Mig Welding Cast Iron

  1. Hi,

    I have a classic mini brake Caliper and the casting has broken above the split pin hole that holds the brake pad in.
    This is not under a great deal of stress and I was wondering if I could clean up the area and weld it up and then re drill the split pin hole.
    Never we’re cast iron (at least I believe that’s what they are).

  2. grim_d

    grim_d Unlikeable idiot.

    Scotland - Ayrshire
    I'd have thought cast steel.

    I would never recommend welding up a caliper regardless of situation.

    However if it's cast steel it should weld up fine with a mig...
    metalmelt and tom2207 like this.
  3. If it were a case of welding in the mounting points I wouldn’t even consider it but it’s the pin that holds the pad in. This is a vital part but under less stress.
  4. Feet 'n Inches

    Feet 'n Inches Out of the rat-race at last

    Devon, England
    If I was to weld such a component, I'd be more comfortable using the equivalent of a Stubs 65 electrode. I repaired a couple of scrapped carver clamps years ago using a Stubs 65 and they're still in one piece today although now looking pretty battered.
    metalmelt and slim_boy_fat like this.
  5. Matchless

    Matchless Member

    Essex UK
    I would weld it with a copper rod where you want the hole, might work, might be too small and melt, nothing to loose? can be hard to drill a small hole through a mix of original metal and weld, break a drill in there and back to square 0 or is it 1.
    slim_boy_fat likes this.
  6. mr haynes Member

    Don't ever recall seeing that happen. My thoughts are how did it happen and subsequent overall condition of said caliper now. They were never that expensive to buy
    Nauticus and johnik like this.
  7. Nauticus

    Nauticus Member

    Lincolnshire, UK.
    If I may make a response -

    As an ex garage owner, engineer, and MOT inspector who has done just about every job there is to do on the old Mini's, - and most other cars of that era, -

    First, why did the casting break in the first place? If it broke while in use, there was at least one crack and it will be probably be more likely to break again after welding!

    Second, If it broke while carrying out other repairs, - maybe some other part of the casting has now acquired unseen cracks.

    Third, welding creates big stresses in castings - iron or steel. Your casting may now be distorted, cracked, and even more liable to fracture again elsewhere.

    Fourth, is a replacement part available? If you can get a replacement, don't even consider "home-welding brake parts".

    IF you are involved in an accident when 'braking' or the lack of it resulted in damage,, you may find that your insurance company may 'disown' you if they can show, or at least suggest your "home welding repair" may have accelerated the problem.

    If you HAVE to have it welded, get it done professionaly by a reputable company with indemnity insurance. Also, make sure its professionally crack-tested. - and keep all the documentation, just in case.

    Sorry to be somewhat negative in my response, but safe, reliable and effect brakes are fairly important on vehicles! They are not an area to try and save a few £££'s.

    Kind regards.
  8. Screwdriver

    Screwdriver Member

    UK London
    @Matchless has already mentioned the first practical issue with that. Castings will contain all manner of impurities and when they get into the weld material it can solidify into a glass hard alloy. Not only can that be brittle it will also be virtually impossible to machine. You'd probably have to grind it out.

    Braze might be a better option, TiG brazing if you don't have oxy but make sure you have the appropriate brazing rods.
  9. A genuine AP Caliper is about £120, so no they are not cheap.
  10. Ok thanks for the info. These are on sale on FB and I haven’t bought them.
    £35 for the pair caught my eye, but I’ll give them a miss.
  11. Popcorn

    Popcorn Member