need to understand how to measure for framing with 45 degree cuts

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Forum topic by dexter posted 09-01-2011 06:01 PM 45684 views 0 times favorited 10 replies Add to Favorites Watch
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2 posts in 2482 days

09-01-2011 06:01 PM

Topic tags/keywords: pine

the how to cut a 45 degree angle is well document throughout the web.
I am unable to find a plain ez way to measure for the correct lenght of the piece.

what do I measure and how do I measure it?
I seem to always be an 1/8 th off plus or minus…
how do i get accurate measure ment…..?

10 replies so far

View Gene Howe's profile

Gene Howe

10521 posts in 3450 days

#1 posted 09-01-2011 06:54 PM

What size wood are you cutting? Are you framing a building, building a box, or making a picture frame? In other words, how precise do you need to be?
If you know the length of the piece you need, cut the first 45, then measure the long side and mark it. Remember, it’s an opposite cut. To help me, I use a saddle square that has a 45 on one leg. It gives me the right cut direction as well as a perfect line at 45.

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

View CharlieM1958's profile


16275 posts in 4240 days

#2 posted 09-01-2011 07:53 PM

I’m not sure if this is what you are asking, but if you cut a 45 degree angle on a board, the difference in length between the short side of the board and the long side will be equal to its width.

In other words, if you take an 8-foot 2×4 (which is 3.5 inches wide) and cut a 45 degree angle on one end, the shorter side of the board will measure 92.5 inches. (96 – 3.5 = 92.5)

Do the same to an 8-foot 2×6 (5.5” wide) and the short side will measure 90.5”. (96 – 5.5 = 90.5)

-- Charlie M. "Woodworking - patience = firewood"

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18283 posts in 3698 days

#3 posted 09-01-2011 08:06 PM

Good point Charlie. I didn’t know that ;-)) I don’t quite understand the question either. Sounds like care in cutting on the line might be part of the issue with 1/8 variance.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View Grandpa's profile


3259 posts in 2697 days

#4 posted 09-01-2011 08:51 PM

Sounds like cutting on the wrong side of the line. If he is using a miter saw and you change from one side to the other for the second cut then you need to cut on the other side of the line. A blades thickness is about 1/8 inch….?

View Dennisgrosen's profile


10880 posts in 3137 days

#5 posted 09-01-2011 10:27 PM

if you make it 1/16 or 1/32 longer everytime and use a plane and shootingboard
to sneak up on it you get right evrytime and take care of slightly out of angle at the same time :-)


View dexter's profile


2 posts in 2482 days

#6 posted 09-02-2011 06:29 PM

thanks guys, just trying to get a handle on the “how to measure” so I can make consistent 45 degree cuts for whatever I am making.
As I understand it, I measure the dimension of what i am framing. e.g. 8 in width. make one cut, then measure the inside dimension, mark the 8 in plus 1/16 for the opposite cut.
I get the blade thickness and take it into account.
As a novice, I get confused about measuring and marking….correctly consistently.
Thanks for your help. Appreciate it.

View chrisstef's profile (online now)


17421 posts in 3028 days

#7 posted 09-02-2011 08:19 PM

Its a good question, and Charlie enlightened me as well. I typically leave one side a bit longer and then sneak up on it.

-- Its not a crack, its a casting imperfection.

View PurpLev's profile


8536 posts in 3670 days

#8 posted 09-02-2011 08:32 PM

also, if it’s always 1/8” shorter try aligning your saw blade on the other side of the marked line. the kerf of the blade is 1/8” by itself which might explain why you are always 1/8” shorter – just a thought

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View BTKS's profile


1986 posts in 3486 days

#9 posted 10-06-2011 05:16 AM

Typically it is much easier to measure the long side of a miter. The point of the miter is a much more precise point to referece. The obtuse angle of the short side is easy to mismeasure.
I also prefer to transfer dimensions rather than measure. Every time you measure you introduce possible errors. Just on one side of the line or the other everytime you measure and every time you mark. If you can transfer the dimension, the measurement does not matter! This is why a story stick is so useful in stair or cabinet building.
Hope that made some sort of sense. Good luck, BTKS

-- "Man's ingenuity has outrun his intelligence" (Joseph Wood Krutch)

View MadJester's profile


2065 posts in 2452 days

#10 posted 10-12-2011 04:45 AM

I always leave a little on the length and then nibble it down with my guillotine….doing this with each piece ensures a more accurate angle and a smoother more snugged up fit…


-- Sue~ Mad Jester Woodworks, "Not what I have, but what I do is my kingdom" Thomas Carlyle

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