Drawing Small Curves

Drawing Small Curves

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If you're drawing challenged, like me, you'll find a set of French curves a real boon when it comes time to lay out graceful curves for a proj­ect. French curves are available individually or in sets in a wide variety of shapes and sizes. Most are made of sturdy acrylic and may be clear or tinted. I prefer the clear curves, as this allows me to easily see the grain so that I can position the curves to maximize interesting grain patterns. French curves are available in most woodworking catalogs and at any art store.

Basic use

I most often use French curves to create patterns or templates. Slide the curve up and down along the work piece until the desired curve is found. Then trace around the curve with a pencil or marking knife (I generally use a pencil, since a marking knife can cut and nick the plastic). French curves can also be used to lay out ovals (inset). Here again, position the curve until the desired shape is obtained, and trace around it. A pair of light pencil marks on the curve will help you align it for the remaining quadrants.

FLEXIBLE CURVES

A flexible curve is basically a lead rod that's cov­ered with a vinyl sheath. This clever lay-out tool can be bent into small, graceful curves and is especially useful for reproducing a curve from an existing part, such as pressing it around a cabriole leg that you want to reproduce. Flexible curves can be found in most woodworking catalogs and at most any art store.

Trammel Points

Trammel Points

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Trammel points (also called a beam com­pass) come in handy when you need to draw a large diameter circle or arc. Trammel points are a set of steel points that can be mounted on virtually any length beam, as long as it's straight. The heads are held in place by tightening a knurled knob on top of each trammel point. Some versions include an acces­sory head that accepts a standard pencil, in case you'd prefer a pencil line to a scribed line. Bridge City Tool Works (www.bridgecitytools.com) manufactures a gorgeous tool (inset) that features a beam with a built in metal rule.

Basic use

Just like the panel gauge, trammel points require two hands for use. One hand holds one trammel at the pivot point, while the other hand moves the opposite head in a graceful arc or circle to mark the work piece. Keep the points razor sharp and you'll need to apply only light pressure to mark your work piece.

Stick trick

If you don't own a set of trammel points and need to draw a large diameter arc or circle, try this crude but effective substitute. Simply drill a pair of small holes the desired distance apart in a thin stick. Use an awl or a brad to temporarily hold one end at the pivot point, and insert a pencil or awl in the other hole to scribe or mark the arc or circle. Naturally this isn't anywhere near as accurate as a good set of trammel points, but it'll do in a pinch.

LARGE ARCS WITHOUT TRAMMELS

Sometimes, you may find that you need to draw a large arc that exceeds the ability of your trammel points, or that would require a really long beam, or you just don't have trammel points. In cases like these, try one of the variations of the old "bent stick" trick described below.

Bent stick

The boat builder adage "If it looks fair, it is fair" certainly applies here. Just grab a thin strip of wood that's long enough to create the desired arc, and have a helper flex the stick from start point to finish. Once the desired arc is obtained, draw along the wood strip with a pencil to mark it on the work piece.

Plexiglass strip

One disadvantage to using a wood strip is the grain of the wood can and will affect how the strip flexes often in an uneven arc. You can get around this if you've got some thin plexiglass handy. Since the plastic doesn't have any grain, any arc you flex in it will be perfectly smooth.

Clamp trick

It never seems to fail that whenever I need to use a bent stick to draw an arc, there's nobody around to help. When this occurs (and the arc is small enough), you can use a pipe clamp or bar clamp to flex the stick. This leaves your other hand free to transfer the arc to the work piece.

Center Finders

Center Finders

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Finding the center of a work-piece is a common layout task. It's so common that a number of tool manufacturers make plastic center finders, like the one shown in the top photo, specifically for this task. These simple tools have lips on two adjacent sides to quickly position the work piece.

Basic use

To use a center finder like the one shown here, press the edges of the work piece up against the lips of the center finder. Then butt a pencil or marking knife up against the center cutout and draw along this to mark a line on the work piece. Next, rotate the work piece 90 degrees and make another mark. Where the lines intersect is dead center.

SHOP-MADE CENTER MARKER

In addition to finding the center of a work piece, you 11 often need to find the center on the edge of a board. The simplest and most accurate way I've found to do this is to make your own center marker. This is nothing more than a scrap of wood with a pair of dowels (or better yet, steel pins) and a hole in it for a pencil. The challenge is locating the pencil dead center. To do this, start by marking out and drilling the dowel holes (or use short lengths of 1/4" steel rod). Then install the dowels with glue (or epoxy for the metal rods). Now use these to locate dead center. Simply place a metal rule on edge between the dowels on a diagonal and make marks in both directions. Drill a hole for the pencil where the lines cross.
NOTE:
For maximum accuracy, size this hole to accept a mechanical pencil.

Dial And Slide Calipers

Dial And Slide Calipers

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Thought of mostly as machinists tools, dial and slide calipers can be quite useful in the woodworking shop. Although you rarely need to measure in thousandths of an inch, these precision tools are great for measuring small parts and checking the thickness of a work piece. Slide calipers are not as easy to read as dial calipers. Whoever came up with the idea of adding the dial deserves a medal, in my opinion. The bodies of slide calipers are usually metal, where as you can find dial calipers with either metal or plastic bodies. The latest in calipers takes advan­tage of digital technology and offers a numeric readout (though these can be quite pricey).

Thickness

I've been using dial calipers for years to measure the thick­ness of stock. I use one so regularly for this that it resides in my planer stand. Once you get used to using one of these, you'll wonder how you ever lived without it. Look for one with a dial that has1/64" measurements as well as thousandths.

Depth gauge

Most dial and slide calipers can also be used as very accurate depth gauges. Just position the end of the caliper over the hole to be measured. Open the sliding jaw until the rod on the end of the caliper bottoms out in the hole; then read the dial.

Dividers And Calipers

Dividers And Calipers

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A spring divider differs from a com­pass in that both legs hold metal points instead of a single point and a pencil or pencil lead. The legs of the dividers are opened or closed by adjust­ing a knurled nut on one of the legs. Although you can use dividers to scribe circles or arcs, they are more commonly used for layout to "divide" (hence the name) or step out equal distances, often referred to as stepping off a measure­ment.

Stepping off measurements

Once you've set the dividers to the desired setting, you can easily "step off" equal measurements along a line by "walking" the dividers along the line. Simply pivot the dividers as you go by holding the post between your finger and thumb and moving the dividers from one point to another.

CALIPERS: INSIDE AND OUTSIDE

At first glance, a caliper looks very similar to a set of dividers. On closer examination you'll find that the difference lies in the legs. On a set of inside calipers, the legs bow in (photo below right); with outside calipers, they curve gently out at the ends (photo at left). Calipers are used primarily to take accurate inside and outside measurements so that these can be

transferred to another layout or to reproduce a part. If you practice holding the caliper so that your fingers can adjust the knurled knob, you can set it with one hand, leaving the other hand free to steady the work.