The quest for a perfect miter joint

[Dick Snyder]

I am making a set of three stacking tables. Each table will have a 2 1/2" wide piece of mahogany to trim the center rectangle of curly maple (still deciding on the center). I got my technique down to get nearly perfect miter cuts on my SCMS but the saw makes a slighly rough end cut that I would like to be able to smooth off to get the best possible fit.

I tried to clean up the cuts with the sanding disk part of my combination sanding disk/belt sander. It is a Ryobi I got for $99 at Home Depot a couple of years ago on sale. Well, now I know why it was only $99. I could never get the thing to sand the cut perfectly smooth. No matter how I fiddled around with the (very cheap) miter gauge on the sanding disk, it always sanded one end of the cut more than the other so I got a slightly rounded surface. I guess $99 was TOO much to pay or more realistically, I shouldn't have gotten it just because it was cheap.

The cuts aren't bad but I can't think of any way to sand the rough ends of the cut to get an even better fit. Have any of you solved this problem?

TIA.

Dick Snyder

[Swingman]

"Dick Snyder" wrote

Got a table saw?

Consider making a "miter sled" like the one on the Jig and Fixtures page of my website.

Big plus is the _exact_ "45 degree" angle basically becomes a moot point (particularly with the usual widths of picture frame miters) because the order of cut, using an established 90 degree corner to build the sled, insures complementary angles, and the jig allows you to use a stop block to insure the sides are all cut the same length.

These two concepts combined make miter cutting a much easier task, with little or no tweaking.

[Dick Snyder]

I do have a table saw and I also have a miter sled I made. Unfortunately the miter sled I made does not have stop blocks. I made it for cutting one end of a piece of wood and it does a fine job at that. I may make a better miter sled like yours that has stop blocks but since my SCMS is doing a perfect cut now, I just want to find a way to smooth the cut ends of the wood while not losing the perfect 45 degree cut. Thanks for the reference to your sled. I like the way you did it and will probably copy what you did.

[Swingman]

"Dick Snyder" wrote

Perhaps a better blade on your SCMS so further sanding is not necessary? I have a Forrest Chopmaster on my Makita and resultant miter cuts are glass smooth and glue ready, no sanding necessary.

With miter cuts, if I don't get the quality I need on the initial cut, sanding seems to add more problems than it's worth. I hope your luck is better than mine in that regard.

[Dick Snyder]

Excellent point on the blade Karl. I have a Forrest Woodworker II on my table saw and it was absolutely worth the high price I paid for it.

[Dick Snyder]

While I am at it, if I do copy your sled are there any improvements you would make if you did it over again?

[Swingman]

"Dick Snyder" wrote

None that I can think of. It does precisely what it supposed to do - give you perfect miters - and it's damn hard to improve on perfection. :)

The most important part of building it (other than getting the miter slot runners parallel), is to be anally precise about insuring a perfect 90 degree angle on the plywood board that makes up the two opposite "fences". I was lucky in finding a factory plywood edge that was nuts on, but it really pays off down the road to be overly picky about this one factor.

Do so, and even if you are a little off in placement of this part on the sled, you still have the complementary angle principle working in your favor when you cut adjacent miters on opposite "fences".

["<<<]

[dadiOH]

Put a sanding plate on your saw.

[Scott Lurndal]

How big is your sanding disk?

I usually use the 12" disk sander and clamp a guide board to the cast-iron table at 45 degrees to the disk. Then just keep the workpiece tight against the guide board. Don't bother with miter gauge at all. You're doing pretty light sanding, I hope, so you don't need to press hard or you'll burn the end.

scott

[SonomaProducts.com]

[Dick Snyder]

For $99 there was no cast iron table and no 12" disk. It was a mistake to get this thing!

[BillB]

[John Grossbohlin]

This situation screams for the use of a bench plane and shooting board. There is a clip in the subscription section of the FWW site and there are tons of other references on the web and in books and magazines...

The upside of using a shooting board over something like a Lion Trimmer is the bench place can be used for myriad other tasks.

John

[Larry Blanchard]

You can get a 10" sanding disk for your table saw. Get the one with one side tapered.

[Leon]

Dick, the problem with sanding or trimming a miter cut after cutting to length on a saw is that it ends up being too short. If you sand, you have to determine how much to over cut and how much to sand off, it's a crap shoot at best unless you have a stop to sand to a particular distance.

I suggest a Dubby Miter Sled or the new Rockler Sled.

cut a clean miter you need a sharp and a good quality regular width kerf blade. The Forrest WWII works well for this purpose. You also need to be certain that opposite parallel pieces are precisely the same length or they will never fit together tightly regardless if you are cutting dead on 45 or not. Because the pieces have to be precisely the correct "LENGTH" sanding will almost always change the length of the piece of wood.

[Keith nuttle]

Just a comment, It does not matter how close to perfection the miter cut is, if the opposite sides of the frame are not absolutely the same length the miter is not perfect.

[Rich]

I've found the best method for me is to glue up two joints 180 degrees from each other then trim as needed after the glue dries to get the last two joints the best you can get then glue them and move on. We woodworkers inspect things on a level that won't be viewed after the painting and glass goes in!

YMMV, Rich

[John Grossbohlin]

This is another place where the shooting board is handy... if pieces aren't exactly the same length, or not perfectly straight, the miters can be adjusted by using paper shims to adjust the position of the stock on the shooting board.

I posted a couple photos of cutting and shooting miters on ABPW that show how a shooting board would be used for this purpose.

John

[Father Haskell]

80T crosscut blade. Even my 50T Freud Diablo will give me glue-ready joints straight off the table saw.