Friday, December 4, 2009

What Mistake?


So here I am, on a roll and ready to breeze through some more stopped sliding dovetails. I've got the process down pat and looking forward to the challenge of hand cut mortises. I finish two of them rather quickly and sit back feeling good about what I've done. Wait... that doesn't look right. I laid out one of the dovetails in the wrong place. Yup, the ones for the front of the case. I'm an idiot.
     After cursing under my breath (Ryan was playing trains in the cottage next to me) I try to figure out how I was going to recover from such a stupid mistake. My first thought was to leave it and move the rear drawer divider up to match. Doing that wouldn't require a patch that may be seen, even if I would be the only one who would notice. It would, however, change the drawer sizes which would be kinda lame since I made an effort to design them to be graduated in size.
       In the end I decided to stay with my design and  patch it. I was skeptical at first, but I decided I could find a reasonable match to make it happen. As a result, I think it works and I have something new to blog about. Here is what I did...

     I used the same cutting guide to make a few pieces to fit in the errant dovetail socket. I'm getting better at being creative with the clamps.

     I glued all three in the socket, leaving the best fitting piece for last. The result looked a bit rough but I was optimistic.

     A little work with the block plane...

     ...and a scraper...

     ...crisis avoided. Now,  I just have to find some way to keep from cutting another dovetail socket in the same place!

     So there you go. I screwed something up, but instead of changing the design I decided to fix it and move on. Design proportions taking a priority? Maybe George Wilson is getting to me after all.


Wednesday, December 2, 2009

Stopped, sliding dovetails... by hand.

     While there is a virtual smorgasbord of information on through dovetails by hand, there isn't much on sliding or stopped sliding dovetails by hand. I did find an excellent tutorial on sliding dovetails by Derek Cohen, a woodworker in Australia. There's also one by Kari Hultman (is it my imagination or do I seem to mention her in almost every post?).  Actually, I'm not even sure of the correct name for this joint. I've read about people calling it a housed dovetail, half blind dovetail, a dovetail dado, and a grooved dovetail dado just to name a few. For now I'll just refer to it as a stopped sliding dovetail, kinda like a stopped dado. Anyways, while similar to the sliding dovetail, it seems to be a different animal when you think about creating one. You can't just saw an angled kerf through to the other side. It's stopped to the width of the piece being housed in it. Most sensible woodworkers just use a router with a dovetail bit and a jig. Some woodworkers prefer to rout out most of the waste with a straight bit and then finish up with the dovetail bit. It's routed out to length and then squared up with a chisel if you wish. Since I didn't find exactly what I was looking for, and since I've never been fond of electric  routers, I decided to accept a challenge to figuring out my own way. After a lot of daydreaming and tinkering in the cottage, I came up with a process that works for me.
     The first thing I did was to make 2 guide blocks for sawing, beveled to the angle of my dovetails. I made two because I wanted to put a fence on them to make for a quicker setup. Not only could they be placed without a square, since the fence was a continuation of the angle I could easily see where the guided cut would end which takes out a lot of guesswork and layout time. I also made another guide block with the same bevel to serve as a paring guide for the drawer support pieces.

     Since the guide blocks take care of my angles I only need to layout and mark the location and thickness of the drawer supports, and the depth of the dovetail socket. I cut two measuring sticks. One to the height of the bottom drawer and the other to the height of the top drawer. I used these to mark the location of the drawer supports on either side to make everything consistent. As with my carcass dovetails, I used masking tape to make everything more visible. I marked the thickness of the drawer support using an offcut (offcuts are great to keep during a project for times like these, just be sure to label them). Then I used a marking gauge to mark the depth of the socket. 

     At this point I have all the info I need to make my cuts. I place the sawing guide block over the layout marks so that the fence registers with the bottom corner of the layout. I start the cut with my crosscut back saw, keeping the saw pressed against the guide block. I try to be careful to saw down to the depth mark on the edge. On the face I saw past the mark because it will make for less work chiseling out the waste, besides it will be covered by part of the drawer frame.  For me the key about using a guide block for this has been to not depend on the guide so much that I forget good sawing techniques. Keep a relaxed grip and your arm in alignment. Wax on the saw blade doesn't hurt either. 

     The rest of the kerf will be cut to depth using a Japanese dovetail saw. This works well because it has teeth at the tip enabling it to cut all the way to the end of the dovetail socket,  and it cuts on the pull stroke which keeps the sawdust from clogging things up. I put a piece of tape on the blade to mark my target depth. 

     After both sides of the dovetail socket are cut I use the chisels and a mallet to knock out the majority of the waste. I pay careful attention to the show side of the joint removing just a little section first. After this I can knock out the rest pretty easily. 

     Two things I found helpful are to take only a quarter-inch at a time and to twist the chisel after splitting each section to try to turn the waste chunk making it easier to remove without getting it wedged-in. If there's still a lot of waste left after the chopping you can run the chisel parallel with the depth to clean it out a bit.

     If you're really good I suppose you could finish it all up with the chisel but I am fortunate to have a router plane. This is neither as loud or obnoxious as its tailed equivalent. I set the depth and rout the bottom to a finished depth. Skewing the blade help to get into the corners. Having a perfect bottom is not important. As long as the angle of the walls are right and the drawer supports are cut right I should have a tight fit.

     Cutting the dovetail tenons are much easier and faster as I had thought. I've seen this done easily with a dovetail plane. I don't have a dovetail plane so that means I'll be using a chisel. After coming up with this next part I don't think I'll be wanting a dovetail plane anyway.
     The nice part about cutting this joint is that the angles are all the same. I made a guide block to use as a paring guide with the same bevel angle as the other guide blocks. The way I use it is about as simple as it gets. I position it at the end of my drawer support on the bench and secure them between the wagon vise and a bench dog. I put a clamp near the middle of the stock to keep it from bowing up from the pressure.

     I make sure the top edge of the stock meets the edge of the beveled guide block. Here I use playing cards as shims to make it even. 

     I've marked the shoulder to the depth of the dovetail socket, made a deep cut with a marking knife and square and then cut a fence for the saw with a chisel. Making a fence, or trough, for your saw to ride in is a great technique. Clean, accurate cuts every time. Using a wide chisel, you can find the depth of your shoulder. I'll cut down to this line with  my crosscut saw.

     To pare away the waste I've found it easiest to cut across the grain with a wide chisel, working down to the angle of the  guide block when half of the chisel is riding on the block and the other half is cutting the dovetail tenon flush. The amount of waste is small so this all goes surprisingly fast.

    At this point you can fit the pieces together and adjust as necessary. The few I've done so far have not needed to be adjusted much at all. Lucky, I guess. What has resulted is a strong joint ready for glue. This may not be picture perfect but it's the drawer support in the back. I need to watch my layout lines better for the ones in the front.

     Well, that's what I've come up with. I'm sure there are other ways to skin this cat. If you have any other techniques please feel free to share. Until then, I have to finish up the rest of these stopped sliding dovetails and move on to mortise and tenons (by hand of course), moulding, the dresser base and eventually  drawers. We're getting there, a little bit at a time. Oh, and if anyone knows what the official name of this joint is please, let me know!