Hundreds of kinds of drill bits are used in woodworking–drill bits of all sizes and types to suit different types of wood and wood based products. Using a drill bit that is not designed for wood can cause chipping, blowout of material, rough misshapen holes, difficulty controlling the drill and even injury. Use a bit that is specifically designed for wood.
Forstner Bit - The Forstner bit is the quintessential bit for making clean perfect cuts in wood. This bit is more like a woodworking knife than a bit. It has horizontal cutting edges forming a circle that are guided by a centered brad tip that steadies and aligns the knife edges. The Forstner bit is designed for the smoothest cutting any bit can achieve. Take care when using a Forstner bit that it never hits any metal object, such as a screw, as this can ruin the bit. The Forstner bit is regarded as the only bit for fine woodworking, such as clock making and anywhere that only the finest result is acceptable. Another advantage Forstner bits have is that they come in all sizes ranging from 1/4 inch up to 1 1/2 inches in diameter. You can purchase Forstner bits individually, but they usually come in a fine hardwood box, each nestled into its own slot.
Brad Tip Bit - Also known as a "dowel" bit, the brad tip bit is the most used of the bits specifically designed for wood. It is similar to the Forstner, as a centered sharp tip guides and steadies the bit as it cuts. The difference is that the brad tip bit has spiral cutting edges more closely resembling traditional drill bits. The brad tip also cuts very clean holes---not as clean as the horizontal cutting knives of the Forstner, but the brad tip lasts longer and is not as delicate as the Forstner. The brad tip is widely used by furniture makers for dowel hole cutting as the point of the brad tip guides the bit in a straight line. The brad tip bit is best used in a drill press or a horizontal Shopsmith drilling machine. The commercial sizes range from 1/4 to 3/4 inch in diameter, but larger diameter bits are available if specially ordered.
Spade Bit - The spade bit is another bit specifically designed for wood. It also has horizontal cutting edges like the Forstner except it is flat like a spade, with no circular radius to clean the sides of the hole. The spade bit is designed to cut large diameter holes fast and deep, but cuts rough and is sometimes hard to handle. A spur-like tip aligns it, but, without the circular configuration of the Forstner, it does not follow a straight line easily. Electricians and builders use the spade bit where a large diameter hole is desired for drilling through 2x4s for wiring. Take care when using a spade bit with a handheld drill because spade bits have the tendency to bind, suddenly twisting the drill in the operator's hands.
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