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  1. #1
    Join Date
    Aug 2018
    Location
    AU
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    12

    Default Squareness comparator

    The decision to fab a squareness comparator came about whilst trying to check if the jaws on my milling vice were square (they were not).

    I rigged up a mag base with a dial indicator attached and a bit of linear rod stuck to the magnetic base as a work around, but knew I needed something a little better and a little more accurate.

    So after hours of scrolling the interwebs I found a design that was perfect for what I wanted to use it for and I set out to make it.

    This is what I came up with...

    -Base is cast iron
    -Knobs are brass that have been blued
    -Pivoting arm, dial clamp and front bumper insert are 4140 hardened and tempered
    -The rest is hardened stainless steel


    Sent from my IN2023 using Tapatalk

  2. #2
    Join Date
    Aug 2018
    Location
    AU
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    12

    Default

    The fabrication process.

    Sent from my IN2023 using Tapatalk

  3. #3
    Join Date
    Aug 2011
    Location
    Melbourne
    Posts
    4,497

    Default

    Nice work John.

    Can I ask what radius did you decide on for the front bumper?

    I've read differing opinions on this, some say there is a specific method to determine the correct radius while others say that's it not particularly crucial. I'm inclined to think the latter is correct as long as the chosen radius is precise.

    Simon

    Sent from my SM-G970F using Tapatalk
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  4. #4
    Join Date
    Aug 2018
    Location
    AU
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    12

    Default

    Quote Originally Posted by simonl View Post
    Nice work John.

    Can I ask what radius did you decide on for the front bumper?

    I've read differing opinions on this, some say there is a specific method to determine the correct radius while others say that's it not particularly crucial. I'm inclined to think the latter is correct as long as the chosen radius is precise.

    Simon

    Sent from my SM-G970F using Tapatalk
    So I don't think the radius really matters, as long as it's not so large you can't get a decent variation on either side of the centre point.

    I used a radius of 100mm to make mine and it works very well.

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  5. #5
    Join Date
    Aug 2011
    Location
    Melbourne
    Posts
    4,497

    Default

    Cheers!

    Sent from my SM-G970F using Tapatalk
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  6. #6
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Age
    54
    Posts
    1,527

    Default

    That's a beautiful piece of work John - you should be very proud.

    Steve

  7. #7
    Join Date
    Jun 2011
    Location
    gold coast
    Posts
    282

    Default

    That's a beautiful job, John

  8. #8
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    4,448

    Default

    Hi Guys,

    I'm probably wrong, but shouldn't the radius be centred on the centre of the column ?

    I do agree that it is a very nice piece of work !
    Best Regards:
    Baron J.

  9. #9
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Age
    54
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    1,527

    Default

    Quote Originally Posted by BaronJ View Post
    Hi Guys,

    I'm probably wrong, but shouldn't the radius be centred on the centre of the column ?

    I do agree that it is a very nice piece of work !
    I initially had a similar thought John. After thinking about it a bit I came to the conclusion that the column is just a structure to hold the indicator in a fixed position.
    The pointer of the indicator is pretty central to the nose radius in this design, but its not critical as the reference points are the base plane, the contact point on the nose and the indicator pointer. Swinging the indicator off center will indirectly shift the contact point on the nose as that stays vertically below the indicator - but when zero'd to a reference square it will still function correctly.

    That's my take on it anyway. Since I haven't actually made or used one I could be completely off track.

    Steve

  10. #10
    Join Date
    Aug 2011
    Location
    Melbourne
    Posts
    4,497

    Default

    I've put some thought into it as well.

    Since its a comparator, it's not critical as long as all the dimensions stay the same (as they would) when moving from one measurement to the next.

    Equally, there is no real need to have the indicator facing out radially from the centre of that bumper radius. Adjustment by eye is close enough.

    Considering the level of accuracy you can achieve, if the radius was as critical, it would be difficult to make this tool at home.


    Simon


    Sent from my SM-G970F using Tapatalk
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  11. #11
    Join Date
    Sep 2008
    Location
    Riddells Creek, Vic.
    Posts
    621

    Default

    As already mentioned the stylus of the DTI does not have to be accurately aligned but it does help to have it reasonably central, I had to make an offset adaptor to get the indicator located on the centerline of this gauge that I made a few years ago.

    I used a 50mm radius on the bumper but I think it could have been larger.

    Surface Gauge.jpg

    Surface Gauge.jpg1.jpg

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