Singer Engineering: Little Magical Salt and Pepper Shakers

When I was about eight years old, my family moved to a new house. The old one, small and near the railroad tracks, was simply not sufficient for the number of children my parents had, nor for the two more they were yet to have. So we moved across town to a larger home with two stories and a big yard. The property had a good-sized garden and several trees. There were some birch trees, fir trees, and even a few fruit trees. The largest of these fruit-bearing trees was a Bing cherry. It was I-don’t-know-how-many years old, and it seemed to have been the victim of some rather undisciplined pruning in the past. Dense, coarse, scraggly branches usually made collecting cherries difficult, which we nonetheless did in a yearly exercise.

My mother regularly planted a garden, and besides the typical weed-extraction efforts we kids were expected to help gather the produce. This was often much more tedious than one might think. The rate at which plants create edible items can boggle the mind. I’m particularly reminded of the annual zucchini fiasco; while a single zucchini plant at its peak of production could feed a small village, we always seemed to have several mounds of multiple plants each. Oh sure, the first zucchinis harvested are sweet and tender. But within a week or so they develop quicker than dinners are being scheduled, and by the time the second wave of matured vegetables really hit we were always begging friends and neighbors to take them off our hands. Finally acknowledging being overrun by zucchinis, we would be forced to just abandon the plants until the end of the season, by which time the things had attained such a size that they might be hollowed out and used for canoes.

The cherries of this tree had a similar tendency to overwhelm our family, at least by quantity. Though we all appreciated the pies made through the cold winters from the jars and jars of cherries lining the shelves of our little storage room, the prospect of collecting all those ripe cherries was always daunting. They would appear in a flurry and if not collected quickly they would make a real mess of the surrounding grass. Unfortunately, the size and shape of this tree made picking the cherries a strain. I recall one summer when I designed a device to assist in the harvest. It was a simple tool, affixed to the end of a broken pole-based garden tool. Two hooked prongs set apart by only a little more than the width of a cherry stem were used to snag the cherry and pull downward on it. Once it popped loose, a small plastic sack supported by a wire loop was waiting to catch it. With this, I was able to pick substantially faster, from the ground or from a ladder. This was actually one of he first fully successful devices I engineered.

I remember climbing this tree as a kid, because it had some main branches which ran nearly horizontal, giving an ideal platform for an imaginary pirate ship or what-have-you. Sticks became swords, or space-rifles, and the view of the surrounding yard was about as good as you could get anywhere outside on the property, which enabled my mind to wander freely.

Delicious as the cherries were, it did not last. For many years prior to our moving into that house, the tree had been slowly dying. Cracks had developed in the bark-included joints between the trunk and major branches. During countless winters, water had dripped in these cracks, frozen, expanded, and further forced open the weakened wounds. On one side of the trunk, a significant portion of the bark was split and the underlying wood exposed to termites and other critters. It was largely hidden from human view, but not protected in any way, by a mess of ivy vines. Eventually one day, years after I had moved out, my father simply decided it was time. The chainsaw was fetched, and in some short hours the tree was no longer. In its place sat a sad empty stump surrounded by sawdust, and a pile of branches, leaves, bark, and logs all formed a soon-to-be-ashes mound in the garden.

There were a few pieces of the tree, however, that my father couldn’t bring himself to just let go up in smoke. Cherry wood can be particularly good-looking, and portions of this tree were no exception. Of course, it wasn’t a huge tree, or a straight one, and the chunks he managed to save were from the relatively gnarly base. Nevertheless, a few runs through the table saw produced some small rough-hewn lumber from which any number of things might be made. There were basically three pieces, each about 12 inches (300 millimeters) long. As he had no immediate use for them, they found their way to the rack of wood in the garage, on a pile of other small scraps. And there they sat…

...until this last December, after some years away from home, (some years out of the country, in fact) I came back for a visit to my family, and stayed in my parents house. During the first of four weeks there, I began to wonder what sort of wood pieces were still in our old garage, and if there might be something interesting that I could make while visiting. It was then that I actually became aware of the old cherry wood. I used a wet rag to wipe off the spiderwebs, and brought them inside.

All that was left of the old cherry tree

My father had long forgotten about this wood himself, and he told me that had he known they still were out there they likely would have gotten burned in a subsequent fire, as he had given up the idea of making something with them. I laid the pieces out on the table, and decided to select the widest chunk (the middle one in the picture above), even though its ends were rotten and bug-eaten and would need trimming. The other two (one of them split) were replaced on the pile of old wood scraps for a future time.

The first machine I would use is a thickness planer.

BRRRRMMMMMMMM! *Smooooth*

I had bought this tool quite some time ago, when I was living in a small apartment. I had little opportunity to use it then, but I knew it would be just the tool for the job. Fortunately, my younger brother Tim (who now owns the machine) keeps it in my parents garage and it was still available for me to use. Inside this heavy yellow box sits a set of three sharp blades which spin fast enough to make nearly 200 cuts for each inch (25 millimeters) of material fed through it. There are also multiple rubber rollers which move the piece at a nice uniform rate for a good even cut. Rough wood goes in, and smooth-surfaced wood comes out. The four metal poles in each of the corners assure that when the cutting device is raised or lowered, it goes the same amount on all sides. When this baby is really tuned up, it will make excellently-prepared wood boards or pieces from nearly anything. I ran the wood through a few times, trimming all four faces and finishing by making both dimensions the same. I now had a nice-looking square stock.

Some rotten ends still, but the body is square, smooth, and straight. ..and the grain is starting to show even more.

As pretty as the sharp corners felt, I knew they had to go. No-one likes getting cut or splinters. The router-table Tim had assembled was just the thing. I put a round-over bit in, carefully adjusted the height (testing on some other cheap scrap wood) and ran the cherry through four times. The ends got a little burned or scarred from my less-than-even feed rate, but they were rotten and going to be removed anyhow.

Adjusting the height is the worst part of this operation. If it's not right, the rounded corner won't transition into the flat sides, but cut a sharp ugly gouge. There is a small roller bearing at the tip of the blue cutting bit which attempts to ensure that the side of the wood is the correct distance away.

Next came the first of the truly point-of-no-return actions. The rotten ends of the wood needed to be removed, and the remaining long chunk cut in half. I went after the sharpest blade with the most teeth to try keeping these cuts as clean as possible.

Tablesaw. Note the blue tape wrapped around the girth of the wood; this prevents jagged splinters from forming where the fast-moving blade exits the material. Also, I used another thin piece of scrap wood as a sled, so that the rusty surface of this old table saw didn't mar the nice cherry as it was dragged along through the blade.

Once both pieces were cut to the same length, it was time to round over the edge of one end. This would form the tops of the ..parts. (Did I mention yet that I'm making salt and pepper shakers? Perhaps not. If you haven't gathered from the title yet, I'm making salt and pepper shakers. Why? Well, that's a long story for another time...)

Keeping the blue tape on, one end of each piece is rounded over. These must be run through multiple directions to make the corners get a full round-over to all flat surfaces without any pointy bits. Something like oil or the metal edges of the roller bearing have made markings on the top surface of the shakers. These must be removed with a thorough sanding.

The pieces after having nearly all preparations on the outside surfaces completed. Sanding has caused some new sharp edges to appear, particularly in the rounded corners. The top surfaces could still use some more sanding, while many pores of the grain have now been caked with tiny sanding dust. The grain is looking nice, but it is dulled from the fine wood dust.

I slept a bit before making another move. This next part was going to be tricky: hollowing out the bodies of these pieces. The first thing that came to my mind was simply drilling them. Of course, as the drill-bit would need to be rather large, and the bigger and deeper you go the harder it is to control, I needed to find some way to do it carefully. A drill press is the ideal tool, but we hadn't one large enough at my parent's house. Fortunately, my grandfather has a nice big floor-base model, and he agreed to let me use it. The first step toward careful drilling: careful marking of the center of the hole.

Here I used a pencil and ruler to find the middle of the workpiece. If I were slightly more clever, I might have marked these before rounding off the edges of the wood. Two lines drawn from corner-to-corner will meet at the middle, even if the piece is rectangular and not square. Of course, now I had no corners, and I needed to use the rule to mark. I got as close as I could with a tight squint of my eyes.

Grandfather's shop is a large metal building, which holds more tools and equipment than I'll probably ever become familiar with. Most of the space is dimly lit by natural sunlight through translucent panels. The drill-press itself had a bulb which illuminated the workspace nicely, even if it gives the appearance of a Hitchcock movie set.

Grandfather's drill press. Probably last used to fix an old tractor part.

A close-up of the vise on this drill press. This is the most important thing!

For those not familiar with a drill press, it is a tool for drilling holes, where the workpiece to be drilled is firmly held and the drill bit forced down in a smooth controlled manner from above. With such an arrangement, the position and angle of the drill bit relative to the workpiece can be set and maintained easily. There is a circular table which can be raised or lowered, and on this sits the all-important vise. The vise is bolted to the table, so it cannot slide off. It has a crank for tightening the jaws closed around the workpiece, and two adjustment cranks which move the whole jaw assembly in any horizontal direction. In this way, the part can be put right below the drill bit where the hole must be made.

One item that needs attention on a drill press is the speed of the drill bit. Electric motors like to run at a constant speed, dependent on the frequency of the electricity being fed to it. In order to adjust the speed of a drill press, the top of the machine needs to be opened and some belts moved around. In the picture below, three spindles with four pulleys each can be seen. The spindle on the far right is driven by the motor (at a constant speed of about 3'600 revolutions per minute); the spindle on the left is connected to the drill bit; the spindle in the middle is used to add extra combinations for more possible speeds. Here, the machine is set up for the slowest possible speed (like for drilling large diameter holes in steel). The motor uses the smallest pulley, driving the biggest pulley on the middle spindle. The middle spindle, turning as slow as it can, is driving with its smallest pulley the largest of the drill bit spindle. I swapped a few around to get a medium speed.

I had purchased a long Forstner-bit from the old pawn shop where I used to work. This has a circular row of cutting teeth on the outside rim which should make a somewhat smooth-surfaced hole. The bottom of the hole is cut with a single broad-edge tooth emanating from the spike in the center. A short section of flute tries to pull some of the cut chips out of the hole. The bit was long enough to make the hole as deep as I needed. I wanted to get within about 0.5 inches (12 millimeters) of the end. If I left more material at the end of the shaker, the salt or pepper might not make it through very easily; on the other hand, if I cut the hole too deeply, I might risk breaking through or at least cracking in a very unfortunate way. The drill bit was therefore marked for appropriate length with a piece of blue tape so I would know when it had gone just deep enough. One at a time, I positioned the individual workpieces in the vise, clamped on either side with some scrap wood I had brought to again protect my good wood from the rusty, oily, sharp surfaces of the metal tool. In addition, a paper towel prevented the bottom of the workpiece from getting similarly dirty.

Final adjustments before drilling. Note how much room there appears to be width-wise between the drill bit and the wood. Don't screw this up!

I had loosened and levelled the table out by eye as best as I could and tightened it back up again. The workpieces would need to be set as perfectly straight up-and-down as possible as well. If they weren't, the drill bit might come close to the edge of the wood before it got to the bottom, and the whole project could be ruined. I felt my hands up and down the pieces and tried to line them up with the vertical shaft of the drill bit. After looking from every possible angle and seeing that I couldn't imagine it being any better, I plunged the drill bit deep into the wood. With a squeal of friction -dry wood against metal- and a mess of wood chips pouring out, the hole slowly was bored, all while nervous sweat dripped from my forehead. Once safely drilled, I cleaned up and collected my things.

The hole halfway drilled.

Before heading home, I wandered out to the field beside my grandfather's house. The day was clear and the view of the local mountain particularly nice when viewed from across the farmland of the valley. I walked up the road a bit and took a picture or two.

Mt. Hood. No time for snowboarding today...

The next phase of the project is a bit interesting. You see, I had never made salt and pepper shakers before. I guess I had dove right into this with mostly rough planning, knowing I would need to make improvisations as the opportunities arose. However, now I came to a rather vexing problem. How big should the holes be, and how many? I decided to tackle the "how big" question first. After all, the end of these shakers is a bit thicker than some common metal-stamped shaker. If I drilled them too small, salt might get stuck halfway down the long holes. I wasn't at all sure how easily something like this might clog. So I did what any self-respecting engineer would do: I made some prototype tests...

I grabbed another unused scrap of wood and quickly drilled a row of holes the same diameter as the one I had made in my workpieces (1 inch, 25 millimeters). These holes were also drilled to leave the same thickness of material at the bottom of the holes.

Main holes drilled.

Then, I drilled several holes of different sizes through the material left in the base of the main holes. The idea was to get a small container with which to test various salts and peppers.

Different size holes made and labeled.

I went to the store and bought four different containers of salt and pepper. They had a typical fine grain table salt, in addition to a noticeably coarser kosher salt. I had my doubts that anyone would use kosher salt at the table, but I figured it would be useful to test as a worst-case. Pepper of course comes in multiple size grinds. When I was kid, I distinctly remember "fine ground" as the typical one my mother would put in the shaker for the table. However, "Pure ground" was the only fine pepper I could find. There were containers of "coarse ground" or "restaurant ground", and these were not quite as coarse, relatively speaking, as the kosher salt. Of course, if anyone wants pepper ground more coarsely than that, they probably will have a pepper mill and will grind it directly (and freshly) at the table. As I had decided on my testing media for the prototypes, I brought the whole setup to the kitchen and began making a mess of my mother's countertops.

First pepper test. The holes were too small, and required a lot of shaking.

One thing became clear almost right away. There is a minimum required hole size. Any smaller and you won't have any luck seasoning your food. However, once you exceed this minimum size, the holes become quite effective at a rapid pace. Finally, after about an hour of testing, a size of 1/8 inches (approximately 3.18 millimeters) was selected, on the assumption that there would be not too many holes. The next question was then: How many holes are needed?

Related to this was the question of how to identify the shakers. As a boy, my family always had these small glass shakers with metal screw-on caps. The glass obviously allowed you to see what was inside each container. Other shakers on the market were made in the shapes of things, or had letters painted on them; neither of these would be useful to me. I couldn't stand the thought of painting over this nice cherry wood, and the shape was already fixed in my mind: Simple and basic monoliths of the dining space, with smoothed exposed edges. How could I make the distinction in a way that fit this aesthetic style? I had seen shaker sets where each shaker has a different number of holes. I had also assumed that there was a real practical reason for doing so (like one spice needing smaller holes and thus more for the same flow rate), but my testing had shown that the appropriate size of the holes was about the same. I decided to take to the internet...

Several webpage searches later, I discovered all sorts of curious information about salt and pepper shakers, but much of it was conflicting and there didn't seem to be any credible authority. Some claimed that the salt shaker should have fewer holes because people should take more care to limit their sodium intake. Others said it was because salt was a more precious seasoning historically. Still others gave the opposite advice, because too much pepper is more likely to ruin a meal than too much salt. On and on it went, with no clear definition in sight. I began toying with another idea, that of using the holes to form the shape of the letters "S" and "P", a technique which I'm sure everyone has also seen applied dozens of times. Fortunately enough, the German words for salt and pepper both also start with these letters, so it would still be appropriate even in my new residence of Switzerland. But forming these letters properly would take a lot of holes, and perhaps this would cause excessive flow rates? I decided I had better prototype it. Back to the kitchen!

My attempt to drill letters in my prototype block. Holes were made slightly smaller than the ideal size of 1/8 inches (3.18 millimeters) because there are so many. Note that the "S" turned out wonky and looking suspiciously like an "8". I would have to pay attention to getting the holes exactly right if I were to use this method.

Results of the last prototyping. Holding the block up to the kitchen light reveals clogged holes after some seconds of use.

This last prototype test had perfect results. Not perfect in that everything worked, but perfect in that it revealed exactly what decision I should make. As the above picture shows, the holes were just small enough to get some of them clogged. Meanwhile, the not-clogged holes had produced such a wave of seasoning particles that they would render the shakers highly impractical unless the diner took care to hold them at a very shallow angle. This is obviously not something you could expect of guests, and therefore the holes-forming-letters idea had to be scrapped. I had no choice but to revisit the concept of identifying the shakers by means of a countable quantity of holes.

I inquired from a good friend back in Switzerland, who's something of an expert in culinary arts, which of the shakers should have how many holes. I received a clear answer without much hesitation, so I knew that even if not all experts agree which is which, the concept itself was not crazy to rely on. I was told that the salt shaker should have more holes for more even distribution. I decided on using three holes for the pepper, and five for the salt. If a guest happens to be holding the strong opposite opinion, at least it will inspire some lively dinner discussion. Before I could drill these holes, however, I needed to complete nearly everything else.

The wood would have to be finished with something, to protect the surfaces from the inevitable kitchen moisture and abrasive nature of the contents. If this coating were applied after the holes were drilled, there would be a serious risk of closing them up again. Thus, the holes had to be drilled after coating. Before coating, however, the base of both shakers needed a counterbore to receive a small insert. You see, the base obviously needs to be plugged somehow, and my first choice of a cork stopper had the disadvantage of needing to protrude a slight bit. If it were simply pressed into this main body cavity as is, the shaker wouldn't be able to sit in a stable manner. No, the cork needed to be pressed inside a hole which was up inside the base of the shaker. To accomplish this, a larger counterbored hole was needed.

I went back to my parents garage, where even the small drill press would be sufficient, as the counterbore only sits about 0.5 inches (12 millimeters) deep. Ordinarily, this hole would be drilled before the main one, because it's usually easier to keep straight in that sequence. However, this new bit was sharp and the setup was solidly fixed so there was little chance of wobbling around.

Getting reading to make the counterbore. Note the vertical-oriented table, scrap wood, clamps, and nice sharp new bit. Also, note the circular groove where the cutter bit has just made a small impression before I backed out for this picture. The counterbore is not concentric with the original bore. However, the counterbore is very closely centered on the wood itself. As the counterbore will be the only one seen from the outside by a user, it is the important one, and the hole I drilled slightly off-center at my grandfather's the other day is forgiven.

Sharp bits make very fine wood powder.

The finished drilled parts. Note the small step just inside, where the counterbore ends. The centering of these larger holes with the bodies of the parts is also quite good.

The final step after drilling all the holes: sanding! Here a dowel is wrapped with sandpaper to enable sanding of all the inside surfaces. Loose wood chips or rough edges could come off later and wind up in somebody's food. Better to remove them now.

Sanding is always important after the major shape-forming. The router had left some slight chatter marks on the rounded edges and these needed to be smoothed before finishing. Also, any sharp noticeable spots could be knocked down by hand sanding. All the inside surfaces were cleaned up with sandpaper as well. So much sanding took place, actually, that the pores of the wood grain again became filled, and the wood started to look dry and lifeless. I went and got some tackcloth (essentially cheesecloth which has been dipped in some petroleum-based stickiness). A few wipes with the tackcloth made the dustiness disappear and the grain started to stand out again.

Before (right), and after (left). Some tackcloth action pulled the light-coloured dry wood dust out.

Interestingly, at the beginning of the project I had pondered over whether the use of cherry-wood as a salt and pepper shaker body was smart at all. Some woods are known to be toxic, and I didn't want anyone getting even the least bit sick by what might be a tiny ingestion of wood dust. Fortunately, my research showed that there was no risk of this. Further, once the bodies of these shakers were coated with a cured waterproof polyurethane, they would be quite safe.

The next phase of the project involved some additional help. The counterbore at the base of the shakers was intended to receive a small insert. Looking like a thick washer, this insert would sit depressed inside the base, with an outer diameter which fits the counterbore, and an inner diameter which fits a cute little cork stopper. This part could be made out of wood, but I didn't like the idea. Firstly, it would be hard to cut and form. It would be flimsy, and at risk of cracking. The grain of such a part couldn't really be oriented in any particular convenient direction. I decided that it should instead be made out of metal. This would be relatively easy to manufacture (for the right guy, with the right tools), and it would be moderately attractive in the base while serving also to lower the center of gravity of the entire shaker, thus reducing the chance of spilling over. When the shaker was sitting upright on the table, it wouldn't even be noticed, so the pleasing unibody look of the shaker would be maintained. What kind of metal should be used? A little more research suggested that a 304 stainless steel would do quite nicely.

Who could I get to help with this project? Fortunately, one of my best friends' family owns a machine shop in their backyard, and my brother James happens to be a machinist by trade. One day when he didn't have other pressing work, we gathered up the plans and headed to do some metalworking. The next sequence of pictures shows what we did.

James setting up a metal lathe.

This little guy is what actually does all the work. "Cutting" metal is actually more like scraping it with a really hard piece of something. Here, that something is some form of carbide, which is clamped into a tool and moved by computer-controlled motors into place while the part to be "machined" is rapidly spun.

While not easily seen, the machine part at the left is spinning quite fast, holding a short round chunk of 304 stainless steel. The cutting bit is mounted on a head full of screw holes and other bits. This machine will cut the outside diameter to the required size, drill the hole in the center for the cork, and slice it off before making a second one for the other shaker.

A long coil of metal forms as the tool cuts the workpiece.

A spray of coolant oil is directed on the part while drilling the hole. The drill bit would heat up too much and likely break otherwise.

Finally, the completed parts are taken home. As the machining leaves sharp edges, here James carefully works over the parts by hand, scraping them free of burrs with his nice little deburring set.

Machining coolant oil isn't the greatest thing to consume. Not that the oil itself is terribly bad, but it's the perfect environment to grow bacteria. After a thorough scrubbing with soap, the parts are boiled to disinfect. (I haven't an autoclave handy, though with my sister being a registered nurse, I did wonder whether she might have some connections.) There are three parts in the pot but only two shakers. The third part is an extra we made just in case we screwed something up halfway through.

Final shaker base inserts, cooling and drying on a paper towel. I always find the regular pattern of machining marks to be oddly beautiful. The left part is actually upside down; there is a chamfer on the edge of the outside diameter (seen at the top of the part on the right) which eases insertion into the shaker.

With the inserts now machined, it's time to focus on protecting the wood with a nice coating. Polyurethane is my product of choice, though I did consider just a wax or some kind of oil. I decided to go with a wipe-on product which gets applied with a rag (I bought some microfiber cloth just for this). Satin finish, it should be a good protection while showing the natural beauty of the wood grain without too much plastic-like glare.

After the first coat. Mmmmm, I like it already. The bright-colored wood is more scraps (you can never have too many scraps in your shop) that I converted into a little drying stand.

I wish I could convey just how anxious I get when finishing wood with a protective coating. These products work like this: The thicker the coat you apply, the more likely you are to have drips, runs, and streaks. Thus, if you want a nice, smooth, uniform final coating, you need to put it on in many, tiny layers. This always tests my patience, particularly when you must wait at least two hours between coats. At any rate, we'll fast forward through what was a week of a bajillion very thin coats of polyurethane. Suffice to say that all the major pore holes and any perceivable rough spots from the initial cutting and routing disappeared with the proper regimen of coating and sanding.

The inside also had to be thoroughly coated, not for appearance, but for functionality. A good thick coating of wood finish would ensure that any stray dust stayed inside the container, suspended in polyurethane. There, a plastic-like look wouldn't bother me, as nobody was going to be looking inside.

Finally, I was at the point where final assembly seemed imminent. The only thing standing in my way was the drilling of the holes. This terrified me, because one wrong move would spoil the shakers and my mood for the rest of January. I designed a template on the computer which had both the hole pattern I wanted (at the vertices of regular polygon shapes) as well as the expected main body hole. These were taped very firmly to the ends of the shakers. The logic is the following: If my earlier efforts to drill the main body cavity were not perfect, the actual placement of the big hole, into which I was going to soon drill, might be off. If it was off by a lot (even if not enough to poke through the wall of the shaker) then there was the risk that some of these small holes would completely miss the internal cavity. Thus, I've made the small hole pattern rather tight, with extra "wiggle room" between them and the sides of the main hole.

Getting ready for the final drilling... quiet please, I need to concentrate.

Ooookay, steady now. No way to clamp this sucker, I'll have to just hold it with one hand while operating the machine with the other.

Drilled. The paper moved a bit, but not much. If anything, the hole pattern didn't come out perfectly symmetric on the salt shaker with five holes. ..but I'm pretty happy with it.

I actually managed to drill these holes during the last night of my vacation in the 'States. I wiped the parts clean of dust and packed things carefully into my suitcase. The final assembly had been delayed until after the small holes were drilled because I wanted to be able to clear all the sawdust out before closing up the bottom. The small holes had been delayed until the wood finish had been applied (and nearly cured). I would therefore have to complete the project on my kitchen table back in Winterthur.

I had purchased a small container of Gorilla Glue. I had heard good things about it, and it seemed the perfect way to bond these dissimilar materials together. This kind of glue activates with water, so the wood part was damped a bit with a wet cloth before applying the glue. It also expands as it activates, meaning that just a small bit was needed in the corner of the countersink, and the glue took care of spreading itself up along the surfaces in contact. I was quite satisfied with the apparent holding power.