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.