Last time in this series I put together some drawer boxes. Next they’d need slides, and for that I went with parallel sliding dovetails, which I first saw GaryK create in walnut here. I’ve wanted since I saw those early last year to try my hand at making some. I spent some time one night last week building a SketchUp model based on GaryK’s photos of his results and designed around a bit I had from the Incra set, then wrote up a plan of attack for how to go about building them. This is the kind of thing where if I don’t have it all detailed out, I’ll screw up somewhere. There are things I’d rethink for next time, especially the retaining peg and groove placements. I got a tad under full extension, when I should have been able to get a tad over.
Anyway, I needed a 3/4” thick piece, and two 1/2” thick pieces, all 3” wide. All of my pieces were 3/4”, so 4 of them had to be thicknessed somehow. My planer is out of commission until I order some parts (I got the bearing in for it awhile ago, but destroyed it trying to press it on with a clamping rig I threw together, sadly). I’m uncomfortable by far (especially with no medical insurance at the moment) resawing on my table saw, and my band saw isn’t accurate enough, especially now that the blade is pretty dull. I don’t have a good way in my router sled setup to hold down a small piece of light 3/4” wood, and the jointer – as we all know – doesn’t ensure parallel sides (I tried anyway, and it got more and more ‘off’ as I went). That left my mini mill.
I lightly surfaced the sacrificial aluminum plate I made for it long ago using a fly cutter, which is like a lathe tool held at a downward diagonal in a bit in the spindle. This scribes a circle which planes a surface when that surface is moved parallel to that circle. This ensured that the surface was trammed without all of the work of setting up test gauges and tapping on loosened joints and such, and it meant I had automatically zeroed out the bit height, and that meant that when I stuck a piece of wood to it, moved the bit up, and planed the wood surface, it would be parallel to its own bottom, and exactly to thickness, and in fact it was ridiculously so, to better than 0.001” by my digital calipers!
Here’s a time-lapse:
And here’s a segment in actual speed:
I had originally used 2 dots of CA glue to hold the wood down, but the fibers tore off, and in the time-lapse you can see me chiseling and sanding the wood off the aluminum in the beginning. After that I went with double-stick tape, and it was actually tacky enough with light cuts (0.05”) to hold securely and still give 0.001” accurate thicknesses, all pretty automatically, as I’d written a few lines of code to have it loop around, planing the parts lower and lower toward the target thickness.
Then it was on to the work. Here’s another time-lapse of setting up my Woodpeckers/Incra table, then grooving the pieces. I didn’t record any of the dovetail creation, so they’re already done in this video. I’m just adding retaining grooves, hammering in the pegs to retain the pieces together, and at some point panicking when slides glued together. I was using CA glue on the pegs, because I didn’t make the sections that hold the pegs thick enough, and was worried they’d torque when stopping the slides and pull out. I was able to hammer them free and clean up the insides, but they’re a little scratchy now in action. They were so smooth before. Sigh…
You can see that I had to chisel away part of the top of each slide in order to fit in the last retaining peg. This was yet more poor design work in SketchUp. I hadn’t fully planned it out in there, and as I said in the first paragraph, if I don’t have it all locked down, I find ways to screw up. Too, the pegs should really be going in the top and bottom of the entire slides, and should be retaining the middle piece. I have 3 (1 one way, 2 the other) retaining the outer pieces. If I want to go full extension (this falls shy about 0.25” or so), then it would be even harder, as the pegs would be more hidden. The problem was that putting in the pegs for one side precluded being able to later put in the peg on the other, as now it was blocked.
I want to say that the Incra LS Positioner makes things like sliding dovetails too easy to brag about. Here’s a little time-lapse of the setup of the lift’s height, and then setting up the fence with an accurately machined square that was exactly 1.000” wide up against the side of a 1/2” shaft router bit. Clicking things into place with the positioner’s click wheel, which is 1/32 of 1/32” per click (1/1024”!), then lowering the bit shaft into the table, removing the square, and moving in by 1-1/4” and zeroing it out, it was trivial from that point to simply move the fence to each position, which were all on half-inches, and run the dovetails. There was almost no thinking involved, and no mistakes. Anyway, setting up the lift/fence (I set up the fence and bit height in the last half):
I’ll skip deep details about the slides, as the video later in this post explains pretty much everything. I’ll say, though, that when I make these again (I’m sure I’ll make more eventually for another project), I will go with smooth hardwood, and I will run some test pieces to make sure I get tight dovetails. I will also leave more wood vertically so the pieces aren’t quite so bendy. These were all just a whisker loose, which was actually helpful with the bendy softwood, which had a kind of fibrous surface that upped the friction. It means there’s the tiniest bit of sag and wobble, however, in the finished product. Here are some fun pics of the scrap tulip poplar (not true poplar) slides:
And here’s me rambling about the drawer carcase, drawers, walnut fronts, pulls, and I get around to talking about and showing off the dovetail slides, which at this point are not installed.
I’ll note here that the video is clipped. Apparently not all of it uploaded to YouTube, so the last minute is missing. It’s no matter, though, as the next video ramble will contain all of that info again. I was just saying what I was planning to do, and in the next video I’ll have actually done it :)
The Incra setup let me come back later and put the retaining grooves and peg holes in basically automatically. You just flip the handle, slide it visually on the ruler, then flip the handle back, which engages 1/32” teeth and pulls it all in to at least 0.001” accuracy. That’s why these grooves are so nicely centered on the dovetails, though it was much later that I added them:
Later I moved from these 1/8” grooves to 1/4”. You can see there’s a little filled 1/8” hole to the left of this groove, because I had the piece in backwards between the stops, cutting toward the wrong end, and realized the error just as I started. I actually took a scrap of the same wood and turned an 1/8” peg in my lathe to fit that, then glued it in and trimmed it flush:
Next time around I’ll show how I got everything installed.
-- Gary, Los Angeles, video game animator