Black & Decker Hand-Held Power Screwdriver

Bucknell Mechanical Design Home

Black & Decker Alkaline Powered Screwdriver Dissection

By: Jessica Hibbert, Andrew Loucks & Lee Markison

Figure 1: Black & Decker Drill Before Disassembly

Figure 2: Black & Decker Drill Control Top

Function

The function of the Black & Decker Alkaline Powered Screwdriver is to insert and tighten or loosen and remove screws. The advantage of this battery powered tool is to offer more power than a manual screwdriver. Furthermore, the tool is hand-held and lightweight for easy use and storage.

User Requirements

• Motor is strong enough to create enough torque to tighten or loosen screws
• Small and handheld for easy use
• Efficient battery so the battery life will be long enough
• Ergonomic design for long use
• Low noise

Possible Engineering Specifications

• Powered by 6V (4 AA batteries) – long battery life
• Maximum Torque for Battery Power, high torque rating
• Powerful motor
• How the planetary gears are set up as well as the material they are made of
• Low Cost maximizes manufacturer profit, use plastic frame and gears, only using metal for parts that needed to be the strongest
• Lightweight --- due to utilization of plastic materials
• Using lube – minimize noise control

How It Works

The motor uses the energy from four 1.5V AA batteries to generate power. This power turns the drive shaft of the screwdriver. This drive shaft is then connected to two planetary gear systems. The second of these gear systems powers and turns the end shaft. The head of the screwdriver which is a shaft rotates the inserted drill bit and consequently the screw.

1) The motor is powered by four 1.5V AA batteries.

Figure 3: Four AA Alkaline Batteries in Casing

2) The motor then turns the drive shaft of the drill.

Figure 4: Motor of the Black & Decker Drill

Figure 5: Drive Shaft of the Motor

3) The drive shaft is connected to the first of two planetary gear sets. These planetary gears are used to decrease the angular velocity created by the rotating motor shaft. This therefore increases the amount of torque that will be exerted to the head of the screwdriver.

Figure 6: One of Two Planetary Gear Systems Connected to Arm

Figure 7: Planetary Gears Outside of Shaft and Arm Connection

4) Finally, the torque created by the rotating shaft is transferred to screw through the rotating shaft at the head.

Figure 8: Casing of Drill Shaft

Figure 9: Drillbit Rotated by Drill Shaft

Renderings

|Rendering of Arm

Figure 10. Rendered Arm

Question	Answer
<center>What decisions were made in the design of this component/module?	Material used for arm Minimize material cost while maximizing strength Minimize Weight Relatively Heat Resistant High strength to weight ratio Dimensions of Arm Minimize Weight Minimize Arm Volume Fit Proportionally Between Planetary Gear Systems
What are the critical features and dimensions?	Thickness of Arm Surface Area of Arm Yield Strength of Arm and Protrusions Maximum Torsional loading of Arm Volume of Arm Shaft/Design of the Arm Number of teeth of the Arm Overall design of the Arm
What kind of loading do we expect to be on the component?	Torsional loading from shaft and gears Axial loading from gears
What measures can we use to evaluate performance?	Torque Rating on Arm Temperature of Arm Loading measures on Arm Dimensions of Arm

|Rendering of Motor Casing & Shaft

Figure 11. Rendered Motor Casing & Shaft

Question	Answer
<center>What decisions were made in the design of this component/module?	Material used for motor casing and shaft Minimize material cost while maximizing strength Minimize Weight Relatively Heat Resistant Holes in Casing Allow for proper cooling of the motor Dimensions of Casing Fit around motor Minimize Weight Minimize Casing Volume Dimensions of Shaft Fit into Gear meshing Needs to be chemically non-reactive with gears and motor Optimize strength to hold up to torque provided by motor
What are the critical features and dimensions?	Thickness of motor casing Diameter of motor casing Length of motor casing Diameter of shaft Length of shaft Yield Strength of shaft Maximum Torsional loading of shaft
What kind of loading do we expect to be on the component?	Shaft Torsional Loading from Motor Minimal Axial Loading Motor Casing Vibrational Loading from Torque on Shaft Axial Loading due to Torque from both Screw and Shaft
What measures can we use to evaluate performance?	Torque Rating from motor Temperature inside motor casing Energy loss from motor to shaft Loading measures on both casing and shaft

|Rendering of Gear

Figure 12. Rendered Planetary Gear System

Question	Answer
<center>What decisions were made in the design of this component/module?	Material used for Gears Minimize material cost while maximizing strength Minimize Weight Relatively Heat Resistant High strength to weight ratio Dimensions of Gears Minimize Weight Minimize Arm Volume Fit Proportionally in Planetary Gear System/With other gears
What are the critical features and dimensions?	Thickness of gears Diameter of gears Diameter of gears Yield Strength of gears Maximum Torsional loading of gears
What kind of loading do we expect to be on the component?	Torsional loading from shaft Axial loading from other gears
What measures can we use to evaluate performance?	Torque Rating on gears Temperature of gears Energy loss through planetary gear systems Loading measures on gears

Parts

The table belows lists the components for the Black & Decker Drill:

Table 1: Black & Decker Drill Component List

Part #	Part Name	Category	Function	Material	Picture
1	Batteries	Power	Supply Power	4 AA Batteries in Battery Carried - Alkaline Batteries
2	Motor	Power	Converts energy necessary to rotate shaft	Low grade steel and plastic
3	Exterior Casing	Frame	Ergonomic design to protect interior components and to conform to users hand; controls readily available for pinky and thumb use	Plastic with rubber grips
4	Motor Shaft	Power	Turns planetary gears as well as acts as teh conversion between the motor power and the torque created by the shaft	Hardened steel
5	Planetary gear system (double)	Torque	First set of three is powered by the motor shaft - this set is then connected to a second set of three gears that power the actual drill shaft	Both sets of gears are made of plastic - gears closed to drill bit are made of a higher strength plastic - gears further from drill bit are made of lesser quality plastic
6	Arm	Torque	Convert torque created by the first set of planetary gears to the shaft that goes through the second set of planetary gears	Metal
7	The Drill Shaft	Drilling	Turns the actual drill bit	Metal
8	Drill Bit	Drilling	Drills	Metal
9	Outer Gear	Setting change	Allows user to lock gears and use the drill manually	Lower grade plastic