Please answer this quick and easy question

[Amy Leigh Baker]

Hey everyone! Quick question...

I am having difficulty setting my miter saw up to exactly 45 degrees, thus my joints are not lining up. (Honestly, I am ready to chuck it in the pond, but I am restraining myself.)

Just as an example, say the saw is set to 44 degrees. If I make one cut on the right side, and I make the other cut on the left side, one board of the miter will be at 44 degrees and the other will be at 46 degrees, therefore making the joint 90 degrees. Can I do this and will it make any other part of the table incorrect?

Thanks,
Amy

[Chris Padilla]

Not necessarily...but cut test pieces to make sure! :)

What miter saw do you have? I just went through cutting a lot of door casings and tuned up my DeWalt 705 to get it cutting on the nose 45s. It was actually pretty easy to adjust the scale which had detents at 45 degrees (and other spots).

[Joe Unni]

Amy,

The quick answer is yes. To me 90 degrees is 90 degrees. Just make sure that you keep track of your parts (i.e. left 44, right 46, etc.) and things should come out fine.

With that said, is there any way you could make this cut on your table saw? In my experience, I've learned to NOT rely on my miter saw for critical miter cuts as it doesn't make perfectly accurate miters. Accurate enough for paint-grade trim, but not for show joints.

Good luck,
-joe

[dustin sellinger]

There are 2 problems with this, especially in making a frame that is to wrap something.
The first one is bottom side blow out. When cutting with both sides of the blade your "top" or "face" will be one side up, and then one side down. The down side of a CMS cut tends to have some blow out.

The second problem is still the angle. You need everything to add up to 360 if you are going to make a frame for something. You could hope your 44 and 46 work out, but chances are your cuts will end up with something else as the middle number. What if your angles are 44.5 and 45.1? Then you have 358.4 deg and you still won't be square.

[Peter Quinn]

I believe this will result in your long point to short point cuts having two different hypotonuses, thus your miters will not fit together correctly. The sum of all angles must equal 360 degrees but any two mating angles must be equal. Get your owners manual and see how to adjust that saw.

[Tom Veatch]

I believe this will result in your long point to short point cuts having two different hypotonuses, thus your miters will not fit together correctly. ...

That is correct. The effect will be the same as if the widths of the mating pieces were different. To be precise, if the angles were 44 and 46 degrees as postulated, the difference at the joint would be as if the width of piece on one side of the miter were about 5% wider than that on the other side.

[Peter Quinn]

As to the bottom side blowout I regularly use a small jig that consists of a 1/2" piece of plywood on the table connected to a 3/4" subfence which is screwed to the main fence. My makita has convienent holes in the aluminum fence which seem to be there for this reason. I set the depth limit to cut 1/8" deep into the plywood base efectively creating a zero clearance back and bottom cut which minimizes or eliminates blowout. Basically essential to me for fine trim with a SCMS.

[Joe Chritz]

I still prefer to use the SCMS for nearly everything under 12" wide. With proper tuning and proper technique it will make perfect miters every time.

A good blade is essential as well. I had perfect cuts with wide miters when the blade was fresh but now I get just a fuzz of flex as it is dulling. A full kerf would help that.

You may be able to make it work otherwise, as stated, but it is better to tune the saw or make a sled for the tablesaw.

Joe

[Mike Henderson]

Even if the joints would fit, I'd NEVER be able to keep track of which side to cut which way. I'd mess up a lot of wood trying to do that.

Mike

[Bert Johansen]

Amy, I agree with Peter. Spend time learning to tune your miter saw. I have a really cheap-o miter saw (Black & Decker) with a really expensive blade. About once a year I re-tune the saw and I get 45-degree miters and 90-degree cuts that are dead on. If you can't get your saw to cut accurately, toss it and get one that can be tuned properly.

Suggestion: get inexpensive plastic triangles (45-45 and 30-60) from a graphic arts supply house like Hobby Lobby and use these for references. Check the angles to be certain they are accurate, then use them to tune your saw.

[Jim O'Dell]

If it all adds up to 360 degrees, then it should be square. What I'd be afraid of is that one leg of each joint would be longer than the other, be it ever so slightly. If you were wrapping this frame around a square object, it might introduce a slight gap between the object and the frame. I'd try to get the unit to 45, or use a good miter sled ont he TS. Jim.

[Peter Quinn]

Funny thing Bert...the makita came with a plastic 45/45/90 triangle. The instructions, in typical Japanese fashion, stated that while the saw was set perfectly during manufacturing, all settings should be checked before use, and that while the saw should hold its settings accurately, all settings should be checked regularly! They even provided the perfectly sized triangle for the job.

The makita was in fact set perfectly from the factory but my rough use has since taken care of that. Luckily it is easy to reset.

Amy, Adjustment on a good saw is fairly simple, if your saw cannot be adjusted to cut properly then the pond is an excellent place to keep it while you shop for another.

[Steve Campbell]

Amy also remember the the sides of a frame have to be STRAIGHT. The two sides have to be exactly the same length and the top and bottom have to be the exact length as well. The only way I know to do that is with a stop block.

Steve

[Scott Vigder]

I vote for pond-chucking. There are too many good saws out there that will not drive you crazy.

[Louis Brandt]

While it's true that, for example, a 44 degree angle and a 46 degree angle add up to 90 degrees, and it's true that all of the angles of a rectangle add to 360 degrees, you won't get a proper miter unless you are at exactly 45 degrees. Just think about it: Suppose you're making a four sided picture frame, using say, 1 inch wide stock. If all that you have to do is to make sure that the sum of the angles at every corner add to 90, then think about cutting one of the angles at 30 degrees and the next one at 60 degrees and trying to put those two angles together to make a corner. As has been pointed out, your hypotenuse(s) will be the problem. You'll quickly realize that you won't have a proper corner this way! No, in order to have all four corners correct, they all have to be at exactly 45 degrees.
Louis

[Carl Fox]

I have an idea. Let's say the miter box is 1 degree off. Build a jig for your TS that will let you take 1 degree off the side that will be facing in. Assemble the frame. Your frame should no longer have the gap problem, but now the inside square will be 1 degree off from the outside square and the frame rails will all be tapered. Run the outside through the jig again to make them line up. The only problem now is that your miter joints will not line up with the outside corners.

[Todd Bin]

How about using one of these. It is a miter trimmer. It is super easy to use and can take paper thin slices off the 45. It will aslo true up your 45. So you cut a tad long on your miter saw and at some odd angle (say 44.5 or 43.2 or whatever) then take it to the miter trimmer and slice off a paper thin slice and true the angle to 45.

These are available at lots of places but I bought mine at highland hardware.

[Chris Padilla]

While it's true that, for example, a 44 degree angle and a 46 degree angle add up to 90 degrees, and it's true that all of the angles of a rectangle add to 360 degrees, you won't get a proper miter unless you are at exactly 45 degrees. Just think about it: Suppose you're making a four sided picture frame, using say, 1 inch wide stock. If all that you have to do is to make sure that the sum of the angles at every corner add to 90, then think about cutting one of the angles at 30 degrees and the next one at 60 degrees and trying to put those two angles together to make a corner. As has been pointed out, your hypotenuse(s) will be the problem. You'll quickly realize that you won't have a proper corner this way! No, in order to have all four corners correct, they all have to be at exactly 45 degrees.
Louis

To put some numbers in:

Let's say the angle is 45°. The hypotenuse will be √2" assuming 1" wide stock.

What happens if we cut a 44° angle instead? The hypotenuse will now be LONGER at √2" + .025" and conversely, one cut at 46° will be SHORTER at √2" - .025".

Now you put those two pieces together and match the outside miters and you should find a mismatch of 0.05" or not quite a 1/16" at the inside miter--you have a 90° corner but is the mismatch acceptable to you? If your error from 45° is less than a degree, then the match gets closer. You are also assuming that when you swing the miter box to the other side, that it will be off the same amount...not necessarily true!

[Amy Leigh Baker]

Okay, you must excuse my late response. Sometimes the extremely amateur WW in me sees all these responses and doesn't know what to think or do :o

Okay, I understand all of your points. A couple things...

If I am reading these explanations correctly, one of the concerns is that the miter cuts will be different lengths. Well, the miters in question are the aprons of a table, and the tabletop will sit on top, thus hiding everything but the front edge (as seen in the sketches here http://sawmillcreek.org/showthread.php?p=794267#poststop). This alleviates this problem, no?

As far as buying another tool is concerned, I cannot. $40 for a handsaw would be a splurge. I have found myself in a very expensive hobby with very little money, but one that I am enjoying immensely. Therefore, I am being incredibly creative in finding ways to do things on the cheap, or with substandard tools. Like the saying goes, "Necessity is the mother of invention."

After reading some posts that said it would theoretically work, I tried cutting these joints this way last evening. The cuts definitely come out 90 degrees. Spot on in fact. But I did notice the slight difference in lengths of cut. I figured because the tabletop will cover these it should work.

Maybe I can have the time to build a miter sled for my TS before I have to cut the frame for the tabletop. (I have no miter fence, miter sled, nothing.)

Thanks for all the input. That's why I love this place!

Amy

[Roger Warford]

Is it possible your miter saw is spot on but your work piece isn't? If the piece you are cutting isn't square, when you push it up against the fence the "perfect" 45 won't be 45 anymore.

[Peter Quinn]

As far as the aprons in your schetch if you cant nail 45 degrees with your saw I'd pick an angle slightly less than 45 degrees for both pieces and cut them from the same side of the saw, as long as the long points close up on that outside miter you wont ever see the open back. Ever cope crown molding? Same basic idea in reverse.

That trick wont work however when its time to make the mitered frame for the top. You'll have to get more creative with that one.

[Dave Bureau]

Even if you get a perfect 90 the joint wont line up the the boards are not EXACTLY the same length. Use a stop block.
Dave

[Greg Cole]

Couple things for miter saws I didn't see perusing the post...
1) Make a zero clearance insert to minimize blow out on the "bottom" and use a backer for reducing blow out against the fence.
2) Clamp your stock to the fence-table or both. Having the stock creep ever so slightly when cutting miters is very common.
3) Depending on the application and visibility of the mitered joint, "backcutting" a weeeee but makes the show faces close up nice n tight. A block plane, rasp, sandpaper can all fit the bill.

And I'll toss in another vote for tuning up whatever saw you are using. Brand name & model number are irrelevant if the tool is out of whack.

Cheers.
Greg

[Rye Crane]

Amy,

Another solution is to talk with your Neander friends at their forum and ask about using a shooting board and a handplane to trim the miters to an exact 45. Or google shooting boards, they are used to trim to exact 90 and 45 degrees or any other angle you desire.

Best of Luck,
Rye Crane

[Chris Padilla]

Amy,

Another solution is to talk with your Neander friends at their forum and ask about using a shooting board and a handplane to trim the miters to an exact 45. Or google shooting boards, they are used to trim to exact 90 and 45 degrees or any other angle you desire.

Best of Luck,
Rye Crane

http://www.whitemountdesign.com/ShootingBoard.htm

An excellent introduction to shooting boards.