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Thread: Mandrel bracket

  1. #1
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    Default Mandrel bracket

    I've got this piece of angle I picked up from the dump shop specifically for making a mandrel bracket to make a couple of gears.
    It's 13mm thick and about 90mm wide. For further size judgement the holes are around 50mmm.
    I need a 'C' shaped bracket so I intend to cut it so I end up with two angles 60mm x 40mm and 45mm wide, then butt weld the two 40mm sides, so I'm left with a 'C' 80mm long.

    Since welding is not my strongest point, I thought I should get some advice here.

    I need to mount the 'C' to my vertical slide on the lathe so it will need machining flat after it's welded. I'll figure out how I'm going to "chuck" it for machining later.
    For welding it, I figured I'd grind a V on both sides of the butt joint and do several runs both sides. Is that the best way to do it ?
    I'm also concerned about weld shrinkage and bending at the joint cos I need to minimize machining and need the ends as close as I can get to 90deg .

    Bracket.jpgP1040005.jpg

  2. #2
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    Default

    I'd suggest
    • Weld the sides alternately (that is, don't do all the welding on one side then flip it over to do all those on the other)
    • Don't weave - do multiple passes if it needs filling (as per above)
    • Even consider a series of tacks instead of a continuous weld


    The aim is to keep the heat even on both sides and not put lots of weld on one side where it will contract without anything to counter it.

    Michael

  3. #3
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    Default

    I was going to suggest the same as Michael. If the angle has a hole on each piece at the top, you could fit a piece of allthread with nuts on either side to help hold and clamp them in place. As it's Mild Steel, you could easily flatten any distortion out.
    HTH
    Kryn
    To grow old is mandatory, growing up is optional.

  4. #4
    BobL is online now Member: Blue and white apron brigade
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    Default

    I agree with what has been said so far, plus if you hold it really firmly while welding each pass you can immediately followup with heat to relax the weld.

  5. #5
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    Default

    Quote Originally Posted by BobL View Post
    I agree with what has been said so far, plus if you hold it really firmly while welding each pass you can immediately followup with heat to relax the weld.
    That's something I didn't know about, and a great tip I'll remember for the future.
    I was going to clamp it down for at least the first tack welds anyway but I didn't realize subsequent heating would relax the weld.

  6. #6
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    Default

    Sorry to put you guys to any trouble, but I've now decided to not weld but leave it in two pieces, else I will have a problem fitting the mandrel into it. It will mean I have a fiddly setup t do but I'll get around that too.
    Still a worthwhile discussion though and I've learnt something once again.

    I'll take some photos as I do this project, I'm sure you'll find it interesting.

  7. #7
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    Twasn't any trouble at all, that's WHAT we're here for, to help one another.
    Looking forward to seeing the pics.
    Kryn
    To grow old is mandatory, growing up is optional.

  8. #8
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    Default

    It's been a slow process this job.
    So busy lately I can only get little bits of time to work on it.

    Vertical slide from my Russian mini lathe fits nicely on my AL350a after making an adaptor plate. At first I thought I wouldn't use the mini lathe very often but now I've discovered there are often times I need to whip up a tool or mod something when I don't want to remove a part from the big lathe. It's an awesome little machine.

    Building the frame to hold the gear blanks.

    P1040012.jpg
    P1040006.jpg
    P1040009.jpg
    P1040008.jpg
    P1040010.jpg

    These are great too....It's a $5 ebay tyre depth gauge. Cut the wings off, glue a couple of magnets on the back, turn a 'top hat' piece and glue a magnet onto that for the slide. Easy.

    P1040011.jpg

  9. #9
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