Breaker Breaker, Good Buddy!

 

Complex Plane Innards

Complex Plane Innards Revealed

I confess that I spent many years of my tool-making life doubting that chip breakers break chips. I went so far as to start calling them cap irons in a feeble effort to shake what appeared to be a grand hoax inherent in the “chip breaker” moniker. My personal relationship to planes convinced me that, for the very thin shavings that fine woodwork finish-planing demands, a sharp blade and tight mouth were the primary contributors to tear-out-free planning. Who needs to “break” a chip that is thinner than tissue paper? I was right. And I was wrong.

Turns out chip breakers do break chips. But they have to be tuned and adjusted to do the job properly. I wrote a brief synopsis a while back.

A chip breaker (aka cap iron or back iron) performs more than one task in the seemingly simple yet elegantly complex machine that is the Bailey pattern-type bench plane (aka Stanley or Record or Millers Falls or Montgomery Ward or Fulton or Preston or Craftsman or Lie Nielsen or Veritas). In bevel-down planes such as these, the cutting edge is cantilevered, unsupported, the whole length of the bevel.

This descriptive diagram courtesy Ellis Wallentine, http://www.woodcentral.com/

This descriptive diagram courtesy Ellis Wallentine, woodcentral.com

Regardless of the thickness of the blade, as the blade “sings” through the wood, that cantileverage allows for some amount of vibration of the cutting edge. A properly made chip breaker has some amount of bend in it – like a leaf spring. While the Stanley breaker has a rather pronounced curl, Hock Tools’ breakers have a slight 1-degree bend. When screwed tightly to the blade, the spring-action of the breaker applies pressure right at the cutting edge. In fact, it’s not uncommon for the breaker to flex the blade with the spring pressure it applies. The very presence of a chip breaker pre-loads the cutting edge – flexing it down to stifle vibration – and making the whole cutting system more rigid.

This illo from is from page 101 of The Perfect Edge

This illo is from page 101 of The Perfect Edge

Another job relegated to the chip breaker is that of blade advancement functionary. While it is stiffening the cutting edge and breaking chips, the breaker is integral to, and serves a vital role in the depth-of-cut system. When you turn the adjuster wheel located in front of the tote to make a thicker or thinner shaving, the wheel moves along a threaded stud to swing a little lever fore or aft. That little lever is hinged in the frog such that it passes through the blade, engages the small rectangular slot in the breaker, and then slides the blade-breaker assembly up or down along the frog.

Breaking the chip. This highly magnified view of a plane iron (1) and cap iron assembly, excerpted from the video by Professors Kato and Kawai, shows the chip-breaking effect of a closely-set cap-iron (2) with a 50° bevel on the leading edge. Note the lack of tearout behind the cutting edge despite the downward sloping wood grain.

Breaking the chip. This highly magnified view of a plane iron (1) and cap iron assembly, excerpted from the video by Professors Kato and Kawai, shows the chip-breaking effect of a closely-set cap-iron (2) with a 50° bevel on the leading edge. Note the lack of tearout behind the cutting edge despite the downward sloping wood grain.  — from Setting a Cap Iron by David Weaver, woodcentral.com

So, we now have the breaker rubbing its tummy and patting its head as it damps the cutting edge and moves the whole business up and down. Why not make it break some chips, too? When set very close to the cutting edge – like a few thousandths of an inch! – the shaving, sliding up the very short edge projection, encounters the abrupt and unyielding wall of the chip breaker and … breaks!

Breaker should be set closer than this.

Breaker should be set closer than this.

That’s right, the shaving is deflected from its desired path, and must bend sharply up, and then out of the plane. That acute bend, combined with the very short edge extension, weakens the wood fibers so that they cannot lever up ahead of the blade and tear out. Voila!

No gap shall be tolerated.

No gap shall be tolerated.

OLYMPUS DIGITAL CAMERA

No gap, at all.

All that said, the breaker’s chip crushing action will work against you if the breaker isn’t meeting the back of the blade with a near air-tight fit. No gaps at all. Finish shavings are very thin – like 0.0005” – and will catch under the most seemingly insignificant gap. When a shaving catches, it creates a miniature Pres-to-log that clogs the mouth of the plane. Some planemeisters go so far as to run the point of a sharp awl along the blade-breaker joint to roll a small burr down against the blade to close any remaining gap.

So, plane performance checklist:

  1. Reasonably flat sole. You needn’t go all NASA on this point. Flatness ahead of the mouth is necessary. No bump behind the mouth can be tolerated. Mostly flat everywhere else. And coarse grit is fine. Relax.
  2. Leading edge of mouth should be sharp and square. That edge wears rounded after miles of shavings rub against it. So, once or twice in your lifetime, check it out and file it sharp and square. It’s holding down that shaving as the blade advances to also help prevent tear-out. Treat it with respect.
  3. Blade – sharp. And if you’re new to all this, sharper than you thought was sharp.
    Polish the breaker's ramp...

    Polish the breaker’s ramp…

    ... to make a smooth slide for the shaving to exit the plane

    … to make a smooth slide for the shaving to exit the plane.

  4. Chip breakers are usually unhardened steel that can be bent if necessary. If your breaker is lifting at one corner, try securing it in a vise and tapping or twisting it flat. Test it fully tightened to the blade, as oftentimes the twist or gap will flatten out when the screw is tightened. And, the breaker can be further tuned by refining the ramp surface similar to how you’d prep a blade: polish with successively finer grits to create a slippery slope for the shaving to slide up.

If all that doesn’t make your plane sing a sweet melody while ejecting lacy, see-through shavings, call me: 1-800-327-2520. Just kidding. That’s Lie-Nielsen’s phone number. But honestly, if you have a plane problem that you can’t suss out, contact me here. I’ll do my best to help.

Good luck,

RonSig

There is a lot of info about planes, blades, breakers, steel, abrasives and so much more in The Perfect Edge: the Ultimate Guide to Sharpening for Woodworkers. Order your copy now!

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How to Fix a Book

page102illo

“d” is Wrong. And Where’s segment “f”?

After over six years and umpteen thousand copies sold, sharp-eyed reader Bernie Vail noticed an error in the second illustration on page 102 in my book, The Perfect Edge, the Ultimate Guide to Sharpening for Woodworkers.

Now I know there are typos; we’ve found a couple and have had some pointed out. But they’re mostly minor things like commas, and such. And while I know that an errant comma can start a war or vacate a verdict, none of ours are that serious, I assure you. (Okay, I renamed Henry Bessemer “Charles” in the first edition but we changed it for the second printing. Sue me.) But this boo-boo renders that illustration useless.

So, what to do? Well, go get your copy of The Perfect Edge and a fine-point Sharpie (I used red), turn to page 102 and do as I did here:

Entries in Red Correct the Error

Entries in Red Correct the Error

That’s right, write in the book! It’s yours, after all, and if not you’ll be doing the owner a favor. You don’t even have to use red. In English: Arc “d” should end at the dashed line that denotes the back bevel. The arc that continues to the sole should be “f”, the clearance angle. We’re missing two arrowheads and an “f”. Make sense?

I hope you’ve not spent too many sleepless nights over the last six years wondering where the “f” is. I apologize for any confusion we may have caused. It’s still a pretty darned good book* and if you don’t have a copy I’d be happy to sell you one. I’ll even sign it for you (if you buy it here.)

Thanks Bernie!

*Unsolicited praise from one of my readers:
Wow! I must say that you have done a masterful job of tying together an enormous amount of technical data. Your sense of humor comes through as well without distracting from the flow. The book is also a visual treat — clear large images leave no doubt as to what you mean to illustrate. There is plenty of hard data to keep the controversies going. I think you have given a very balanced view of the great variety of methods available. In my opinion you have the absolute top book on the topic — period. Congratulations. — B.B.

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2016 Fine Woodworking Mid Winter Show!

Lightweight, by Laura Mays, European White Oak, European Ash

“Lightweight” by Laura Mays. European White Oak and European Ash

The students at College of the Redwoods* Fine Woodworking Program have opened their 2016 Mid Winter Show and it is stunning! The students start working on these projects after the requisite six-week training in the fundamentals every fall semester. They are urged to keep this project “small, simple, sweet and constructed of solid wood.

Linda and Laura Mays with Greg Smith's box.

Greg Smith’s cylindrical box.

Linda and I saw the show on Saturday but there were still a couple pieces yet to be installed so we’ll be going back for another viewing today. The show is only on for little more than a week — until the 24th — so don’t dawdle or you’ll miss it.

WinterShow4

“This Must Be The Place” by Kendra Wolfe. Bay Laurel with Elm Drawer Fronts.

The reception that starts at 5:00 this Friday, the 22nd, is always a great party. The local community turns out in large numbers and many former students make the scene, some traveling great distances through the rain and snow to get here. As usual, yours truly will be behind the bar opening beers and pouring wine. (Some tasks you just can’t leave to amateurs.) I promise it will be a wonderful evening and hope to see you there!

*James Krenov‘s world renowned Fine Woodworking Program has operated in Fort Bragg, California since 1981 as a program of the College of the Redwoods.  Next year, however, the program will become part of the Mendocino College Fort Bragg Campus. Mendocino College is a geographically closer auspices as the main campus is located in the city of Ukiah, an hour and a half drive from the Fort Bragg. College of the Redwoods is based in Eureka, a 3 hour drive from here. So, whatever the name change will be, the same great woodworking program will continue.

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Sharpen the Saw — Part 3

Jointing

Jointing

these file holders work well for saws and scrapers. one or two light passes will usually suffice.

These file holders work well for saws and scrapers. One or two light passes will usually suffice.

Careful sharpening can help avoid the need for jointing the teeth but when the teeth are of an uneven height, the first step in saw sharpening is jointing them even. It is extremely easy to joint the teeth with nothing more than a flat file, but there are scads of saw jointer
file holders on the market. Use an 8″ or 10″ smooth-cut flat file and just run the file lightly along the entire length in one pass.

the shiny flats produced by jointing. they’re different sizes because the teeth were different heights.

The shiny flats produced by jointing. They’re different sizes because the teeth were different heights.

With your lamp adjusted properly you should be able to see a small, shiny flat on the top of each tooth. Different tooth heights will make different sizes of flats. If there are any teeth without a flat, take another jointing pass. If there are any teeth missing or much shorter than the others, don’t try to joint all the others to match unless there are many missing in a row (in which case you will have to joint all the way down to them and reshape all the teeth to match). Just leave them for now and subsequent sharpenings will eventually catch up to them as the other teeth are jointed and shaped over time.

Shapingsaw teeth final annotated

Skip this step if the teeth on your saw are uniform, properly shaped already and simply in need of sharpening. However, if the teeth are in need of reshaping, get the right file, the prepared alignment guide — that scrap of wood with the hole in it — and clamp the saw tightly in the vise, with the teeth just clear of the vise jaws. Start at the handle end and work toward the toe of the blade. Study the flats on the tops of the teeth that were made when you jointed the saw. The goal is to reshape each tooth, with the proper rake angle, such that the flat disappears — but no more than that.

hold the file so that it is horizontal (0° slope) front to back and the rake angle guide horizontal side to side.

Hold the file so that it is horizontal (0° slope) front to back and the rake angle guide horizontal side to side.

Assuming you are working from right to left, at each gullet you are filing the face of the right tooth and the back of the left. You need to reduce the flat on the left tooth by half, and, while doing so you will finish shaping the face of the right tooth (whose flat was already reduced by half during filing in the previous gullet.) If one tooth’s flat is larger than average, press harder against it when filing — favor it, or crowd it, slightly — so that all the teeth are filed to the same shape. When you finish here, joint lightly to check your work. If the teeth are still not uniform, do the shape-filing again.

advance the fleam angle guide as you progress down the blade, filing every other tooth (the ones that are facing away from you). turn the saw around and repeat for the rest of the teeth.

Advance the fleam angle guide as you progress down the blade, filing every other tooth (the ones that are facing away from you). Turn the saw
around and repeat for the rest of the teeth.

Filing

Check your file to be sure it’s still sharp. Filing is the step that actually sharpens each tooth and deserves a sharp file. Assuming the handle of the saw is on the right, and you are working toward the left, find a tooth that is set away from you. Place the file in the gullet to the left of that tooth. You want to file the face of the tooth that’s set away from you (you’ll be filing the back of the tooth to the left, the one that’s facing toward you.) It is the faces of the saw teeth are doing the cutting of the wood and filing them in the same direction that they are set allows the file to chatter less and do a neater job on this more critical surface. The surface of the back of a tooth isn’t as vital to the saw’s performance as the surface of the face, so you want the face to receive the best treatment from the file. Filing requires that you maintain three angles: rake, fleam, and slope. The rake angle guide is the scrap of wood with the file stuck in it. The fleam guide is another scrap with the angle-slot sawed in it that rests over the blade (or an angle guide on the bench behind the vise.) With rip-saws, you probably don’t need a fleam guide because the fleam is 90° and fairly easy to maintain by dead reckoning. The slope angle is the angle of the file relative to the floor. It hasn’t been mentioned yet because it should simply be square to the blade, parallel to the floor. Some saw filers adjust the slope angle in relationship to the fleam angle, but for most common fleam angles it makes little difference in the performance of the saw.

If it seems that all these angles pose something of a juggling act, you’re right. But it only takes a few teeth to get into the rhythm and keep all the balls in the air. Check your setup for all the angles and file a tooth. Don’t be surprised by the noise it makes; that’s the back of the tooth that’s set toward you that’s chattering and screeching. The closer the teeth are to the vise jaws the quieter it will be — to a point. Ear plugs are a good idea. Filing should only require light file strokes because the shape of each tooth was created during the shaping step. The goal here is to remove whichever flat spot may remain, creating a sharp, zero-radius tooth. Skip a tooth — remember, you’re filing every other tooth so that you’re filing in the direction of the set — align your file in the gullet, check your coordinates and file another tooth. slide the fleam guide as needed so that it’s a useful reference. reposition the saw in the vise as needed, too. When you reach the end of the saw, turn it around and start again from the handle end going left to right, flip the fleam guide over so it’s angled the correct way. Remember to reverse the rake guide, too, to file the proper angle on the rest of the teeth.

Setting (after filing)

Some sawyers think it best to set the teeth after all the filing is done. Pete Taran says: The conventional wisdom is to set a saw’s teeth before it is sharpened. I disagree with this approach for several reasons. If a saw is set before it is sharpened, then part of the set
is removed when the teeth are filed. It is very difficult to try to figure out how much the set is decreased in filing as it is dependent on many factors such as how sharp the file is, how hard you bear on the tooth with the file, and how uniform the saw teeth are filed. I prefer to set the saw after it has been sharpened. By setting the saw’s teeth after it has been filed, a very uniform set can be achieved, which not only makes the saw cut well, but also makes a very nice finish on the piece being cut. It only takes one or two teeth to be over-set to make the edge of a cut piece of wood ragged and rough.

Mike Wenzloff disagrees: when being set, a tooth will rotate outward at the face. For a rip, it presents the face all wrong. For a cross-cut, the fleam angle changes at the point of the set upwards to the tip of the tooth. One cannot escape this. While reducing the fleam on a cross-cut isn’t too big a deal, the rotation is on a rip. Very little set is removed if the setting is done precisely before the final light filing. It is just a couple light swipes per tooth except on the larger rip profile teeth.

Quite often, the previous setting from the last sharpening is still within specifications and you don’t need to do it again. Because, after shaping and filing, you’ve removed some of the set, why do it before hand? Make a test cut to verify. If the saw cuts well: straight and clean. Ta-da! Go saw something. If it drags or binds, add wax. If it still drags, you need to set the teeth. The set gets a little smaller with each filing but you may be able to file the teeth three or four times before needing to set them again.

If a test cut wanders off line, the teeth on the side that the saw is cutting toward are set too much. Use a fine stone on the side with too much set and gently hone those teeth a bit. Lay the saw flat and run the stone flat on the side of the blade to hone down the teeth on that side. Take one or two passes with the stone, test again and repeat if necessary. If the saw cut is difficult to control or wobbles around in the kerf, you may have too much set altogether. Measure it with the above specs in mind and if you find you need to reduce it, try clamping the teeth in a vise with smooth, metal jaws and squeezing them to reduce the
set. Squeeze a vise-worth section, advance the blade, squeeze again trying to use the same amount of pressure, advance the blade, etc. Check the cut, hone or reset as needed. Kevin
Drake adds: I much prefer re-setting over honing here, mostly because it has worked
for me when honing has just made matters worse. Besides that, set diminishes with use
so just re-setting may make a saw behave as if it has been recently sharpened.

Be sure to coat those freshly cut teeth with rust preventative. You’re done!

That concludes this three-part excerpt from The Perfect Edge: the Ultimate Guide to Sharpening for Woodworkers by Ron Hock. Thanks for reading. Now go sharpen your saw!

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Sharpen the Saw – Part 2

It only requires a few specialized tools and some practice to sharpen a saw.

It only requires a few specialized tools and some practice to sharpen a saw.

Tools

A simple saw vice can be made from a couple of solid- or plywood boards 8" to 10" and up to the length of the saw. hinges keep it aligned; leather or rubber jaw liners help with “grip” and dampen some of the noise generated by filing.

A simple saw vice can be made from a couple of solid- or plywood boards 8″ to 10″ and up to the length of the saw. Hinges keep it aligned; leather or rubber jaw liners help with “grip” and
dampen some of the noise generated by filing.

Saw Vise

To sharpen a saw, you need a way to hold it securely while you’re filing it. “Official” saw vises are available at second-hand sources (or this great new one from Gramercy) but it’s very easy to make a superior one from a scrap or two of plywood. And, you can make a saw vise that’s closer to the length of your saw than commercial ones, which will save you time re-positioning the saw as you’re working on it. Be sure to have good lighting available. One or two easily adjusted, swing-arm lamps are perfect for the task.

Saw set

a typical saw set. i’ve colored the plunger red for visibility in this photo.

A typical saw set. I’ve colored the plunger red for visibility in this photo.

 it’s easy to set teeth too much. the dial on the saw set should be used as a rough guide, so use caution and calipers to check the set.

It’s easy to set teeth too much. The dial on the saw set should be used as a rough guide, so use caution and calipers to check the set.

Saw sets are readily available and affordable, both new and used. The basic “pistol-grip” style works well. As you squeeze the handle, a small steel plunger pushes against an adjustable, beveled anvil. Some saw sets have a rotating disc with a ramp that’s beveled such that as you turn the adjuster, a different part of the ramp is presented to act as the anvil, modifying the amount of set that the tool will perform with each squeeze. Others have a sliding beveled anvil that is adjusted up and down to dial in the amount of set. The teeth are set in the same direction that they were set previously. Setting a tooth the wrong way — bending it all the way to the other side — can weaken it or even break it off. Take care to match the set direction. The saw set is positioned over the saw blade, a suitable tooth is located, the handle squeezed and the plunger pushes the tooth against the anvil,
bending it the right amount (more later).

Files

the simple guide on the end of the file offers a visual reference to keep the file cutting the proper rake angle on each tooth. the fleam guide, the parallelogram with a slot pictured here on the bench gives a similar reference when filing cross-cut teeth that need an angled bevel. you simply hold your file parallel to the fleam guide as it sits over the saw blade.

The simple guide on the end of the file offers a visual reference to keep the file cutting the proper rake angle on each tooth. The fleam guide, the parallelogram with a slot pictured here on the bench gives a similar reference when filing cross-cut teeth that need an angled bevel. You simply hold your file parallel to the fleam guide as it sits over the saw blade.

The simple guide on the end of the file offers a visual reference to keep the file cutting the proper rake angle on each tooth. The fleam guide, the parallelogram with a slot pictured here on the bench gives a similar reference when filing cross-cut teeth that need an angled bevel. You simply hold your file parallel to the fleam guide as it sits over the saw blade.

You’ll need an 8″ or 10″ smooth-cut flat file for jointing and a small triangular file for tooth shaping and filing. There is plenty of advice available about triangular file sizes, but Mike Wenzloff of Wenzloff and Sons says to use the smallest file that will fully
file the back of the next tooth. A smaller file has a sharper corner and will cut the gullet — the concavity between teeth — deeper for better chip clearance. He also tells me that he can sharpen over twenty saws with a file before the file wears out.

Always use a file handle. The control required, and the comfort you deserve, make this mandatory. Also, those small triangular files have tangs that will hurt you if left unhandled. You can make a handle easily enough but they’re inexpensive to buy and reusable. Filing is usually a two handed job so some sort of “handle” on the other end of the file is a good idea. This outboard handle can be a simple scrap of wood with a hole drilled all the way through to receive the file. The hole should be small enough that the file can be lightly driven in. This additional handle will act as a guide to keep the file rotated to file the proper rake angle in the teeth. To make it easier to reuse this rake angle guide, you may want to mark the rake angle on both sides and to identify which side the handle of
the saw is on so you can line everything up next time you use it.

Speaking of guides, a fleam or bevel-angle guide is handy for filing cross-cut saws. You can lay a bevel gauge set for the correct angle on the bench behind the saw vise or cut a slot in a scrap of wood (both sides) that you slip over the teeth near where you are filing. Either will serve as a visual aid and help keep your file at the proper angle.

Setting (before jointing)

Setting saw teeth before jointing assures that the tops of the teeth will all cut in the same plane. If you set after filing, your flat-topped, jointed teeth will be bent slightly outwards. And, those flat-tops will be bent out of plane with each other. Because professional saw sharpeners debate whether to set before or after sharpening, it seems to me to be a matter of personal preference. As your experience with saw sharpening grows, the difference(s) should become more obvious and you’ll probably end up in one camp or the other. To set the teeth, you can clamp the blade in the saw vise such that the teeth are enough above the jaws to allow comfortable access with the saw set. As sawmaker Kevin Drake says: “I find it more comfortable to just hold the saw in my left hand and set the teeth with my right. My hands sort of wiggle down the saw as this happens.” Sawmaker Mike Wenzloff adds: “holding a saw in one’s lap works with smaller back saws. Not so well on 28″ 4 tpi rips.”

Begin setting with the teeth closest to the handle. Because those teeth get far less use you can use them to fine tune your settings. Adjust your saw set according to the manufacturer’s instructions. often the anvil adjustment is based on a scale of teeth per inch, but when it comes to any one saw, this may not be accurate. And some saw-set scales are just arbitrary reference numbers. Start with a setting that corresponds to more teeth per inch than your saw actually has. That should make for a smaller amount of set; a good
place to start as the saw set’s settings aren’t the code, they’re more what you’d call guidelines than actual rules. Select a tooth that’s set away from you and position the saw set over it with the plunger pointing at the tip of the tooth. Squeeze the handle to set the tooth. Move the saw set over, skip a tooth, and set the next one that’s going away from you. Do a couple more, applying pressure evenly with each tooth, turn the saw around and set the teeth you jumped over in that same section so that you have an inch or so of set teeth. Now measure. Compare the width of the blade stock to the overall width of the teeth you just set. The set of the teeth should increase the thickness of the blade by about 20% for dry hardwoods; up to 30% for soft- and green woods.toothsetExample: A saw blade with a thickness of 0.035″ (0.9mm) should be set to a width of 0.042″ (1.1mm) for hardwoods and 0.045″ (1.2mm) for softwoods. Notice how little set there really is: the total thickness is increased by only .007″ (.18mm) to .010″ (.25mm) so any one tooth is set just .0035″ (0.09mm) to .005″ (.13mm) — that’s only three and a half to five thousandths of an inch. That’s not very much, and because it is easier to add more set than it is to remove, use care not to over do it. After measuring and subtracting, adjust your setting procedure to accommodate the new data and continue to set the saw.

This concludes part 2 of this excerpt from The Perfect Edge: the Ultimate Guide to Sharpening for Woodworkers by Ron Hock. Stay tuned for the thrilling conclusion.

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Sharpen the Saw – Part 1

I’ve fielded a few questions lately about saw sharpening (obviously from woodworkers who haven’t yet read my book on sharpening for woodworkers) and thought this would be a good time to give away (most of) a sample chapter. I hope you enjoy it and that it helps you to keep your saws in optimum condition.  — Ron

From Chapter 9 of The Perfect Edge, the Ultimate Guide to Sharpening for Woodworkers:

courtesy www.toolsforworkingwood.com / gramercy tools.

Photo courtesy http://www.toolsforworkingwood.com / Gramercy Tools.

A saw is a long row of small chisels – sort of. It helps if I keep that image in mind when
I think about sharpening one. But the row-of-chisels analogy is only so good; my imagining must also include the set of the teeth. As the row of chisels cuts through the wood, the rest of the saw, the flat blade that the teeth are part of, follows along through the
cut. The path through the wood, the gap or slit, created by the teeth is the kerf, and if the kerf is the same width as the saw blade, the saw will rub, drag and bind during cutting, making the cut difficult if not impossible to finish. To solve this problem, the teeth of a saw are set by bending them slightly outward, one tooth bends one way, the next tooth the other way and so on along the edge of the saw, so that they cut a wider kerf and allow the rest of the blade to travel unimpeded. Bending the teeth is possible because saws are usually hardened to a mid range hardness — hard enough to hold an edge for sawing but still soft enough to set and to sharpen with a file.

row of chiselsUnfortunately, my “row of chisels” image does not take into account the fact that most saw teeth are sharpened to a negative rake angle and actually cut more like scrapers than chisels. My powers to visualize reach only so far.toothsetA saw tooth’s singular purpose is to remove wood. While a chisel or a plane iron may be called on to do the same thing, we often demand that they leave behind a fine, smooth surface at the same time. To ensure that fine surface, we hone and polish the edges on plane irons, chisels, carving tools, anything that we use to create a smooth surface. Though all the woodcutting edge geometry applies, saw teeth are sharpened to achieve a different goal: they must simply remove material efficiently. A smooth, finely honed, polished cutting edge is not called for; therefore we sharpen saws with a file — an efficient tool to do an efficient job of making an efficient tooth.

Some contemporary saws have induction hardened teeth that can’t be sharpened or re-set; they’re too hard for filing or bending. You can tell induction hardened teeth by the rainbow discoloration at the toothline. These saws will tend to stay sharp for a long time but when one is finally dull, you will have to replace it. Being able to file a saw yourself isn’t only about keeping it sharp. You can also modify the shape of the teeth for different cutting situations. A saw’s edge geometry can be adjusted for optimum performance in, say, green softwoods, which require more set compared to dry hardwoods.

There are two fundamentally different sawing tasks: ripping and crosscutting. Ripping is cutting more or less in the same direction as the grain runs in the wood (with-the-grain) while cross-cutting, as the name implies, is cutting across the grain (cross-grain, see Chapter Four: How Wood is Cut). A rip saw is usually used to narrow a board while a cross-cut saw usually shortens one. Each cutting action calls for a different cutting edge geometry. A cross-cut saw is used for almost any angle of cross-cutting, whereas rip-sawing is most commonly used to cut close to parallel with the grain.

ripset

Tooth geometry of a typical rip saw.

Ripping is done with teeth that resemble square-edged chisels held at a near-vertical scraping angle. Each tooth makes a small, curly shaving much like a small version of the shaving made during with-grain planing. Rip saw teeth are usually filed with a rake angle between an aggressive 0° and a more laid-back 15°. The larger rake angle makes it easier to start a cut; the more vertical teeth will cut faster. Pete Taran (www.vintagesaws.com) suggests a 4° rake as a good compromise for rip saws.

tooth geometry of a typical cross-cut saw.

Tooth geometry of a typical cross-cut saw.

Cross-cutting wood fibers requires some special cutting action. The end-grain fibers that line the kerf must be severed then rolled up and out of the path of the blade. So, to facilitate cross-cut sawing we add an angle to the tooth of the saw in order for it to achieve the fiber-severing goal, allowing a clean cut that leaves a relatively smooth surface along the sides of the kerf. This angle on cross-cut teeth is called fleam, which is also the old-fashioned term for the lancet used to open a vein for bloodletting. Fleam is an angle on the face of the tooth (and generally on the back as well) much like a skew chisel, compared to a rip tooth’s similarity to a square-edged chisel. The sharp point of the skew cuts deeper than the rest of the tooth in order to sever the wood fibers along the sides of the cut, while the rest of the tooth cleans out the kerf.

Courtesy of toolsforworkingwood.com/ Gramercy Tools. Illustration by Timothy Corbett

Courtesy of toolsforworkingwood.com/ Gramercy Tools. Illustration by Timothy Corbett

Rip-saw teeth are filed straight across, the file held at 90° to the saw blade. Cross-cut teeth are filed at an angle from 10° to 45° with 15° being popular for a general-purpose cross-cut saw. Cross-cut teeth have a less aggressive, negative rake angle of 12° for a fast, aggressive cut, to 30°, which is more typical and gives a smoother though slower cut. Another aspect of saw tooth geometry is slope, which refers to the angle of the file from horizontal.

Though it may seem a daunting task (all those teeth!) you can sharpen your saw yourself. Most power-saw blades are either carbide, which is sent to a specialized shop for sharpening, or disposable and simply replaced with new blades when dull. Keep in mind, though, that a good hand saw is another of the many hand tools that will last for generations if cared for and kept sharp. There’s nothing difficult about filing a saw; like everything else it’s a skill to learn and with a small amount of practice, you can make your
saw work better than it did new — a finely tuned tool that you’ll find myriad uses for.

These days, much of your sawing tasks are likely done with one of the power saws that we all seem to have, but there will always be a place for hand saws and hand sawing in any fine-woodworker’s tool kit, and skill set. As your saw sharpening skills improve, you’ll find yourself sharpening your saw more often because you are using it more often, and vice versa. A hand saw is frequently your best tool for many sawing tasks. When you keep your hand saw in good fettle, you’re likely to find yourself turning your back on the noise, dust and danger of power saws in favor of your uncle’s classic, well-tuned Disston (et al), or
one of the beautiful new-generation of saws being produced today.

This concludes part 1 of this excerpt from The Perfect Edge, the Ultimate Guide to Sharpening for Woodworkers by Ron Hock. Stay tuned for part 2.

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Trip Report — International Boatbuilding Training College

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“…there is nothing—absolute nothing—half so much worth doing as simply messing about in boats.” — the Water Rat, from The Wind in the Willows, Kenneth Grahame, 1908.

We didn’t really get to mess around with boats much on our visit to the International Boatbuilding Training College last week. But we did get a grand tour of this remarkable facility on Oulton Broad in Lowestoft, Suffolk, said to be England’s easternmost settlement. Our thanks to the proud owner of the college, Mike Tupper, for taking the time to show us around.

Students from all over the world learn every aspect of boat building and repair, general woodworking and furniture-making — professionals and hobbyists alike. IBTC offers 47-week courses on Practical Boatbuilding and Joinery and Furniture as well as shorter courses: Build Your Own Boat (24 weeks — yes, you sail away at the end of it in your own boat), Woodworking Skills (12 weeks),  Introduction to Boat Surveying, and many more courses that cover all aspects of boatbuilding. And they include the whole gamut of non-woodworking boat-related skills: Glass Reinforced Plastics (4 days), Rope Work — Knots and Splicing (30 different knots!), as well as Rigging, Lofting, Caulking, Welding, and so much more.

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There are boats of every style everywhere in this facility, in every stage of manufacture and repair. The work gets done on each as the curriculum dictates, moving from boat to boat as the students progress. Most of the boats are brought to the school by their owners who contract the school for repairs. They pay for the needed materials plus a small percentage but even though accepted for repair, there is no guarantee when a boat will be ready — could be years.

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Hold on, though. If you need a repair done more quickly than the repair college can offer, it offers a perfect solution: right next door to IBTC, the school operates full-service repair facility that is staffed by many of the college grads. Here are some photos of their work:

Anyone interested in the design, construction, outfitting and repair of boats should seriously consider the offerings of the International Boatbuilding Training College. It’s a resource not to be missed.

 

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