Most efficient way to remove aluminium weld tops

  1. TommyB New Member

    Messages:
    5
    Location:
    Hobart, Tasmania, Australia
    Hello everyone,

    I am currently building an aluminium catamaran out of 5083 and 6060, 6082. I tacked one of the hulls together and paid somebody to come in and do the majority of welding for me (so it doesn’t fall apart on its maiden voyage) and now I have to begin the arduous task of taking all the tops off the welds on the outside of the hull (Approximately 120 metres per hull). I tried many different grinding discs, flap discs, sanding discs that claimed they were for aluminium and obviously they all clogged up with aluminium so I’m just wondering what everybody recommends I should use to do it? I’ve heard of waxes and everything but I’m worried about buying the wrong one and using it one day to pre grind for a weld I might have to do and having that weld fail at a later date? Or just any other ideas on a quick way to remove the tops? I have a 4” and 5” electric grinder plus a 4” pneumatic grinder set up as well.

    I should also point out that it doesn’t have to be neat yet, I just need to get it flush for now and then I rough the whole thing up later with 36grit for the paint to bond to

    I’m also in Australia just in case that matters!

    Thank you all in advance, Tom
     
  2. Hitch

    Hitch Moderator Staff Member

    Messages:
    11,959
    Somerset
    I'd use fairly course fibre discs, nothing fancy like zirconia/ceramic. Just change it when they start clogging. You'll get through a fair few.
    Wax does help a bit, a dab of tip-dip does well in a push.
     
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  3. pedrobedro

    pedrobedro Man at Matalan

    Messages:
    9,794
    Location:
    CX Derbyshire
    Fibre disc something like 60 grit and a flexible backing pad but you need to use something like WD40 to stop the aluminium from loading the disc then you will need to clean down before painting.
     
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  4. TechnicAl

    TechnicAl Member

    Messages:
    6,518
    Location:
    Rotherham
    They usually use the ceramic discs or specialist Aluminium Burrs
     
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  5. Brad93

    Brad93 M J B Engineering

    Messages:
    5,917
    Location:
    Essex
    You need to get onto Pferd.

    They do a variety of carbide burrs specifically for aluminium. They’re the best I’ve used.

    They also sell the Alumaster grinding system. It uses carbide inserts in a grinding wheel.

    https://www.pferd.com/alumaster/?lang=en

    Otherwise I just use the cheapest Zirconium fibre discs in 36 grit I can get my hands on. Usually 30p a disc if you buy 100.

    Once they clog with Ali, they still work on steel. Just don’t go back to grinding ally after grinding steel.

    As for wax. Beeswax works well. WD40 works to an extent.
    I’m sure there are purpose waxed out there for the job.
     
  6. bletchmonster

    bletchmonster Member

    Messages:
    402
    Location:
    Cheshire. England.
    Keeping moving rapidly back and forth along the weld to avoid localised heat build up will also help to avoid clogging
     
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  7. henry Kadzielski Member

    Messages:
    768
    Location:
    Australia Wollongong
    Good evening @TommyB. You have two options 1. use a pneumatic grinder with a alli milling blade on it. These things are fab but can be dangerous if not careful. This is for getting the bulk off first, then followed by a 60grit alli oxide sanding pad with wax. 2. just use the sanding pads, start with 36 grit and follow up with 60. The 60 is to reduce the size and depth of the scratches. Both sanding pads will require wax. If you intend to paint afterwoods then you will need to remove the wax. Now the wax is just a hard whiteish substance, which you apply to the sanding pad whilst it is still running down from speed and hot. The ground wax will melt into the pad's grit around the clogged alli pieces and release them. It is not perfect but much better than without. Makes the pads last minimum 5 times longer, the wax also lasts quite some time:thumbup:
     
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  8. Ali

    Ali Member

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    301
    Location:
    Cheshire
  9. Arc Tourist

    Arc Tourist Member

    Messages:
    996
    Location:
    California & Wales
    Thinking outside the box, you could consider using a router with a milling bit, use a wide base with a small size hole, and adjust the bit accordingly to be just short of being flush with the bottom of base ?
     
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  10. 8ob

    8ob Forum Supporter

    Messages:
    4,299
    Location:
    moscow on thames
    I was wondering how a leccy wood plane would fare up if it had carbide blades :scared:

    Bob
     
  11. Arc Tourist

    Arc Tourist Member

    Messages:
    996
    Location:
    California & Wales
    Might work ok for long straight runs ? But the smaller the cutter the less chance there is in gouging the parent material.
     
  12. anto44

    anto44 Member

    Messages:
    1,200
    Location:
    ireland
    A leccy planer actually does ok on ali as long as you have a sturdy grip on it, or so I heard :scared:
     
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  13. eLuSiVeMiTe

    eLuSiVeMiTe Forum Supporter

    Messages:
    8,555
    Location:
    Bedfordshire England
    Normally TC inserts and there very brittle.
    Never tried em on Ali but nails and screws take no prisoners

    You can get big hss blades to replace the insert and holders. They may fare better
     
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  14. TommyB New Member

    Messages:
    5
    Location:
    Hobart, Tasmania, Australia
    Thank you all very much for your replies

    Thank you brad, I’ve sent an email to Pferd as those discs look amazing so hopefully they ship to Aus!

    I have got one of those deadly looking blades on my pneumatic grinder atm thank you Henry so I might give that a go in the meantime to see if I can do much good with it and then try a bit of wax to clean it up as I’ll be going over the whole thing again later with acid wash which I assume will sort out the wax!

    Thank you again everybody for taking the time to respond to my question, very much appreciated!
     
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  15. 8ob

    8ob Forum Supporter

    Messages:
    4,299
    Location:
    moscow on thames
    Don`t forget Tommy without pics there was no boat :)

    Bob
     
  16. TommyB New Member

    Messages:
    5
    Location:
    Hobart, Tasmania, Australia
    Haha sorry bob I wasn’t aware of that rule!

    It’s a 48’ mumby catamaran (or will be once I’m finished) have been working on it over the weekend for about 5 months now and have just cut all of those tacks out ready for the welder to come back in next week hopefully to finish off the outside, Will then sand this hull back a little bit before pulling it out of the shed and starting on the next hull over Christmas hopefully ;)
     
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  17. graffian

    graffian Seer unto the end of his beard

    Messages:
    2,703
    Location:
    gatwick
    Weld shaver.
     
  18. henry Kadzielski Member

    Messages:
    768
    Location:
    Australia Wollongong
    Good afternoon @TommyB. Here is what I have
    air grinder 003.jpg

    air grinder 004.jpg

    Now just for info. The blades then selves last quite some time and are 125mm diameter(quite a long time) and will remove a LOT of alli in there life span. What is important is the grinder, above is the pic of mine, have had it for years and from memory is speed governed and has quite some torque. They do require and consume some air, about 20cfm from memory too be run flat out. As the air pressure reduces so does the torque and the load you can put onto the work piece. This reduces the amount of material that you can remove. I have a bigger than required air compressor so this setup WILL REMOVE SOME ALLI. I have seen the difference from others on site and you need to be covered up. I at Brisbane used mine in shorts because of the heat and the swarf coming off badly cut my legs. I just thought it was the heat from the chipps until the owner of the boat that I was working on told me that I was bleeding:o. Never done that since. The right equipment makes a massive difference. The disk that @Brad93 showed is along the lines of this milling cutter that I have, the replaceable incerts are bigger in width, which can be an advantage, however the blade I have is also for gouging out welds as well as back gouging, milling out tacks for welding. Ultimately it is up to you what works for you and what you feel comfortable with:clapping:
     
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  19. northwest Member

    Messages:
    469
    Location:
    Manchester UK
    On your job they would probably be a worthwhile investment and I would seriously consider it. However, for the occasional user it was a good job I was sitting down. I am used to some pretty outrageous prices with tooling but Clucking Bell:

    https://www.zoro.co.uk/shop/cutting...s/hsd-f-115-125-alumaster-hicoat/p/ZT1128296P
     
  20. 8ob

    8ob Forum Supporter

    Messages:
    4,299
    Location:
    moscow on thames
    @ £7.49p I would have winced, @£74.99p I would have cried and @ £749.99p I would of been sponging my legs off :vsad:

    Bob
     
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