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:

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:

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:

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:

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:

(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.

From Pinewood Derby Times Volume 9, Issue 7

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Maximum Velocity Pinewood Derby Car Plans and Supplies

Pinewood Derby Car Showcase – October 23, 2015

Radio Controlled Propeller Car – Bill Klingler

This is my radio controlled propeller driven car. It is powered with a motor, a 7.2 volt battery and the receiver/speed control from a Losi Mini-T RC car. The joy comes from watching the scouts laugh and run along side the track as the car is zooming past. Since it is radio
controlled it will also back up. Lots of fun.

Corn Dog Propeller Car – Bruce Kempf

Every year after NASCAR season is over we have a party and a corn dog Derby race. We use a three lane pinewood derby track, pinewood derby car kits, etc. The only difference is racers have to use a corn dog with the car.

This car was made from your Propeller Car Kit. I attached the corn dog to the propeller car with Velcro, so I could remove it for the race — although it blew away the field with the corn dog attached.

From Pinewood Derby Times Volume 9, Issue 6

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Shop Talk – Keep it Square

Drawing lines square to the side of pinewood derby block is a very common step. To do this accurately requires a tool called a “square”. A common type of square is the “Engineer Square”. This is a simple, but highly accurate square (see Figure 1).

Figure 1 – Engineer Square

However, I prefer to use a “Combination Square” (see Figure 2). The Combination Square is sufficiently accurate, and has features not available on the Engineer Square.

Figure 2 – Combination Square

The Combination Square provides the following features:

– Draw 90 degree and 45 degree lines,
– Adjustable ruler position (allows use as a depth gauge and a drawing guide),
– Simple bubble level,
– Scribe tool – I use this to make an indent in the wood where I plan to drill. This minimizes drill bit “wander”.

Combination Squares come with 6 inch or 12 inch rules. For carpentry work, the 12 inch version is generally used, however, for pinewood derby use, the 6 inch version is much more handy.

Adjusting the Ruler Position

1. Loosen the locking knob,
2. Slide the ruler to the desired position,
3. Tighten the locking knob.

Drawing a Line Perpendicular to the Block (see Figure 3)

1. Ensure that at least 1-3/4 inches of the ruler is extending beyond the head of the square,
2. Hold the head of the square tightly against the block at the desired position,
3. Draw the perpendicular line.

Figure 3 – Drawing a Perpendicular Line
(User’s right hand not shown for clarity)

Drawing a Line Parallel to the Block (see Figure 4)

1. Extend the ruler the desired amount beyond the head of the square (i.e., if you want a line 1/2 inch from the edge of the block, set the head at 1/2 inch),
2. Hold the head of the square tightly against the block,
3. Place the pencil at the end of the ruler, then
4. Slide the head of the square along the block, keeping the pencil tight against the end of the ruler, and the head of the square tightly against the block.

Figure 4 – Drawing a Parallel Line
(User’s right hand not shown for clarity)

From Pinewood Derby Times Volume 9, Issue 6

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Pinewood Derby Car Showcase – October 9, 2015

Street Rod – Janel Davis

This car wasn’t particularly competitive, but I wanted to use up an extra PineCar kit that I had lying around. It took fourth place, in the Outlaw behind the extended wheelbase cars with four disk wheels (instead of the two disk wheels on this car).

Green Stealth – Stephen Davis

This car came from my son’s imagination. The green ball is a plastic marble that is just there to “look cool”. The car is painted with flat black paint, and trimmed with 1/4 inch green pinstriping. We used needle axle wheels, allowing the car to easily blow away the competition to take first place. In addition, it took third in design.

(This car, and its twin will be further discussed in an article on needle axle wheels later this season.)

From Pinewood Derby Times Volume 9, Issue 5

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Pinewood Derby Car Showcase – October 2, 2015

(I am dedicating the Car Showcase this week to a car
built by Stephen Parks).

I was browsing your newsletter archives, and saw the article on the direct drive outlaw car that you built Volume 8, Issue 3

It was interesting to me because, as an engineering student, I competed in the ASME student design competition, and designed a “string transmission” for a transport device.

For last year’s pinewood derby event at work, I wanted to make an electric car for the Outlaw class, and initially thought of using the same type of transmission. However, it has some issues. If the
wheels spin, then you may not have enough string to power all the way to the end, and if the wheels don’t spin, then you probably should have used more power! Eventually I abandoned the idea of a string transmission, and decided to just use a gear drive. A co-worker races electric RC boats, and sourced a Lithium-Polymer battery. These batteries are expensive, but relatively light, and have almost no internal resistance. I found a few motors that looked to be a reasonable size, then built a dynamometer to test and compare them. This approach wasn’t very consistent, so in the end I simply picked the motor that sounded and felt the strongest.

So far, this wasn’t nearly complicated enough for me. I figured that this drag car ought to look like one, so I decided to hide the drive train, switches, etc. into a drag car model so that it would be a “sleeper”. The model I chose was the Stone, Woods, and Cook Willys.

Model Box Photo

My Car

The start switch is hidden behind the grille. When it is race time, a pin fits through one of the holes in the grille and into the switch, and rests against the start post on the track. There is an arming switch underneath the car just in front of the rear bumper. There was also a cutoff switch underneath the car, so that when the car falls down onto the stop strip at the end of the track, the power is cut (well, that was the idea).

Quite a bit of work was required to transform a model kit that was intended to be stationary into a rolling, self-powered, self-guided vehicle. Here are photos of the chassis, showing the motor and gear layout. The silver rectangle is the battery pack. The gears are out of a broken DVD player.

Top of Chassis

Bottom of Chassis

I should mention that the track is not set up until the night before the day of the race (after the impound). So, testing is very difficult. But I did get the coordinator to allow a couple of practice runs. On the first run, the tires had too much traction and lifted the front end when they caught on a track joint, resulting in a
derail. But that run put enough graphite on the tires to reduce grip enough so that didn’t happen again. The next run was 1.998 seconds, on 49 feet of BestTrack!

Video of a Run (WMV format)

On race day, the car got a lot of interest for looking good, though some thought that it was “just a plastic model.” No one expected a two second run, and it was easily faster than the other Outlaws, all of which were gravity powered. The run times gradually increased, not because of the battery, but because of graphite buildup on the tires. Going fast was not a problem with this car, but getting it stopped was. I seriously underestimated the speed at the end of the track, and didn’t have a good way to stop the car. At the end of the fourth run, one of the guides that keeps the rubber wheels from contacting the center rail broke, and the car could not stay on the track after that. I took the car out of the race instead of needlessly damaging it further.

This year I’ll probably reuse the motor and battery, but forgo the fancy body in favor of a much more robust frame, and I’ll build a stopping device to fit onto the end of the track. I may also switch to front wheel drive to eliminate the possibility of wheelies, and I can then clean the graphite off of the tires after each run to maximize traction and maintain consistent times.

Stephen Parks

From Pinewood Derby Times Volume 9, Issue 4

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