Hexagon Patterned Plywood Coasters

Plywood can be cut up and glued back together to produce all manner of interesting patterns. I opted to make a hexagonal pattern and then inlay it into offcuts of engineered oak flooring (basically, that's plywood with a layer of oak on top) to make a set of coasters. It's a lot easier than it looks and a great way of using up scrap ply and flooring to create something both useful and attractive.

Full credit is due to the king of patterned plywood, Michael Alm, whose Hexagon Patterned Plywood video showed me how to make the hexagons. However, if you watch his video you'll see that I've cut a few corners, like only using diamonds to make my hexagons instead of a combination of diamonds and triangles, and not running the hexagonal prisms through the bandsaw to tidy them up. This simplifies the process and, I think, still produces a good enough result.

You'll need

• offcuts of good quality plywood, about 12mm / ½" thick - I used 11mm
• scrap pieces of engineered hardwood flooring, at least 12mm / ½" thick
• a table saw
• a fine-toothed bandsaw or a hand saw and mitre box
• wood glue
• rubber bands
• a chisel
• a mallet or hammer
• double sided sticky tape
• sandpaper, and preferably a powered sander
• wood finish, eg linseed oil
• a router with a pattern guide (not essential)
• backing material such as thin cork, baize or felt (optional)

First, choose your plywood. External grade ply tends to be better quality than the stuff meant for internal use only. Look at the cut edges and reject any pieces with voids. Also, you want the layers to be attractive colours that have a good contrast between them.

A piece of 12mm / ½" thick scrap measuring about 30cm x 10cm / 12" x 4" will make several coasters, a little goes a long way. If you use plywood of a different thickness, you'll end up with differently sized hexagons which might either be too small to handle easily or too big for a coaster. You can use the dimensions on the drawing above to estimate the "across flats" size of the inlay that will result from any given plywood thickness. For example, 12mm ply will produce inlays that measure 12 x 66/11 = 72mm across, which will fit comfortably into a circular coaster. 18mm / 3/4" is definitely too thick but you can arrange 6 diamonds into a star shape on a coaster instead of making hexagons - see the final step.

You need to start with at least one long straight edge on the plywood, so cut that any way you like before going any further.

That done, set your table saw so the blade is tilted 30° off the vertical - check it rather than relying on the scale on the saw unless you're sure it's accurate. Then, with the straight edge of the plywood against the fence, take a cut off the other long edge to give a face that's at 60° to the horizontal.

With the fence to the right of the blade (assuming the blade is tilted to the left), place the newly cut edge down on the saw table next to the blade, as in the photo. The plywood should lean at the same angle as the blade - flip it around if it doesn't - so that one face is in contact with the blade. Now move the fence towards the blade until it can't go any further because its base is touching the bottom edge of the plywood, being careful not to squeeze so tight that the plywood rides up the blade, off the table. Lock the fence in this position.

Flip the plywood around so that it's lying flat on the table with the wider face down and the edge against the fence - see photo. Rip a strip and check the dimensions, the ends should be perfect parallelograms (diamonds) with all four sides the same length. (In case you're interested, that length will be 2/√3 x the thickness of the ply.)

Assuming no adjustments are needed, go ahead and rip two more strips, then hold them together to make a hexagon as in the photo. They should fit together with minimal gaps - if they don't, check the set-up on the table saw again, something must be off. When you're happy, rip more strips. As a rough guide, you'll get about 10 hexagons (each composed of 3 diamonds) from a 30cm / 12" long strip, maybe up to double that if you can slice them up more thinly than the 8mm / 5/16" slices I achieved. Each coaster is inlaid with 7 hexagons. Cut more diamond cross-section strips than you think you're going to need to allow for some rejects when you get to the hexagon stage.

If the strips are long, cut them into manageable lengths of no more than about 30cm / 12".

You're going to be gluing 3 strips together to make a hexagonal prism. First, you need to decide how to arrange them - take a look at the first photo in this step and also the 2nd photo in the next step. One way has rotational symmetry, the other gives the effect of a cube, like the Tumbling Blocks quilt pattern. To complicate matters, each is capable of giving different effects in the 7-hexagon combination that's at the centre of these coasters, depending on how they are positioned next to each other. So play around a little with your diamond-section strips, maybe holding them in bunches of 3 with elastic bands so you can see how they look when one hexagon is placed beside another one. There are a lot of possible combinations.

When you've chosen the pattern you want for the hexagons, bundle the strips up in groups of 3 the correct way around, using an elastic band on each end. Then stick strips of masking tape every few inches along them to hold 2 of the 3 longitudinal joints in the right position. Remove the elastics, unfurl the strips onto something that you don't mind getting glue on (I covered the workbench with vinyl wallpaper) then paint every part of both faces of all 3 joints with a generous amount of wood glue. Roll the bundles back into hexagons (the masking tape should still be in place) and give each one a good squeeze along its length before holding it together with a few elastic bands wrapped around enough times to be quite tight. Some glue should have squeezed out of the joints, wipe away what you can with a damp cloth.

Leave the hexagonal prisms to dry before removing the elastic bands. Using ordinary PVA, I gave mine 48 hours to be on the safe side. Then sand off any glue that's visible on the long faces and edges so that the prisms fit together tightly.

The next job is slicing the prisms up. I started by using a hand mitre saw (see photo), because I assumed that a powered saw would be too aggressive and would tear the thin plies out of the surface. But after one cut I realised that cutting dozens of slices by hand was going to require more patience than I possess and I gave the bandsaw a try. With a 10tpi blade it worked fine. A crosscut sled on a table saw should work too, as long as it has a reasonably fine blade. Whatever type of saw you choose, use a fence or stop to get all the slices exactly the same thickness. The cut faces must be perfectly square to the long sides of the prism.

I cut fairly wide slices of 8mm / 5/16", thinking that anything much thinner probably wouldn't hold together and would be hard to glue into the 7-hexagon arrangement because the glued joint would be such a small area. But that just meant I had to rout deep recesses (see Step 7) which took longer. (Fortunately, I was using thick engineered flooring.) I suggest that you experiment by cutting slices thinner and thinner until you find how thin they can be without falling apart. And if the hexagons won't glue to each other, that's not the end of the world because you can always stick them individually into the coaster recesses. Obviously, the thinner the slices are, the more you'll get.

Reject any slices that don't have at least one perfect face. Lightly sand around the edge of each face to get rid of any splinters. Don't bother about sanding the faces to make them perfectly flat and smooth at this stage, because one face will be glued in the bottom of the recess and the other will be sanded again once it's been inlaid to get it flush with the surrounding surface. However, it's a good idea to sand any deep saw marks out of the "good" side now, otherwise you might end up cutting the coaster recesses too shallow to allow such marks to be removed later, when the patterned plywood inlays have been stuck in, without having to remove some of the surrounding hardwood. Sanding the face of a slice is best done by hand, with the sandpaper on a flat surface, moving the slice face down, in circles.

Arrange the hexagons in groups of 7, in whatever orientation takes your fancy. Then glue each set; paint glue onto all 6 sides of the central hexagon and the 3 innermost sides of the remaining ones, then push them all together and hold them in place with a tight elastic band. Put a weight on top of each to keep them flat. (I made the mistake of using steel weights for some of mine, which produced dark rust marks on the surface - not a disaster because I put the stained sides downwards into the coaster recesses, but it would have been nice to be able to choose which side looked better rather than just having a choice of one. A jam jar full of water makes a good, rust-free weight.)

Leave to dry then remove the elastic bands.

For my first coaster, I simply drew around the 7-hexagon group I was planning to use with a sharp pencil onto an offcut of engineered oak board. Then I chiselled it out to a depth of just less than the thickness of the plywood slices, which took me about 2 hours (I'm no expert with a chisel). The end result was pretty good, a nice tight fit, but it took far too long.

I then marked the centre of the recess by drawing lines between the concave corners, and drew the circular outline of the coaster with a compass. I cut round it on a bandsaw, following the line by eye, but that required a fair bit of sanding to make it smoother and more circular. I was left with a disc of the same thickness as the flooring, 20mm / 3/4", which is much too thick for a coaster. I needed to bring the thickness down to about 10mm / 3/8", however it's not easy sawing the back off something that doesn't have at least one straight edge. I ended up sticking several discs onto a board with double-sided tape and running them through the table saw, but they tended to come unstuck and fly off. Not good.

After this, I came up with a better method, using a router with a pattern guide and only cutting the coasters partial depth until the end of the process, ie keeping them attached to the backing ply for as long as possible. In essence, the stages are:

1. Use a router to cut coaster-sized circular outlines in the engineered board, to the depth required for a coaster (but less than the full thickness of the board and deeper than the thickness of the patterned plywood inlays).
2. If you have access to a laser cutter or 3D printer and can make a suitable pattern/template, then use it with a router guide to cut recesses/pockets for the patterned plywood inlay. You'll still need to sharpen up the rounded, outer corners with a chisel, and the fit at the inner corners may not be as good, but it'll be a lot faster than doing the whole thing by hand.
3. Glue in the inlays and sand the surface flush.
4. Finally, run the board through a table saw or bandsaw to free the coasters from the unwanted layers of backing ply.

The following steps cover this process in more detail. Of course, if you have a CNC router then you can simply use that to cut the circles and the recesses.

Most routers come with a removable guide that surrounds the bit and allows you to follow a pattern cut from a sheet material. Using a negative/female pattern is a great way of cutting a recess/pocket for an inlay (such as the 7-hexagon group), because the guide is constrained within the pattern and it's impossible for the bit to stray beyond the desired outline. All you have to do is run round the edge of the pattern and then remove material from all the area within it too, either with the router or a combination of router and chisel. Pattern routing with a negative needs a little more care when cutting an inlay (or the circular coasters) because the guide must be kept pressed against the pattern's edge to prevent the bit from straying into the material that you want to keep. That problem could be avoided by using a male pattern (ie a disc), but then there's less area to stick it down securely onto the workpiece and any sticky residue is on the material you want to keep rather than the scrap.

If you have a pattern guide - or maybe even several differently sized ones - you probably have some circular patterns too. Work out which combination of available guides, patterns and straight cut bits will come closest to producing coasters of the size you want. Small coasters for wine glasses could be around 80-85mm diameter (a little over 3"), but for mugs something around 95-100mm is better (up to 4").

A detailed explanation of how to work out what size circle you'll end up with is beyond the scope of this 'Ible, but as long as you're using a negative pattern with a central hole (rather than a disc that the guide will run round the outer edge of), the equation you need is:

offset_inlay = guide radius + cutter radius

which means the radius of the pattern must be larger than the inlay by the sum of the guide radius and the cutter radius.

In other words, pattern diameter = coaster diameter + guide diameter + cutter diameter

I used a guide with a 14mm outside diameter (a little over 1/2") and a 6.3mm (1/4") diameter straight cut bit. The diameter of my pattern to give 95mm diameter coasters was therefore 95 + 14 + 6.3 = 115.3mm.

Draw lines that cross at 90° where you want the centre of each coaster to be, to help position the recess centrally later. Then stick the pattern down with double sided tape - my pattern has the quarter points marked around the circle, to enable me to line it up on the cross by using a ruler (see photo). Rout out the circle, being careful to keep the guide pressed against the edge of the pattern all the way around. Take cuts of no more than about 3mm / 1/8" at once. Go down a little deeper than the thickness you want the finished coaster to be, but leave at least 2-3mm of engineered board at the base of the cut to keep it firmly attached to its backing for the next step, cutting the recess. If you plan to back your coasters with cork or anything else, remember to allow for the thickness of the backing material.

Save as much fine sawdust as you can from the hardwood, wear layer of the board, it'll be needed later for filling gaps.

Unless you have the capability to create a custom template to suit your 7-hexagon inlays, you're going to have to draw around each inlay and chisel out the recesses by hand as I did for my first one. Just make sure you place them centrally within the routed-out circles.

But if you have a laser cutter or 3D printer and can use a CAD system, then you can speed up the recess creation process considerably by using a router.

This time, the relevant equation is:

offset_recess = guide radius – cutter radius

which means the pattern must be larger than the inlay by the difference between the guide radius and the cutter radius. Also, the guide can't get into sharp external (convex) corners, so it's a good idea to give them a radius that's no smaller than the radius of the guide. That makes it easier to move the router smoothly round those corners.

Don't assume that the inlay dimensions will be exactly the same as they should be theoretically, based on the thickness of the plywood you used. I found that my "across flats" measurement (see drawing) was on average 65mm not the 66mm (or more, allowing for the glue) I was expecting. Measure several of the inlays and base the pattern for the recess on the smallest.

I laser-cut this pattern (and the circular one) from 6mm / 1/4" plywood, placing the cut-out centrally within a square. That way, all I needed to do to line it up properly to ensure the recess was placed centrally on the coaster was to place all 4 corners of the square on the diagonal lines I'd drawn before cutting the circles in the previous step.

When choosing what thickness to make your pattern, remember that a) it needs to be thicker than the height of the guide above the router's baseplate, and b) the thicker it is, the longer the cutter needs to be to give the depth of cut you want. I wouldn't go any thinner than 6mm though or you may have trouble keeping the router steady enough to follow the edge of the pattern.

Using the same guide (14mm OD) and bit (6.3mm) as before, the outline of my pattern was (14 - 6.3)/2 = 3.85mm beyond the outline of the recess I was aiming to cut.

Rout around the outline of the pattern and then remove as much of the material within it as possible. (It's actually quite hard to see, or feel, what's going on once the guide is no longer in contact with the pattern's edge, but a clear acrylic pattern ought to give a better view than a plywood one.) As before, go down by no more than about 3mm / 1/8" at a time, especially while you're in the hardwood layer. Aim for a depth that's just slightly less than the thickness of the patterned plywood inlay, say 1mm / 1/32" less.

Once that's done, remove the pattern and take out any residual material that the router has missed at the bottom of the recess with a chisel. Then use the chisel to finesse the shape of the recess, trying an inlay in it every so often to see where more material needs to be removed. It helps to pencil a mark near one corner of the recess and a corresponding one on a corner of the inlay so you keep them in the same orientation with respect to each other. Don't worry if there are some small gaps around the edges, they will be filled later.

When it feels like the inlay is going in and you're sure the sides of the recess are vertical or possibly tapering slightly outwards with depth rather than inwards, it's time to move on to the next step.

Spread glue generously in the bottom of the recess and all the way up its sides, then position the inlay in it, lining up the corners you marked previously. Place a piece of scrap plywood over the top and tap with a hammer or mallet to drive the inlay fully into place. It should be just proud of the surface.

Wipe away the glue that's squeezed out, place a weight on the inlay and leave it to dry.

Once the glue is dry, sand down the surface with a powered sander until the inlay is very nearly flush with the hardwood layer. However, if you are going to be sanding by hand, it's easiest to free all the coasters from their backing before sanding each one individually, face down on a piece of sandpaper on a flat surface. So if you don't have a powered sander, go to the next step before coming back to this one for initial sanding and filling.

I used a random orbit sander with a coarse grit, no. 60, and that did the job well. With several coasters all in the same offcut of flooring, you should have plenty of room to clamp it down securely. Finish in the direction of the grain of the hardwood. Save the fine sawdust.

Now that the inlay is only protruding very slightly above the surface of the hardwood any gaps between the inlay and the wood, or between one hexagon and the next one, should be obvious. Mix up some sawdust with wood glue to make a not-too-stiff paste and push it into the gaps. It will dry fast as the sawdust sucks moisture from the glue. Once it's dried a little, wipe the excess off the surface with a damp cloth, then leave it to dry fully.

Lightly sand again, in the direction of the grain, to remove any remaining filler and bring the surfaces perfectly flush.

The individual coasters can be freed from their backing board by running the board through a table saw or bandsaw, with the fence position chosen to give the required coaster thickness. (Obviously, this needs to be less than the depth to which circles were cut in Step 6.)

The only problem with this is that the coasters are liable to fly off as they're released, which is more of an issue with a table saw. One solution is to position all the coasters the same distance from a straight edge of the engineered board in Step 6, then set the table saw's blade height to leave a small tab holding each one in place. The coasters are finally freed by sawing through those tabs by hand.

Once you have a bunch of coasters, sand away any roughness around the edges before applying the finish of your choice to bring up the grain. Bear in mind that a shiny, varnished surface is best avoided as it will be slippery and you don't want glasses to slide off. I gave mine two coats of boiled linseed oil.

Finally, stick circles of cork, baize or felt on the base if you wish.

As mentioned in Step 1, 6 diamonds cut from 18mm / 3/4" thick plywood can be arranged into a star shape and will still fit comfortably into a 95mm diameter (a little under 4") coaster.