Group 16 - DeWalt 4 1/2 in Angle Grinder Gate 1

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Dewalt 4 1/2" Angle Grinder



Over the course of this project our group will be dissecting, analyzing, and reverse engineering the DeWalt 4 1/2 in Angle Grinder. This product is a commonly used tool in many machine shops for its versatility. Through the use of a motor and drive system along with varying attachments the angle grinder is able to grind, cut, and polish various materials. By analyzing how the angle grinder currently works at various system levels our group hopes to not only gain an understanding of what allows the angle grinder to do its jobs effectively, but also what could be done to improve it.

In this gate our group developed a plan to efficiently dissect our product and analyze its components. Part of developing this plan was first taking into account the qualities and capabilities of each group member, as well as the times they are available. The plan for dissection and group-member analysis can be found under Work Proposal. Once our group had created an initial assessment of each member's capabilities and the jobs that would need to be completed we created a tentative division of labor. Roles and associated expectations were assigned to each member based on what tasks they preferred as well as which tasks they were qualified for. This tentative division of labor can be found under Management Proposal. Finally, our group conducted a thorough evaluation and analysis of our product without first dissecting it. This initial inspection and analysis can both be found under the Product Archaeology section of this gate.

Project Management

In this section our group provides a self-evaluation of each member's capabilities and lays out our plan for completing this project. In addition, we provide the framework for how our group intends to function both through internal interaction and conflict resolution.

Work Proposal

Plan for assembly and disassembly

Our group plans to perform the disassembly October 10 and 12 in the lab. Given the relatively small size of our product, we do not expect the dissection process to take longer than these two three hour sessions. During the disassembly process we will have one member take pictures of the product after each step of the dissection and one member record a written description of each step. This will facilitate the eventual reassembly of the part. Once the product has been fully disassembled and analyzed, we will reassemble the product by putting the parts back together in the same order we took them apart. The same tools used for disassembly should suffice for this part. Our preliminary dates for completing the reassembly are November 19 and in the lab. The remaining jobs such as part analysis and written submissions will as a rule be completed two days before each gate is due. A timeline of our activities is provided in Figure 1 for reference.

Based on an initial assessment of the product's exterior and the fasteners in place, these are the tools we expect to need for reassembly and disassembly:

  • 1/16”-1/8” Phillips Head and Flathead Screwdrivers
  • 5/32”-1/4” Crescent Wrenches or Sockets w/ Socket Driver
  • 4 mm-6 mm Crescent Wrenches or Sockets w/ Socket Driver

In addition, these are the tools our group may or may not need, depending on the nature of the internal components:

  • T-15-T-25 Torx wrenches
  • Needle Nose Pliers
Figure 1: Proposed Timeline of Events for Project

Analysis of Group Members

In this section our group provides a brief summary of each group member's skills and flaws relevant to the project. The primary traits we were concerned with were general experience with machines, experience with angle grinders, computer and solid modeling skills, people skills, and availability. We decided that these factors would provide an adequate idea of which parts of the project each group member would be best for, as well as helping us figure out which skills we would have to develop over the course of the project. This self-evaluation is provided in Table 1 below.

Table 1:Evaluation of Relevant Group Member Qualities
Group Member Experience with machines Experience with angle grinders Computer and Solid Modeling Skills People Skills Availability
Ethan George Has limited experience with machines Has never operated an angle grinder before Has limited computer skills: No solid modeling experience or skills Works well with people Very open schedule: readily available to work on project
Michael Halloran Has worked extensively with gas powered machines Has limited experience with angle grinders Poor computer skills: Some solid modeling experience and basic skills Decent people skills Fairly open schedule: readily available to work on project
Zachary Picciano Has worked extensively with machines Has worked extensively with angle grinders Good computer skills: Good solid modeling experience and skills Decent people skills Very busy schedule: needs advanced notice to work on project
Has no experience working with machines Has no experience with angle grinders Decent computer skills: No solid modeling experience or skills Decent people skills Moderately busy schedule: needs advanced notice to work on the project
Tharaka Gabadage Has no experience with machines Has no experience with angle grinders Very poor computer skills: No solid modeling experience or skills Poor people skills Very busy schedule: Needs advanced notice to work on the project

Overall analysis of group

Our group currently possesses all of the skills it will need; however we are overly reliant on certain group members in certain areas. All of our members will need to familiarize themselves with the general function of an angle grinder. Also, those with decent or poor computer skills need to improve these in order to aid in communicating with other members and submitting work. There is no way to “fix” the limited availability of some group members, so we will instead have to work around this by accommodating meetings to their schedules and doing large portions of the work individually. This will also require our group to develop good electronic communication skills so that we do not waste time or fail to cover certain aspects of the project. Lastly, we will need to get at least one other person to learn about solid modeling, as having only one person with those skills will be crippling if he cannot get the work done (it should be noted the one member who currently has these skills has a very busy schedule). By improving in these areas, our group will be able to function effectively for the duration of this project.

Management Proposal

Work Distribution

The general rule for distributing work will be to first allow group members to volunteer for any part of a given gate that they feel they could best complete due to their specific skill set or group role. After this initial process, the Project Manager (see below) will assign any remaining tasks in a manner he feels most appropriate, using the same criteria as above, as well as considering how much work each person already has to do on the project.

Contact Information

Our group can be contacted at any time through Communication Liaison (see below) Michael Halloran. He may be emailed at or (both forward to the same address, so there is no preference in which address to email), and will respond promptly with any information you may require, as well as inform the group about any emails he may receive.

Meeting Plan

Our group will be meeting on a specific set of days that we have already agreed to. All group members are expected to attend every meeting given that the schedule was created to accommodate each member's schedule. If however a member cannot attend for an unforeseen reason, they will be forwarded meeting minutes and asked for their position on any relevant votes. All other information on group meetings is provided in Table 2 below.

Table 2: Group Meeting Plan
Date and Time Duration Location Reason for Meeting Tasks to Accomplish at Meeting
October 10 at 6PM 3 Hours Furnas Dissection Lab To assign tasks for Gate 2 and begin the dissection of the angle grinder Disassemble angle grinder, take photographs and create a log of each step
October 12 at 6PM 3 Hours Furnas Dissection Lab To complete the dissection of the angle grinder Finish disassembling the angle grinder, take photographs and create a log of each step
October 25 at 5PM 1 Hour Capen Library To collectively review Gate 2 before submission Read through all parts of the project, check for spelling and/or grammar mistakes, and verify that all parts were completed with a sufficient level of detail
October 27 at 5PM 1 Hour Capen Library To assign clarify and assign tasks for Gate 3 Go through Gate 3 assignment, divide jobs, and collectively discuss the interpretations of any tasks
November 14 at 5 PM 1 Hour Capen Library To collectively review Gate 3 before submission Read through all parts of the project, check for spelling and/or grammar mistakes, and verify that all parts were completed with a sufficient level of detail
November 17 at 5PM 1 Hour Capen Library To assign clarify and assign tasks for Gate 4 Go through Gate 4 assignment, divide jobs, and collectively discuss the interpretations of any tasks
November 26 at 6PM 3 Hours Furnas Dissection Lab To assign tasks for Gate 4 and begin the reassembly of the angle grinder Reassemble angle grinder, take photographs and create a log of each step
November 29 1 Hour Capen Library To collectively review Gate 4 before submission Read through all parts of the project, check for spelling and/or grammar mistakes, and verify that all parts were completed with a sufficient level of detail

Group Roles

In order to facilitate group communication, conflict resolution, and overall project completion, our group has created the following roles and assigned group members to them based on the information provided in the self evaluation.

Project Manager (Ethan George)- The project manager will be responsible for assigning work to other group members as well as laying out a timeline for meetings. In addition to taking some tasks for himself, he will contact other group members regularly to make sure they are moving at a proper pace and try to prevent parts of the project from being overlooked. In addition, he will make the final decision on issues such as requirement interpretation, changes of schedule, and whether work submitted by other members is of high enough quality or not.

Communication Liaison (Michael Halloran)- The communication liaison will be responsible for being a reliable point of contact with the professors, as well as organizing and posting the group’s work through the wiki page. He will disseminate any information or feedback the professors provide and ask any questions the group has. Below, the contact information for the communication liaison is listed again:

Technical Expert (Zachary Picciano)- The Technical Expert will be responsible for having an in depth understanding of the product’s function, structure, and components. He will through research and prior experience gain an in-depth understanding of these aspects so that he can lead the dissection and reassembly. On these parts of the project, the Technical Expert and NOT the Project Manager will have full authority as he will have the greatest knowledge of what needs to be done and how to do it safely. In addition, the Technical Expert will do any solid modeling of the product, although he will be working with the other members in describing what exactly must be drawn or designed.

Research Experts (Takur Phuyel and Tharaka Gabadage)- The research experts will be responsible for doing any research not already covered by the technical expert. In addition to completing tasks that are specifically research oriented, they will also look into any other questions that may arise over the course of the project. They will then be responsible for informing the group about their findings so that the entire group will have a clearer understanding of the project.

Conflict Resolution Plan

All group conflicts will be settled by a discussion of the disagreement at either the next meeting or a meeting scheduled by the project manager to specifically deal with urgent issues. Once the conflict has been discussed other group members will be allowed to suggest alternative solutions, and all group members will then vote on the course of action they most prefer. Individuals who ignore group decisions, do not complete the required work, or fail to attend meetings without a legitimate excuse will be worked around by delegating all significant assignments to other group members. As recourse the other group members will collectively give such individuals poor scores on the group evaluation at the end of the project.

Product Archaeology

This section contains our group's findings after performing background research on our product and performing an inspection without completing disassembly.

Development Profile

The first angle grinder developed by Flex Company consisted of an electric motor and a flexible shaft for grinding attachments.

The first angle grinder was developed by Flex Company in the late 1920s. While this angle grinder does not bear much resemblance to modern angle grinders, it was the first handheld tool to allow the user to perform grinding functions. The DeWalt Heavy Duty Angle Grinder family of products was later developed in the early 2000s ( At this point in time the primary global and economic concerns for the angle grinder were the functionality and price point for the intended audience. These concerns are listed below:

  • Global: The DeWalt angle grinder was developed for countries with developed economies. The tasks angle grinders are intended to do, such as finishing wood, polishing doors, and removing weld seams, are not usually done in developing nations. In addition, a lack of reliable power grid would make the electric angle grinder inferior to those with other power sources.
  • Economic: The DeWalt angle grinder reduced cost by using less cast iron than traditional angle grinders and replacing many auxiliary parts with plastic. It also uses less power than other similar angle grinders in order to reduce electrical costs for the user. (

Our angle grinder is only intended for sale in North America, primarily the U.S. and Canada. This is because the product must undergo special testing for certification to be sold in Europe, and “DeWalt Europe” is a similar but different version of this product for sale there. (

The angle grinder was designed to make many household tasks easier. This product furthers that goal of the original angle grinders by making the angle grinder lighter weight and easier to use, which is ideal for both household use and extended use in a professional setting. The overall intended impact of this product was therefore to make grinding an easier task to accomplish.

Usage Profile

This user is using an angle grinder to sand a deck much faster than could be done with sand paper.

The intended use of the angle grinder is grinding various materials. In addition to grinding, multiple attachments can be fitted allowing the angle grinder to cut, sand, and polish. In combination with the ability to use a grinder almost anywhere, these array of functions make the angle grinder a great "all-purpose tool" for material removal. Angle grinders can be used for both home and professional uses, but this angle grinder was most likely designed with an emphasis on professional use. This is because the parent company of DeWalt (Black and Decker) already produces an array of cheaper product alternatives. DeWalt is instead a more expensive heavy duty brand, which suggests the intended customers were either professionals or home owners with hobbies (i.e. carpentry) that required a large amount of grinding.

The following is a list of the most common functions an angle grinder might perform in a professional setting.

  • With the use of various qualities of grinding disk an angle grinder can grind metal weld seams to make them smooth.
  • Cutting metal, concrete, and stone can be done by attaching a cut-off disk (usually with a diamond blade).
  • Sanding disks allow the user to sand wood quicker than with sand paper.
  • Polishing disks and wire brush disks allow the user to polish metal and remove corrosion, rust, and paint from metal.

These functions, along with other more obscure uses, are what make the angle grinder so versatile. It is one tool that allows the user to perform a wide array of tasks for a given job. (All information for this section taken from

Energy Profile

The product uses AC electrical energy and rotational kinetic energy, which changes direction at the grinder head. Electricity is the only energy imported into the system, which is done by connecting the plug to any standard U.S. AC outlet. The electrical energy imported into the system is then transformed into rotational kinetic energy by an AC motor in the bottom of the tool. This motor drives the main shaft which in turn rotates a gear. This gear redirects the rotational kinetic energy by turning the axis of rotation 90º at the head of the grinder, which in turn delivers its rotational kinetic energy to the grinder’s disk and the object the tool is being used on. This flow of energy is summarized in Figure 2 at right. (All information for this section taken from

Complexity Profile

Based on observation of the product, group members' collective experience with electronic motors, and our theory of how the angle grinder will work, we have determined that the following components are present in our product. Components in regular font are observable, and therefore definitely present in the product. Components in Bold are not clearly visible, but our reasons for believing these components are present is given alongside the component.

  • Power cord
  • Electric Motor:Based on the presence of a power cord and the fact the grinder outputs kinetic energy, it is safe to assume
  • Main shaft:There must be some component present to deliver power from the motor to the grinder head. We theorize a shaft is used to carry this energy.
  • Gear box
  • Backing Flange
  • Handle
  • Power Switch
  • Housing

Our method for assessing the complexity of the components was based on the number of parts we theorize will be present and the possible energy flows that may be associated with the component. Each of the components will therefore be rated on the following scale:

  • 1: This component is very simple and only contains one part that either does not contain any energy flows, or only delivers simple energy flows.
  • 2: This component is somewhat complex and may contain multiple parts or contains simple energy flow.
  • 3: This component is very complex and contains multiple parts as well as complicated energy flows.

Based on this rating scale, our group has constructed Table 3, which contains all of the observable and theorized parts as well as the complexity of each part and a brief justification for this rating:

Table 3:Component Complexity
Component Complexity Rating Justification
Power Cord 2 The power cord consists of at least two parts: the rubber insulation and the copper wire which must branch off to any electrical components at some point. The power cord also allows electricity to flow through it, which is a fairly simple flow of energy.
Electric Motor 3 The electric motor must consist of several components including magnets, brushes, wire coils, and an armature. There is also a complex flow of energy as the electrical energy input into the system is converted to kinetic energy as an output.
Main Shaft 1 The main shaft would only consist of one part (the shaft) and would deliver a very simple form of energy; it would take rotational energy from the motor and deliver rotational energy to the gearbox.
Gear Box 3 The gearbox must contain multiple gears in order to take the rotational energy from the main shaft and turn it 90 degrees. In addition the gearbox must contain ball bearings in order to allow the free rotation of the helical gear. These many parts and the complex flow of energy make the gearbox a very complex component.
Backing Flange 1 The backing flange only consists of one part and that part only takes rotational energy from the gearbox and delivers it to whatever disk is put on the grinder.
Handle 1 The handle is only one piece and does not contain any energy flow.
Power Switch 2 The power switch must consist of at least two parts (the visible switch, and some bar that moves electrical contacts to start the motor). The switch takes a signal from the user and changes it into a signal to start or stop the electric motor. This makes the power switch a moderately complex part.
Housing 2 Even though the housing does not allow for any energy flows, it does contain several pieces that must be assembled properly in order to hold the functional components of the angle grinder in place.

The component interactions can be broken up into three main groups: the electrical interaction, the initial rotational interaction, and the output rotational interaction. These three groups and the complexities of their interactions are given below.

  • Electrical Interaction: The electrical component interactions consist of the switch, power cord, and electric motor. Moving the switch results in moving metal contacts that allow energy to flow into the electric motor when the switch is on, but not when it's off. These interactions are simple because they only contain simple energy flows and are very intuitive.
  • Initial Rotational Interaction: The initial rotational interactions consist of the electric motor, main shaft, and gear box. The electric motor takes the electrical energy supplied by the power cord and converts it into rotational energy by varying the flux in a coil in a magnetic field. This rotational energy is then delivered by the main shaft to the gear box. These component interactions are the most complex as it is the only place in the device where energy completely changes form. A significant part of our investigation of this product will include how these components interact to produce this initial kinetic energy.
  • Output Rotational Interaction: The output rotational interaction consists of the gear box and backing flange. This interaction will be fairly complex as the gearbox must take the rotational energy from the main shaft and redirect it, which will include the interactions of at least two gears. This redirected rotational energy will then be applied to the backing flange, which will then apply the rotational force to whatever attachment is being used on teh angle grinder.

The remaining components not addressed above do not interact with any other components in ways that contribute to the overall function of the angle grinder (i.e. Handle to housing interaction). The complexity of these component interactions are therefore trivial and non-applicable.

Material Profile

What materials are clearly visible?

• Rubber (cord)

• Copper (cord)

• Steel (guard and wheel nut/screw)

• Plastic (housing and power switch)

What materials are not visible, but present?

• Magnetic iron (electric motor)

User Interaction Profile

How does the user interface with the product(s)?

The two primary user interfaces are the power switch and the wheel nut.

• The power switch allows the user to cut power to the motor, apply power to the motor, and lock the grinder in an on position where power will be applied until removed.

• The wheel nut allows the user to place different attachments on the angle grinder’s drive head and then secure them to prevent the disk from falling off.

How intuitive are the interfaces?

• Both interfaces are very intuitive. The power switch has an O and and I marking power on and off respectively, with a small picture of a lock at the position where the power will lock on.

• The wheel nut is a standard nut as it must be turned counter-clockwise to remove it, and turned clockwise to secure it and whatever head may have been placed on the angle grinder. Placing the head is also very intuitive, as it slides right over the screw the wheel nut came off of.

How easy is the product to use?

The product requires minimal knowledge to use, as one can literally “flick the switch and go.” However, there are certain safety measures the user must first familiarize himself with. While they are not all intuitive (such as allowing the machine to fully accelerate before applying to the material, or fully decelerate before unplugging) they are quite simple, and require minimal user effort once the safety measures are known. In addition, specific materials and jobs come with their own safety measures, but just like the general safety tips, these are not a challenge once known.

Is regular maintenance required?

The primary form of maintenance the user will face is replacing the attachable heads, which is simply a matter of unscrewing the wheel nut, removing the old disk, putting the new one in, and replacing the wheel nut.

The only other forms of ordinary maintenance are replacing the brushes and main shaft bearing. Both of these are slightly more complicated.

• The brushes can be replaced by removing the cover plates located to the rear of the motor (near the bottom of the tool). There is a screw that must be removed, but once it is and the cover plates are off, the brushes can be extracted, replaced, and the cover plates can be put back on.

• The main shaft bearing is replaced by removing the guard, removing four screws in the grinder housing where the guard was clamped, and then removing the housing and bearing. The new bearing is then inserted, and the other parts are replaced.

Alternative Product Profile

What product alternatives exist?

Alternative 1: Milwaukee 11 Amp 5 in AC small angle Grinder with Trigger Grip

What are the advantages?

• 5 years limited warranty, comparing to DeWalt's 3 year limited warranty

• Variable speed available

• Bigger size of wheel: 5 in comparing to 4.5 in

• CSA listed ( meaning product complies with national and international standards)

• 1400 MWO motor that powers through tougher jobs

What are the disadvantages?

• It is heavier than DeWalt (6.88lb and 4.6 lb)

• Uses more electricity (11 A vs. 10 A)

• 10 dollars more expensive than DeWalt

How does this alternative compare?

• Both with maximum speed of 11000 rpm

• Both are 90 days returnable

• Both have an AC motor designed for maximum performance

• The DeWalt uses less electricity during operation

• The DeWalt does not have as much power as the Milwaukee

• The DeWalt does not allow for speed adjustments

What are the differences in the cost?

• DeWalt costs about $89, which is $10 cheaper than Milwaukee's angle grinder ($99).

Alternative 2: Black & Decker G950 4-1/2-Inch Small Angle Grinder

What are the advantages of this product?

• 3-position side extended handle and contoured body with rubber grip for added comfort and control in a variety of applications.

• Metal gear case for added durability and extended life.

• Trigger switch allows for ease of use, even when wearing gloves.

• Spindle Size: 5/8 to 11 inches

• Two year limited warranty

• Spindle lock which provides easy accessory changes

• Included with angle grinder: metal grinding wheel, spanner wrench, and side hand.

What are the disadvantages of this product?

• 2.4 lb heavier than DeWalts (DeWalt's 4.6 lb vs. 7.0 lb)

• After sale service is one year less than DeWalt’s.

• Limited warranty is one year less than DeWalt’s.

• 1,000 RPM less than DeWalt’s.

• No Dust Ejection System.

• No auto-off brushes system which avoid tool damage.

Similarities of the products

• Both are 90 days returnable

• Quick-Change system, allows tool free wheel removal without need for a wrench.

• Equal Spindle Size ( 5/8 to 11 inches)

• Side rubber handle for better control


11 Amp 5 In. AC/DC Small Angle Grinder with Trigger Grip-6121-31A at The Home Depot. N.p., n.d. Web. 06 Oct. 2012. <>.

"4 1/2" Small Angle Grinder." N.p., n.d. Web. 06 Oct. 2012. <>.

"History of the Angle Grinder." FLEX. N.p., n.d. Web. 06 Oct. 2012. <>.

"Sign Up Today!" Grinder Buying Guide. N.p., n.d. Web. 06 Oct. 2012. <>.

"How to Use an Angle Grinder." The Family Handyman. N.p., n.d. Web. 07 Dec. 2012. <>

Links to Other Gates


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