Mitre cuts...what am I doing wrong?
 

I'm fabricating braces for a small door overhang.I cut the pieces on my table saw and as you can see by the speed square the angles are looking good. Yet, you can also see that there is a gap between the two pieces.

WTH?
The gap after mounting in place
http://forums.pelicanparts.com/uploa...1749914968.jpg

The right angle

http://forums.pelicanparts.com/uploa...1749915022.jpg

the 45 degree cut


http://forums.pelicanparts.com/uploa...1749915072.jpg

When I ran into this problem making some picture frames it was a combination of things that caused it.
Chop saw I was using needed some 'fine' adjustment as I assumed it was good to go 'as is'. My son had used it to cut some angles that weren't standard and I assumed he had returned it to factory specs.
I also found that I needed to be sure I was measuring things from the same edge every time. In machining speak, a datum edge. Wood isn't always parallel so the edges don't translate from side to side correctly, if you get my drift.
Hope this helps, it's my attempt to answer the question, but, I'm not a wood worker by any stretch and actually, uh, dislike working with wood because it's so hard to hold to a close tolerance. I used to be a machinist and could hold 0.0005" all day long once I got to know the machine I was using.
Good luck, I'm going out the garage to work on my RC truck now.

Your angle guide for your table saw isn't calibrated would be my guess. Use "speedy" to mark the angle on the piece you're cutting and see how it lines up while cutting using the saw guide.

^^This

^^And this

Thanks guys. I was thinking I just suck at this.

You do, apparently.

When you're done, send some pics to Glen, so he can post it in the Random Pics thread.

For starters you’re spelling “miter” wrong but other than that, earlier responses have you covered.

He's just speaking in the Queens English. He's modelling his cuts in wood, before he changes to aluminium and then paints them a bright colour. He'll have to get the paint at the shoppe, and pay a few guineas for it.

He’s from Jersey too. You’s guys shud just be happy we speak any kinda f’in English. Capice?

I used to support Bellatlantic dial up Internet. It was separated into 2 areas, the NY/NJ area and then the stuff farther south (MD, VA, etc...). We weren't supposed to support the NY/NJ folks, that was another group. When we asked "May I please have your email address" if they said "<something>@banet.net" we were supposed to cold transfer them. We also knew based on their accent and if their response to the email question is "why you fsckin wanna know?" then we knew...

had you cut it a half inch or so longer it would have prolly be right on. had it been open on the long end that would have indicated it was a tad long.

cut many a rafter in my carpentry days.

I say keep cutting until it’s long enough.

That’s what I do.

Well, that's always a possibility too. :D

Try a framing square instead of a speed square. Turn the framing square both ways. Once you do that, you may need to dial in your fence and or an angle.

You pay in Italians?

you need to buy a machinist square:
https://en.wikipedia.org/wiki/Machinist_square

Once you get one you'll see how poorly built almost every speed square is.
Machinist squares are built, speed squares are stamped out.

I cut a mitre, then turn it over and line it up like I'm gong to take a millimetre off it. You will see if it's not correct. Adjust the saw until it's right.

I do this with my picture framing guillotine and my drop/chop saw.

You guys are killin' me! :D

You can’t be a genius at EVERYTHING!

Actually it looks good to me, given the quality of the wood. Doing rough work like that I lay the brace to be cut in place on the “square” corner and mark the cut lines it against the square sides. You don’t need no stinkin square.
When the carpenters were framing my room addition 10 years ago a worker was up in the rafters measuring the pieces he needed and the boss was on the ground cutting them. The worker yelled down, “Twenty-four and an eighth.” The boss yelled back,”This is framing! Ain’t no such thing as an eighth!”

Ya, I was the guy down on the ground cutting after I was a seasoned carpenter. Rarely actually measured for every rafter. Took the room dimension, slope of the roof, set the ridge based on that and the rafter seat cut (also referred to as the "birds mouth"). Cut one for each side, when they fit, I cut the rest them as fast as the two guys up top could set and tack them in place.

On a hip or valley, you would use the room dimension, get the length, see a speed square Hip/Valley & notice it's different than a common rafter/jack for the plumb and seat angle. A hip/valley has to be longer and have a different plumb cut than a common rafter cause it's generally running at a 45* angle. Once the hip/valley is set a rafter book will tell you how much to add or subtract from each "jack" rafter based on layout spacing, 16" or 24" generally. You always wanted to set a left, then an opposing right rafter as to not push the hip/valley out and bow it. The jack rafters landing on a hip or valley take the same plumb cut as a common rafter.

I was not good enough to cut an entire roof with just dimensions & slope, I would test fit pieces before I went to cutting all the common or hip/valley "jack" rafters. I worked for a guy who would do just that, cut an entire roof with a set of plans, a rafter book, a calculator, a framing square with stair stops, a unit of lumber and a skill saw.

He was a witch!

I'd cut the piece an inch long, hold it against the face of the framing where it's it going with my speed square lining up the 45° and pencil mark both sides of both ends to be cut. Id use my chop saw and line up my marks by eye but a table saw will work.