Somethings not lining up...

[tango]

I was working on a really small project yesterday and realized that my tools are not in agreement with one another.

I was cutting a section out of a board; about 3" x 3" from a 5" x 8" board. What I did was took my square and drew a line on the board where I wanted to cut. I used the factory cut edge as a guide and ran my pencil down the edge of my square; then I cut it, but the cut and the line didn't line up. The line I drew seemed to be at a bit of an angle to the cut. It was only off by a few degrees, but as we all know those few degrees add up.

My question here is how do I figure out if my square isn't square or if my miter gauge isn't adjusted properly?

Dilemma: if I use my square to adjust my miter gauge, but the square isn't square then won't I simply be misaligning the miter gauge... ?

I'm sure there is some magic way of eliminating this dilemma, but so far nothing is coming to mind... I just keep staring at my miter gauge and saw scratching my head...

Tango

[rayjack]

To check the accuracy of a square use the square to scribe or pencil a line across a board with the handle of the square to the left of the blade. Flip the squre over so that the handle is now on the right of the blade and line up with the previously scribed line. The square should match up exactly with the line, if it does not then the square is inaccurate. Also remember that the inside and outside edges of the square are not always exactly parallel so both need checking.

[dusty]

To check the accuracy of a square use the square to scribe or pencil a line across a board with the handle of the square to the left of the blade. Flip the squre over so that the handle is now on the right of the blade and line up with the previously scribed line. The square should match up exactly with the line, if it does not then the square is inaccurate. Also remember that the inside and outside edges of the square are not always exactly parallel so both need checking.

Remember, there are four (4) critical edges on a square. When attempting to certify your square, check the characteristics of all four sides with respect to the others.

This is a very simple tool that can get you into a lot of trouble (inaccuracies).

[Gene Howe]

One suggestion....MiterSet.

[mikelst]

It sound to me like it could be an alignment issue with the ShopSmith. Have you checked the blade to table, blade to fence and blade to miter gauge for proper alignment.

I state it this way as I like to check everything from the blade, if everything is square to the blade they should be square to each other.

Of course this also goes back to your square, if it isn't (square) then nothing else will be.

[JPG]

[quote="tango"]I was working on a really small project yesterday and realized that my tools are not in agreement with one another.

I was cutting a section out of a board]


To set/check the 90° setting of the miter gauge, get a FLAT piece of 'scrap'; wood of reasonable size (6" square). Cut using the miter gauge across one edge. Rotate the board so the newly cut edge is against the mitergauge. Cut the second edge. Repeat around the board two more times.

Place the last edge cut against the miter gauge. make a 'test' cut just inside the edge(it will be the same as the first edge cut). Cut enough so that you can measure the cutoff. If the miter gauge IS square. the dimension(cutoff width) will be the same at both ends.

This 'test' multiplies any error by 4x.


ALSO when setting the mitergauge with the square. check from BOTH sides of the mitergauge bar. If the square IS 'not square' then it will be obvious since both sides will not agree.

Sadly there are a lot of 'squares' out in the world which are not 'square. If you want to have fun sometime. ask a clerk which of two non-agreeable squares is 'CORRECT". Not my idea but interesting!!!;)

The combination squares(the ones which have a part which slides along the ruler) are more prone to error.

BTW a 'FEW DEGREES' is a humongus error.

[Ed in Tampa]

Once you find a square square don't drop it. Everytime you drop one it tends to knock it out of square unless you have one of the triangle ones. I forgot to mention it doesn't matter if you dropped it or you simply knocked it off a table or bench the fact it hit the floor did the damage.

What I do is have a triangle square that I know is square I then use it as a master to all my other squares. I have found after a years normal use in my shop all my working squares end up slightly out of square.

Some can be adjusted back into square and some get sent away with in the big smelly green truck that comes down my street twice a week.

Lately I have been favoring a draftsman's plastic square. It is cheap, doesn't seem to lose squarness when I drop it and did I mention I can buy about 100 for the price of one the "guaranteed" square squares that go out of squareness on the first drop. Of course I'm cheap!

I found an interesting square the other day. It was perfectly square as best I could tell but on all four surfaces the edges were not perfectly flat each one had either a cup or a bow yet the angle formed was a perfect 90 degrees you just could not mark a straight line against it. Talk about expensive junk!!!!

[kalynzoo]

Don't forget the ruler. I just discovered that my favorite trusty ruler measures 1/32 different from one scale to the opposite scale. Must have rubbed off a little of the end.

[robinson46176]

On my saws I generally just flip the miter gauge upside down with the knob loose and shove it up against the front edge of the table and tighten the knob. You should check first that your table front is square to the miter gauge slot. You might find some odd ones that are not.
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You can also use the miter gauge slots to check your square.
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Far more errors are caused by careless marking than crooked squares. I have watched guys make a mark along a 2' span and change the slant of the pencil "substantially" from one end to the other and swear that they held it straight all of the way. "Somewhere" just recently I saw a picture of a device like a mouse that held your pencil at a constant angle to prevent that.
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It is also very easy to misread a measurement. That is why you should where possible avoid measurements and superimpose where ever you can. Marking with a Sloyd knife is also more accurate than a pencil.
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If all else fails specialize in "rustic" items.

[kalynzoo]

Gee thanks Guys.
I was just about to use my favorite adjustable square, passed to me by my father from my grandfather. I believe it was used in building the Empire State Building. When matched against a my reference fixed square (purchased from SS and stored in the padded blue box) I can see light.
Probably not critical for most work. For sure I will NOT retire this fine tool.
Just a reminder to measure twice before you cut, and perhaps measure from opposite sides.
Well, back to the train.