Checking a frame for flatness

  1. indy4x

    indy4x Forum Supporter

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    Location:
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    I have made a couple of frames for a job I am doing and I want to make sure they are not twisted

    I had a think about it and made 4 aluminium blocks and they are machined so they are all the same size

    Drilled a recess in the bottom and glued in some neodymium magnets

    Have placed these on each corner and tied some thin cotton thread across the diagonals and where the cotton crosses in the centre it just touches

    Can the collective give me a second opinion as to does this actually make sense and give me the result I'm looking for as my brain is mush ATM

    DSC_0188-2992x1688.JPG
     
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  2. Paul.

    Paul. Moderator Staff Member

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    6,004
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    on a small frame like that you should be able to pick up one end and sight it with the other end, for something bigger I would use a spirit level, I have a precision engineering level for important jobs.
     
  3. brightspark

    brightspark Member

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    just do that with door frames sight it through . easy enough to do and accurate if your mince pies are good
     
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  4. highseas Member

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    47
    Location:
    cumbria, nw
    i like that idear! i always struggle with flatness on larger jobs (think 12x20 steel doors) given that my workshop, was once a cow shed with some serious farmer concreating on the floor, their is not a inch of it leven even or flat in any plane!

    i normaly make a frame and run a spirit level over it as many times as i need to and chock the twists out
     
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  5. frank horton

    frank horton V twins are great but 4"s rule.........

    Messages:
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    Soon 2 B Crete
    winding sticks are what is normaly used........just tow accurate lengths of anything wood or steel.....
    placed at the ends of the frame in both directions will tell u if it's straight or not.....
    and done by eye.....
    straightning the frame if twisted is another story.....
    when making frames I try always use box section as it's quite stable and stronge but u need to be more particular to be accurate start with.....
     
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  6. Munkul Member

    Messages:
    480
    Cumbria, UK
    if you're asking if the crossed stringlines will indicate flatness, then yes indeed they will :) The two stringlines should definitely touch in the middle if it's flat.
     
  7. MoreWellie Member

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    972
    Location:
    Bedfordshire, UK
    an old fashioned way that works over longer distances a clear plastic tube with sufficient red wine in it

    you can then fix it so the liquid level is aligned on one corner and wander about with the other end to check that it is at the same height in other places

    terrible waste of red wine but it works
     
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  8. lchris21

    lchris21 Member

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  9. rockweasel Member

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    This what I used on the base of my camper build. IIRC if you make the sticks two contrasting colours (apply coloured tape to them), it makes it easier to tell when there is an error.
     
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  10. indy4x

    indy4x Forum Supporter

    Messages:
    1,391
    Location:
    Pontypool, South Wales. UK
    Thanks everyone for the replies, much appreciated.

    I like the winding sticks idea, nice and simple but it's good to know that the string across the diagonals works as well
     
  11. gaz1

    gaz1 Member

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    cheap enough now to get a lazer level and check it with that
     
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  12. Yamhon

    Yamhon Member

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    492
    Location:
    Yorkshire, UK
    I've thought about getting one for that purpose, as where I plan to fabricate there isn't much of anything level. How would you use one, just put it on a corner measuring corner to corner, then comparing the measurements from corner A to C and B to D to make sure both measure the same length?
     
  13. gaz1

    gaz1 Member

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    7,850
    Location:
    westyorkshire
    nope does all sides on same length this room is 4.5m square so had to be lazer leveled all the way around the room

    a,b,c,d should have a light red line on the front edge of the metal if it drops or has no mark then its lower than required the red line drops lower on the metal then the metal is too high

    44244CA6-58E8-46AF-AA48-11DD6187C2E5.jpeg 42D46D6D-0C77-43A4-8D7B-EF7FEB53764C.jpeg 20190623_151751.jpg

    a lazer level can be sat on the material your leveling and can be measured all the way down its length to each and every corner

    if you want to be precise then it would be like this way



     
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  14. Hitch

    Hitch Moderator Staff Member

    Messages:
    11,879
    Somerset
    Small stuff, sit it on a good bench if avilable, medium stuff- eye it through, its suprising how accurate your eyes are.
    Big stuff, a laser level is ideal.

    Also bear in mind the purpose of the frame and how flat is actually needed.

    Winding sticks are good for viewing twist in narrower bits, but not much use on wider frames, unless you stand well back to get it all in eyesight.

    The way you have done it certainly works though. Its a method i'd long forgotten to be honest. Think i was shown that once on some large timberwork a long time ago.
     
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  15. daedalusminos Member

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  16. gaz1

    gaz1 Member

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  17. eLuSiVeMiTe

    eLuSiVeMiTe Forum Supporter

    Messages:
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    Location:
    Bedfordshire England
    Any camera tripod fits there threads.
    I use a platerboard prop and a GoPro handlebar mount.
    Stick it in the corner of a room and level at any height. Tripods are a pita.

    Got a pls 180 dirt cheap with no case. Serves me well.
     
  18. slim_boy_fat

    slim_boy_fat Forum Supporter

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