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Pinewood Derby Stories and Photos from Maximum Velocity
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SHOP TALK
Drilling With Accuracy
If you were reading a book and the phrase "drill bit" was used, what mental image would you conjure up? Most people would think of a standard high-speed steel (HSS) drill bit that is part of the drill bit set in most people's toolbox. This type of drill bit is certainly the most popular, but it is not the best drill bit choice for many woodworking tasks.
Today, we will discuss the various drill bit types available for woodworking, and how they apply to pinewood derby cars.
Regardless of the drill bit type, make sure to know the chuck size of your drill. The chuck size determines the maximum shaft diameter of the drill bit that can be used. Most drills today have a 1/2 inch chuck, but there are some drills that have a 3/8 inch chuck. If your drill has a 3/8 inch chuck, make sure to purchase bits with a shaft no larger than 3/8 inch.
Drill Bit Types
For woodworking, you will find the following drill bit types at your local hardware store:
Forstner - Produces a flat-bottomed, clean edged hole with no chipping. The center point ensures that the hole is drilled where desired. For drilling holes over 7/16 inch, Forstner Bits are generally a better value than Brad Point bits. Some Forstner bits have a saw tooth edge (as seen in the photo) while others do not. Either type works well for pinewood derby use.
Forstner bits are commonly used for creating wheel wells for attaching to the side of a pinewood derby block. They are also used for creating holes for tungsten rounds.
Figure 1 - Forstener Drill Bit
Photo Source: www.rockler.com
Brad Point - Produces a clean edged hole will no chipping. The center point ensures that the drill bit doesn't wander. For drilling holes between 1/8 and 7/16 inch, Brad Point bits are usually a better value than Forstner bits and do a better job than HSS bits.
Brad Point bits are commonly used for drilling weight holes in pinewood derby blocks
Figure 2 - Brad Point Drill Bit
Photo Source: www.rockler.com
Auger - Produces a clean, accurate hole. The screw tip causes the bit to "power feed", and the auger shape helps in chip removal, so this type of bit is beneficial for drilling very deep holes.
Although Auger bits can be used for pinewood derby cars, Brad Point or Forstner bits are usually a better choice. The screw tip on the Auger bit is not desirable for pinewood derby cars as it makes the hole too deep, and the power feed action can be a bit unwieldy for novice woodworkers.
Figure 3 - Auger Drill Bit
Photo Source: www.toolbarn.com
HSS - A general purpose drill bit for use in wood, metal, plastic, etc. Especially in larger sizes, HSS bits often chip the edge of the hole, and can "wander".(1) But for holes in a pinewood derby block under 1/8 inch, these are the only real choice.
To minimize chipping, keep the drill speed high, but the feed speed low. To minimize drill bit wander, make a small dimple in the wood at the drilling location with a nail or a punch.
Figure 4 - HSS Drill Bit
Photo Source: www.rockler.com
Spade - Also known as a "Paddle Bit" this type of inexpensive bit is used for rough boring. Typically they are used in carpentry where a clean hole is not necessary. I strongly recommend avoiding Spade Bits for pinewood derby use.
Figure 5 - Spade Bit
Photo Source: www.drillspot.com
(1) For drilling axle holes, a cobalt "split point" drill bit is desirable. The split point prevents drill bit wander, and the cobalt material keeps the bit from flexing. You can find cobalt split point drill bits for standard axle holes (#44) Here.
