?
     
  9. johnny bondo
    Joined: Aug 20, 2005
    Posts: 1,547

    johnny bondo
    Member
    from illinois

    looks like you tried using a propane torch or something(which wont work!!). or you have the oxy acet torch setup wrong. it needs to be a neutral flame. http://www.bikewebsite.com/weldlight.htm

    that black on there makes me think that you had to much acet not enough oxygen. basically it looks like you got the entire area heated up. thats wrong, what you need to do is heat up a tiny spot and then quench it with a wet rag. heres a video of my buddy doing it.


    http://s11.photobucket.com/albums/a175/TheGraves666CC/Bobs Model A/?action=view&current=HPIM2131.flv
     
  10. John_Kelly
    Joined: Feb 19, 2003
    Posts: 535

    John_Kelly
    Member

    It looks as if you are trying to move the metal by shrinking instead of straightening it with a hammer and dolly first, then deciding whether or not it needs to be shrunk or stretched. The panel should be as straight as you can get it before trying to change the surface area, otherwise you cannot know what it needs.

    John
     
  11. robleticia
    Joined: Oct 15, 2007
    Posts: 2,496

    robleticia
    Member

    so you apply the heat to the high spot next to the low spot and when you cool it it pulls up the low or??
     
  12. johnny bondo
    Joined: Aug 20, 2005
    Posts: 1,547

    johnny bondo
    Member
    from illinois

    think of it as, you pinch your shirt, and then twist it. it pulls the metal from around it. start from the outside and work your way twords the middle. shrink it more then it needs, then hammer it flush with a hammer and dolly.
     
  13. pitman
    Joined: May 14, 2006
    Posts: 5,148

    pitman

    Part of the explanation is the "trapped" growth, that happens when you heat the high spot. As this is cooled, the zone contracts and tightens or flattens a stretched area. I like Mr. Bondo's example!
     
  14. robleticia
    Joined: Oct 15, 2007
    Posts: 2,496

    robleticia
    Member

    Gotcha! I got a little impatient with the tack welds on my hood and got a couple of "oh shits" that I would like to try and fix. Trying to keep the bondo to a minimum. No pun intended Johnny!
     
  15. Da Tinman
    Joined: Dec 29, 2005
    Posts: 4,222

    Da Tinman
    Member

    I think you should be stretching it not shrinking it.

    When the patch was welded in that area shrunk a bit. Try some hammer/dolly work around the spot and see what happens.
     
  16. Automotive Stud
    Joined: Sep 26, 2004
    Posts: 4,304

    Automotive Stud
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    I was using oxy acet but I did it in several spots, and I did try heating a larger area and trying it that way. Like I said I never used this technique before so I'm trying to figure it out. I'll try heating, then hammer/dolly, then cool and see what happens. Does this panel look like it can be fixed this way or am I wasting my time and it needs to be replaced?
     
  17. Da Tinman
    Joined: Dec 29, 2005
    Posts: 4,222

    Da Tinman
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    stop putting heat on it, it was shrunk before you started and shrinking a shrunk doesnt fix it.

    put a flat dolly under one of the worser spots and whack it a few times with a hammer and see what happens.
     
  18. chopolds
    Joined: Oct 22, 2001
    Posts: 6,208

    chopolds
    Member
    from howell, nj
    1. Kustom Painters

    You guys better listen to DaTinman and oldgoaly!!!!!!!!
    If the damage was caused by HEAT, then the area is SHRUNK.
    Shrinking isn't going to fix it...stretching is!
    My advice would be to cold work it the best you can...a slapping file, or smoother version would be my choice, as the panel is so flat.
    Then decide where you need to stretch it, which won't be easy, even for a pro. It IS a very flat panel!
     
  19. KrisKustomPaint
    Joined: Apr 20, 2007
    Posts: 1,107

    KrisKustomPaint
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    Quenching (cooling with water) is counter productive when shrinking, unless you wait for the metal temp to drop below about 500 degrees or so. Quenching steel when its red hot hardens it, making it a nightmare to work. Its best to let it cool down on its own, but cooling with compressed air can make things go a bit faster with out causing any damage. The martin tools book "the key to metal bumping" has a very good section on shrinking with the exception that they too recomend quenching with water. Never try to shrink a spot larger than the head of the hammer you're using.
     
  20. John_Kelly
    Joined: Feb 19, 2003
    Posts: 535

    John_Kelly
    Member

    Which is exactly why it is not necessary to heat steel red hot to shrink. Quenching while shrinking is actually the best way to shrink in my opinion. First of all, it allows you to determine whether or not you got the metal hot enough to shrink by showing steam when quenched. It also allows you to check the surface with your hand right away, as well as making it easier to feel the surface. You can shrink many times in the same spot using low temperature shrinking, and you can hammer and dolly as much as you have to knowing that you can relax the surface with low temperature shrinking anytime. A beginner can go back and forth between straightening/stretching/smoothing with a hammer and dolly and shrinking with a shrinking disc without fear of over-working the metal. A great way to teach yourself metal finishing.

    It is completely unnecessary to use a hammer and dolly for heat-shrinking. Friction alone does a better smoother job. See my collection of video snippets below to better illustrate the techniques (parts 8-12 Custom Metal Bodywork).

    Another illustration of low temperature shrinking that would be nearly impossible by heating to red hot and shrinking with a hammer and dolly is in this album. It shows a stretched lump being shrunk back down using a shrinking disc about 50 times in the same spot (metal stayed soft and workable):

    http://allshops.org/cgi-bin/community/communityalbums.cgi?action=openalbum&albumid=9980124046566

    John
     
  21. johnny bondo
    Joined: Aug 20, 2005
    Posts: 1,547

    johnny bondo
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    from illinois

    everyone has there own methods. we learned from local old timers so if they did it for 50 years i think we can do it too.
     
  22. Da Tinman
    Joined: Dec 29, 2005
    Posts: 4,222

    Da Tinman
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    People used to drink radium to improve their health too.:D
     
  23. floydjer
    Joined: Feb 4, 2010
    Posts: 212

    floydjer
    BANNED

    There is always the choice of spending a couple bucks for a piece of steel and making a new panel:rolleyes:
     
  24. darkk
    Joined: Sep 2, 2010
    Posts: 456

    darkk
    Member

    Well, I'm one of the old timers...they do make shrinking hammers. A little heat, a shrinking hammer and dolly.
     
  25. Da Tinman
    Joined: Dec 29, 2005
    Posts: 4,222

    Da Tinman
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    Its the heat that shrinking,, the hammer is only adding dents. you should at least try a shrinking disk before you knock it.


    You know how you oldtimers look at us and say you kids never listen? well for once the deal is reversed.
     
  26. darkk
    Joined: Sep 2, 2010
    Posts: 456

    darkk
    Member

    look at a shrinking hammer, it looks more like a meat tenderizer. when the metal is caught between the hammer and dolly,the metal between the teeth is drawn up between the teeth on the hammer. essentially pulling the piece together...ie: shrinking the metal. Don't pound the snots out of it, but just medium taps.I've been doing this type of work for over 45 years and trust me it works for shrinking. even overworked metal. And I do admit, once in a while one of you youngsters does teach and old timer like me a thing or two.:)
     
  27. Da Tinman
    Joined: Dec 29, 2005
    Posts: 4,222

    Da Tinman
    Member

    I got a shrinking hammer in a kits with some other hammers one time, worked great after I ground all the teeth of it.

    Trust me the shrinking disk and some practice and your shrinking hammer will go to the wife to use on steaks LOL!
     
  28. Dave Zapatka
    Joined: Oct 14, 2009
    Posts: 74

    Dave Zapatka
    Member

    Shrinking Disks work great ! Sometimes we need to go on the inside of the panel . Old Salts can still get it done ! ;)
     
  29. KrisKustomPaint
    Joined: Apr 20, 2007
    Posts: 1,107

    KrisKustomPaint
    Member

    I ground all the teeth flat on mine too. Shrinking hammers do a good job on high crown panels, but it was more useful as a flat hammer, to me anyway.
     
  30. KrisKustomPaint
    Joined: Apr 20, 2007
    Posts: 1,107

    KrisKustomPaint
    Member


    Are you talking about quenching strictly with the shrinking disk? I don't have a shrinking disk so I use the torch, And if you quench when you torch shrink the metal gets very hard. I haven't had much luck trying to torch shrink with out getting the metal red hot. While it may be "completely unnecessary to use a hammer and dolly for heat-shrinking" for you, not all of us have a shrinking disk.

    It looks like a great way to do it, but I'm poor so i have to use the tools i have.
     

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