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  1. #1
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    Default The Journey for a Master Square

    While pottering about the workshop today I started to think about making a set of two master squares,
    The best design I can imagine for this is a box section or square section of cast iron, since then they could be self proving to each other to the accuracy of a surface plate. However I do not have any box section lying about and seeing as it is a little hard to come by around here, I'm putting the call out: Where to get hollow square cast iron?
    -Josh

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  3. #2
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    Default

    What about a cylinder square - they are pretty useful.

  4. #3
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    I'm not sure that you would get square box section unless you had it especially cast. Thinking about how the metal would solidify, I suspect that those inside corners would tend to distort when cooling, running the risk of throwing the whole section out of square. No manufacturer would want to make it because the size specifications would be so broad to get a saleable product (and people would be unlikely to buy it because they would have to machine so much off to get the finished size they wanted - which would then distort in unpredictable ways because of the uneven amounts taken off...)

    Could you use round hollow section and square it up on the outside? Round on the inside would at least have cooled evenly when cast.

    Michael

  5. #4
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    It's a shame this didn't come up in a few weeks or I could show you the finished product. I'm about to do this myself, and have been giving it a little thought, however just need to get a couple of jobs out the way first. I intend welding a "U" shaped section, however creative minds may well be able to come up with some steel sections. Assuming it's to be ground and not scraped, there is no particular reason squares should be made of cast iron, and many of the commercial cubes or grinding fixtures I've seen aren't. Instead of closing in the top of the cube with another plate I will weld in a brace. Once welded I will pop it in the oven, stress relieve it, then grind it. While I'll drill and tap mine for fixturing, I can't see any good reason that it couldn't be used as a master square. I've seen others in 4140 and hardened, however I will simply use mild steel. More technical information in this field can be found in "Design of Weldments" if I recall correctly.

    Pete

    Edit: A search for "Grinding cube" or "Grind cube" will possibly reveal more useful information.

  6. #5
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    Quote Originally Posted by dave4 View Post
    What about a cylinder square - they are pretty useful.
    I really like cylindrical squares, I think they are the absolute best for quick inspection but they have two problems for what I wan't from a master square
    1. they are not self proving (at least I don't think they are? anyone?)
    2. you cant transfer squareness from them to another part.

    The main reason I'm interested in making a set of master squares is so that I can easily square all my second hand angle plates on a surface grinder. They are all out of square by enough to make me want to true them up.

    I'm scraping one of the larger plain ones ~200x200x200 for the same purpose at the moment but without 2 more I have to rely on indicators and parallels to prove square.

    Ideally I would love to make a set of 3 scraped master surface plates as well, you know just for fun.

  7. #6
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    Ueee is offline Blacksmith, Cabinetmaker, Machinist, Messmaker
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    Why not look into a small granite square to scrape everything to? I'm not sure how Christian is going with the mob i put him onto, but i can get a 00 400x250x40 out of China and shipped to my door for $220.....and if the Xinxing surface plates are anything to go by they should be pretty good. Can't you test then with the Laser anyhow?
    I was planning to be the guinea pig on buying a square from them and reporting back on what it is like.
    1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.

  8. #7
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    A cylindrical square is self proving by first confirming it has no taper and then rotating it against an indicator.

    Both have their advantages and disadvantages. It's typically not possible to fixture directly to a cylindrical square, and they need to be used in pairs for that. On the other hand a cube can be made with tapped holes for fixturing and is (in my opinion anyway) more easily proved using just an indicator.

    Pete

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    Probably not that hard to make, might be involved though.... I have been considering making a toolmakers cube myself...

    My initial thoughts have been along these lines...

    fabricate an open ended cube out of 16mm mild steel plate.. place in kiln and anneal the cube.. Rough machine the cube to size and squareness, all holes slots as required....

    Case harden cube in kiln... Next up is the final grinding.... Cannot take too much off otherwise you will go beneath the hard skin....

    To get square you could use the same technique I used in the post where I described making a rectangular block...

    I doubt you will get it fantastically near perfect on a generic grinder.... Probably need lapping for the finish, depending of course on what perfection you desire...
    Light red, the colour of choice for the discerning man.

  10. #9
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    Hi Josh,
    What size are you thinking?
    Whats the biggest Z you can get on the grinder(if you are going to grind them)

    I wonder if Interlloy really have 310x310 cast square bar?
    You could drill out the center and make a set of blocks like mateyoshka dolls?
    Its only 727.8kgs a meter.

    Stuart

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    Stu, if the pricing i have seen and been charged for Flocast is right, it will set Josh back about $1250 just for a 310x310x310 cube......

    Why not fab one from flat bar CI if you really want CI? Weld, stress relieve and then you can grind/scrape to finish. You really only need one cube and 2 angle plates to make them all square.
    1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.

  12. #11
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    Just for info, a cube can be proved using only an indicator, no other angle plates etc are needed.

    Pete

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    So you mean something like this, Josh?
    Angle Plates,Box Angle Plates,Slotted Angle Plates
    Cheers,
    Joe
    9"thicknesser/planer, 12" bench saw, 2Hp Dusty, 5/8" Drill press, 10" Makita drop saw, 2Hp Makita outer, the usual power tools and carpentry hand tools...

  14. #13
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    Sorry I have been in the swing of scraping....

    Yes Joe, that is what I have in my head.

    The process I intend to make them is a little convoluted but it is the same idea as making a set of master plates by comparing 3 plates to each other until you get an even spotting patten, same goes for an angle plate you use 3 plates with the surface plate being you datum for flat. A cube box can be done with just 2 since you initially effectively have 4 faces, hence the pair. The other reason for the pair is so that they can spotted against each other for calibration latter on down the track with no need for a gauge.

    I was thinking that I would take a few shortcuts with the surface grinder so get them pretty close.

    and like pete said if the faces are parallel then I can also do a simple reversal test for square with an indicator.

    Reason for cast iron over granite or mild/tool steel is just so that it can be easily trued by scraping. Also it would stick to the mag chuck.

    And if push comes to shove I could always cast my own, but they would have to be a little smaller than what I had in mind which was about 200mm cube, and I would also have to get over the imperfections in the casting.

    The Surface grinder will do about 305Zx300Y600X. so 200mm seems like a nice size for both it an the mill.

    at $1250 for a solid 310mm cube kind of puts it out of contention. not to mention the weight.



    So it looks like a special casting then. Nobody sells square hollow sections???

  15. #14
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    Quote Originally Posted by Brobdingnagian View Post
    Nobody sells square hollow sections???
    You may consider importing a box parallel from the US, and regrinding it to tighter specs. If you're prepared to settle for a smaller size the freight should make it feasible. I don't know if they still sell them but Shars sold a 5 x 5 x 5 for US$58 weight is 17 lbs. Check their catalogue under 202-4361 as I doubt you could buy raw stock for that.

    Pete

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    Thats a great idea, I will have a look see.

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