grinding stainless steel fittings

Discussion in 'Metal Boat Building' started by partgypsy, Sep 12, 2010.

  1. partgypsy
    Joined: Jan 2007
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    partgypsy Junior Member

    I am putting new stainless 1" dia tees on an older boat with 1" stanchions. Well, it seems that 1" has shrunk over the years and the holes in the tees are too small for the old 1" stanchions. I have tried grinding them, but nothing touches them with any efficiency. Machine shop quotes are way expensive. What is the best way to enlarge the holes in these fittings. I reckon I need to grind off about 1/32".
  2. gonzo
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    gonzo Senior Member

    If the pipe shrunk, which is hard to believe, how is it more than 1" now and the tees don't fit? What is that you are grinding, the stanchion? That will weaken them and make them unsafe.
  3. PAR
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    PAR Yacht Designer/Builder

    Not to mention ruin their passivity.
  4. pdwiley
    Joined: Jun 2008
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    pdwiley Senior Member

    Which part of the tee is too small diameter? The short leg or the through leg?

    Fastest way is to put them in a mill and run a multi-flute cutter into the hole. Grinding out the inside diameter of the hole(s) is a waste of time and slooooow. Also you'll never manage to keep the roundness. It'd be quicker to change the stanchions to suit the tees if you try that.

    Be aware that there are pipe sizes & tube sizes. The 2 don't interchange worth a damn. You may have pipe tees and need tubing tees, or vice versa. A good catalog here is your friend.

  5. alan white
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    alan white Senior Member

    Get a 6" dial caliper ($29.99 will do) and do some measurements. Get a list of common tubing and pipe sizes from the web. Get familiar with the technology, in other words. Stainless doesn't shrink from just sitting. Not as much as a thousandth.
    You can't afford to modify the fittings so match new tubing to them and try to remember why you ended up with mismatched parts. It will come to you.
  6. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Partgypsy means that an inch is not what it used to be because his new tees do not have the proper inside diameter.

    The problem is lack of quality control at the manufacturer's side. I've seen that many times already. In my country you must always buy bolts and nuts at the same time: if you buy a nut for a bolt you already have, it doesn't fit.

    Especially with stainless steel there is a lot of tool wear, so you need to check tolerances frequently and replace a tool in time. Small Chinese manufacturers simply keep using a tool until it breaks.
    Others think 1" is the same as 25 mm.....
    Last edited: Sep 13, 2010
    1 person likes this.
  7. Landlubber
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    Landlubber Senior Member

    "Others think 1' is the same as 25 mm....."

    ...think you nailed it there CDK
  8. mark775

    mark775 Guest

    "I reckon I need to grind off about 1/32"." - I reckon the number is 1/16".
    Okay, I believe that you actually bought fittings for 7/8".

  9. partgypsy
    Joined: Jan 2007
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    partgypsy Junior Member

    no humour zone?

    Interesting assortment of answers. Thanks
    I was trying to suggest in a light-hearted way that it seems that many items now are built with sloppy tolerances and lighter materials than in the past.
    I bought a decent grinding burr and used a tapered plug as a guide. Deed is done.
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