Cutting through a steel hull for water in and outlets

Discussion in 'Metal Boat Building' started by AWegener, Jul 1, 2007.

  1. AWegener
    Joined: Jul 2007
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    Location: South Africa

    AWegener New Member

    What is the best way of a) cutting through, and b) joining pipes to the outer hull
  2. MikeJohns
    Joined: Aug 2004
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    MikeJohns Senior Member

    For larger holes You use a hole saw in your electric drill just like you do for cutting holes in wood panels. For smaller holes a HSS drill bit.

    The inlet/outlet is usually a pipe section with a threaded end to take the sea-cock. the other end is either butted up to the inside of the plate or inserted through and fully welded.
  3. Frosty

    Frosty Previous Member

    Ive cut many holes in steel hulls up to 5-6mm I use a 3/16 drill bit and make a series of holes in a circle. Try to get them as close as possible. Then very very gently tilt the drill to elongate the hole in the direction of the circle. Finish off with a chisel then a big half round file.

    These three tools will cut any size of hole.
  4. Bergalia
    Joined: Aug 2005
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    Bergalia Senior Member

    Cutting through a steel hull for water in and etc

    Frosty your idea is feasible - but requires a steady hand and eye, whereas Mike's method is by far the easiest and quickest, and will offer a 'cleaner' tighter fit for the final weld.:)
  5. Frosty

    Frosty Previous Member

    Berg. --they are expensive you know, --and it will only cut one size.

    Again done properly it is just as good as any hole cutter. Its more than likely your hole,- after the cutter will need filing anyway.

    A tight hole for the pipe is not what you need for welding actually Berg.

    A sloppy pipe in your hole is a reall joy to weld.

    It has to be sloppy to get the right vertical any way. You dont weld metal to metal there has the be a v or a gap.
  6. M&M Ovenden
    Joined: Jan 2006
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    M&M Ovenden Senior Member

    I could no longer see my life a positive way without a plasma cutter. I don't drill any hole under 1/4 in anymore, just trained my hand to making circles with the plasma torch. Ok, not everybody has a plasma cutter....with the drilling and hole saws, use cutting oil it will cut better and save your tools. Also, beware with big hole saws on powerfull hand drills, when it bites into the steel, it will yank an elbow or shoulder, even on a big guy.

  7. Bergalia
    Joined: Aug 2005
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    Location: NSW Australia

    Bergalia Senior Member

    Cutting through a steel hull for water in and etc

    In Australia we have 'adjustable' hole cutters. Pricey, yes...but a valuable tool. As for not welding metal to come the faces have to be clamped ? You stick to your method Frosty and I'll stick to mine. It's served me well for the past forty years - I'm too old to start learning anew...:)
  8. Frosty

    Frosty Previous Member

    Did any one notice the question came from SA. I doubt if he has a Bunnings round the corner.

    I think that was his point!!!
  9. Bergalia
    Joined: Aug 2005
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    Location: NSW Australia

    Bergalia Senior Member

    Cutting through a steel hull for water in and etc

    Damn. I never realised South Africa was that primitive....
  10. Frosty

    Frosty Previous Member

    I wasnt suggesting it was Berg.

    Well if my little method withan electric drill stired up a hornets nest you wont like this then.

    If you turn up the amps to as much as you can ,strike an arc and get a good puddle going. Try to jab the rod through the puddle, sooner or later it will go and you can blow a hole. Once youve got a hole you can blow and cut a hole.

    Ha Ha Ha

    Grind and file to shape after. Hey--It all depends how good you are.

    I love steel you can do what you want with it.
  11. Bergalia
    Joined: Aug 2005
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    Location: NSW Australia

    Bergalia Senior Member

    Cutting through a steel hull for water in and etc

    Have to confess Frosty, I've done it more than a couple times...but by accident when working on thin guage steel...and a pig to repair once done...Usually results in more holes than a fish net.....:(
  12. Trevlyns
    Joined: Oct 2006
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    Trevlyns Senior Citizen/Member

    Well lads, being a South African myself, and also noticing AWegener’s join date (July 2007), first we must give him the traditional boat forum welcome.

    Altogether now, Welkom hier by ons, boet! (Don’t worry, AW will understand) :p Next I think we need to refer him to another notable Sarf Efrican, Wynand. Check out his website on steel boat building.

    And Frosty, your quote “A sloppy pipe in your hole is a real joy to weld.”… Well REALLY, man – behave yourself! :D
  13. alaskatrawler

    alaskatrawler Previous Member

    Mike Johns is right on a hole saw is the way to go for cutting holes in the steel hull. If you use a little cutting oil on the teeth they will last a long time. Also I would use schd 80 pipe for the section welded to the hull I would weld it both inside and outside. You don't really want to have a gap as a tight fit is best here.
    Make the pipe at least 6 inches long before any threads preferably longer

  14. Frosty

    Frosty Previous Member

    If you put through your cutter you then need to file it. You dont want the pipe to be at 90 degrees the the hull you need it vertical and up to the water line.

    This is called a stand pipe. This done so that your boat wont sink if you have a damaged filter.

    You dont use threads you weld on a 4 bolt flange. This so you could remove the cock easier.

    If you have metal to metal contact you will not be able to weld but stick it. You will not get 100 % penetration. It will not weld at the point that the hulls meets the steel. All youve done is lay a filler weld.

    Yes you will need to weld both sides to try to get 100% penetration.

    This is not good work. A pipe sould not break off from the hull but distort the hull plate first. Yours will break off.

    Tight fit?? ---metal to metal?? Your winding me up arent you?

  15. Poida
    Joined: Apr 2006
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    Poida Senior Member

    Cutting a hole in steel with an arc welder, done that Frosty. Keep dipping the electrode in water to keep it cool. Good way to cut cast iron. I've cut many holes in steel with an oxy. mark the hole out and go around the the circle with a centre punch so you can see it when you are cutting. With practice the holes come out quite acurate. A cutting burr in an electric drill will remove the few high spots to make a perfect fit.

    Hole saw is alright but a large diametre means the saw's cutting speed is often too fast.

    There is nothing wrong with Frosty's method of using a small drill around the circle, I've done it many times, not always the correct size hole saw at hand. Once again a burr in a drill takes out the scolloped edge.

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