Archive for ◊ April, 2018 ◊

Author:
• Monday, April 30th, 2018

winding sticks

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:

pinholes for winding sticks

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.

Category: Techniques  | 5 Comments
Author:
• Saturday, April 28th, 2018

winding sticks

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.

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Author:
• Sunday, April 22nd, 2018

shop space

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.

shop space

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.

Category: Tools and Shop  | 8 Comments