Shedding Light on Compound Angles
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Convenient line lasers and a simple configuration make perfect angled drilling.
II am a 21st century president of Windsor. I build chairs using mainly manual tools: froes, hand knives, raiders, travishers, scorps, an adze and other tools that, even in the fast-paced computer age, still represent the most efficient way to follow the intrinsic strength of a tree .
I also do many holes. An average Windsor can have up to 40 holes, and most of these holes are drilled at compound angles, which in part give Windsor strength, stability and grace. Composite angles can be achieved in many ways, for example by tilting the table on a drill, and using various masks or gauges and mirrors using sight lines. It is this last method – lines of sight – that I have been using for years to perforate my chairs, which in turn has triggered a method of perforating compound corners with lasers. Yes “laser”. Not the type that gets you in trouble on planes, but very cheap airliners.
Several years ago, I was teaching a student to build a Windsor stool. And while we were installing the bevels and mirrors to pierce the top of the stool, he mentioned how difficult it was to look at both mirrors and focus on the bevels in two directions. We talked about how nice it would be to look at a point while drilling these holes, and that’s when the line lasers hit me. We went to the hardware store and, for sure, they had what we needed.
Teaching has been the biggest gift of my career: it keeps me focused on practicing and perfecting my methods as I rebound ideas about students who are usually smarter than I am. They always have a great input. Thus, at the beginning of February 2011, my technique for drilling angled holes composed with lasers was born.
For those who are not used to looking at aiming lines and thicknesses, constantly drilling or reaming the correct geometry is a great challenge. We were approaching – and most of the time the closure is acceptable – but now with the help of lasers my students are simply looking at two laser lines that intersect on the drill or reamer with a confidence that I have never seen before. And a laser guide configuration is cheap and easy to configure: believe me, if it wasn’t simple I wouldn’t fool myself.
Presidents use sight lines to determine angled holes. A line of sight is a line that passes through a leg when it appears at 90 ° (vertical) to our eyes. Yes, a right angle in the manufacture of chairs! The resulting angle is how far the leg tilts forward or backward along the line of sight. They are based on rake angles (front to back) and splay (side to side) – concepts explained in detail in Peter Galbert’s “President’s Notebook” (Lost Art Press) and “Compound Angles, No Math “by Christopher Schwarz (June 2015) Popular carpentry magazine, number 218).
Build some laser bases
First, go to your local hardware store and purchase two inexpensive line lasers. Your new lasers will have a small magnet on the bottom that will keep them at the bases, and out of the packaging I had to wrap the plastic wrap on the bottom of each laser on sandpaper to prevent them from swinging. (Did I mention they were cheap?)
I built the rotating bases from hardwood scrap recovered from the trash. The laser works best sitting 9 ″ from the work bench. Building the thick base for stability. I use a 5/8“Dowel that slides through a slotted hole in the neck with a pinch bolt and the laser is magnetized on a metal nut embedded and glued in the swivel head. I also glued some rubber on the bottom of the base to prevent the unit to slip on the workbench. Once you’ve built your bases, you’re ready for some visions.
Create an angle meter
Using a simple 10 “x 12” piece of plywood cut well and square, draw a vertical center line of 90 °. Now trace your resulting angles in both directions, on both sides from the center, with a chamfer meter and label each corner you want to punch above each corresponding line. This is what we will use to set up the lasers before drilling. I like to create a dedicated corner for each type of chair that I make.
Now is the time to trace the model of the seat (or whatever you are drilling) with the positions and lines of sight of the hole for the legs. In the position of each hole to be drilled, draw a short perpendicular line. Place the first laser along the line of sight towards the hole at 90 ° to the seat. Place the second laser along the set perpendicular line on the resulting angle. (Just be sure to lean in the correct direction.) That’s right, simple! This creates the hatch – two laser lines – to follow the hole.
This is the process of transforming the standard driver’s drill bits into wood cutting bits. I start with high-quality high-speed steel drill bits that I purchase from a machinery supplier, Victor Machinery, in New York.
So I use my dressing tool to create a shape on the edge of the grinding wheel that will correspond to the wing of the brad point. The use of a coarse grinding wheel for initial grinding speeds up the removal of the material, but any grinding wheel can be used as long as it is well dressed and used with light pressure. I always make sure that the angle is less than the plane of the wheel that I use for general grinding. The sharper the angle, the deeper the wings on the resulting bit.
Another factor that determines the function of the tip is the angle set on the tool holder and the resulting relief behind the cutting edge. I measured the angle a little bit that I used for most activities and found it around 35 °. The steeper the corner, the more aggressive the bit; at some point, the edge is too thin to be effective. I always use high speed steel because it doesn’t lose patience until it’s hot, so a little bluing is fine.
On the right is the mask configuration that I use during grinding. The simple wooden fence positions the point about 4 ° from the wheel axis. As you can see, it is the side of the wheel that actually forms the center point. By adjusting the position where I fix the block to the rest, I can adjust the length of the center point of the tip. The further the barrier is to the right, the longer the center point will be.
Below is the first cut. I make sure that the existing cutting edge is horizontal and I proceed to grinding. After a moment, I judge whether the position of the fence is set correctly (from left to right) to form the correct point. Obviously it is better to have the point too fat and long because it is simple to move the fence to the left to remove more material.
Once the wings are formed, you will notice a thin sheet of metal on the parts of the tip that were vertical during the grinding process. I call these straps. These are removed using the same wing configuration, but need to be aware of a couple of other concerns. To begin grinding, position the belt so that it is now in a horizontal position and the cutting edges were in the first phase.
The difficult part of grinding the wings left by grinding the center point is that the wing pointing downwards is dangerously close to the grinding wheel and the slightest encounter will bring you back to the beginning. It’s not a big deal, but it’s best to avoid it. I avoid hitting it with the wing facing upwards a little vertically (towards the grinding wheel). By keeping the wing that I can easily see near the grinding wheel, I generally manage to keep the other free. The other key to grinding the web is that as I continue to push the tip into the wheel, I let it detach a little from the block. This happens in a completely natural way because when I press the wheel, the amount of metal that is cut increases and the piece wants to slide sideways. You can see the result of this in the numbered drawing 3 below.
—Extracted from “President’s Notebook”,
by Peter Galbert (Lost Art Press)
I use a grind on the tip of my high-speed steel twist drills to give me a long advantage. This creates clean holes and allows a lot of freedom to place the drill on the corners without the tip going through the wood. See the section “Drill bits for grinding” to know how to achieve this alone.
I use the drill casing to find the central axis of the bit when drilling. You can also draw or create an ox eye on the back of the drill to find the center.
Now line up on the cross hatch and pull the trigger. If you don’t hear me talk about something else, remember this phrase: “High speed, slow feeding”. The drill bit must enter clean at the maximum speed of the cordless drill while retaining all its weight and power through the hole. Trust me, this will make the holes much happier. Think full throttle on your car while you’re on the brake: great control. Practice in scrap wood to get the feel. Complete the hole while watching the hatch all the time. It gets easier every time you do this.
The accuracy that is obtained by punching with lasers is surprising and simple. It is a generator of trust. But the real magic in the construction of the Windsor chair is the tapered, bored leg and the arm joint. Laser-guided reaming can fine-tune any hole drilled incorrectly to rake and widen perfectly. The setting is exactly the same as drilling straight holes, but an advantage of manual reaming is greater control in each turn, while still being able to easily see the hatch on the top of the reamer. Each turn can perfect your alignment. And while perfection isn’t essential on a regular chair, rockers find it helpful to keep the same things on both sides. The same goes for stools with a stretcher design: the balance keeps the box nice and square.
Now that you’ve drilled holes with lasers, what else can you do? How about finding the real center of a chair before drilling the back? Just place the laser in the center of the seat positioned at 90 ° to the surface, dividing the chair in two – real center. A line floats pleasantly through everything that crosses its path.
Lasers are also useful for finding the central axis of the legs and stretchers when drilling. Simply turn the laser from one guide center to another during turning and it indicates where to place the drill bit and helps keep the drill perpendicular.
There are many other areas of use waiting to be explored, and I seriously hope you try lasers. They may not be for everyone, but a pair of lasers are not a great investment – if you don’t like them, pass them on to a friend. Happy drilling!
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