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Thread: Project #6 from Spike : Aluminum Seat Pan Hole blow through repair

  1. #1

    Default Project #6 from Spike : Aluminum Seat Pan Hole blow through repair

    I was making an aluminum seat pan yesterday for a project i'm working on, when i made a liitle 'oops'.

    While annealing the seat pan i got a little over-zealous with Oxy-Acetylene torch and blew two holes into the aluminum of my seat pan. The holes are on the other side of the picture, but it shows what i was working on.

    Normally, this type of blow-through is not generally considered to be repairable with satisfactory results... the paper thin edges of the holes blow away easily, it's hard to form properly because of the thicker metal where the aluminum retracted around the hole. I have an interesting method for repairing stuff like this, and that is to use a backing metal.
    First i formed out my seat pan, i didn't want to fill the hole and risk filling the holes and then having the weld crack or break when working the material ( the hole was in an area that had a very deep draw in the shape). Since this thread isnt' about making the seatpan, but fixing my holes, i'll skip to the fixing bit.

    I took a piece of aluminum, one step thinner than original base metal (this is important!). I hammered it around the form, so that it had the same contour, and fit flush to the back of the seatpan where the holes were.

    I clamped it in tight with some vise-grips, and then ran the tig torch quickly around the outside of the holes. This retracts the paper-thin metal back to a make a larger hole, but a hole with thicker and usable thickness material around the edge.

    To fill the hole, first start welding to the thinner backing metal. Feed the filler metal in for buildup and walk the puddle over to the edge. Now touch your weld filler puddle on the backing material to the edge of the hole *quickly*. Continue the weld around the hole until it's all filled in.

    Both holes filled in.

    and while i was there, i had to fill in a crack along the edge, where i went to fast in the draw and put a little stress crack in the material. No big deal. When you fill these cracks, though, it is important to do it correctly. First, walk the torch around the cracked area, and bring the end points of the crack up to welding temperature. This will take the stress and surface tension off of the metal, and keep it from either re-cracking as soon as you're done, or cracking worse and becoming uneven while you are welding it. After that, drop a couple spot welds on the ends of the crack to keep it still, and then weld it up. Even on small cracks, you still need to use all of these steps. To go one step further, i will usually run my weld a little longer than the crack at both ends.

    After some handy work with the angle grinder smoothing out the welds, it looks good as new, and still strong to boot.

    QUICK NOTE: If you are going to do any more metal work on the repaired area, or the project will be exposed to heat cycles/expansion-contraction, then you will need to take the oxy-acetylene out and re-anneal the heat affected area.
    Last edited by Spike; 02-16-2012 at 04:04 PM. Reason: incorrect title
    Spike Customs, Inc.
    Fresno, CA 93727
    ph- 559-549-RIDE(7433)
    -Follow me on twitter!-

  2. #2


    You are the man! I'm not sure I have the patience and do not have the talent for what you do. What kind of bike is that?
    Lincoln Eagle Engine Drive
    Everlast MTS 250
    Everlast Power Tig 225lx
    HTP Mig 2400
    Everlast Power Plasma 60C --> Just need to finish my CNC Plasma Table!
    Miller Spectrum 375 Extreme Plasma cutter
    Victor cutting torch
    HF 20 Ton Shop Press
    HF 4x6 Band Saw
    HF Air Compressor
    Northern Tool Drill Press

  3. #3


    I want to see a pic of the rest of that project. Is it an old motorcycle, lawn mower, or ultra light?

  4. #4


    Very cool and practical. Let's see the rest of the project!
    My review on Youtube of the Everlast Powermaster 205
    Just a noob having fun with metal.

  5. #5


    I'll probably post up some pictures of the "aluma-liner" when it's closer to finished. I'm turning a triumph Daytona 675r into an aluminum streamliner/ touring bike for a customer.

    Sent from my SGH-T989 using Tapatalk 2
    Spike Customs, Inc.
    Fresno, CA 93727
    ph- 559-549-RIDE(7433)
    -Follow me on twitter!-

  6. #6


    I see the acdc in the background. Older model but they work great. You used 4043 on it?
    Mike R.
    877-755-9353 x203
    M-F 12 - 7PM PST
    FYI: PP50, PP80, IMIG-200, IMIG-250P, 210EXT and 255EXT.

  7. #7


    Great repair! I'm with everyone on this I'd love to see the complete project also!
    Miller 210 MIG
    Eagle 3-Cylinder Compressor
    Air Tools
    Body Tools, Shrinker, Stretcher
    Bead Blast Cabinet
    Homebuilt Car Rotisserie

    1971 Dodge Challenger, Pro-Touring, 6.1 Hemi, Fikse Wheels, 335/275 Tires (in progress)

  8. #8
    Join Date
    Apr 2012
    Washington State


    Nicely done! Thanks for all of the tips you provided. Great information on this. Cheers!
    Is it OK to want to break something just so that you can weld it back together?

    Everlast PowerTIG 185 Micro IGBT AC/DC Welder

  9. #9


    Quote Originally Posted by everlastsupport View Post
    I see the acdc in the background. Older model but they work great. You used 4043 on it?
    Yep, it's an old super 160p I bought back in '07. It's been a workhorse for me in the shop and I've only rarely had a problem with it.

    Yes, I used 4043 rod. It makes a softer weld and is less prone to cracking. With motorcycle stuff it's almost always better to give up a little tensile strength if you can gain elasticity and vibration resistance!

    Sent using Tapatalk 2
    Spike Customs, Inc.
    Fresno, CA 93727
    ph- 559-549-RIDE(7433)
    -Follow me on twitter!-

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