Accurate 45% cuts:

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Can someone tell me how to make accurate 45 % cuts that actually fit together nicely? I was building an deck and have some herringbone and mitered joints that were an devil to do , using number 2 grade spruce. I love making sawdust.
Sal
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Making an accurate 45 degree cut is really no harder than making an accurate 90 degree cut. What exactly is the problem that you are having? What saw are you using?
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Hi Leon my problem is fitting the material together because of the poor grade wood I am using.I thought there might be some profession tricks I might use. Sal

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sal wrote:

...
Again, what are you using to make the cuts? Blade choice is important, too, of course.
If the material is construction-grade lumber that isn't fully dry, it'll almost certainly shrink when it dries and any 45 will open up anyway though...
--
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I don't understand. You want to make an accurate 45 deg cut, but they don't match because of the poor grade of wood? If the cut is accurate it will fit no matter the grade of wood.
You need either a good miter box, a good miter saw or an accurate square. What are you doing now? The only professional trick is to have both cuts accurate.
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Edwin Pawlowski wrote: ...

...
/Crystalballmodeon...
Perhaps the problem is there isn't a good straight edge so the miter box or saw doesn't have a consistent registering edge???
/Crystalballmodeoff
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That would be my guess too.
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Best regards
Han
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Not really. On a table saw, use two miter guides set to 45, one on each side of the blade. Make one cut on one side, then make the mating cut from the other side. Even if you don't have exactly 45, the two cuts will be complementary and join perfectly.
Same thing on a radial saw, except the blade is set to 90 and you build a jig that holds the work piece at 45 on either side.
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On Sun, 07 Sep 2008 13:06:21 -0400, Richard Evans

Incorrect. The two surfaces may meet but the resulting angle of the two boards will not be 90 degrees unless the cut is exactly 45 degrees. The OP implied he needs the resulting angle to be 90 degrees.
G.S.
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If the outer edge of the V-shaped guide is 90, then it will be 90 even if the miter isn't exactly 45. (e.g. 45 1/2 and 44 1/2.)
Both the interior and exterior edges may not line up (picture a 30/60 combined angle).
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He'd building a deck. Cutting the 45's on the end of a 12' board on a tablesaw will be a PITA.
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Agreed. It's a deck, not piece of ornate furniture. Even if there's a little splintering, it would go unnoticed and if it doesn't, it only adds to the rustic nature of decks. A suitably sized speed square is all that's needed for a deck.
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accurate
I'm willing to bet that his "cheaper wood" is splintering a lot. Only suggestion I can offer is to score it first with a razor knife.
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Go to an art supply store and pick up a drafting square, and us this to make a jig assuming you are using a circular saw. Place the jig on the wood and use this to guide the saw
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From What I have read:
It has to do with the force from the blade, how it cuts the kerf, and how the wood is supported (or secured from movement.)
The force of the motor is way more than you can hold with your hand the wood against movement. A 90 degree crosscut usually has a lot of support by the geometry of the cut which prevents wood movement. However a 45 degree cut as a lot a force working to shift the wood due to the blade. Vector math, resultant forces, and all that.
Step 1, therefore is to check and double check that the wood is secured in such a way as to prevent the wood from movement during the cut. Stop blocks do work well in this case.
Several very well written articles in Shopsmith magazine over the years on this subject. And I believe in the results of the jigs I have built from Shopsmith to overcome this 45 degree gap problem.
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"sal" wrote:

You can't get there from here, the lumber will get you.
Make a perfect fit on day 1, buy day 5 it will be gone.
Lew
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You never explained what the problem is. It is a common carpenter "trick" to backcut all miters so that just the top finish surfaces comes together. The amount of backcut is really small, I would guess about 1 degree. On trim work, setting the piece up on a nail close to the blade gives about the right relief.
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Thanks for all the help , much appreciated.
Sal

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One last thing to consider. If you are trying to come up with a particular angle and the boards do not intersect at the correct angle the cuts will never fit. Often a novice when trying to make a square frame with 45 degree mitered cuts one of the joints will not close properly. This is because either the opposite sides are not perfectly parallel or the opposite sides are not exactly the same length.
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sal wrote:

Cut them at exactly 45 degrees. <G>
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