The original coaster was made with tapered plugs which were almost cylindrical but with a 3° taper to the sides. By tapping one of these plugs into a hole, it would wedge in at the top which made for a very tight joint. The excess still sticking above the surface would be cut off and discarded. The problem was that good part of the joint was only skin deep which prevented any contouring of the top surface. Conversely there are gaps on the backside where the diameters of the plugs tapered smaller.

The obvious plan was to replace the tapered plugs with un-tapered cylindrical plugs so the joint would be good through-and-through. The issue with that approach is that all the plugs would need to be almost perfectly-sized for a good fit. Now theoretically if one could get a decent set of straight plug cutters, one could turn out barrels of perfect round plugs to use for one's coaster. However based on my experience I feel confident in stating that one can't get a decent set of plug cutters so one is left with a bunch of empty barrels.

Now to get the classic wood grain look, you really need to display the side grain rather than the end grain. In the plug coasters, the ends of the plugs are what's visible so these ends need to show side grain. To achieve that a circle must be cut into the face of the wood which puts the cutting action at all angles with and against the grain and you can bet that some of those angles are going to cause a problem.

The tapered plug cutters that worked well for the original plug coaster shear the grain continuously due to the taper, and this (along with good tool design) seems to be able to make clean cuts. Normal cylindrical cutters; not so much. So it was a matter of figuring out how to make suitable cylindrical plugs.

The first step was to figure out how to make suitable plugs - or if it was even practical. They could obviously just be individually turned on the lathe but since I'd need hundreds that approach was a bit short on the practicality end.

One idea that comes up commonly for making accurate-diameter plugs is use a sharpened open-end wrench as a cutter while turning on the lathe.

This was one of the first things I tried. Sharpening a wrench was a matter of a few seconds on the grinder.

In short order I had a nice set of sharp wrenches to try out.

Unfortunately despite the promisingly-high level of shininess I found that they weren't very effective cutters. They worked best when shaving off only a small amount of wood but even careful use chewed up the grain on many woods (since the cutter edge is going directly into the end grain for part of the diameter) and they weren't a good solution.

The other obvious approach was a plug cutter. This one is from a Ryobi set and other manufacturers make very similar-looking parts. unfortunately it worked very poorly, cutting undersized plugs and sometimes breaking off the plug in mid-cut.

I tried another couple sets but they were as bad or worse than this one. One set advertised with Imperial sizes on Amazon.ca turned out to be a metric set with sizes I couldn't use. Which was fine since they also cut poorly.

Lee Valley had a promisingly good-looking set with carbide cutters and a robust construction. Yet they were still crap at cutting a cross-grain plug. It cut some woods undersized, some oversized and some both - an oval instead of a circle. Novel!

Some plug-cutting issues can be traced to insecure wood holding or drill-press runout but the best setup I was able to make didn't help appreciably.

I eventually decided it wasn't feasible to make accurate-diameter plugs. My fallback approach was to make oversized plugs and trim them down individually using the lathe. To that end I modified some cutters to cut oversized plugs. They still had some break-off problems but the majority of the plugs were usable.

This one is a tapered plug cutter of the type that actually works well. I used this to make 1/2" plugs which were then trimmed down on the lathe to get rid of the taper. Unfortunately the tapered cutters for the smaller sizes produced plugs too short to use on the lathe.

So then the question became how to trim down the various sizes of plug on the lathe for an accurate outside diameter.

I had some success cleanly shearing plugs with a skew cutter on the lathe although the size was difficult to control. This was an attempt to replicate the shearing action to achieve a 1/2" diameter.

It worked essentially not at all.

Another thought was to use two accurately-spaced files to get down to the final diameter. However when either sanding or filing on the lathe, the side grain is affected more than the end grain so the plug becomes oval.

I ended up using this a bit but only on specific woods for very small diameter changes.

Another option was what I called a burnisher tool which consisted of a hole of the desired size in a thick piece of metal with some grooves filed into the interior. Pushed onto an oversized plug it would shear off the excess.

For some diameters of some woods this worked well but mostly it produced too much torque and the plug just broke off.

Above is an example of the burnisher working well. It worked maybe 10% of the time so it wasn't a slam-dunk by any means. Sometimes I could get close enough with the skew chisel or a conventional turning gouge could be used to reduce diameter or sometimes I could use the double files or sometimes a single file would work OK. So armed with this haphazard selection of techniques I decided to push ahead.

I had in mind to do a step-by-step photo shoot of making the coasters so it made sense to check this out with the test coaster as well.

The first thing I needed was some reliable technique to mount the camera and coaster with some repeatable lighting. I built this little setup with a slot for the coaster that held it in a fixed position relative to the camera. I spaced things out so the focus and default zoom on the camera worked out decently.

Then for consistent lighting I acquired a light tent and used a couple of my LED photo lights flanking it. This was set up in another room so it wouldn't need to be moved for however long it took to make the coaster (a couple weeks, as it turned out).

In this shot I'm putting the 3/4-done coaster into the holder for a shot.

This shot shows the light tent and one of the photography lights.

I took photos at every stage - a hole drilled or a plug added or partial sanding so it was usually between 30 seconds to a couple minutes between shots. I'd turn the camera on, take a shot and shut it off again. There were 320 shots by the time I was done and while the camera setup was just in the next room, I estimate I walked about 5 km for the photography.

The original plan was to make a set of four coasters but I thought I'd be better off making a single test coaster to start and see how practical the construction would be.

I used birch for the coaster blanks. This piece would be enough for the four coasters plus the initial test coaster.

Once the birch was trimmed to a of thickness 0.33" and cut into 4.5"-squares, I added the 3.5" coaster outline to show what area needed to be filled.

This shows the backside of the test coaster after drilling 1/2" holes. This was done with it hand-held to a backing board but that evidently wasn't sufficient to prevent chipping. This seemed like a problem (although it actually wasn't since eventually all the birch would be replaced by plugs) so I later glued on a thin piece of plywood which had the added advantage of strengthening the birch to prevent splitting.

Which I eventually did, um, after it split.

This shot shows some 1/2" plugs being cut with one of the modified cutters (ground out so it produces an oversized plug).

The plugs were cut free using the bandsaw.

The plugs were then put on the lathe one at a time and reduced in diameter using one of the techniques previously mentioned until they fit tightly in an appropriately-sized hole.

Or got reduced too far. Or chipped. Or got too oval. Or cracked and broke off. Success rate was rather dismal at maybe 60%.

Plug installation proceeded in a succession of stages with more of the coaster being filled in with each one.

Each plug-insertion stage involved:
- drilling holes,
- gluing in plugs and
- sanding them flush.

This is the fourth stage and I'm drilling holes for the 1/4" plugs.

Once the holes were drilled, I glued in the plugs one at a time.

Plugs were made longer than needed which explains why they are poking out of the wood blank.

The plugs could be pretty tight in the holes so I added some snap-into-place custom jaws to the bench vise to make a plug press.

This shows the press in action.

This shot is actually of an earlier stage where a batch of 3/8"-diameter plugs have been inserted. The glue is dry so the next step is to sand the plugs flush with the surface.

...like that.

This shot shows the plywood on the bottom, added to help prevent splitting.

This group of photos summarizes the stages of plug insertion, of which there were nine in total. Each photo was taken after the plugs had been sanded flush.

Eventually I ran out of birch to cover up with plugs. That happened after 110 plugs of 5/8", 1/2", 3/8" and 1/4" diameter.

Oh - and plug woods included African Blackwood, Amboyna burl, Bubinga, Cherry, Honeywood, Lacewood, Mahogany, Maple, Oak, Padauk, Purpleheart, Tigerwood, Walnut, Wenge, Yellowheart and Zebrawood.

This video is composed of individual stills taken of the test coaster, one after each hole drilled, plug installed or marking or sanding operation. It compresses the 2 weeks or so of action down to a bit over a minute.

The next action was to shape the coaster and to that end it was cut into a round using the bandsaw.

Since the blank didn't really have any extra thickness, it needed to be glued or taped to the faceplate. I went with the tape option and in this photo the backing is being removed from the thin double-sided tape. The aluminium faceplate has had a couple layers of wood added to make it easier to access the coaster's edge and back.

With the blank on the faceplate, it was ready to start turning.

Unfortunately, use of a conventional turning gouge resulted in a number of, well, gouges. Or more precisely: popped-out plug sections. I'm thinking the grain of the plugs conspired with the low level of glue (due to tight plug fit pushing out the glue like a syringe) to produce this disappointing result.

I was going to need a method to reduce diameter past the plug notches without losing any more plugs.

So while ideas for edge turning burbled away, I worked on the top of the coaster.

A bowl gouge (shown) followed by scrapers worked well to form the hollow in the top.

So then it was back to diameter reduction; I decided to try a belt sander to less-traumatically reduce the diameter. That worked but didn't result in a very constant diameter. Better roundness was achieved using a small drum sander since I was able to mount it securely to the tool rest.

And after the side sanding and then some scraper action on the backside it was left with the profile shown here.

With the top and edge done, the coaster needed to be flipped around so the bottom could get some attention.

I made a jam chuck from that big mahogany disc, flipped the coaster around and glued a short piece of dowel to the bottom. I made sure to support the coaster top in the jam chuck so pressure on the bottom from the tailstock wouldn't crack the wood.

Once again the bowl gouge followed by scrapers worked to remove the plywood and form a circular foot on the bottom.

Off the lathe, the glued-on support needed to be removed. I started by cutting it off close to the bottom.

That was followed by some grinding and finally sanding with this Dremel-mounted sanding disc.

I had reduced the diameter by sanding to eliminate some missing-plug notches but the worst one was still there. That one I filled using a section of a plug as shown here.

Then a bit of sanding and Bob's yer uncle.

And that's the woodworking done for the test coaster.

Making more coasters was not looking very promising at this point so if this was going to be the only one, it made sense to add varnish and at least finish it off.

The completed test coaster.

It had taken about three weeks to make the single test coaster with a laborious and uncertain method for making plugs. Given the broken-out edge pieces when turning, I was also concerned about the coaster strength due to glue-starved joints. Plus some of the plug joints were not as tight as I wanted. I couldn't really see making another four coasters under these conditions.

I was almost prepared to leave it at one coaster. If only I could use the tapered plug cutters and didn't need to "tune" each plug individually (which was a multi-minute operation with a depressing failure rate). So I wondered: could I actually use the tapered plugs but then cut tapered holes to match?

First up was seeing if the tapered hole idea would hold water, so to speak.

On the lathe I turned three "tapering sander" bits from maple. They were cut with a 3° taper to the sides to match the plugs.

A long-lasting 150-grit sandpaper was adhered to the business end of each using window film tape.

Then on a coaster-blank-like piece of birch I drilled and tapered two holes each for 1/2", 3/8" and 1/4" plugs.

The sanders seemed to work decently but the sandpaper peeled off the 1/4" version after just one hole. As a replacement I ground a taper into the end of a 5/16" twist-drill bit at the requisite 3° angle and that worked well to shape a tapered hole.

Then after the test holes were tapered and the plugs glued in and sanded flush, I cut the board down the centre of the plugs to examine the joints. They looked pretty decent so I figured this was worth trying.

The coaster blanks cut many photos ago had plywood glued to the base and then they were ready to go.

In addition to the 1/2", 3/8" and 1/4" plugs, I decided I should add some 5/8" plugs. I didn't have a 5/8" tapered cutter so the plugs were cylinders formed on the lathe and went into standard holes.

This shot shows one of the plugs being made using a skew chisel which could cut the sides cleanly.

The photo grouping below shows the first plugging stage which consisted of drilling and gluing in the plugs. I started with a few of the 5/8" plugs in each coaster.

I used a syringe to apply glue to these first plugs but it turned out to be very hard to squeeze so I gave up on it for subsequent stages and just used a toothpick to apply glue.

Here the first stage of plugging is completed except for sanding the surface.

Subsequent stages will install 1/2", 3/8" and 1/4" plugs, all tapered.

Here a 1/2" hole is being tapered with the sander.

I checked the taper of each hole with a test plug (here I'm checking a 3/8" hole) and did a bit more sanding if the plug didn't go in far enough.

Here the left forefinger sports a bandage covering five stitches worth of a workshop goof featuring a utility knife and an inadvisable hand position.

This is a shot of the 1/2" plug cutter in action on a piece of walnut.

I typically formed a bunch of plugs and then cut them all free later on the bandsaw. This is a pile of 3/8" plugs ready to hit the saw.

Above is the annotated plug selection, spread out on the workbench. I didn't install the plugs to any particular plan, although I generally tried to arrange them for a good colour contrast.

Below shows one of the plugs going in. I applied glue to the inside of the hole and while that soaked in, put it all around the outside of the plug as well in hopes it would be sufficiently infused. However based on some break-outs while turning I'm not convinced there was much in there.

As with the test coaster, it took 9 stages of adding plugs before I covered all the birch. This composite photo tracks the stages of coaster #3.

The last few stages were mostly filling small areas and didn't involve many plugs.

It again took a couple weeks of (nose not really very close to the grindstone) drilling and plugging to complete the coasters. Of course this time I did four but the plugs were much easier to make and perhaps not running out to the camera 320 times helped with construction efficiency.

I needed some method of holding the coaster blanks in the lathe for turning. On the test unit I had taped the back side to a faceplate but the backs on these are much rougher so that wasn't practical.

On the test coaster I had also eventually glued a dowel to the back for the tailstock live center and I thought I could just do that one step sooner and use it for the main turning too. I made up the four lathe-jaw-compatible adapters seen here and would glue them on.

In this shot I'm using a cardboard pattern to mark the center on the back sides to position the adapters.

Ready to hit the lathe.

This is the first coaster cut out in a crude circle and mounted to the 4-jaw chuck on the lathe.

I used a skew chisel to round the outer perimeter which worked decently and didn't knock out too many plug fragments. Then I switched to shaping the top side using a bowl gouge to remove most of the wood, then a large flat scraper to even out the center area and finally a small circular scraper to define the rounded lip.

When the top side was done, I recut the jam chuck I'd made for the test coaster a bit larger to fit the new ones. Then I flipped the coaster and mounted it to be able to work on the bottom.

The excess thickness was cut off and a circular foot about 0.07" high was formed. The glued-on adapter piece was also thinned to make it easier to remove.

Then three more like that and the set was pretty much done.

On each coaster the lathe adapter piece was cut off as close as practical to the coaster and the remaining nub was ground down and then sanded off for a smooth bottom.

I whipped up a 4-place cardboard 'n nail holder and then started applying varnish.

Here the coasters have been given the first coat of varnish (done with that little piece of foam brush).

They received four or five coats of Fast-Dry Polyurethane varnish which should make them waterproof (and coffeeproof and beerproof, etc.)

The set.

A set of coasters kind of needs a home so I thought I'd make a holder to store them.

This odd-looking piece of wood is a stamp (well, three-quarters of a stamp) used to print the funky pattern seen in black. The remnants of yellow paint stand witness to it's use probably back in the 70s in my childhood home, although I can't remember which wall it was used on. It may have come originally from Expo '67 which was attended by my parents and I speculate from an African display of some sort.

However its stamping days were done and I decided to use another quarter as the raw material for a coaster holder.

I took a few shots of the fabrication and the photos below make the process pretty self-explanatory.

Unfortunately I managed to fumble the holder during the sanding process and a roving gang of malicious gravitons grabbed it and slammed it against the planet. It did not survive.

Yah, so then a second try was in order, ideally with something less brittle.

I started with this piece of mahogany that should be just barely long enough if I cut it into four using the bandsaw which has a smaller kerf than the radial arm saw.

I needed a good four inches of width but the wood was a bit less than two inches. Hmmm.

My solution as can be seen here was to offset the pieces to get the needed width, filling the resulting center void with a 1/4"-square piece of maple for some nice contrast.

As before it went onto the lathe for turning, followed by some hand work to give it that modern angled profile.

The completed holder, intact.

A few coats of varnish and it's good to go.

The completed set.