Clayton Boyer Clock Designs

 

 

CLOCK MAKING TIPS AND TRICKS


Or, Things I Wish Someone had Told me Before I Started


Disclaimer: The following does not purport to describe the right way to do anything. It is just a description of what I do, and 40 years of marriage have taught me that I am often wrong.

by
John Hilgenberg
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SCROLL SAW
Don't assume that the thinnest scroll saw blades do the best work. Very fine blades, such as "puzzle blades" are best only when you need a really thin kerf or extremely tight radius, but they are slow, break easily, and are not as easy to "steer" on straight lines or gradual curves. For pieces too large for my bandsaw I use a raspy hook-tooth blade and cut wide of the line. Otherwise I use medium blades consistent with the smallest radius I need to cut. The Flying Dutchman Ultra Reverse #9 is narrow enough for tight turns, thick enough to hold up well, but not wide enough for smooth steering. It can be tiring to use reverse blades, because you have to hold the work down firmly, and for most clock parts, a little tearout on the back that the reverse teeth are designed to prevent is not visible.

BAND SAW
Except for inside or intricate cuts requiring a scroll saw, or long straight cuts suited to a table or radial arm saw, a band saw is easier (and safer) than any other kind of power tool. You can buy a 9" tabletop reconditioned Ryobi band saw for about $100. Quarter inch blades are better for straight lines and heavier work, such as frames, if the radii are not too tight. I use a 1/8" blade for rough cutting the faces of gear teeth -- faster than any blade on a scroll saw -- then sand to the line. Not all suppliers offer these short blades, but I’ve found the the Morse blades available on Amazon cut way better than the generic blades I started with.

PATTERNS
For laying out patterns, I don't use messy spray. Instead I go to an art supply source (like Blick’s online) and get

A medium-size can (with brush) of Best-Test rubber cement
A pint can of the same for refilling
A pint can of Bestine rubber cement thinner (don't try to use mineral spirits!)
A rubber cement pickup block (looks like a block eraser)
A small flip-top squeeze bottle or spray-top bottle, to fill withBestine.


Before cutting, use the pickup block to lift any cement from the lay-out so that wood dust will not adhere when cutting. To remove the paper after cutting the wood, if it wants to tear when peeling, spray or squeeze the Bestine onto the paper, wait 30 seconds for it to soak through and soften the cement, and just lift off. Bestine dries rapidly, so work fast. Two minutes later the wood will be dry again, and the remaining cement can be easily rubbed off with the pickup block.

For a slower and cheaper method, use mineral spirits, but that must dry for 10 minutes after pattern removal or it will be gooey on the pickup block. I hear a heat gun works well by softening up the cement, but I don’t have one so can’t comment. Remember: never use mineral spirits as a rubber cement thinner! You’ll ruin the cement.

I like the minute or two of working time wet rubber cement provides to adjust the pattern before it sets up, but to get a very firm, fast bond, use a thin coating on both surfaces and let dry before sticking them together.

Some of Clayton Boyer’s larger and more curvaceous frames are may require a glue-up of two pieces together. And, the shapes of the separate pieces may be devilish hard to accommodate clamps. So plan ahead, and add to each side of the pattern “ears” or flats sticking out with parallel surfaces to facilitate the clamping. After the glue sets, then cut off the ears to the final profile.

GLUES
Of course, while rubber cement is wonderful for paper, it is no good for joining wood pieces together. There is no one adhesive best for wood.

Polyurethane glue (like Titebond II) expands as it sets and causes a foamy squeeze-out that must be scraped off when firm but not cured – 30 or 40 minutes. Excess can be cleaned with alcohol when wet, but that won’t prevent squeeze-out. It requires moisture to act, so in dry conditions, the wood can be moistened lightly before application. This expansion absolutely requires clamping to prevent the pieces from being pushed apart, but it is a distinct advantage when joining end grain or pieces with uneven surfaces or voids. Stronger than wood.

Elmer’s glue is also stronger than wood and is easier and less messy, because it is water-soluble when wet. It benefits from clamping, but since it doesn’t expand when setting, it’s the stuff to use if clamping is not practical. The white kind dries clear, and never reaches 100% hardness, so I’m told it can creep over the long term under heavy load. The yellow kind does not dry clear, but it reaches full hardness. It sets up faster than white, a property which I like.

Super glues are fast and easy. I am using them more and more, especially for non-porous materials. Keep an alcohol swab handy to clean up spills before they harden, which happens fast.

SANDING
Always buy the more expensive grades of sandpaper, and never bother with the old-fashioned cheap stuff.

I find the most useful all-around sandpaper to be the yellow 220 grit, but when significant smoothing is required, don’t try to save time by starting with too fine a grade. You’ll spend more time and get less done than if you work down with two or three grades of increasing fineness. Don’t bear down hard with sandpaper. I do not know why, but a light pressure not only makes the paper last longer without filling but also seems to remove more material than heavy pressure.

I also love the 3/16”-thick sponge-backed “All Purpose Sanding Pads” made by 3M in three grades. They follow curved features nicely and on flat surfaces with a first coat of shellac to smooth out, they are less likely than sandpaper to sand through to bare wood at the edges.

I found the cheap 1” belt sander sold by Harbor Freight and others lousy for any purpose – too loose and unpredictable. But if you have a band saw, you can buy band saw sanding belts incredibly cheaply from customsandingbelts.com. These work so well I have stopped trying to cut teeth to the line and now sand to the line instead. I’m using the 180 grit, ¼” width belts but perhaps a wider belt would be more easy to control.


For manual correction of dental and other detail I usually use a flat sanding stick. Take a regular paint stir stick and sand the profile down so that one edge is sharpened to an acute angle and the other remains flat or is rounded to whatever radius you like. A sanding stick sharpened at the end is useful for working on clocks that are already assembled. Use rubber cement to hold 150- or 220-grit sandpaper so it bends snug around the edge of the stick. When the paper fills at the edge, peel it up and shift the edge to fresh paper, which will often adhere again to the old adhesive.

For flats, edges, and the ends of rods and tubes, a belt-disk sander is essential. A cheap 4” model such as the smallest Craftsman is just fine for clock work. Don't be concerned about some user complaints that the Craftsman is underpowered – those users are just trying to push it too hard.

For sanding the insides of curves, Ridgid makes an absolutely marvelous spindle/belt sander, a recent luxury purchase I would not now want to be without.

WHEELS AND PINIONS
When cutting wheels and pinions, I start with a 1/16" or 5/64” hole in the center regardless of the final arbor size. It’s easier to locate a small bit accurately than a larger one, which will then center itself nicely in the pilot hole. Cut the outside circle of the wheel or pinion a little larger than the final diameter. Either before or after cutting the tooth side profiles, sand the circumference to the line on the belt sander. If concerned about concentricity, you can mount the gear on a 1/16" rod set in a piece of scrap wood clamped to the table of the disk sander and turn it down to exact radius relative to the center. To assure smooth running prior to assembly, you can optionally set wheel and pinion pairs on a fixture of scrap plywood with the 1/16" pins at the correct spacing per plan. You can then check the mating of the two and make any adjustments to either teeth or final spacing before committing the frame. Usually, I do this step on short brass stubs on the open back frame itself, after drilling holes to the final size but before doing any assembly.

To drill out the 1/16" holes to final diameter while keeping true the center location, you can use brad point bits, but be careful that the point is right on center -- they can be bent, or even come from the seller off-center. In general, I don’t much like them, but they have the virtue of reducing tear-out if they’re sharp. Forstner bits are better than brad points, but I’m not sure whether you can get them in the odd 64th sizes often needed. An interesting tool for enlarging holes is the "center bit" available from buydrillbits.com and others. They are made for metal lathes, I think, but are great in a drill press if you’re mindful that they overheat easily. They’re very robust and will not bend or drift, but are available only in a few sizes. The small or “pilot” tip diameter is of minor importance, as this bit tends to center nicely in just about any pilot hole. I’ve just started using this nifty bit, and wish I had known about it earlier. Do not confuse this tool with the "self-centering drill bit" sold by Rockler and others. The one I mean is short and double-ended, without much by way of grooves.

When enlarging pilot holes, I used to clamp the work down, tap it carefully into place, and use a brad point bit, but all that didn’t always keep the bit in the center. Now I just use a regular or center bit, get it spinning, hold the work to the table by hand, and let hole find the bit as the bit comes down. It sounds mighty sloppy, but for me it works better, and it’s easier and faster.

KEEPING TRACK
Sometimes a clock will run reliably from the beginning and need little attention except for winding and occasionally regulating. But a wood gear clock is next thing to a living organism, and it can take weeks or months to work out its little issues. Even with simply regulating (adjusting the pendulum screw), it is helpful to know when the last adjustment took place and what that adjustment was. I keep an index card near each clock and use a notation system to record its history as I go to wind it each day. My notation system is:

. [period] New day
, [comma] Set hands. If you find five dots between commas, you probably don’t need to regulate the pendulum – it’s pretty accurate. If you see a comma occurring after every one or two dots, then you probably want to give the pendulum screw ¼ turn and see if it starts keeping better time.
+ [plus sign] Running fast
- [minus sign] Running slow
~ [tilde] Running true. Combinations can be used: a tilde above a plus would mean “Running slightly fast.”
Vertical zigzag or sawtooth Sanded a problem tooth or other part
“A” plus a fraction Adjusted pendulum. A ¼ means I turned adjusted screw ¼ turn
S plus a time of day Clock stopped at a particular time indicated by its own hands
// Double slash Serviced clock in a way that its wheels no longer show the same positions at a given indicated time.

Many would not bother to keep this little log, but I would never not bother. It helps me see trends and decide what to do next to keep the clock running true.

TROUBLESHOOTING STUCK CLOCKS
The first order of business, before even starting up for the first time, is to mark one location on each wheel and pinion pair where they are going to meet every time you assemble the works. There’s no point in fixing a problem spot and then lose the fix by changing the relative positions later on.

I keep a log to record the times of day when a clock tends to stall, and by referring to the periodicity of the various wheels, the precise location can often be identified.

Running problems usually occur in the "going train" where big gears ("wheels") are driving little gears ("pinions") . As noted in Ward Goodrich’s classic, The Modern Clock (modern as of 1905 anyway) the business of such "spur gears" is accomplished in general by the addendum (top half of the tooth) of the wheel acting on the dedendum (bottom half of the tooth) of the pinion. Problems in the meshing of gears, on the other hand, frequently occur when the less important addendum of the pinion collides with the less important dedendum on the wheel on the way in, instead of grazing into position. This is called butting. What this means, in practical terms, is that if you find stoppage problems where butting occurs, the first order of business, after marking the location, is to adjust the upper part of the pinion tooth (its addendum) and/or open up the part of the wheel tooth that lies toward the valley (its dedendum). As explained above, this should not affect the integrity of the working surfaces, assuming you have shaped those correctly. Also blunt any sharp top corners of the teeth on both wheel and pinion, usually a good practice across the board. I have found that some wood clock plans seem to incorporate gear profiles that are theoretically correct but not forgiving enough for the vagaries of wood and woodworkers. So I’ve overcome my fear of removing too much material when shaping gears and sand fully down to the line. Gears normally won’t stop if they’re a little loose.

The above paragraph applies only to cases where the wheel (the larger one) drives the pinion. Where the opposite is the case, as in the motion works (gearing down to move the hour hand), all these rules are void -- but you rarely find a problem in this part of a clock.

In no case should the top of any tooth meet the “bottom land” of any opposing tooth: If this happens, your cause may be bad centering of the wheel and/or the spacing on the frame. Even if the frame is already drilled, dowling and redrilling if needed may be a better idea than going around messing with tooth profiles everywhere.

Stoppages are not always due to gear problems. Failing to balance the escape wheel (by drilling and inserting brass plugs) can definitely stop a clock, I’ve found. If the crutch pin is too tight or too loose in the pendulum slot, you’ll have trouble. You should have pin clearance of about the thickness of a dollar bill. Rarely, riding turns can occur on the wind spool, decreasing torque.

Checklist for troubleshooting a stuck clock, based on things that have gone wrong for me:

Butting teeth – usually pinion addendum entering against wheel dedendum
Tooth jamming between opposite teeth -- tooth too fat or valley too thin (relieve the non-functional surfaces of tooth or valley)
Wheel out of round, no clearance with pinion
Out of balance arbor, especially escape
Side of wheel scraping something
Not enough drive weight
Too much drive weight (excess friction)
Pins on contrate wheels not of even length
Hands scraping or hitting other parts
Tube binding on rod, sometimes from excessive setscrew pressure
Arbor too tight in frame, or not co-linear with both arbor holes in the frame. (The latter issue can happen even if the arbor seems to spin nicely at each end when frame is disassembled). To make a nice curette for gently shaving out a tight or misaligned arbor hole, take a suitable size brass tube and grind an oblique lengthwise flat through one end, making a blade form perfect for enlarging or cleaning the arbor hole of shellac or varnish.
Arbor compressed lengthwise (no endplay)
Crutch pin too tight or too loose
Damaged or misplaced pendulum pivot
Riding turn on wind spool
Pallets out of adjustment
Fouled weight cord
Fouled weight cord pulley

I do not think I have ever had a stoppage that did not fall into one of the above categories.

RODS AND TUBES
One of the rookie gaffes of my first try at clockmaking was using the hacksaw to cut tough stainless rod (took forever) and delicate brass tube (I don’t even like to think about that). I quickly realized that the Dremel abrasive cutoff wheel was better than a hacksaw. But I didn’t like the way it walked and jumped and soon found an even better answer. Harbor Freight has a 6” cutoff saw, including motor, for $29.95. Well worth it. The chopper makes a rough end that can be finished nicely on the disk sander. Arbors should be placed in the drill press and polished with a sequence of medium to ultra fine sandpapers, or with wood or leather clamps.


BEARINGS
Bearings are seldom specified in clock plans, but I now use them on all parts with heavy loads – normally the first one or two arbors. I used to use KMS plastic bearings but after a couple of failures now mostly use VXB metal ones. KMS makes nice plastic spool bearings for rigging weights, though.

WOOD FINISHING
I won’t say much about this, because I am not very good at it.

A good grade of birch plywood is the usual choice for making wheels and pinions, and for many other parts requiring strength, but it doesn't finish very well. American birch ply grades sold locally are often lousy: weak and full of voids. I have settled on www.dndplywoodonline.com, which offers many other hardwood plywoods as well, as my regular supplier. Or try to get “Finnish birch,” which has more plies and is better quality than generic Baltic. With any plywood and with some other woods as well, stains and other finishes may not apply evenly and tend to blotch. To minimize this, you can rub in (not brush on) some 1-2 pound dewaxed shellac before applying any other stain or finish. If it doesn't say dewaxed, don't buy it. Some top applications like polyurethane will check (crack) over ordinary canned store grades.


I use dewaxed shellac flakes from shellac.net: super blonde or “platina.” Darker shellacs like garnet tend to turn out too yellow or orange. Plan ahead if using flake: depending on strength of mix, temperature, and frequency of agitation, it can take up to several days to fully dissolve in a half-pint canning jar. In that size container, use one ounce of flake per “pound” strength desired. I store flake in the freezer sealed in several layers of plastic bag, and keep mixed shellac in the fridge. Moisture ruins shellac, so use only the freshest alcohol, and always let mixed shellac come to room temperature before opening to avoid water contamination through condensation. Very inflammable – keep it away from a gas range or other flame. Always strain through a paper towel before using.

My method is to use platina shellac (from flake) for all steps except the final coat. Alcohol-based, it dries fast and can be mixed in all different ways. The first coat of shellac will seal (and optionally stain) the wood and raise the grain. When thoroughly dry, the raised grain is brittle and can be easily sanded or steel-wooled (with synthetic wool, not metal) down to a smooth base for the next coat(s). Never allow any finish to get on gear teeth, except perhaps a soft paste wax, though even that might raise the grain.

I’v recently started using dyes called Transtint. Forrest Burnett, kinetic sculptor and clockmaker par excellence, has described a method of mixing three cups sanding sealer with 2/3 cup of lacquer thinner, then adding tint drop by drop until reaching the desired shade. He uses a costly airbrush-type sprayer and gets splendid results. I don’t have such a sprayer. In my limited exploration of the subject, I have found that the brown shade of Transtint in a thin 1-2-pound shellac-alcohol is quite good for darkening birch to a handsome faux walnut grain, and the colors like blue or red are marvelous for allowing the grain to show through a beautiful, bright hue. None of the other staining gels or liquids I’ve tried can come close to the Transtint results. I always conclude with one coat of the most expensive satin polyurethane I can find, using one high-grade brush for application and a smaller dry artist or chip brush to pick up the sags and globs before they set.

FRAME
If you don’t have a router but have a Dremel tool, get the cheap little Dremel router table and the small quarter-round router bit. It will apply a lovely little radius to such elements as your frame and your wheel cutouts. It’s a cheap, sloppy little tool, but it’s little inaccuracies can easily be sanded out by hand.
You’ve got to be able to take down the clock for service. If you have to use any kind of permanent anchor to mount it to the wall, consider what I did with my Marble Strike (which you can see on YouTube). I made a mounting frame slightly larger than the original back frame of the movement, countersank T-nuts into the back facing forward, and then attached it permanently to the plaster wall with wing anchors. The clock now mounts and dismounts easily from the mounting frame with bolts joining the original back frame to those T-nuts.

HEALTH AND SAFETY
Wood dust can disable and even kill. Really, look it up if you don’t believe that. If you can smell it, you are breathing it. Larger-scale woodworkers like cabinetmakers spend thousands on dust control. Before you start making dust, make quite sure that this problem is addressed. If you work in a shed or other location suitable to exhausting air directly to the outside, flexible ducts leading from the tool via a strong blower (like the Delta) to the outside make the cheapest solution. Whether you choose that or an expensive vortex filter system, the suction should be concentrated on the tool you’re using, preferably with a separate overhead filter box nearby to capture ambient dust. I don’t have one of those. Instead, I use two hoses: one connected to the tool’s dust port and one near the work to draw away dust thrown up from the table. Blast gates can route the suction to different areas of the shop. A truly correct procedure would include a dust mask, but the ones I’ve used interfere with my eyeglasses or vice versa.

Never stand edge-on to a spinning cutoff wheel or sanding wheel. I have tried several different pairs of goggles for eye protection – the kind with an elastic strap around back of the head. I almost never used them because they were so fussy and uncomfortable. Now I have slip-on safety glasses of the kind used by many dentists, and I use them all the time. They fit over eyeglasses and are easy to wear. A fine inexpensive product is the Encon 1400 available from Practicon.com.

Never place a foot, hand, or cat under a drive weight. Weights drop – that’s their job, and sometimes they do it at the wrong time.

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