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Thread: How square is square enough?

  1. #16
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    The two towers of the Golden Gate Bridge are exactly vertical as determined by optical devices. But they are about six inches further apart at the top compared to the bottom. There is nothing wrong with their relative orientation.
    Bill D

  2. #17
    Joint one face and one edge, make a slightly oversized cut on the bandsaw, then plane the other two sides to dimension. If your jointer and planer are set up accurately, the resulting boards should be ready for cross cut and joinery or assembly depending on what you’re making.

    I rarely check for square in the manner you describe except when setting up machines. If I do check, it’s the two reference surfaces created on the jointer.

    So yeah, it’s probably square enough for me because I doubt I can hand feed through the jointer with that level of accuracy and do so consistently.

    Any issues are resolved in final fitting and assembly, which are usually minor.

    I don’t enjoy ripping solid lumber on the table saw either. I leave a crosscut blade on that tool and do all my ripping on the bandsaw, which is always set up for resaw and ripping.

  3. #18
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    Vertical, as in reference to the center of the earth. Two vertical lines on the surface of the earth that were a distance apart will be further apart at the top and meet at the center of the earth. Two parallel lines would be the same distance at the top and bottom, but they both wont be vertical

    Quote Originally Posted by Bill Dufour View Post
    The two towers of the Golden Gate Bridge are exactly vertical as determined by optical devices. But they are about six inches further apart at the top compared to the bottom. There is nothing wrong with their relative orientation.
    Bill D

  4. #19
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    I have never seen woodworking measuring tools any where near the accuracy of those for metal. It just does not matter that much for wood since it moves so much. No woodworker I know of worries about body heat from their hands affecting measurement instruments, metal workers do. The claim is a jump of 1/1000 of an inch, on a flat surface, is visible to the human eye.
    Bill D.

  5. #20
    I don’t know I’m somewhere in the middle on this well not really I’m all the way to the right of it absolutely matters. The wood moves argument only holds as much water as ones willingness and ability to mitigate and manage the factors that cause it to move. Same with square really. As mark suggested get your shop “machines” setup so they cut square then keep them that way and generally you should be building square stuff.

    It comes down to this imop and in my own building regarding square and wood movement. Sure wood will move but generally I plan my builds as to process parts and assemble them in a timely enough manner that they don’t have to time to go out of flat or fall out of square. Well not all aspects of a project but the ones that matter. It tends to be that most matter to me.

    Square on Theo edges of the jointer absolutely matters. Being able to repeat those two edges on a planer or however you do absalutely matters if you going to join something to both edges and or if both edges with reference something else where a gap needs to be non existent or square must be maintained.

    The edd cuts on stile and rail stock for doors or frames absalutely matter in a metal like precision or you fight square doors and panels. Out of square end panels are a royal pain in the ass.

    Out of square on a machine compounds itself. Out of square in the project compounds itself. How much it matters depends on the application and or how many times this out of squar is going to repeat in a project and in a line or independent from the other parts.

    Everyone gets from here to there different. That’s cool. For me the frustration and aggravation of dealing with crap not fitting perfect day in and day out “then guessing why” and figuring some work around to fix it just is not worth the frustration. Much more easy to get the machines properly setup then take the care they stay that way.

    Also much more easy to purchase high quality tools such as squares or know how to tune them “I don’t” so I spend on someone’s tools I trust then check them as mark suggested.

    It’s all perspective really. For instance, I just painstakingly built the top portion to the case of a pipe organ. I went through unbelievable pains to make sure the tiers having tall stiles of sorts with almost not rails to hold them parallel to each other would be flat “like dead flat” as when you put this thing together and stand it up if they are not it will look like shit.

    So that meant milling and building slow and using joinery that would assure it have the best chance at staying flat after built. So get this I haul all the crap from my shop to my employers shop “I’ve been working from home” during the pandemic. I make clear as I always do we need flat surfaces to store theses parts. I get the brush off on the phone so I know what’s coming “the same thing you get from any boss or guy that did not actually build the stuff” so I show up and he has me put all these parts stacked atop each other on a bench all overhanging unsupported non the same thickness all leaning tower like real I’ve to a pice of wood staying flat.

    So that’s last week. Then yesterday I drop by the shop,to get more material. I’m on one side of the bench he is at the other, he has a scrap of plywood he wrote a measurement on, he tosses it across 12pm of bench at me and I miss. It’s crashed down onto the work I went to great lengths and unreal pains to make perfect. Like perfect perfect perfect. Not one bit of tearout anywhere. Every edge a perfect 1/16 round over finished with 320. Like ready for the spray booth perfect. Some people’s idea of good just and or good enough are just worlds apart.

    And that’s fine I’m not saying one guy is better than the other. As you know everyone has a different opinion. Sometimes one guy is right many times nobody is.

    I just make stuff and I like perfect, I also like to struggle as little as possible and stack as many card in my favor as possible as the universe will surely have it way with me and I’ll struggle regardless of my best preparation. That being said and that being enough for me to have to accept a few consesions In my work limiting them from the behind and along the way with maniac like attention seems reasonable. Again responsible for me..
    Last edited by Patrick Walsh; 05-14-2020 at 7:17 AM.

  6. #21
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    Wood moves across its cells, doesn’t change its length. So there are areas where .002” can matter and areas where it will not.

    Woodworkers routinely work to very tight tolerances, they’re simply unaware of it.

    On squareness, I prefer better than .002” over 3”.

    Combo squares aren’t very square, I don’t care who made them. Some brands are better than others but they are a layout tool and not for checking squareness.

    Checking for square is a task for a try square, typically and after it’s been verified.

    Personally, I feel spending effort here saves considerable time later and generally makes a better product.
    Bumbling forward into the unknown.

  7. #22
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    Also, not sure where .005” machine shop tolerance comes from. It depends on the job, some jobs are not needing to be blueprint accurate, but rather they need to be repeatable. Other jobs, like interference fits, are at least one decimal place better.

    Most shops will find a comfort zone in which they are not building things to toolroom tolerances but where they are not causing undue grief and headaches, that may be .0005” in some cases and .005” in others.
    Last edited by Brian Holcombe; 05-14-2020 at 8:02 AM.
    Bumbling forward into the unknown.

  8. #23
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    Quote Originally Posted by Dan McGonigle View Post
    I had thought about using the planer to dimension the width, but the length of these pieces are so close to their finished length, any bit of snipe would be a big problem. I try to rely on hand tools when accuracy is paramount, like in small or delicate pieces. In reality, I could take a few plane shavings off these boards and probably dial them in closer to perfection. The parts I'm working on are for a workbench base, so I think the level of square is acceptable. It just annoys me when I triple check all my machines and end up with anything other than perfect. Like I said before though, it may just be the limitations of my tools.
    You may want to see if you can dial out some snipe from the planer. For the most part on my humble DW734 snipe is very minimal, difficult to see or feel, and comes out with a pass or two with the smoothing plane (which I would be using on the surface anyways).

    Another thing that occurred to me is to check that the planer is cutting parallel. A few thou out across the width could cause some squareness issues that you might be blaming on the TS. Although your theory about the TS blade deflection on a skim cut makes sense. What kind of blade? I would venture to guess that a full kerf dedicated rip blade would be least prone to deflecting like this.

  9. #24
    Quote Originally Posted by Robert Hazelwood View Post
    You may want to see if you can dial out some snipe from the planer. For the most part on my humble DW734 snipe is very minimal, difficult to see or feel, and comes out with a pass or two with the smoothing plane (which I would be using on the surface anyways).

    Another thing that occurred to me is to check that the planer is cutting parallel. A few thou out across the width could cause some squareness issues that you might be blaming on the TS. Although your theory about the TS blade deflection on a skim cut makes sense. What kind of blade? I would venture to guess that a full kerf dedicated rip blade would be least prone to deflecting like this.

    Maybe I’ll run a board through the planer and measure thickness on each side with a caliper, see if it’s tapering along width at all.

    TS blade is a Freud Premier Fusion 40T. I have a Freud thin kerf rip blade but I don’t use it too often, although It’s the better blade for ripping thicker stuff. I’m using a Grizzly 2hp table saw, The accuracy of this saw is not as high as a high dollar PM or SS or something. I accept that because that’s just what’s financially doable for me.

    Regarding the comment that combo squares commonly are not square - I do have a set of “engineers” squares, that I use for set up sometimes. These squares are “square” visually if testing then by drawing a line, flipping, and drawing another line. They’re also square if standing up back to back with my Starrett. Those are about the only way I can check them. I’m not validating the accuracy of these tools, I’m just saying that I’ve checked them to the best of my ability, which to some may not be accurately checking them at all.

  10. #25
    Quote Originally Posted by Robert Hazelwood View Post
    You may want to see if you can dial out some snipe from the planer. For the most part on my humble DW734 snipe is very minimal, difficult to see or feel, and comes out with a pass or two with the smoothing plane (which I would be using on the surface anyways).

    Another thing that occurred to me is to check that the planer is cutting parallel. A few thou out across the width could cause some squareness issues that you might be blaming on the TS. Although your theory about the TS blade deflection on a skim cut makes sense. What kind of blade? I would venture to guess that a full kerf dedicated rip blade would be least prone to deflecting like this.
    Forgot to mention. I also am using the DW 734, and I rarely get snipe, maybe because I also use lift slightly on the workpiece as it enters and exits the feed rollers. Seems like when I do get snipe, it’s random and unexpected.

  11. #26
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    Woodworking and metalworking are different, the materials are different and so are the properties different. You have to work within the properties of each. Wood, metal and granite move under certain conditions. People that work with these materials understand this and work around it.
    High end metrology labs are temperature and humidity controlled.
    Metrology tools like micrometers have plastic heat shields.
    My surface grinder requires coolant to keep the surface of stock from distorting.

    Woodworking requires you adapting to the properties of the material also.
    It's all a game of working within the needs of keeping the material in a stable state while you work.

    All of the boards that I have ever glued up were handplaned to probably 0.001" maybe less. I never "measured" meaning I never used a tool to measure the "gap" I did however use a method to check the feel of the fit, and that method is a close to the same method that is used in tool and die shops for fitting parts, where they use a surface plate and ink and rub parts. My mortise and tenon joinery were also fitted by feel, probably to even tighter tolerances. The difference is in woodworking you don't have high tolerance specifications for joints, so each person does them to their own preference; some maybe okay working to 1/16th gap other push on chasing 0.001" or higher. You can fit woodworking by feel to very high tolerance, and you can also measure it and machine it to high tolerance. I also use digital calipers and micrometers and machine to my own specifications when appropriate.

    The example of the supersurfacer is a good one. you have a knife that is over a foot long,( on some machines over two feet long) with a back-knife ( chipbreaker) set a few thou back from the cutting edge and you can take a shaving 0.001" thick, you have some serious fine setup on these machines, you simply cannot be a couple of thou out, it wont function. The back=knife setup is a micrometer jig.
    supers28.jpgmicro_setting_gauge2.jpg





    Quote Originally Posted by Bill Dufour View Post
    I have never seen woodworking measuring tools any where near the accuracy of those for metal. It just does not matter that much for wood since it moves so much. No woodworker I know of worries about body heat from their hands affecting measurement instruments, metal workers do. The claim is a jump of 1/1000 of an inch, on a flat surface, is visible to the human eye.
    Bill D.
    Last edited by Mark Hennebury; 05-14-2020 at 11:50 AM.

  12. #27
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    You need 3 squares and a reference flat surface to verify squares.
    Stand square #1 on the flat surface and check square #2 and #3 against it, if they fit perfectly together, that tells you that 2 &3 are both the same angle and that they are complimentary angle to #1, but not what the angles are.
    Now check #2 and #3 against each other, if they fit perfectly, then all squares are 90.
    If not you will see the error, and it will be half of the error between #2 and #3



    Quote Originally Posted by Dan McGonigle View Post
    Maybe I’ll run a board through the planer and measure thickness on each side with a caliper, see if it’s tapering along width at all.

    TS blade is a Freud Premier Fusion 40T. I have a Freud thin kerf rip blade but I don’t use it too often, although It’s the better blade for ripping thicker stuff. I’m using a Grizzly 2hp table saw, The accuracy of this saw is not as high as a high dollar PM or SS or something. I accept that because that’s just what’s financially doable for me.

    Regarding the comment that combo squares commonly are not square - I do have a set of “engineers” squares, that I use for set up sometimes. These squares are “square” visually if testing then by drawing a line, flipping, and drawing another line. They’re also square if standing up back to back with my Starrett. Those are about the only way I can check them. I’m not validating the accuracy of these tools, I’m just saying that I’ve checked them to the best of my ability, which to some may not be accurately checking them at all.
    Last edited by Mark Hennebury; 05-14-2020 at 11:50 AM.

  13. #28
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    Are we talking woodworking here or lunar landings?
    Accuracy usually degrades as any project develops. Nice “dialed-in” machinery and tooling is a desired start but it’s only the start. I’ve never in my life checked how square my squares are. I’ve never used a feeler gauge ever in woodworking. The most geeked out I get is in wood thickness, weather after final milling or joinery parts. For that I use a digital caliper.

  14. #29
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    I don't agree with this idea at all.
    Accuracy doesn't degrade if you have sound process and do good project management.
    I have done lots of complex joinery that requires accuracy and precision within one or two thou.
    When you have multiple parts fitting together you have to develop a system to check and reference every step to prevent accumulating errors, if you don't error will rapidly compound and prevent the job going together.

    I also said that you don't need a ton of high end metrology equipment to be accurate, just need to understand how to check you setups.

    The credit card holders i produced hundreds of these, so tolerances had to be held tight, a couple of thou off and they are trash.




    pedestal joint.jpg SAM_1266.jpgProfil40.jpgProfil21.jpg

    Quote Originally Posted by John Sincerbeaux View Post
    Are we talking woodworking here or lunar landings?
    Accuracy usually degrades as any project develops. Nice “dialed-in” machinery and tooling is a desired start but it’s only the start. I’ve never in my life checked how square my squares are. I’ve never used a feeler gauge ever in woodworking. The most geeked out I get is in wood thickness, weather after final milling or joinery parts. For that I use a digital caliper.
    Attached Images Attached Images
    Last edited by Mark Hennebury; 05-14-2020 at 3:00 PM.

  15. #30
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    Life is easier with accurate equipment. I don't second guess my findings and that is valuable in and of itself.
    Bumbling forward into the unknown.

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