How can you tell if a square is square?

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I've got a couple of them. Old ones. I use them alternately. I noticed the other day when something was square with one of them, it wasn't with the other. I went to a big hardware store and they had heaps of them. And some of them them contradicted eachother. So how do you blokes tell if a square is square?Yeah, I carry.House keys, wallet, some change, usually a newspaper, maybe a pen.
Reply:3 4 5 method.   You can use 6 8 &10 or 9, 12, &15 whatever as long as you keep the same principle.DewayneDixieland WeldingMM350PLincoln 100Some torchesOther misc. tools
Reply:What's the 3 4 5 method?Yeah, I carry.House keys, wallet, some change, usually a newspaper, maybe a pen.
Reply:Scott, the 3,4,5 method is easy...you just measure out a ' L ' shape with one leg at 3 foot long, the other leg at 4 foot long and then the distance between the two ends will be 5 foot if the ' L ' is square or 90 degreesYou can use any multiple of 3,4,5 you want, as noted above...All you will ever need to know about this..http://www.bing.com/search?q=Pythago...um&form=OSDSRCLast edited by TEK; 06-12-2009 at 03:35 AM.
Reply:Find a piece of plate or plywood with a straight edge. Using the tongue of the square draw a perpendicular line on the plate using the edge of the plate for the blade to register against. Flip the square over and compare the line just drawn with the edge of the tongue, half the distance is the error.Depending on which way it has to go you can either tap the flat surface with the ball end of a ball pien hammer on the inside or outside to stretch the material......Mike
Reply:I check my squares the same way I check a spirit level,  SPIRIT LEVEL.      place level on a surface that is expected to be level and then check bubble position,mark around spirit level for location, then swing level around 180*and locate in original position, check bubble position again. If they do not read the same the spirit level is not true, The ammount of error is half the difference in readings.  SQUARE,  Place square on flat surface,  then scribe a fine vertical line, then swing square around     180* and see how the vertical lines up with the original scribed line. if not the same square is off  true,   Both methods take only seconds and no measuring involved sorry about the poor explanation, but I'm sure you guys will understand how it works,  Cheers  Gordon.Last edited by gordon stephenson; 06-12-2009 at 05:13 AM.Lincoln SP-170 MigHypertherm powermax 45Lorch T220 AC/DC TigButters FM 215 synergic MigKemppi 180 adaptive mig RULES ARE FOR THE OBEDIENCE OF FOOLS AND THE  GUIDANCE OF WISE MEN.
Reply:You beat me to it.  "Flip it over"  Real world weldin.  When I grow up I want to be a tig weldor.
Reply:A squared + B squared = C squared The above is the Pythagorean Theory and is where the 3, 4, 5 method comes from. As stated you can use multiples of these numbers.Because a typical framing square measures 16 inches along the tongue and 24 inches along the blade then it should measure 28 13/16 outside tip of the blade to outside tip  of the tougue diagonally. ( hypotenuse ).You can tell if the legs are not straight by placing it flat and drawing a line along the leg. Then flip it over without changing its location and draw another line along the same leg. If the two lines are not parallel then it is bent.
Reply:Originally Posted by mrmikeyFind a piece of plate or plywood with a straight edge. Using the tongue of the square draw a perpendicular line on the plate using the edge of the plate for the blade to register against. Flip the square over and compare the line just drawn with the edge of the tongue, half the distance is the error.Depending on which way it has to go you can either tap the flat surface with the ball end of a ball pien hammer on the inside or outside to stretch the material......Mike
Reply:Originally Posted by scott brunsdonI've got a couple of them. Old ones. I use them alternately. I noticed the other day when something was square with one of them, it wasn't with the other. I went to a big hardware store and they had heaps of them. And some of them them contradicted eachother. So how do you blokes tell if a square is square?
Reply:Are you sure you didn't wander into the sporting goods section by mistake? Those "not square squares" are termed boomerangs I believe.
Reply:There are many ways to check for square. The one not mentioned is measuring the diagonals from corner to corner. If the object is square, the diagonals will be of equal length.
Reply:Originally Posted by transitThere are many ways to check for square. The one not mentioned is measuring the diagonals from corner to corner. If the object is square, the diagonals will be of equal length.
Reply:Hard to beat flipping it along a known straight edge and scoring a line.
Reply:Gordie, Don’t let Norm Abrams hear that.
Reply:I think I got this from here  http://zo-d.com/stuff/how-do-i/how-t...ng-square.html Framing or carpenters squares last a long time and are big enough that they can get stepped on or dropped or have something put them out of square sometime over their life. Fortunately it is easy to check and adjust them. To do this simply find a flat surface that you can draw lines on. This may rule out the dining room table.First draw a straight line twice as long as the leg of the square. With the heel of the framing square in the middle of the line, draw a line up along the edge of the framing square (perpendicular to your base line). Then flip the square over with the heel in the same place and draw a similar line.Framing SquareThe two lines should match. If they don't then the square is not square.To correct it is simple, but go slowly. If the square is at an angle of less than 90 degrees (bent towards itself) then take a punch and a hammer and make some small dimples near the inside corner of the square. This will expand the metal and make the legs of the square bend further apart.If the square is wider than it should be, make the dimples near the point of the square. This will bring the legs closer together. Keep checking while you are doing this. If you don't have a punch you can get away with placing the square on a hard surface and whacking it with the corner of the hammer face. Repeat until you get a square square.
Reply:Bridgeport table..Clamp it down and indicate either X or Y in to zero and then see what the other side is readingThat's the ultimate way.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by zapsterBridgeport table..Clamp it down and indicate either X or Y in to zero and then see what the other side is readingThat's the ultimate way.....zap!
Reply:Not really..If you are only using the head to hold a indicator it don't matter if it's upside down..Sometimes I just use my lathe set up and stick it on the "In Out" ram..Just as long as it is stationary..The table moves not the head ...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by zapsterNot really..If you are only using the head to hold a indicator it don't matter if it's upside down..Sometimes I just use my lathe set up and stick it on the "In Out" ram..Just as long as it is stationary..The table moves not the head ...zap!
Reply:Yeah, we all have a Bridgeport just sitting over in the corner of the shop so we can check our framing squares. Any more useless advice?
Reply:Originally Posted by TSOR Any more useless advice?
Reply:Originally Posted by zapsterNope..From what I have read in various threads you all seem to have that covered,,One word of advice though..Do not challange your machine to a fight..You WILL lose....zap!