Showing posts with label Bird's Mouth Joint. Show all posts
Showing posts with label Bird's Mouth Joint. Show all posts

Saturday, November 3, 2007

Saturday's All Right For Making Saw Dust

The remnants of hurricane Noel were passing off the coast today, making for a chilly and overcast day. So I went out into the shop and worked on the joinery for the cabinet. It turned out to be a good day, work wise, though I did scream at one point. No one was hurt, though I wanted to hurt something at one point.

The first order of business was to cut all the leg glue-ups to size. The blanks are 3" long & started out roughly 2.5" x 2.5". I won't tell you what procedure I used to rip them, because I really didn't do it in a very safe way. I thought about it later & realized that, given the size of each blank, I should have actually used my band saw to rip them. This would have been a lot safer. Luckily, I can still count to 10 without removing my shoes. But this isn't what made me scream.

The next operation was to cut the birds mouth joints on the 6" wide sides. The first step was to get a piece of scrap from the oak to use as a test piece. I ended up two offcuts. One was the actual test piece and the second was a piece only about 1/2" long. I used this piece to help lay out the birds mouth on the end of the test piece.

To lay it out, I used my combo square to draw a 45° line from one corner. Then I layed the 1/2" long piece against that line & drew another line that was square to the first & interesected the opposite face. Here's a picture of the test piece taken after the birds mouth was cut, but you can see the remaining layout lines on the end.

Next, I set the blade to 45°. I took my zero clearance insert (ZCI) out of the table saw's throat and inserted the original stock throat plate. I next noticed that the original plate wasn't flat; I don't remember bending it, but it clearly wasn't flat. I tried to make it flat but then I noticed a crack on one side. I guess this was defective from the factory, but since I don't use it often, I'm not going to worry about it.

Using a plastic drafting triangle, I set the saw's bevel angle to 45°. I then used a piece of scrap plywood & using the procedure in John White's Care and Repair of Shop Machines, I verified that the blade was actually at 45°.

Now I placed the rip fence on the left of the blade (my saw is a left tilt) and set it to 6" (the width of the boards I needed to cut) and set up a feather board. Finally, I was ready to make a test cut.

I only pushed the board in enough to nick the corner. I had no idea if the blade was going to cut in the right place or not, so I needed to see where the blade actually cut to make sure I had the rip fence right. Sure enough, I had to move the fence further away about 1/8" or so before the blade was cutting exactly where I wanted it.

Again, I didn't take a cut down the whole length of the board. I had to adjust the height of the blade until it cut to the exact depth I needed. A couple of adjustments and it was there, so I ran the whole length & verified the cut was OK down the whole length.

Next I ran the two boards for the base cabinet. I had to put the outside faces down to get the cut right. After these two were run, I ran the boards for the upper case. These cuts all went fine.

Now that these were done, I grabbed my test piece and turned it over. I had to adjust the fence, moving it in to get the blade to cut in the right place. I also had to lower the blade--I wanted to sneak up on the right height. Once all of the settings were on, I made a full cut to make sure the set up was good.

I ran the boards for the base cabinet. These ran fine and I got great birds mouths. I ran the first board for the upper cabinet. As I finished making the cut, I noticed that somehow, I had run the board with the wrong side down! This is when I started screaming. Unfortunately, my son was home & he heard me. He had no idea what was wrong -- I think I scared him.

So I turned off the saw, hung up my apron, and went inside to cool down. I was much too angry with myself right then to be anywhere near power tools. After watching a little TV, playing some Lego Star Wars I with my son, and eating a sandwhich for lunch, I figured out how I was going to recover from the mistake.

What I decided to do was to finish the remaining board, then reset the saw back for the first cut. Then I'd cut the screwed up board with the opposite face up. This would give me a birds mouth on the same edge, but oriented in the direction opposite of the intended direction. Essentially, the face I intended to show would become the inside face & vice-versa. The interior face was OK, except for one knot I wanted to hide, but it's going to show now. I'll have to fill it with epoxy or something when I finish.

After that, I set up the dado stack & cut all the rabbets. Each board I had just cut a birds mouth on needed a rabbet on the opposite and top edges of the inside face, and three edges of the top / bottom shelves needed rabbets, too. These went fine.

Next, the boards with the bird mouths & rabbets needed dados for the bottom shelves 3" up from the bottom edges. It took me a while to zero in on the correct dado width to make this cut. This was because I forgot that a 3/32" chipper was thicker than a 1/16" chipper. Once I had the right chipper installed, with the right size & number of shims, I got fantastic dados.

Here are the inside faces of the finished base cabinet sides showing all of the joinery cut into them. The bird mouth joints are on the outside and the rabbets are next to each other. The dados are at the bottoms and the short rabbets are at the top.

The sides for the upper cabinet are similar, just longer. All of the joinery is in essentially the same places.

And finally, here is a sample top / bottom shelf with the three rabbets cut in them. The three pieces for the back will fit into these rabbets and be glued & brad nailed through the sides into the shelves. The brad holes won't show because the backs will be against the walls. I'll have to be careful to angle the nailer so the nails don't blow out through the inside face of the plywood. And that was my day in the shop. It turned out to be a productive one with only one mistake. I still have an issue to deal with from that mistake -- the one birds mouth that I screwed up has a kerf in the middle of it. I believe I will mix up some Bondo & force it into the kerf. The bondo will be stronger than regular wood filler and will never show, since it will be hidden in the middle of a joint, and the ends will be either sitting on top of the base cabinet or covered by a top molding.

Tomorrow, if I get into the shop, I'll dry fit everything I've made so far & cut all of the back pieces to final length & width.

Tuesday, October 30, 2007

Thank God for WoodNet!

I was just over on WoodNet, reading a posting called How to clamp 135-degree joint? Near the end of the thread, there's a posting by ezflier with a link to a web page by WoodNet's own Edwin Hackleman. Edwin is a very intelligent guy who seems to delight in geometric puzzles and how to make them with the simplest possible set ups.

The page in question describes the Bird's Mouth Joint. This is a joint specifically designed to simplify cutting & putting together 8 boards to form an octagon. While I'm not building an octagon, the angle at which the face frame meets the "sides" of the corner cabinet is exactly the same. This joint looks like it will be easier to cut. Let me explain why.

Originally, I was planning to cut 67.5° miters on the edges of the side boards & the face frame stiles. I don't know about you, but I don't have any precise 22.5° or 67.5° reference angles lying around, and I don't know where you'd find any. So there would be a lot of trial and error cutting of scrap to get the saw blade beveled to the right angle.

You then have to glue these boards to each other. I had come up with a clamping caul and had posted a picture of it in that thread. As Ms. Nomer says in the thread, there might be a problem with this configuration not providing enough clamping pressure to keep the mitered edges up against each other.

The bird's mouth joint, on the other hand, looks pretty easy to glue-up. The angled board essentially sits in a socket & is self-aligning. All you have to do is clamp a beveled block to the angled piece, then run a clamp horizontally. And you're done!

So I'm gonna give this a shot using some poplar scraps I have lying around at home tomorrow night. Tonight, I'm going to WoodCraft after work & use their jointer. And maybe a table saw to make sure I have all the edges straight & parallel. Or maybe I'll do the ripping another night at home. Let's see how busy the place is.