Introduction: Adding Wooden Splines and Some Nice Feet to Your Wooden Boxes

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About: Just a hobbyist. I make stuff from wood, play with my CNC Router/Laser and generally just turn big bits of wood into sawdust and smaller bits of wood. Made some furniture pieces, a couple wooden clocks and so …

Splines & Wooden Feet

Small wooden boxes are a great way to use up odds and ends of different woods you have laying around the workshop. Unfortunately, small wooden joints, are typically not terribly strong and sometimes need a little extra work to make them more robust. One simple method of making a joint stronger, is to add wooden splines that are glued diagonally across the joint. Done correctly, and using a contrasting coloured wood, these splines can add a nice bit of detail to your work and make a plain box, stunning.

I'm assuming you already know how to make a basic box carcass (four sides with no top or bottom). These can be made with mitred joints (45 degree edges that glue together like in my example), but they could also be simple butt joints that are glued, dowelled or **nailed together.

The following steps will show the general process, but won't go into a huge amount of detail.

As well as the table saw, we'll also use a router to cut out the base of the box to leave behind some wooden feet. Again, this is a very simple process that can give some nice results.

**Warning. Later in this project, we'll be cutting through these corner joints with power tools. If you've used metal nails (as opposed to wooden nails) it is critical that you know where these nails are so you don't hit them with your blade. High-speed blades hitting metal can cause catastrophic failures of the blade. Serious injury or death is a distinct possibility. If you use metal nails. Don't use power tools.

Step 1: Gettin' Things Flat...

Flatten the Top and Bottom

Your box carcass needs to have a nice flat top and bottom. This can be done using general woodworking tools, with you choice largely dictated by:

  • How much wood needs to be removed
  • How strong the box is currently
  • What type of wood you're using, and
  • What tools you have available

I'll often use my larger planes to smooth around the top of the carcass, and using the plane diagonally, allows me to get the ends and sides all roughly the same height.

Care needs to be taken doing this, as this can place a lot of stress on those glue joints we're trying to protect and can also cause chipping and splintering if you're cutting across the grain. A very sharp plane and some nice whisker-fine cuts are what we need here.

If you don't have a plane, just bypass this and go straight to the sandpaper...

Sanding to Finish off

When things are getting close, depending on the finish left by your plane, a simple way to finish things off, is to lay a sheet of sandpaper on a flat surface and to just gently rub the box across it until all edges are nice and flat.

Most hardware shops carry cheap sanding blocks that have clamps at each that'll hold a nice long strip of sandpaper, these can be great for sanding off high-spots, sanding the sides and ends, and just generally cleaning things up.

I'm perhaps stating the obvious, but:

  • At this stage, we're basically just trying to clean things up and to get everything flat & square.
  • ALWAYS sand "with" the grain of the wood. Yes, this is difficult when flattening the top & bottom, but the more you sand "across" the grain, the more work will be needed when finishing things off.
  • Start with reasonably coarse paper (240 grit) and whenever the paper becomes too dull, change it for a new piece

Step 2: Fill and Sanding Smooth Any Blemishes

As you're sanding, now's a good time to fill any minor defects, crack or holes that may exist.

One technique I prefer, is to use coloured wax. Most woodworking shops will have these waxes and you'll find they'll generally have a bundle you can buy containing six or seven different colours. If needed, these colours can be blended and mixed to suit whatever timber you're using. I've generally found more success with wax for small defects than I have in using other wood fillers and putty - keep in mind I generally prefer to use oils and wax finishes rather than stains, so make some tests on a few scraps first.

To apply, I'll generally just rub the wax into the defect, allowing the hole to be filled in and the surface to get a nice thick coating of wax. Alternately, you can use a small flame to drip molten wax into the defect - this works well for deep cracks and holes you're trying to fill completely.

Once filled, gently remove the excess wax from the surface with a sharp chisel (careful here, keep in mind we're removing wax - not wood).

Take your time. Fill defects, sand with 240 grit paper, then check and refill as needed. Check all the joints for glue gaps and cracks. Glue gaps can be filled with additional glue if they're not too wide, otherwise, consider using the abovementioned wax. Clean up any glue on the surface - this will be a pain later if not done properly.

Wax, sand, inspect, repeat...

When things are looking good, then move on to 400 grit paper and begin the process all over again.

Remember, you wont remember the hours you'll spend doing this, when your able to enjoy the beautiful results for the next few decades...

Step 3: Sanding Sealer (and More Sanding...)

Now for the "one simple thing, that will amaze you" part of the process. Sanding Sealer

One of the secrets to a beautiful surface, is to use a Sanding Sealer. This hardens the wood fibres allowing the finer sandpapers to cut them off, it fills microscopic gaps & cracks and generally just makes things smoother.

One the easiest sealers, is to get some liquid Shellac and to dilute it with Methylated Spirits. I'll generally dilute it roughly 8 or 10 parts Metho, to 1 part shellac (too thin, it doesn't do much, too thick, it gunk's up the sandpaper and adds extra work).

Using the sealer is simple. Wipe it on generously with a cloth until the surface is nice and wet. I'll typically flood the surface and wipe off the excess. You want the wood thoroughly soaked.

When dry, sand the surface with 400 grit paper until it looks nice and flat and smooth. Give it another coat and sand again. SANDING WITH THE GRAIN AT ALL TIMES - A small cork or wooden sanding block will help enormously. Keep the sandpaper from clogging up and change it regularly as required.

Remember, we're not adding anything here (it's not like painting), we're simply sealing and hardening the surface of the wood, and then sanding it smooth.

Step 4: Cutting the Spline

Ok, enough with the sanding - there's more of that later. Now we need to add the splines we first spoke about.

I'll be using my table saw, but this can be done equally well using a router table. Depending upon your design and taste, your splines can be nice and thin, alternately they can be thick and chunky. Once you see the how easy they are, you'll quickly see a million different ways you can use them.

The one critical requirement in whatever method you choose - the cuts you make must be even, and they must be repeatable. I've made a jig to assist doing this, which is simply a thick piece of wood attached to a board at approx. 45 degrees.

  • The angle isn't critical. Providing the box is clamped the same way for each cut, even if there's a bit of an error from one face to another, you'll never notice it. If any of the cuts are different on the same face however, it'll look terrible
  • The box is clamped against the jig and the depth is set.
  • The jig is 'sacrificial' - the saw cuts through the jig and the box
  • The wide part of the jig rides against the fence
  • Once the distance is set, turn the box to 'mirror' the top and bottom cuts - don't try and adjust the fence

Typically, I'll set the depth so the blade doesn't cut 'through' the box. I have however, sometimes purposely cut these splines deep enough that they become internal supports for a removable tray.

Step 5: Cut Some Contrasting Splines

Once the box carcass has been run through the saw or router to make the cuts for the splines, we now need to make the splines themselves.

  • Generally, it looks nicer to use a contrasting coloured wood, but like anything in woodwork, the choice is entirely yours
  • Cut the splines a fraction thicker than needed. They can then be sanded down to size (not critical if your saw leaves a reasonably smooth face). The faces don't need to be smooth (a rough surface helps the glue) but they do need to be flat.
  • Once you're set up to cut the correct thickness, make some extras - they'll be handy for your next project...

Step 6: Time to Glue the Splines Into Place

Some 'Tricks" for your splines:

  • The splines need to be a nice firm fit into the cuts in the sides of the box. They don't need to be so tight you need a hammer (they'll break), but you don't want gaps either...
  • Have a close look at the profile of the saw or bit you used to make the cuts in the box. Does the kerf (the cut you made) have a square bottom or is it rounded? The kerf from my circular saw blade is square bottomed, but many are not. Whatever the shape is in the bottom of the kerf, you'll need to make the edges of your spline roughly the same. If the bottom of the kerf is rounded or angled slightly, run some sandpaper along the edges of the splines to roughly match it (doesn't need to be perfect). If the kerf is flat bottomed, leave the edges of the splines nice and square.
  • If you're using very light coloured woods, use a glue that dries clear. If one of the wood types is dark, any glue will be fine.
  • Most wood glues will be fine. General purpose glues will soak into the spline allowing it to swell slightly, filling any minor gaps.
  • Wipe the glue onto the spline, put a small amount into the cut and then fit the spline firmly into place. A few gently taps with a soft hammer will help seat it. Pay attention to ensure the spline is fully seated in both ends of the cut.
  • Wipe away excess glue with a damp cloth - this will make clean-up easier later and reduce sanding

I use a "flush-cut" saw to cut off the excess after the glue has dried.

Then, it's back to:

  • Sand with 240 grit to get the splines and sides of the box nice and smooth and to remove any glue
  • Fill small gaps with wax
  • If one of the splines didn't go all the way in and you have a large gap - you'll need to fill that with the same coloured wood as the spline (or use wax of the same colour). cut a small "wedge" of spline material and tap it into the gap with some glue. Alternately, sand some of the spline material until you have enough sawdust to fill the hole. Mix the sawdust with some glue and fill the hole.
  • Once the box is looking good, move on to the 400 grit paper and keep going. Feel free to give it another good dose of sanding sealer, with a good sanding with 400 grit after each coat.

Step 7: Now for the Base and the Feet...

To make the base with the feet, cut two pieces of wood so they're approx. 20mm (approx. 1") wider and longer than the box. One will be the Lid, the other will be the bottom.

Flatten & prepare them as you would with any timber.

For the Bottom, I'll put a nice wide chamfer on it with either my router or a plane. For this box, I've made it so that the 45 degree chamfer reduces the 'flat' surface of the wood so it's roughly the same size as the box. This was approx. 10mm (1/2") all the way around - which is why I made it 20mm larger...

Using the router table, I then used nice wide bit with a rounded profile, to make a series of cuts all the way across the bottom surface, stopping approx. 15mm (3/4") from each edge. Turn the wood 90 degrees and cut again until you're left with four square bits in each corner. these are the "feet" The depth of cut was sufficient, to stop just short of the chamfered edge.

Sand and smooth this as best you can, paying particular attention to the four feet, making sure not to chip them. Smooth away the router marks as much as you can, however these wont be visible in the finished box.

Step 8: Hinges Cut In, Bottom and Lids Attached

As mentioned, I've assumed you know how to do most of the basics, so I'll not go into too much more detail.

Measure & mark your hinges, then carefully cut them in with a chisel. Screw the lids on, and glue and pin the bottoms into place.

On mine, I added a low-angled chamfer to the lids and engraved a name into them to add a little personalisation.

The bases are put into place and a couple of 1.5mm holes are drilled through the base and into the sides. These holes allow me to use four small 1" brads (nails) to keep things in place, while the base is glued into position. The brads add a little strength, but the glue is what actually hold the bottom in place. The head of each brad is punched below the surface and the tiny hole is filled with wax and sanded until it's invisible (I usually dislike using nails, but I'm not keen on just using glue on its own - mind you, the result is really strong).

Many thanks to those who've bothered to follow this. I've never tried making anything into an Instructable before and the images used, were taken for showing a friend. Maybe if I do this again, I'll get my camera out, instead of just using my phone...