I love spade bits, and I will always recommend them for people getting started in chairmaking. The bits are dirt cheap, widely available, sharpenable and are easily customized to do things other bits cannot.
But like many chairmakers, I am always game to try new drill bits. If someone told me there was a new drill bit made from hard cheese and rat pelvises, I would buy a few to try.
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These bits cut quickly and cleanly and – insanely – leave a clean exit hole without any backing board. For the chairs I build, this is a big deal when drilling the holes between the armbow and the seat. With these bits I don’t need to clamp backing boards to the armbow. And I can easily drill through the seat – making the joint between the sticks and the seat incredibly strong with more surface area and wedges.
But the bits have a learning curve. Because the flutes along the body of the bit are sharp, you have to keep a steady hand when freehand drilling, otherwise you will make weird overly elliptical holes. And you need to learn how to start them properly. And to deal with what happens when the cut stalls.
The OverDrive Bits
These bits are widely available in the United States. But after using them for 16 months in chairmaking, I don’t recommend them for making chairs. The bit’s center spur is too short for anything but shallow angles.
Why is this bad? Angles greater than 12° or so are difficult. You have to start the bit vertical then move into the correct (sometimes compound) angle. And you might have only a second or two to do this.
Wait, can’t you do this at “sloth speed” and ease into the cut? No. The bits are (in my opinion) designed to be used at high speed. When used at low speeds, they tend to tear up the wood. The OverDrives are great bits for furniture making where the bit is 90° to the work and in a drill press. But for chairmaking? Pass.
The Star-M, F-Types
I buy these bits from Workshop Heaven in the U.K. If they are sold elsewhere I don’t know. But I haven’t found them in the U.S. These bits are similar to the OverDrive bits, but the center spur is radically different, which makes all the difference.
The long center spur and cone-shaped tip allow you to use this bit at radical angles (though I would argue that you shouldn’t do this without a stern warning, which is below). And because of the bit’s shape you can get the bit settled into the work with slow rotations until you spin things up to full speed.
STERN WARNING: When you use any bit at a radical angle, you tend to bring the flutes into the cutting equation. With a traditional auger, the flutes aren’t sharp, so it’s not a big deal. But with many modern augers, the flutes are pin-sharp. So it’s easy to make the hole an elliptical mess when the flutes start whacking at the rim of your hole.
During the last couple years I’ve found that while the bits allow you to start the hole at a 40° angle, that’s a bad idea. As you approach 20° off vertical, the risk of the bit’s flutes making a mess of things increases radically. Stay under 20° off vertical, and you’ll be OK (with a steady hand).
When I have to angle the bit more than 20°, I switch back to spade bits, which cut slower and don’t tend to ream the hole as much.
So here are a few tips for using the Star-Ms.
- Start the bit’s spur slowly (or make a divot with an awl to start the bit). Otherwise the bit can skate across the work when cutting compound angles.
- As soon as the bit is started, run up the bit to full speed without pushing the drill downward. The cut will be cleaner.
- One you get to full speed, plunge in and let the bit determine your feed speed.
- The bits are sensitive to changes in grain direction (like when you laminate two boards together. And when you drill through the far face of the board). No matter how powerful your drill is, the bit will sometimes stall. When this happens, ease off on any downward pressure on the drill. Run the bit up to full speed with no downward pressure then plunge gently again.
The Star-Ms can be difficult to find in stock, particularly in the 16mm (5/8”) size, which is common for chairmaking. But they’re worth the effort and the wait.
— Christopher Schwarz