If you want to know what a man’s like, take a good look at how he treats his inferiors, not his equals.

J.K. Rowling, Harry Potter and the Goblet of Fire

Introduction

This is the second in a two part series about Japanese exchangeable-blades handsaws (“kaeba saws”).

In Part 1 we examined the history of how these saws came to be, how they are manufactured, and the market forces that made them so popular in Japan and even overseas. In this conclusion we will consider their advantages and disadvantages compared to traditional fixed-blade saws, and explain a few simple techniques Gentle Reader can employ to improve the performance of one variety.

I think all who have used them will agree that exchangeable-blade handsaws (“kaeba saws”) are effective and convenient products. However, Gentle Reader may be pondering, no doubt with exquisite grace and dignity, the question: “Do kaeba handsaws exhibit performance superior to well-made traditional handsaws?” The simple answer is unequivocal: sometimes yes, sometimes no. The Okey Dokey list below summarizes the reasons supporting your humble servant’s decisive answer.

But to avoid too much confusion, let’s briefly review the materials and techniques used in making the kaeba handsaw before attempting to navigate Okey & Dokey.

Review of Materials and Production

You will recall from Part 1 that kaeba saw blades are manufactured in automated CNC production lines using pre-hardened, pre-sanded, sheet steel of uniform thickness purchased from rolling mills. The sawmaker’s machinery cuts out the blade blanks, deburrs them, punches the teeth, shapes and polishes them with automated precision grinders, adds set to the teeth, and sometimes tensions the blades between rollers. The teeth of some blades are also instantaneously induction heat-treated (what some manufacturers call “impulse hardened) producing teeth harder than a sawfile.

Unlike the blades of traditional, high-quality saws, however, kaeba saw blades are not differentially hardened, taper-ground, trued or hammer-tensioned, nor are their teeth professionally sharpened, tuned or quality inspected. And of course, the backs of backsaws like dozuki are not carefully fitted. These are big, decisive differences not apparent to the untrained eye.

So with these physical differences in mind, let us next consider the pros and cons.

The Okey Dokey List

Some Advantages of Kaeba Handsaws Compared to Traditional Handsaws

1. Lower Initial Cost: The initial cost of kaeba saws is less than traditional hand-forged saws. This is to be expected as they are mass-produced on automated machinery involving zero handwork by craftsmen.
2. Greater Convenience: Dull or damaged blades can be quickly replaced with new, sharp blades improving convenience and obviating the need to carry entire bulky spare saws, and to have their teeth resharpened.
3. Greater Durability: Kaeba sawblades with induction-hardened teeth (aka impulse-hardened teeth) are more durable and remain sharper longer than traditional fixed-blade handsaws, especially when cutting EWP (engineered wood products) such as plywood, MDF, OSB, LVL, glulams, etc. which contain hard adhesives and abrasive sandpaper grit. This is not the case for all kaeba sawblades, of course. From the craftsman’s viewpoint, this is perhaps their most significant performance advantage, and is nothing to sneeze at.
4. Disposable: Like cat litter, plastic beverage bottles, and modern marriage, kaeba saws are a “use and toss” product that need not be repaired, only replaced. Fortunately, unlike marriage and cat depositions, lawyers don’t get involved much.

Disadvantages of Kaeba Handsaws Compared to Traditional Handsaws

1. Less Economical Long-term: While cheaper when new, and although some kaeba saw blades can be resharpened (except those with induction-hardened teeth), the cost of a new replacement blade is typically more expensive than the direct cost of a professional sharpening job, another profit motive for planned obsolescence
2. Limited Blade & Tooth Options: While popular blade and tooth shapes/quantities are readily available, the specialist blade shapes/teeth required for woodworking trades and tasks other than carpentry (e.g. luthier, fine interior joinery, kumiko zaiku, large rip and crosscut work, smooth cutting of hard woods, etc.) are simply not available as kaeba saws often leaving craftsmen who rely solely on kaeba saws bereft of adequate tools. Case in point: most kaeba saw blades are designed to cut the varieties of softwood commonly used in housing construction quickly and efficiently but are not well suited to cutting most hardwoods smoothly or precisely. On the other hand, some craftsmen and certainly professional saw sharpeners can readily modify the teeth of a traditional saw to satisfy specific job requirements. Younger craftsmen that grew up using only kaeba saws do not even realize this sad state of affairs. I encourage Gentle Reader to learn how to sharpen your own noble saws.
3. Unknown Materials & Quality: As mentioned above, kaeba saw blades are made from pre-hardened, pre-sanded sheet steel (chemical content undisclosed) of uniform thickness supplied by rolling mills (nation of origin undisclosed). When your humble servant first inspected a kaeba saw maker’s plant around 2010, they were using high-quality, clearly-identifiable steel of known chemical composition produced by a reputable Swedish mill (specs and QC marks etched on the surface of the steel), but now that kaeba sawmakers have effectively conquered the handsaw market in Japan, the “bait and switch” principles taught by Harvard Business School and exemplified by McDonalds hamburglers have been fully implemented. Not unlike BS, B&S is an extremely profitable business management tool, one considered wise by some short-sighted business executives and those who can’t count past 20 without dropping their pants. Caveat emptor, my dear.
4. Differential Heat Treatment: Although some Gentle Readers may be unaware of the importance of differential heat treatment in an excellent sawblade, much less the pros and cons thereof, kaeba sawblades lack the advantages of the differentially hardened plate found in quality, traditional Japanese (and Western) handsaws resulting in:
   1. Decreased toughness of the plate
   2. Increased springiness and resonant vibration in-use often harming precision;
5. Taper Grinding: Being made of uniform-thickness sheet steel, the kaeba sawblade is not taper-ground resulting in:
   1. Increased binding and kinking in use. A kinked sawblade, of course, is irritating and destroys precision. It’s also less than worthless because it interrupts the user’s work as he replaces it, an inconvenience and expense the uninformed user typically blames on himself even though the true culprit is the inferior sawblade.
   2. Greater set is required to avoid binding and kinking, which equates to more energy and time expended to create more sawdust, a positive factor for weight loss, but not so much for efficient work.
   3. Greater tendency of the blade to wander in the cut increasing irritation while reducing precision.
6. Sketchy/No Hammer Tensioning: Although some kaeba blades are tensioned between steel rollers in the same way circular sawblades are, the tensioned area in kaeba saws is a band across the length of the blade, and not the ideal oval shape sawsmiths typically produce by hand resulting in greater susceptibility to warpage/buckling as the blade heats up in use resulting in increased friction in the cut, reduced work efficiency, increased irritation to the user, and more damaged blades requiring replacement thereby increasing the profits of sawblade manufacturers, distributors and retailers. Another of Baldrick’s cunning plans?
7. Less Precision: The precision achievable using kaeba backsaws such as dozuki is significantly less than that of high-quality hand-forged traditional dozuki backsaws for the following reasons:
   1. The back may not be straight;
   2. The back is not secured to the blade as securely permitting more slop;
   3. The plate has never been trued and may not track as precisely.
   4. The set of kaeba saw blades is decidedly excessive for precise joinery work.
8. Rougher Cuts: Kaeba blades typically have greater set compared to traditional sawblades necessitated by their lack of taper grinding, making the saw cut less smoothly. In addition, uneven left-right set often encourages the sawcut to wander into the weeds.
9. Landfill Stuffing: As mentioned in Advantage 4 above, like cat litter, plastic beverage bottles, and modern marriage, kaeba saws, are “use and toss” products, veritable landfill stuffing in-waiting. I will leave it to Gentle Reader to decide if this is good or not, but I am convinced kaeba saws find the transition from valued tool to rubbish lonely and emotionally damaging, which explains the increased demand for board certified metallurgical psychologists such as ton modeste serviteur.

Only Gentle Reader can answer the question of which type of saw is superior, but despite my sometimes negative observations listed above, I freely admit to liking and using both types in the context of “horses for courses.”

User Improvements to the Kaeba Dozuki Saw

Many moons ago I associated with a group of young, energetic and extremely pragmatic carpenters in Tokyo intent on finding solutions to deficiencies in modern tools anyone could put into effect. For instance, one item they studied to death was how to get the most from synthetic waterstones, a highly-successful bit of research IMHO.

Another tool they researched was the kaeba dozuki. While they didn’t propose any new, earth-shattering innovations, some of their techniques are worth employing.

Improvement No. 1: Side-jointing the Teeth

This first tuning technique is one that works on all handsaws and can especially help your kaeba dozuki saw cut straighter and more precisely, leaving a narrower kerf and smoother surfaces. This is traditionally performed using a file in the case of standard sawblades, but in the case of a kaeba dozuki saw with induction-hardened teeth, we need to use a harder tool and with more precision; Enter the Arkansas stone stage right.

You will need a new kaeba dozuki blade, a hard (not soft), flat Arkansas whetstone (novaculite) dimensioned approximately 8″x3″ (larger is OK but much smaller won’t work well), a piece of white copy paper, a can of light-weight spray lube such as WD-40, CRC5-56 (not PTFE), or brake cleaner, a relatively clean toothbrush, and a clean cotton rag. Please note that India stones, carborundum stones, waterstones, diamond plates won’t get the job done.

1. Lay the paper down on a flat, stable, wooden board or workbench. Place the sawblade on top.
2. Give the blade a light spray of lube.
3. Gingerly place the hard Arkansas stone lengthwise on the blade parallel to the cutting edge, with one end hanging approximately 25mm (1″) off the toe end of the blade, one long edge resting on the blade, and the opposite long edge hanging off the blade about 6mm (1/4″) past teeth.
4. Without placing any downward pressure on the stone, pull it towards the heel (handle end) of the blade, parallel to the tooth line, in a single smooth stroke until the end of the stone is hanging about 6mm off the heel of the blade. Slow or fast, it makes no difference, but I prefer slow. Just one stroke, mind you. The goal is for the stone to lightly abrade the sides of the tips of the teeth essentially “jointing” and bringing them all into line. In addition, and perhaps more importantly, even if your sawblade has perfectly uniform teeth, kaeba dozuki blades almost always have too much set, which this technique will reduce, improving the smoothness and precision of the cuts it makes.
5. Turn the sawblade over and repeat steps 1~4. With this the stone will have made a single pass over both sides of the tips of all the blade’s teeth. In the case of blades with induction-hardened teeth, you may need to make 2 passes of the stone per side, but be aware that every pass reduces the useful life of the blade significantly. Also (and this is very important if you value your sanity), be sure to make the same number of strokes in the same manner to both sides of the blade.
6. Take the blade outside and blast it with your can of spray lube to remove any particles of stone and metal left in the teeth. You may not be able to see this swarth (mixture of stone, steel and lube residue), but it is there, and if not removed, it will dull the blade during the first stroke in wood sure as eggses is eggses.
7. Use the toothbrush and more spray lube to scrub the teeth to remove any remaining swarth residue.
8. Spray the blade with lube or brake cleaner from both sides with the teeth pointing downward flushing any remaining swarth out of the teeth.
9. Wipe the blade with the cotton rag from the blade’s back over its teeth. You don’t want the teeth to cut the cloth, or the cloth to catch on the teeth. If you observe any swarth residue on the cloth, repeat steps 6, 7 & 8. Do not use the saw until all the swarth is gone.

Tasting the Pudding

Now that the sawblade’s teeth have been side jointed, let’s test them to see if they need further persuasion.

You’ll need a piece of flat, knot-free softwood like pine with one straight/square edge, perhaps 150mm (6″) wide and 19mm (3/4″) thick. Use your marking knife and hardened square to mark a line on the wide face perpendicular to the straight edge. Clamp this board to your supporting bench or sawhorse with the line you just made hanging off the side.

With the saw’s edge angled about 30˚from the horizontal plane (surface of the board), begin a cut from the far end of the line. use a light touch and let the saw cut where it wants to cut. Does the saw cut a straight line, or does it tend to wander to the left or right?

You may not be able to tell from this initial test, but pay attention when using the saw to see if it tends to wander from the line. If it does, the teeth on the side of the blade it tends to drift towards may have too much set, in which case use the same stone and lube to joint the teeth on the offending side. Be very gentle because there’s a risk of making it worse.

Again, be aware that side jointing the teeth means you will have to joint the top of the teeth more than usual next time you sharpen them reducing their length and the overall lifespan of the blade that much more. This is not a big loss for kaeba saws, but will reduce their lifespan.

Improvement No. 2: Tuning The Back

Dozuki saws have steel backs used to stabilize the thin blade and protect it from buckling. In the traditional saw this is a folded strip of steel that clamps over and tightly grips the back of the blade, much like Western backsaws. In the case of kaeba dozuki saws, however, the back cannot tightly grip the blade too tightly or it will be impossible to replace the blade, reducing the money, money, money, money, mo-ney the manufacturer needs Gentle Reader to contribute towards his purchase of that new Italian sportscar and the Greek vacation he promised two of his girlfriends (at the same time?).

The problem is that this necessary “tolerance” (aka “slop”) often allows the blade to wander more than is necessary. But what to do? I propose three useful techniques below for Gentle Reader’s kind consideration.

Deburring the Slot

The first item we need to check for is burrs inside the slot in the back. This is not a frequent problem, but it does occur.

Begin by removing the blade from handle/back, reversing it, inserting the nose or tail of the blade in the slot, and without cutting your hand, running it back and forth in the slot. This should give you a good idea if there any big burrs or restrictions in the slot. If you find any, mark the location on the back with a marking pen.

Next, and while it may imperil your extravagant income and glamorous lifestyle as an international hand model, run your fingernail inside the slot checking for burrs that might tend to tweak the blade this way and that.

If you detect any burrs, a skinny deburring tool might get rid of them. Be careful that bits of metal don’t fall inside the slot.

Or, you can fold a piece of wet/dry sandpaper (220 grit?) in half and run it back and forth in the slot where the burrs are hiding removing/smoothing them. Some of that spray lube might help. When doing this, once again be careful to prevent large pieces of metal from falling inside the slot. When done, thoroughly flush out any swarth and bits of metal with a few squirts from your can of spray lube or brake cleaner while swinging the handle like a helicopter rotor blade. I guarantee The Mistress of the Blue Horizons will neither understand the importance of this manly ritual nor appreciate the artistic spots it may leave on her walls and ceilings, so I suggest you perform it outside, with style and grace of course.

Straighten the Back

With the slot safely deburred, let’s next consider the back’s straightness. Obviously, if a saw’s back isn’t straight, the blade won’t be either, and the cut it makes will tend to wander. So you need to check the back, and if you determine it’s out of wack, correct it.

The back, being made of folded sheet metal, is not a precision-milled component, so please don’t expect perfection, and firmly quash any OCD persnicketiness.

With the blade installed, use a precision straightedge held against the sides of the back with a lightsource to check for bow and gaps. Be sure to check both sides. A steel straightedge like that of a combination square will work, but a thinnish beveled-edge straightedge like our 400mm stainless steel straightedge by Matsui Precision works best.

A feeler gauge may be helpful in evaluating any gaps.

Straightening the back is not something readily done with a hammer for a number of reasons, but we can bend it straight if we are careful. To do this, lay the saw, with blade attached (this is important), on a flat workbench top or board with the cupped surface facing up. Place a stick of wood under and perpendicular to the back at the lowest point of the cup. The thickness of this stick is key and will take some trial and error.

Place one hand pressing down on the end of the back where it joins the handle, and the other hand on the far end. Press down slowly and carefully, bending the back without taking it past the yield point where the back will permanently bend. The back should rebound when you remove pressure, returning to its original shape without permanent deflection. Repeat this until you develop a sense of the pressure required to reach, but not exceed, the “plastic limit” of the back. You may need to add to the thickness of the stick used to spring the back.

When you have a good sense of the pressure required to just reach the plastic limit, press down on the back again with a little bit of extra pressure causing the back to permanently bend just a tiny bit. No pro-wrestling moves, please. Check the back with your straightedge to determine any improvement in straightness.

The same bending action can be achieved by placing the back, with blade attached to keep the slot from closing up, in a vise with padded jaws. Don’t clamp the saw in the vise tightly, but leave a little gap, and press on the back where it joins the handle, not the handle itself. This technique works well, but since it’s a bit more difficult to feel the plastic deformation of the back, and to control the point of flexure, it requires more self control. Please keep that darned inner badger under tight control.

If the back is snaking this way and that (very unusual), you can try the same technique in various directions.

Check progress with your beveled straightedge frequently.

If this doesn’t work, and your dozuki still refuses to make high-precision cuts, bite the bullet and replace it.

Tuning the Slot

Now that the blade slot is deburred and the back is fairly true, the next step is to determine if we need to improve the gripping pressure of the back on the blade.

This is a difficult job because we need the back to apply enough pressure on the blade to hold it in place without wiggling, but too much pressure will make it difficult to remove and replace the blade without damaging it. So begin by checking the fit of the blade in its slot.

Insert the blade and, while holding it under a strong light, push it right and left paying attention to any gaps that may open between blade and back.

If you discover any significant gaps, mark the locations on the back with a marking pen. A feeler gauge may be helpful. You will need to judge if the blade wiggle caused by these gaps is enough to warrant an attempt to close the gaps.

There are two ways to close any gaps; Both are risky. The first is to use a small hammer to tap tap tap on the back. The second is to use a vise or a C clamp to close the slot. Either way, be sure the blade is in the slot when you execute.

This concludes our tome about handsaw history, advanced business management techniques, rodent cuisine and modern marriage. I hope you found it informative.

YMHOS

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