Accuracy of what?

You square the blade to the table saw surface – the setup. Looks perfect; you swear it does. But the workpiece is what matters – the outcome. So you take some test cuts, only to be swearing again, this time in a different way.

What going on? Well, your thinking is right. It is best to work as directly as possible. Assessing the test cuts is closer to the actual goal, which is to make a square edge on a piece of wood so it will fulfill its role in the project. The squareness of the table saw blade is one step removed from that goal.

Another advantage of relying primarily on outcome is that sometimes the error assessment can be magnified. Testing a crosscut for square is an example. The error can be doubled by pairing two cut ends together, or quadrupled by crosscutting around a rectangle.

In theory, a good setup should yield a predictable outcome. As Yogi Berra said, “In theory there is no difference between theory and practice. In practice there is.” Gremlins lurk in the table saw example and in nearly all such matters in the shop. Sometimes decent accuracy can seem impossible to achieve.

The problem is simple (kinda): there are other factors that come into play. You’ve made assumptions. Sometimes these are difficult to measure or account for. For major shop machines and most small power tools, the gremlins can usually be traced to these three key factors:

• Table/surface flatness. There should be no dishing, no bumps, and no twist. Any defects should hopefully be where they do not matter.
• Fence flatness. Fences need to be straight, but also without twist.
• Arbor alignment and runout. The rotating part has to run true.

In the simple table saw example discussed above, perhaps you squared the blade from the left side, but rip cuts performed on the right side are a bit out of square. Check if the table is flat. As another example, imagine the error stacking that can result if jointer tables are twisted and/or bowed.

Looking at that list of three key factors, unfortunately, they are things that you cannot correct easily, if at all.  What’s the answer? Buy the best quality tools you can afford, and check them for good bones. That’s where cheap stuff usually falls short. Of course, other factors come into play but without these basics in order, it will be rough going. Do not be distracted by cute features that are added to make tools sell.

There’s one more issue. When trying to produce accuracy based on outcome assessment, it may be difficult to quantify the adjustments needed to alter that outcome. In other words, how much of a change in the setup will result in how much change in outcome? This happens a lot with the bandsaw. Sometimes trial and error is the best you can do. Sometimes it’s best to make the setup as good as you can and just go with that. An example would be making the table saw slot parallel with the blade.

The main points are:

• Recognize the difference between setup accuracy and outcome accuracy.
• Be cognizant of the multiple factors that may affect outcome accuracy.
• Be aware of the common culprits.

Remember too, you’re going for excellence, not perfection.

What is the most likely pitfall to cause your next woodworking project to fall short of your hopes? Answer: injudicious choice of wood.

OK, sorry, I’ll state it positively: each project has the potential to be greatly elevated by smart choices in choosing and using wood. But let’s look more closely at this matter.

On the one hand, there is knowledge of wood in general. This includes things like wood movement, strength properties, and grain. As you design a piece, you choose species of wood, and then, much as an engineer, use that knowledge to work out the details.

However, wood is not clay, steel, or plastic. Each board is the product of the incredible diversification of the biological world. For this reason, to be really successful at using wood, you must be intimately familiar with the species of wood that you are using. Go beyond your designer and engineer mentalities to that of a biologist.

For any species, there is so much to be cognizant of when choosing the specific boards and deciding how to make the best use of them. Where was the tree grown? How was the log sawn? Were the boards air-dried or kiln-dried; were they steamed? How does this affect the working properties and color? What defects is this species prone to? How will the color change over time? And on and on.

Let’s take cherry as an example, but the important point is that every species has its own large set of potentials and quirks. Cherry’s generally wide availability and easygoing workability can lull you into complacency.

Of course, cherry darkens with time and exposure to light to produce that legendary brownish, brick red color, but this is accompanied by a varying amount of softening of the original figure. Some people like this, others may be disappointed. Some boards have more distinctly etched figure, sometimes with a greenish tinge, and seem to retain it better. Speaking of figure, I find the quartered surface of most cherry to be somewhat disappointing.

More vexing is cherry’s tendency to produce a blotchy effect with some finishes, especially oil. If a board has the tendency to blotch, it is virtually impossible to fully avoid, but it varies widely among boards, so, again, the key point is to recognize this and choose wisely.

Gum streaks are a defect to the eyes of some woodworkers, others may like a few. I’ve also encountered some cherry boards that have fairly heavy gum streaks along with an unappealing “dirty” look that is hard to detect in the roughsawn state. As for the lighter sapwood, some reject it entirely (accepting only “all red”) but some may like the effect, such as with live-edge boards. Cherry from northwestern Pennsylvania is said to be the best available.

When choosing curly cherry, it is a mistake to suppose that it is similar to curly maple. Curly cherry is essentially very blotchy cherry in a nice pattern. Thus, cherry that is sold as “curly” but contains only minimal curl looks poor, and you’ll pay more for it. I’ve also found that curly cherry that is sanded or scraped never looks quite as good as when it is handplaned to the final finish (and that can be tricky pull off), even when a film finish is applied. Curly cherry is quite a different matter than curly hard or big-leaf maple.

I could go on. It sounds like choosing players for a baseball team – good batting average but can’t hit left-handers . . .

I enjoy using a lot of different species of wood, and I’ve paid the price, literally and figuratively, for sometimes falling short in this area. On the other hand, knowing wood really well is a joyful and fulfilling part of the craft, well worth deeply exploring.

Have you listened to your woodwork lately?

We are all cognizant of the visual beauty of wood, its tactile warmth and texture, and the memorable scents produced while working at least some species. But here is a reminder to tune in to the sweet sound of wood.

Notice the resonance when closing a lid or drawer made of solid wood. Or the sound of a ceramic bowl placed on a solid wood table. Compare those to the discomforting clamor of melamine-coated particleboard. The sound of real wood just seems like the ease and contentment of home.

Our lives are filled with the cacophony of sheet metal, glass, plastic, and concrete. How welcome is the comforting sound of solid wood.

We woodworkers create in a very special material.

I recall even early in my youth intuitively sensing that there was something special about wood, and some of that came through its sounds. I remember particularly a sturdy solid wood truck in the kindergarten room and the sounds of loading it with solid wood blocks. That rig had a dignity unmatched by plastic stuff.

Of course, the sound produced from wood reaches its full potential in musical instruments. Remarkably, even with all the advances in materials science, the best acoustic strings and woodwinds are still made from wood. And some of that acoustic magic is present in the solid wood furniture and household objects that we make.

Take notice and enjoy!

Available now is a new and bountiful collection of images of James Krenov’s work through many years, commentary on some of the pieces, videos, and other interesting materials.

The Krenov Archive is an important component of The Krenov Foundation’s mission to continue the legacy of James Krenov, his values, approaches to woodworking, and teaching. It is largely the work of David Welter, co-founder of The Krenov Foundation and a staff member at Krenov’s school for many years, Dave Matthews, Krenov’s son-in-law, and Kevin Shea. The archive will grow significantly beyond the rollout, so stay tuned.

Those familiar with the master’s work can better appreciate its breadth and further their insight by exploring the archive. I know Krenov’s books exhaustively, yet I’ve found plenty of valuable and interesting material to study in the archive. I particularly enjoy seeing the drawings and construction process photos. Those woodworkers and anyone who appreciates the craft who are new to all that is JK will also undoubtedly find this resource exciting and enriching.

Please consider supporting the Krenov Foundation. Read here on Heartwood for one easy way that I’d bet just about any woodworker can do! Your help will directly support and encourage young woodworkers in their journey in the craft we love. Ultimately, the fruition of their efforts will give more people the opportunity to experience the “quiet joy” of work “from wakened hands.” And that, dear readers of Heartwood, is a very good thing in a too noisy world.

Thank you,

Rob

As with any tool, especially a simple one, winding sticks must be used correctly to gain their full value.

The setup

Place the darker stick on the near end of the board or surface in question, and the white stick parallel to it on far end. Shine diffuse light on the far stick to improve the visual contrast between it and the darker near stick.

As much as possible, ensure that the sticks are placed on unambiguous surfaces. The assessment will not be meaningful if, for example, one of the sticks is placed on the convex side of a cupped board, seated on one side of the “hill.”

The vision

Understanding some basic optics can help you use winding sticks with ease and precision that you may not have thought possible. On this, I can speak with special expertise, but here are the basics that matter.

Regardless of the optical status of your eyes, it is impossible to simultaneously maintain a clear focus on the near and far stick, unless they are both within the “depth of field.” Think of depth of field as simply the range – how close to how far – where things are in acceptably clear focus.

You want both sticks in focus (i.e., within the depth of field) so you can compare their top edges. Therefore, you want to make that depth of field large. Just as with a camera, do this by using a small viewing aperture (i.e. the hole you look through), and/or don’t position yourself too close to the nearest object (in this case, the near stick).

Viewing technique #1 – at least do this

Position yourself at least a couple of feet back from the near stick. This will give you a better chance to get both sticks within your eye’s depth of field. (For many reasons, this varies from person to person, and with viewing conditions.) Experiment, but avoid getting right up to the near stick.

Viewing technique #2 – this is the cool one

Artificially make your viewing aperture very small by viewing the sticks through pinholes. This is usually described in other sources as viewing through a single pinhole. This does not work well because your view is not wide enough to see the full width of the sticks, forcing you to move your head side to side to see them. The inevitable inaccuracy in this movement will degrade the assessment of twist.

Instead, use a trick that I have been using for decades, and also published ten years ago in Woodworking magazine (an excellent publication that has long since folded).

Cleanly drill a row of about seven 3/64″ holes, 5/32″ apart on center, in a 3 1/2″ x 2″ rectangle of 1/64″-thick brass, or similar clean-drilling material. Round the corners of the piece for safety. The completed tool looks like this:

Get your face to the level of the sticks. Hold the row of holes horizontally up to your eye, and sight the sticks. The rectangular shape of the tool will help you orient the row correctly. Both sticks will be in clear focus, and you can view their full widths. It is quite surprising once you see it.

I simulated the eye’s view with photographic technique in the photo at the top of this post. Note the thin white line of the far stick peeking up just above the black line of the near stick. The sticks are a few feet apart. (The cherry board in the back is there just to block out the visual confusion of the shop background.) The photo below is of just the left side of the sticks in a magnified but not resharpened view:

Accuracy and utility

Using the pinhole technique is easy and quick. It is very helpful for woodworking where accuracy is important, and, I think it is essential for assessing reference surfaces such as jointer tables.

You can test your system for accuracy by placing thin shims under one stick, near its end. Depending on your setup, you’ll probably be able to detect a difference between one side of the sticks and the other side of .006″, maybe better.

The approach to winding sticks that I’ve described in this and the previous post is a good example of using a simple tool well.

Twisted boards and twisted work surfaces can thwart accurate woodworking as surely as twisted logic.

You can test small pieces for twist, such as a small door frame, by simply placing it on a verifiably flat surface such as your table saw top, jointer bed, or workbench. Press or tap on diagonally opposite corners, and look and listen for rocking.

Of course, those reference work surfaces must first be vetted. And that method is impractical for larger pieces. You cannot reliably detect twist with only a single straightedge, and so you need winding sticks in the shop. These are simply two sticks, one placed at the near end of a board, the other at the far end. You position yourself back from the near stick and sight along the top edges of the sticks to see whether they are in the same plane, and thus detect any twist in the surface of the board.

Let’s explore this essential tool, starting with building it.

I prefer to keep this tool simple and functional, without adornment. You can find many variations, such as those with elegant inlay or cute little windows. If you want to gussy them up, go for it, but keep the fundamental requirements in mind.

The geometric requirements are simple: two sticks with straight top and bottom edges. With the two bottom edges aligned, the two top edges must be parallel. (Technically, the top and bottom edges of each stick do not have to be parallel to each other, but you probably will make them that way.)

2 – 2 1/2″ is a decent width for the sticks, and they should be thick enough – say 3/4″ – to stand on edge reasonably stably. Chamfer the top edges to about 3/32″-thick for easier sighting. Stable, quartersawn wood is a good material.

For length, 12″ is too short – it won’t adequately magnify the twist error. Much beyond about two feet long and it gets harder to scan your sight side-to-side to the ends. My 21″ winding sticks work well for my mostly small to medium-sized furniture making. They used to be longer. If you work with big slabs, make big winding sticks.

Long ago, I made what I thought would be a quick version, but I have been using them ever since. I simply ripped 3/4″ MDF, and with a little tweaking, brought the edges straight and parallel to less than .002″ tolerance.

This is a visual tool, so it is necessary to create obvious contrast between the two sticks at their top edges. I painted one white to use as the far stick, and used a Sharpie marker to blacken the area around the top edge of the near stick. If you want to use holly and walnut inlay, enjoy.

Some woodworkers prefer to mark incrementally spaced lines, say 1/16″ -1/8″ apart, on each end on the rear stick near its top edge. The idea is to quantify the twist error. I prefer to leave the rear stick unmarked and work more intuitively. I also find that the clean white background avoids the visual confusion of the lines. I suggest experimenting to see what you prefer.

In the next post, I’ll cover methods of use, including a nifty trick, refined in a way that I don’t think you’ll read about from other sources.

I think we would all welcome more shop space but realistically most of us contend with making better use of the space we have. Here’s another tip for that.

For combined machine and hand tool woodworking, shop space is usually governed primarily by the major machines, and then by wood storage, and the workbench. For the table saw, bandsaw, jointer/planer, and router table the required space includes not only the machine itself but, even more, the ranges of the infeed and outfeed. Manipulating these ranges can produce more functional shop space.

Coordinating the different heights of the machine tables is one trick to help. I covered that in a previous post. However, sometimes that can be difficult, so think also of the angle of the tables. Tiny differences there can pay off.

This is what you have to do when your shop is only 200 square feet.

During a recent bandsaw tune-up, I re-shimmed the table on the trunnion assembly. Oops, that made the bandsaw table just at the same height as the nearby table saw top. There was no infeed clearance for using the bandsaw in its usual location.

No problem. A pair of wooden shims, only about 1mm thick, placed on one side of the bandsaw base, tilted the machine enough (less than 0.2°!) so that the infeeding wood safely clears the table saw, plus some allowance for bowed boards. In the photo at the top, the straightedge is flat on the bandsaw table in the right of the photo, but notice in the left of the photo that it clears the table saw surface.

The only interference that this arrangement causes with table saw work is very wide ripping, on the order of 24″, which I rarely do, but all my machines are on wheel bases, so they can be moved to allow those jobs too.

Gluing up is the culmination of lots of work. It’s also exciting in that the piece is beginning to take shape and look like itself. However, it carries with it a potentially intimidating finality, and the process is strictly time limited.

And so gluing up can generate considerable anxiety. The usual recommendation is to check things with a “dry glue up,” but I suggest to expand upon that and think of a “rehearsal.”

This is the time to leave nothing to chance – summon your inner control freak. I cannot think of everything in advance for a unique project at hand, and I doubt you will be able to either. That’s why a Glue Up Rehearsal is essential to ensure success.

Hide glue aficionados will point out its extended open and closed times, and potential for reversibility, but still, there are limitations.

As you rehearse the process, you will fashion answers to questions and dilemmas such as the following. How exactly will you apply and spread the glue? How will you support the parts for this? Can you finish the glue application before there is any chance of it skinning over before the parts are joined? You dripped a big blob of glue – what, exactly, will you wipe it up with?

A big question: would things go better if the assembly were glued up in stages rather than all at once?

What is a convenient opening to preset the clamps? In what order will you apply the clamps? How will you keep the parts aligned? How will you support the pieces in the intermediate stages of the glue up? Will the all of the clamp handles be accessible for tightening? Will you have visual access to see if the joints are closing satisfactorily? Do you need a hand light?

Another big question: how will you assess alignment and squareness, and how will you make corrections as needed?

How will you deal with squeeze out, and when? How and where will you move the assembly after clamping?

It is almost always worth it to build special support structures if they will facilitate the process. The unconventional leg-and-apron assembly in the top photo required a two-stage assembly and special support structures to ensure that all my previous hard work would pay off in a good assembly.

And so forth. The point is that there are surely more questions than one is likely to think of. A rehearsal, albeit a dry rehearsal, along with thought and experience, will cause these issues to become apparent so you can prepare for them.

Glue up is game time, but you want no doubt as to the outcome. Rehearse victory.