Best way to cut an interior 90 degree angle for L-block

[Win]

Hello experts,

I am new to woodworking and am trying to make a picture frame clamp, which calls for 4 identical jaws or L-blocks with a 90 degree interior angle. The blocks will each be cut from 3/4" stock 2"x2" square. I can either cut out the angles first or cut out the 4 square blocks followed by cutting the interior angles (which is preferred?)

What's the best method and tool to use to create these 4 identical 90 degree L-shaped blocks? I guess what is more important is the exact 90 degree cut than the shape or sizes of the 4 pieces. The 2 cuts are 1" into the block.

The tools I have at my disposal are: table saw, band saw, compound mitre saw, and a router. If using the table saw, I would prefer clean cuts where the table saw blade does not "run" or cut into the wood beyond the interior corner. I tried making multiple passes using my table saw by raising the blade up 1" but found out my blade leaves a curved cut at the top (is this what you use a dadoe blade for, which I don't have yet?)

Do I need a jig to accomplish this, or is there a good trick to doing this?

Thanks for any help on this. My wife has been waiting patiently for me to finish my custom frame project, which I'm all set and ready to glue. Just missing the clamp!

Cheers,

-Win

[Jim Wilson]

ex - former spurt - a drip under pressure expert - a former drip under pressure

(G)

Note that when you cut an L-block out of a solid piece of wood, the two legs won't have equal strength if the cuts are perpendicular or parallel with the grain. The side with short endgrain will be very weak. You would be slightly better off to cut them at a 45-degree angle to the grain.

Secondly, instead of an L out of the corner, you can have even more strength by cutting a V out of the side of a block, like in this nifty ASCII diagram:

----- | / | / | \ | \ -----

That interior angle should be 90 degrees -- so much for nifty ASCII diagrams... BTW, the grain should be going up and down in that picture.

With this geometry the work can be clamped along the diagonals, using only two clamps instead of four. The direct diagonal control also makes it easier to square the frame.

Since the blocks are so small, all your cuts for the L's can be accomplished safely and accurately using a crosscut sled on the tablesaw with the blade tilted to 45 degrees. If you don't already have your crosscut sled, now is the time to make it. You'll wonder how you ever got along without one.

Cut your blocks 3" square or 3" long x 2" wide instead of 2"x2" because the diagonal of a 2" square is almost 2-7/8". Clamp a stop block on the crosscut sled fence about 2-7/8" from the kerf. Raise the blade so almost

2" projects above the sled (measure along the blade, not vertically). Butt the first block against the stop, cut, flip the block and cut again. Raise the blade just enough to finish the inside corner of the V, and then cut the remaining blocks.

If you still really want to make L-shaped blocks, then the crosscut sled is still the right tool for the job, but you may need to clamp the workpiece to the sled fence to keep your fingers...safely away from the blade.

If you don't have a crosscut sled and really don't want to make one (just yet), then bolt a board to your miter gauge and use that.

Cheers!

Jim

[Scott Brownell]

Cut your blocks to size. Mount a sacrificial face to your mitre guage, clamp a stop block to it set at whatever width you want the legs to be, raise the blade to your depth of cut and holding the blocks vertically against sacrificial face make your cuts. Bingo-bang done.

Scott

[Jay]

I made something similar for what others might call a pitiful cabinet door clamping mechanism (Worked fine for me, though.)

I used 2" thick board so that I could more easily clamp from the sides as well as the tops without my clamps fighting each other.

I took a 2" X 12" X 6' and measured in 11 1/2" inches to make a square. Then I drew a concentric square (My high school geometry teacher would love my bastardization of that term) that was 9 1/2" X 9

1/2". I set up my router with a straight edge guide and a 3/4" straight bit and a 3/4" depth of cut (I was using these for 1" pine boards). I roughty routed out the innerds of the inner square, starting at the center and working my way out. After I had gotten a good chunk cleared without getting too close to the edge, I clamped down my stright edge router guide and carefully routed the inner square's edge without crossing over the sides of the corner. I was left with a rounded-corner square. I used a chisel to square off the corner, double checked with a metal square. After that, it was three cuts of the circular saw and I had four perfectly size corner clamp fixtures.

After all of that, I decided I couldn't do without dust collection anymore :)

Jay

To reply, replace junk with jay

[Larry C]

I'd personally use the bandsaw, but my real reason for replying is to give you some alternative ways of thinking about this.

It sounds like you want exact 90 degree corners on the blocks so they will square your picture frame. If you measure diagonally across your frame you can easily adjust your clamping pressure until the diagonal dimensions are equal rather than relying on the clamping blocks. In fact, you should measure the diagonals regardless of how you clamp the frame. When the diagonals are equal the frame has to be square, or more accurately the corners of the frame have to be 90 degrees. Therefore, you don't need an exact 90 degree block when clamping. With that said, I'd still want the blocks to be as close to 90 degrees as possible.

I don't understand why you're concerned about the tablesaw cut extended past the corner. Raise your blade up as high as possible, use something bigger than a 2x2 block and cut away until the cut on the top of the block reaches your mark. Yes, the bottom of the block will have a cut line beyond the corner, but big deal; it's only a clamping block. If you use plywood for the block it'll be even less of an issue.

Another way of ensuring the picture frame is square would be to use an L-shaped jig. Just screw two boards onto a piece of plywood. Be careful and make sure you get the two boards exactly 90 degrees to each other. Then just slide your picture frame into the corner and you know the frame is square. Then you can clamp across the frame. I'd still measure the diagonals as mentioned above to ensure it's square.

-- Larry C in Auburn WA

[Andy Dingley]

I used MDF, cut with a knife and fork (probably the bandsaw).

The angle isn't critical. It's probably best to use about 92° anyway, just to get pressure right on the corner. This thing is a clamp, not a jig. You need to put the squareness in by some other means, not just squeezing the corners.

My clamps are 2" disks, with a string groove around the edge, and a missing quadrant. Coat of wax stops the glue sticking. _Hot_ hide glue is good for framing, or Titebond - because both have good initial tack. Make a dozen - if you're doing frames, you're often doing several. .

-- Die Gotterspammerung - Junkmail of the Gods

[Win]

Thank you everyone for your valuable input, tips, and ideas. This is all really useful and have given me a new "angle" on how to look at this problem.

Regards,

-Win