45 degree cuts?

[VB...]

Hello,
I have a table saw I can cut 45 Degree cuts. I have a miter saw I can cut 45 degree cuts.

Once I glue and shoot a couple of brad nails into my joinery they seem to pull away at the corners.

I understand that my 45 degrees are obviously not 100% right.

What are the best ways to get it right the first time?

Thank you in advance,
VB...
I'm sure people will laugh at me for asking this one. LOL
</IMG>

[Bill Wilson]

No laughter here. Getting tight fitting, accurate miter joints is a challenge for every woodworker. Unfortunately there are so many factors and variables that play into the quality of mitered joints that it's impossible to go into a lot of detail here. However, in my opinion here are some of the basics;

Lets start with your saws. Every tool needs to be properly adjusted and tuned in order to give accurate, quality cuts. This starts with a good quality blade and carries through to the adjustments and alignment of the saw itself. Your owners manual should get you started in making sure your saw is adjusted properly, but there are a number of books out there that go into much greater detail, describing how to tune your saws to maximize accuracy and consistency. Bottom line is that your blades need to be adjusted to cut true and your fences, miter gages and other accessories all have to work in harmony. The slightest variances in any of these will result in a cumulative error that will prevent you from getting a tight fitting joint.

Next there are some jigs and fixtures that can help you compensate for or overcome some of this cumulative error and/or help you make consistent cuts. Many woodworkers build their own miter sleds for the table saw. There are a number of designs for such jigs and many claim that a well built one can give you as good or better joints than the best compound miter saws. Whatever method you use to cut miters, one key, yet very simple aspect is the ability to hold the wood tightly enough to prevent it from moving during the cut. Often sandpaper is mounted to fences and miter gages to prevent slippage of the wood once it engages the blade, even the smallest of which will result in a less than perfect joint.

The last area to be addressed is that of technique. Since there are so many places where slight error can be introduced into the process, it is critical that the operator use proper and consistent technique. Check your set-ups every time you make a cut. Get a feel for where the error is occuring and then take steps to miminize it or eliminate it. Make test cuts first, then adjust accordingly until you get the results you want. Use stop blocks to maintain consistent cut lengths. Plan your work so that once you have your saw set up properly you make all the necessary cuts for your project at the same time.

Well, I've rambled long enough and hopefully some of this helps. Good luck and have fun making sawdust!

[wood-n-things]

Bill pretty well summed it up. Thanks for the great information Bill. Spot on!

Let us know how it comes out for you. I personally don't like 45's but if I use them I place a spline in them for more strength.
Just my 2 cents.....

[Pajaro]

Originally Posted by VB...

I'm sure people will laugh at me for asking this one. LOL
</IMG>

Do like I do. Cover them up with some kind of trim if it is a picture frame

[ubgoofy2003]

VB, are you saying that you shoot brads into the mitered corners to assemble the pieces? Is it picture frames or what. It is difficult to keep the wood together when forcing a brad into it. Picture framing, as I do it, is difficult as you say, but, I just use my disc sander to even the miters out. I dry place the pieces & then if needed, I just sand the heal or toe depending on what is needed to square it up. There are some jigs that will work nicely on your table saw too.. Hope you get it worked out OK, I know how it is. Perk

[Mick Walker]

VB, you can cut perfect 45° angles but if the opposing sides are not "EXACTLY" the same length the whole thing will be off. I am assuming you are talking about picture frames. I either stack cut the opposing sides or use a stop block to insure exact length. I use a miter saw with an 80 tooth Freud blade. Just a tiny opening at the joint, I thin some "Elmer's Glue All" with water, paint it into the joint with a small artist's brush then sand the joint filling in the tiny gap.

[unixpro]

There is actually a secret to mitered cuts -- use both sides of the blade. Set your blade (either table or miter saw) at 45 degrees. Cut one part with the line on the left side of the blade and the other with the line on the right. Hmmm...that doesn't communicate it well.

OK, take the table saw. Set up your miter gauge at 0, but have a jig that is a 45 degree triangle. Set the miter gauge into the slide on the right side of the blade and put the jig on the miter gauge with the 90 degree angle on the right side of the gauge. Put one piece of wood on the hypotenuse of the triangle and make the cut. Now move the entire setup over to the slide on the left side of the blade. Flip the triangle over so the 90 degree angle is on the left and place the other piece of wood on the hypotenuse. Make the second cut.

Since you've used the same jig with the miter gauge set at the same angle and the blade at the same angle, the two cuts will line up to exactly 90 degrees.

Oh, and make sure that UP is the same on both pieces. That is, the side that faces front in the frame should be up on both cuts.

Does that make sense? Maybe the picture will help.

[VB...]

I was actually using old 4" molding to build a bird house. When I joined the bottom sides manually they looked good. But when I used a little wood glue and nailed them together they started coming apart on both sides. I will try to attach a picture tonight. When I started posting to this forum I was looking to build a jewelry box for my wife. I still want to do that but I was 100% sure that I would be using 45 degree mitered sides to put the whole thing together.

I built the bird house just to get some practice making the cuts. But I seem to have had the same issue back when I built my shop drawer as well. The cuts seem to want to pull apart when final assembly is ready.

I did make sure that they were the same size boards. I confirmed their size after I mitered them and I stacked them back to back. They lined up perfectly. Once I glued them it was another story. I was thinking maybe I should glue one side at a time?

[Bill Wilson]

Another factor is in the assembly of the mitered joint. It is important to keep the members square to each other and to apply clamping pressure evenly. It could be that when you nailed the joint, it was forced apart. If your joints all fit well upon dry fit, then I would look closely at your assembly process.

Did you clamp the joint together before nailing? If not, I would try that. If you use a glue with some open time, it gives you a little opportunity to fuss with the joint, making sure it lines up before it becomes permanent. If the joint isn't going to be under any stress after assembly, you may not even need any mechanical fasteners.

[VB...]

Thank you folks. As always lots of good ideas. I will try a few and see if I can get better results.

VB...