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How do I test a 45 setting with wood?

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Forum topic by WoodNSawdust posted 05-21-2015 01:10 PM 1018 views 0 times favorited 18 replies Add to Favorites Watch
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WoodNSawdust

1417 posts in 639 days


05-21-2015 01:10 PM

Topic tags/keywords: saw alignment question chop saw

There is a common method of checking a 90 degree cut for accuracy by making a cut and then flipping one piece of wood and looking at the gap. The error being half of the width of the gap.

I am looking for a similar test for a 45 degree cut.

More Details: I what to check the accuracy of the 45 degree setting on my chop saw. I want to lay a 2×8 onto the saw and do a 45 degree crosscut.

Thanks in advance.

-- "I love it when a plan comes together" John "Hannibal" Smith


18 replies so far

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Slemi

103 posts in 1004 days


#1 posted 05-21-2015 01:19 PM

You put four pieces together and test for 90 degree

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gfadvm

14940 posts in 2153 days


#2 posted 05-21-2015 01:22 PM

A digital angle gauge should work or use a plastic draftsman’s square. OR you can make 2 cuts, butt the left pieces together at the 45s and use a straight edge across the top to look for any gap.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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firefighterontheside

13466 posts in 1319 days


#3 posted 05-21-2015 01:23 PM

Cut two pieces, both on the same side of the blade then set them on a flat surface and try to bring the 45’s together. if they don’t match, the angle is not 45.

-- Bill M. "People change, walnut doesn't" by Gene.

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gfadvm

14940 posts in 2153 days


#4 posted 05-21-2015 01:24 PM

Bill, That’s kinda what I was trying to say :)

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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firefighterontheside

13466 posts in 1319 days


#5 posted 05-21-2015 01:30 PM

We think alike. ;-))

-- Bill M. "People change, walnut doesn't" by Gene.

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WoodNSawdust

1417 posts in 639 days


#6 posted 05-21-2015 01:49 PM



Cut two pieces, both on the same side of the blade then set them on a flat surface and try to bring the 45 s together. if they don t match, the angle is not 45.

- firefighterontheside

Are you assuming that both edges are parallel? If not I don’t understand.

-- "I love it when a plan comes together" John "Hannibal" Smith

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Tim

3113 posts in 1424 days


#7 posted 05-21-2015 02:38 PM

Cut two pieces, both on the same side of the blade then set them on a flat surface and try to bring the 45 s together. if they don t match, the angle is not 45.

- firefighterontheside

Are you assuming that both edges are parallel? If not I don t understand.

- WoodNSawdust

Yes, if not, rotate one piece so the two 45’s make a 90 degree angle and check it with the most accurate square you have. This requires a flat reference face to work and keep it on the inside of the 90 degree angle. This seems straightforward so maybe I’m missing something. Slemi’s way is probably more accurate than using a square. Make a box and test for 90.

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BurlyBob

3673 posts in 1728 days


#8 posted 05-21-2015 02:53 PM

Like previously mentioned a digital bevel gauge is a winner. Just make sure the gauge is lined up on the blade teeth at both the front and rear of the blade. If not, you can be off by as much as 2/10ths of a degree. That doesn’t sound like much, till you get to that last miter on a picture frame.

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DrDirt

4169 posts in 3205 days


#9 posted 05-21-2015 03:34 PM

I always saw making a square like a small picture frame. You have to use cuts from the same side of the blade, because the opposing cut will come together at 90.

Usually I just cut at 45…
Take the piece from the other side of teh blade, and recut it (so both pieces ultmately cut on the left side of the blade)... and check with a square.
Never needed it closer than that, because unlike a crosscut sled… the mitersaw generally isn’t ever looking at 45’s wider than a couple inches anyway.

-- 'Political correctness is fascism pretending to be manners' ~George Carlin

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firefighterontheside

13466 posts in 1319 days


#10 posted 05-21-2015 04:55 PM

Yes, I’m assuming straight boards with all parallel edges. I’m thinking if the boards aren’t straight then no method is going to work.

-- Bill M. "People change, walnut doesn't" by Gene.

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Yonak

979 posts in 984 days


#11 posted 05-21-2015 05:59 PM


Are you assuming that both edges are parallel?

- WoodNSawdust

If the sides are not parallel, and you have a trustworthy carpenter’s square, lay the square on your bench, align the reference edges of your two pieces along adjoining sides, inside or outside, whichever is appropriate, and look for a gap between the 45s.

Otherwise, if the face and back are parallel, align one’s reference edge with your fence, flip the other one over aligning the 45s, and measure from the fence to the corners of the reference side of the second piece to see if they’re the same.

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HornedWoodwork

222 posts in 677 days


#12 posted 05-21-2015 06:14 PM

Cut one, roll the board, cut again, this will make a triangle offcut. Measure for 90 at the point of the triangle and check for uniform thickness of the flat bottom.

-- Talent, brilliance, and humility are my virtues.

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TheFridge

5765 posts in 949 days


#13 posted 05-21-2015 06:22 PM

I think that’s a winner.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

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Ghidrah

667 posts in 685 days


#14 posted 05-21-2015 07:22 PM

12” machinist square

-- I meant to do that!

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DrDirt

4169 posts in 3205 days


#15 posted 05-21-2015 07:34 PM


Yes, I m assuming straight boards with all parallel edges. I m thinking if the boards aren t straight then no method is going to work.

- firefighterontheside

No you cut all of the 45’s on the same side of the blade with the same edge against the back fence

So I am flipping the board over each time but it is then alternating face down/face up to maintain that reference surface.

You just need one straight edge…. that gives you 8 cuts for the 4 corners of the square… so any misalignment will be magnified 8X.

I usually just cut 2 45’s and check with a square. for 90 degrees

-- 'Political correctness is fascism pretending to be manners' ~George Carlin

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