Group 21 - Black and Decker Drill

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Executive Summary

Black and Decker DR202

Carpenters, craftsman, and the all around handy man need a tool that is capable of placing screws into material accurately, and reliably. Utilizing a powered drill is the most viable option because the drill provides mechanical advantages that far surpass the conventional screw driver. With the slight pull of the trigger a powered drill can provide many foot pounds of torque that are capable of placing screws into various materials accurately and effectively.

By carefully analyzing the Black and Decker DR202 it is clear to see why this drill has been a consumer favorite over the years. At first glance one may be attracted to the black and red color scheme that has became the standard for Black and Decker products. The outer covering is made of a sturdy plastic along with rubber grips for added comfort and control. Other features that help to separate the Black and Decker DR202 from other powered drills on the market is the level on the back of the drill as well as the key-less chuck. Taking a closer look under the outer casing a powerful 5 Amp motor is utilized to provide adequate power for the toughest jobs.

Granted, Black and Decker has created a drill that accurately and reliably drills screws into various materials there is still room for improvement. By disassembling and reviewing the manufacture processes, material type, and function of ease individual component of the DR202 our team was able to suggest some design changes. These design changes could be implemented to keep the Black and Decker DR202 drill on the top of the competitive marketplace.

Before Disassembly Section


The objective of this project was to examine the Black and Decker DR202 powered drill. By disassembling, reassembling, and reviewing the inner workings of the drill our group was successfully able to grasp how the DR202 was manufactured and how to improve upon the design of the DR202.

Our group was a collaboration of five dedicated individuals whose contributions are noted below

Andrew Klahr (group leader)- Presentation, Parts Analysis
Anne-Marsha Joseph- Presentation, Disassembly
Katie Weber- Disassembly, Part Analysis
Anthony Beeman - WIKI Page, Reassembly
Yan Liang- CAD Drawings, Reassembly


The purpose of the Black and Decker DR202 was to fasten and remove screws into materials such as drywall, sheet rock, and wood. The DR202 is able to accurately and reliably place screws into various materials with the aid of the level that is provided on the drill. Drill bits can be removed by utilizing the keyless chuck. The DR202 chuck is capable of holding drill bits that fall within the range of 1–10 mm. Each bit can perform specific functions when utilized with the DR202. For example some bits are used to create holes in materials while other bits can be utilized to drive screws into materials. The DR202 is powered by 120 volts of alternating current and has the capability of rotating clock wise as well as counter clockwise.


Our group estimated the DR202 powered drill would consist of 30 parts. Some of these parts are listed below:
1 Directional Switch
2 Gears
3 Motor
4 Cord
5 Outer Casing
6 Chuck
7 Power Trigger
8 Screws
9 Bit


Prior to disassembling the Black and Decker DR202 our group believed the power drill consisted of 4 types of materials.
1 Copper
2 Steel
3 Plastic
4 Rubber

Disassembly Procedure

Step # Description Tool(s) Level of Difficulty
1 Took out the nine screws. Flathead Screwdriver Moderately Difficult
2 Pried the plastic bit holder out. Flathead Screwdriver Easy
3 Separated the right side of the casing from the left side of the casing. As doing so the directional lever fell out. Hands Easy
4 Placing the left side of the casing down, we pulled the motor and attachments out of the casing. Hands Easy
5 Removed two more screws which were holding a metal plate down, which was holding the wires leading to the cord in place. Flathead Screwdriver Moderately Difficult
6 Pulled out the chuck and attached gears. Hands Easy
7 Separated the gear system from the motor. Hands Easy
8 Separated the individual gears that made up the gear system. Hands Easy

After Disassembly

Parts Table

Part Number Part Name Quanity Materials Manufacture Process Purpose Picture
1 outer casing (left) 1 PA6/G40 plastic and rubber Injection Molded Cover is made to hold the inner parts.
Left Outer Casing
2 outer casing (right) 1 PA6/G40 plastic and rubber Injection Molded Cover is made to hold the inner parts.
Right Outer Casing
3 3/4" Screws with #15 Torx heads 9 Steel Extruded and Machined Holds separate components together
3/4" Screws
4 1 7/8" Screws with #15 Torx heads 2 Steel Extruded and Machined Holds separate components together
1 7/8" Screws
5 Bit Holder 1 Plastic Injection Molded Holds one bit
Bit Holder
6 Bubble Level 1 Plastic Extruded Bubble level is used to ensure the user that the screw is being driven into the material at a right angle.
Bubble Level
7 Directional Lever 1 Plastic Injection Molded Allows the drill to spin clockwise and counter clockwise.
Directional Lever
8 Double sided bit 1 Steel Extruded and Machined Insertion of Phillips and flat head screws
Drill Bit
9 Power Cord 1 Plastic
Extruded Provide AC current to the power inverter
Power Cord
10 Inverter 1 Plastic
Woven glass
Injection molding
Silk screen printing
PCB milling
Converts current from AC to DC allowing the motor to utilize the provided current.
11 Trigger 1 Plastic Injection Molded Utilized as switch to open and close the circuit.
12 Internal Wiring 2 Copper
Plastic (Insulation)
Extruded Transport current from the inverter to the motor.
13 Motor 1 Steel
Machined Spins Shaft that rotates the gear system.
14 Cooling Fan 1 Plastic Machined Keeps motor from overheating.
Cooling Fan
15 Key Less Chuck 1 Plastic Injection Molding
Metal Casting
Holds a bit that can be removed by the user.
16 Gear System
(Table Below)
1 Steel Noted On Gear System Table Through a series of gear reductions the gear system creates a torque.
Gear System

Gear System Table

Part Number Part Name Quanity Materials Manufacture Process Purpose Picture
17 Motor Shaft 1 Stainless Steel Extruded Connects to the motor to rotate the gear system.
Motor Shaft
18 Plate (a) 1 Stainless Steel Metal Casting Fits firmly onto the outer casing in order to secure the motor shaft.
Plate (a)
19 Plate (b) 1 Stainless Steel Metal Casting Fits firmly onto the outer casing in order to secure the motor shaft.
Plate (b)
20 Gear 1 Stainless Steel Machined Connects to the motor shaft to rotate the gear and pinion.
21 Gear and Pinion 1 Stainless Steel Machined Connects to the gear in order to create a torque.
Gear and Pinion

3D Computer Aided Design

Assembly Part 1 Assembly Part 2 Assembly Part 3 Final Assembly


Step # Description Tool(s) Level of Difficulty
1 Connect the individual gears that made up the gear system. Hands Easy
2 Place motor into the left cover. Hands Difficult
3 Place the gear system into the left cover. Hands Easy
4 Place the two screws into the metal plate and used them to secure the wires within the left cover. Phillips Screwdriver Easy
5 Place inverter and trigger back into left cover. Hands Easy
6 Connect the directional lever to the motor. Hands Moderate
7 Place right cover over the drill. Hands Easy
8 Place 9 screws into Left cover and connected left and right cover. Phillips Screwdriver Easy

After Assembly

How It Works

After disassembling the product, the function of each part, as well as how the overall product operated, was accessed.

This drill has a universal motor. It runs off of an alternating current (AC) power supply, which comes from an outlet. The motor contains a rotor that has copper wire wrapped around it. The copper wire is used to create a magnetic field. As the AC power is supplied to the rotor, it creates a magnet. The rotor is also surrounded by another magnet with the north pole of the rotor’s magnet attached to the south of the additional magnet. According to the magnetic theory, the opposite poles of each magnet attract each other, while the like poles repel each other. With this relationship, the two magnets begin to repel each other, which cause the rotor to turn. The motor is also made up of small pieces of metal called “brushes”. These brushes rub against a disk that’s attached to the shaft. When the AC power is supplied to the motor and the rotor turns due to the magnetic forces, the brushes transfer electricity to the shaft, which causes it to turn. As the shaft rotates, it causes the gears to turn as well, which then makes the chuck rotate. As the user applies force to the drill and the chuck rotates, the screw enters the targeted material. There is a cooling fan attached to the shaft that helps keep the motor from overheating. It also rotates as the shaft rotates. After reassembling the drill, it ran the same as it did before the disassembly.

Product Analysis

Note To The Reader: The purpose of this product analysis is to walk you through the engineering thought process while solving the analytical problem noted below.

Problem Statement: Calculate the max torque of the Black and Decker DR202 gear system.

Gear System Free Body Diagram

Please Note: positive X is to the left, positive Y points up, and a positive moment is counter clockwise.

Motor will provide an initial torque (Represented by "m" on the FBD)
Gears in the gear system are different sizes
Motor is capable of providing a torque that turns the gear
Gears don't slip while rotating
The motors torque doesn't vary with time
All surfaces are frictionless

Governing Equations:
(Sum of the systems angular moment)01 +(Sum system angular impulse)0(1-2) =(Sum system angular momentum)02
Moment of Inertia: I=m*r*r
Angular Moment of Inertia: L=I*w
Torque = moment of inertia * angular acceleration

The calculations to the gear system would require extensive understanding of many dynamics concepts and will be explained in the discussion

Solutions Check
One would verify numerical values as well as unit consistency.

By calculating the angular moment of inertia and angular acceleration "w" of each gear one could then sum the torques of gear system in a piecewise manner. The sum of the torques would be the final output torque of the systems. Torques rotating counter clock wise would be considered positive while torques rotating clock wise would be considered negative. By varying the gear ratios and the initial torque of the motor one could vary the output torque of the system. The assumptions make sense when calculating the max torque of the system. One benefit of this system is that it can be adapted to calculate the torque as a function of time; the motor torque varies. In order to calculate the torque at a given time the motors torque would have to be illustrated by a function M(t). This function would be non-linear in nature due to the exponential increase in the motor torque over time; Until the max moment is reached. By carefully analyzing and optimizing the system above a new max torque could be created.

Ergonomic Analysis

By testing the user interaction with the product, concepts such as center of balance and user comfort can be tested. With the use of a working prototype the analysis can take place. Issues such as grip comfort and handling of the drill can be addressed.

Disassembly/Assembly Discussion

The disassembly and assembly procedures were the reverse of each other. The disassembly process was very easy and only required the use of a flat head screw driver and our hand. Once we had opened the casing the process was very easy because the housing of the drill was the only component holding the parts in place besides 2 screws on the inside. The assembly process was more time consuming due to the fact that each part had to be put back together in working order, which with the aligning the gear system, the process was somewhat tedious. The same tools were used in both the disassembly and reassembly process. The drill is back together in working order, same as when we received it prior to disassembly.

Recommended Design Changes

The drill has a few small weakness in its design. With the following recommended design changes, the product will be more appealing to the user:

1. Directional Changer - The directional changer was very large and awkward to use. With a simple button or small sliding mechanism, the directional changer would be much easier to use.

2. Screws - Black and Decker uses two different types of screws that both contain hexagonal screw heads. With the use of phillips or flat-head screws, repairs and disassembly would be much easier. Also, eliminating the the different screws and replacing them with a uniform design would be more cost effective for Black and Decker.

3. Cord - A battery operating drill is a more practical design choice. The cord seems to just get in the way and a battery operated drill does not limit the use of where the drill can be used.

4. Drill bit - The bit that is included with the drill is a very basic design. The use of a magnetic bit, or a bit with a sleeve over it would be more user friendly.


Black And Decker. (2007) . Instruction Manual for Models DR202 Power Drill.. Retrieved November 7, 2007, from the World Wide Web:
Power Drill. (2007) . Power Drill Principles. Retrieved November 13, 2007, from the World Wide Web:
How Gear Ratios Work. (2007) . How Gear Ratios Work. Retrieved November 15, 2007, from the World Wide Web:
How Electric Motors Work. (2007) . How Electric Motors Work. Retrieved November 15, 2007, from the World Wide Web:
Hibbeler, R. C. (2006). Engineering Mechanics Statics and Dynamics (11th ed.). St. Louis, MO: Prentice Hall.