Group 28 - Ryobi Angle Grinder

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Angle Grinder


Executive summary

Through the disassembly of the Ryobi angle grinder, we found that there were four main physical components that contribute the most to the functionality of the product. This report aims to discuss the various procedures we performed in both the disassembly and reassembly of the product. We found that the AC converter, armature, bevel pinion, and bevel gear were the four highlighted components we found through the disassembly. Essentially, through these main components, the explanation of how the functional capabilities of the grinder are achieved is basically summarized. Beginning with the AC converter which obviously corresponds to the energy source, and ending with the bevel gear which connects directly to the physical rotation of the grinding plate, these four components are essential to the functional success of the product. Likewise to the disassembly, the success of the reassembly hinges upon these four main components as well. The AC converter needed to be directly connected to the armature to convert the electricity into working energy. Once a stable connection was achieved, the bevel gear and pinion were reassembled mechanically in a basic manner.


Project created by:

Kyle Zimmermann-Disassembly, assembly, presentation, wikipage

Zach Nothnagle-CAD drawings, bill of materials, presentation, Wikipage

Joel Santora-Presentation, Executive summary

Anthony Samoraj-Presentation, assembly, wikipage

Udeep Dhungel

Our team was in charge of the reverse engineering of the Ryobi Angle Grinder, model AG402. Ryobi Angle Grinder is compatible with 4.5” grinding plate. Its dualities include the grinding of various different metals and the ability to sand both wood and metal surfaces. Its 120V and elctrical motor that yeilds a current of 4.4 Ampheres, produces a speed of 11,000 RPM. With a net weight of 1.8 kg, it's considered to be very light weight.

Before Disassembly

The angle grinders purpose is that its used for a lot for grinding and polishing. It can also be used to cut and sand. Angle grinders are found in your average work shops and in many service garages. They are commonly used in construction and metal working. They are also used a lot in emergency rescues. The Angle grinder works with several different types of material such as wood, metal, concrete and plastic.

It is powered by an electric motor. The Ryobi angle grinder derives its power from a 120 volt field assembly piece. The AC current flow allows the field assembly unit to create an electromagnetic field which enables the armature, or motor, to run. There are no ground wires within the field assembly because it is double insulated, meaning that all the exposed metal parts are isolated with protective insulation from the motor’s metal components. The grinder transfers electrical energy into mechanical energy in the electric motor. When the switch gets activated it is sent to the motor which polarize the stator and the rotor. This allows for the poles of the stator and the rotor to resist one another. Which allows for a constant spinning motion.

When the product was operated, it ran perfectly smooth as far as we could tell. It was brand new out of the box, and seemed to be in perfect working condition. In terms of external motion, the grind plate operates in a circular motion. It produced a high pitch sound, typical of any hand held power tool.

We believe when starting this project that it was made of about 50 different components and about 5 different materials.

                                 Electric Power Source

Disassembly Process

Overall, the Disassembly process of the Ryobi Angle Grinder was extremely easy. The entire product was able to be taken apart using only a Philips screwdriver. After a few central screws (all of which were the same) were removed, the remainder of the angle grinder was then able to be disassembled using only your hands.

The following is a list of the components, and the order in which each was removed:

1) Grind Plate Guard

-Required the removal of 1 screw

-Easy to remove

Grind Plate Removal

2) Gear Case

-Required the removal of 4 screws

-Easy to remove

Gear House Removal

3) Gear Case Housing

-Required the removal of 4 screws, 4 washers, and 4 lock washers

-Easy to remove

-Seperated immediately after removal of screws and washers

Gear Housing Removal

4) Bevel Pinion, Gasket, and Key lock

-Required the removal of 2 screws and 2 washers

-The Bevel Pinion and Key lock were able to be removed without taking out the screws, however the gasket was not. The diameter of the gasket is slightly smaller than the bearing directly behind it. This prevents the bearings from potentialy moving from their position.

Bevel Removal

5) Armature Assembly and Fan Baffle

-Required no tools

-After the Gear Case was removed, it was able to be pulled out of the motor housing freely

Armature Removal

6) Brush Assembly

-Required the removal of 2 screws, 2 washers, 1 pair for each brush, and the disconnecting of attached wires

-Easy to remove

Brush Assembly Removal

7) Field Assembly

-Required no tools

-Once connecting wires were detached, the Field Assembly slid right out of the housing.

Field Assembly Removal


After Disassembly

Part Number Name Manufacturing Process Material Picture
1 Grind plate shield machining Iron grind shield
2 Grind plate screw machining stainless steel Grind Shield Screw
3 Grind plate nut machining steel Grind Plate nut
4 Gear case housing Die casting steel Gear Housing
5 Grind housing screws machining steel Gear Housing Screw
6 Bevel Gear machining steel Bevel Gear
7 Bevel Pinion machining steel Bevel Pinion
8 Armature forged steel and copper Armature
9 Bevel Gear Key die casting steel Bevel Gear Key
10 Bevel Pinion Key die casting steel Bevel Pinion Key
11 Gasket die casting stainless steel Gasket
12 Gasket Screw machining steel Gasket Screw
13 Gasket Washer machining steel Gasket Washer
14 Side Handel Injection Molding ABS plastic Handel
15 Disc Flange die casting steel Disc Flange
16 Clamp Nut machining steel Clamp Nut
17 Gear Case Die Casting steel Gear Case
18 Fan Baffle Injection Molding ABS Plastic Fan Baffel
19 Wrench Die Casting stainless steel Wrench
20 Motor Housing Injection Molding ABS Plastic Motor Housing
21 Back Handle Injection Molding ABS plastic Back Handel
22 Field Assembly forged steel and copper Field Assembly
23 Retaining Ring Die Casting steel Retaining Ring
24 Wavy Washer Die Casting steel Wavy Washer
25 Gear Case Washer Die Casting steel Gear Case Washer
26 Gear Case Lock Washer Die Casting steel Gear Case Lock Washer
27 Brush Assembly machining steel Brush Assembly
28 Brush Washers Die Casting steel Brush Washer
29 Brush Screws machining steel Brush Screw
30 Field Screws machining stainless steel Field Screw
31 Power Cord extrusion copper Power Cord
32 Gear Case Screw machining steel Gear Case Screw

Gear Case and Bevel Gear Assembly

Unexploded view of CAD drawings Exploded view of CAD drawings


The reassembly of the Ryobi Angle Grinder was exactly the same process as the disassembly, except in reverse. Therefore the same tools were used and the level of difficulty stayed the same. Starting by placing the field assembly back into the housing, and working from there. The only noticeable difference however, there was a small amount of extra patience that was required for putting the key locks back in their original position and guiding the wires connecting to the field assembly through their designated holes. Besides those two small issues, it was very easy.

After Assembly

After disassembling and reassembling the angle grinder we obtained a better understanding of how the angle grinder worked. We saw by its components how it takes the electric power source and converts that into mechanical power which spins the grind plate. The angle grinder worked the same after we reassembled the product. We think a good model that could represent the angle grinder for analysis is a functional diagram. This would make it easy to see what goes into the product and what work comes out. This model would help show how efficient the angle grinder is and you could use estimated numbers.

The disassembly and assembly process were pretty much the reverse of each other. The same tools were used at to disassemble components and reassemble them. Which allowed us to be able to reassemble the whole product.

Improvements: Throughout the machine assembly of the grinder, several different sizes of screws were used. Rather than having different sizes, the assembly and disassembly of the product would have been made much easier had the size of the screws been consistent throughout.

The plastic armature housing is intended to be the “handle” of the tool, in operation. Essentially, the operator of the grinder grips the plastic housing to manipulate the movement of the grinder plate. Its physical structure is somewhat awkward and bulky making it difficult operate precisely. We would suggest ribbing the texture of the armature’s housing to better fit the hand of its user.

When using the grinder to cut through various metal samples, hot metallic embers erratically spew from both the grinding plate and the samples as well. We would suggest mounting some sort of protective shield on the armature housing that ideally would protect the operator’s hand.