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11.1 Common Surface Grinders

Tim A. Bacon

A grinder is a machine that removes material from a workpiece through the use of an abrasive grinding wheel. Grinders are used to achieve high precision, surface finish, and the overall shape of a workpiece that cannot be achieved through other machining processes like turning, milling, or drilling.

There are different types of grinders used in machining, each designed for a specific purpose. The main three types are horizontal, vertical, and cylindrical grinders.

Horizontal

Picture of horizontal surface grinder
Figure 11.1. Typical horizontal surface grinder / Image Credit: T Bacon, courtesy Bates Technical College, CC BY 4.0

Horizontal spindle surface grinders typically use the outside diameter (OD) of the solid wheel to grind the part surface, as seen in the picture at the start of the chapter.

The most common type of grinding machine is the horizontal spindle with a reciprocating table. The “head” of the machine holds the grinding wheel while it spins. It is moved up and down in a direction perpendicular to the table. This is also referred to as the Z axis. The hand wheel of the head controls the movement in the Z axis. The amount of movement per gradation, or line on the dial, is typically .0001. This is called a “tenth” by a machinist.

Diagram of horizontal grinder
Figure 11.2. Diagram of horizontal grinder / Image Credit: Nicholas Malara, CC BY 4.0

Visualize the axis in the image above on the horizontal grinder. The X positive is to the right, Y positive is up away from the part, and the Z positive movement is towards the machinist. The X is workspeed, the Y is in-feed, and the Z is the crossfeed.

Picture of grinding wheel above a part on the table. Arrow shows rotational direction and table movement.
Figure 11.3. After adjusting the head, always approach the grinding wheel from the left side. / Image Credit: T Bacon, courtesy of Bates Technical College, CC BY 4.0

The part will travel back and forth along the long dimension of the table, the X axis, and the short dimension of the table, the Y axis. The X axis is the “work speed” direction, and the Y axis is the “cross feed” direction. The wheel will spin in a clockwise rotation. The right side of the wheel is the ingoing nip that will pull the part in. The left side of the wheel is the outgoing nip that pushes the part away. Passing a part under the grinding wheel from right to left is similar to making a climb cut on a manual mill. Similarly, moving from left to right is a conventional cut on a manual mill.

Critical Safety Note

Never walk or stand on the left side of the grinder when the grinder is being used. The left side of the surface grinder is where parts are ejected if they come loose.

Vertical

Machines with a rotary table will rotate the work beneath the grinding wheel.

Blanchard rotary table grinder. Setting up to grind large plates.
Figure 11.4. A Blanchard rotary table grinder is set up to grind large plates. / Image Credit: Nicholas Malara, CC BY 4.0

Pictured above is a vertical grinder performing a Blanchard operation where the part can rotate independently from the grinder.

Machines with reciprocating tables move the work back and forth beneath the wheel.

The grinding is done on the side of the wheel. This is also referred to as Blanchard grinding.

Vertical spindle grinders typically use the side of the grinding wheel to grind the workpiece. The wheel may be solid, or cup shaped. The tables will either be reciprocating or rotary in motion, just like the horizontal grinder. Vertical surface grinders are also referred to as Blanchard grinders. These grinders are mainly used for large, flat plates. In the automotive industry, large flywheels will be Blanchard ground for proper clutch assembly.

An example of a flywheel after grinding.
Figure 11.5. An example of a flywheel after grinding. / Image Credit: Nicholas Malara, CC BY 4.0

Vertical surface grinders will remove substantial amounts of material quickly and efficiently due to the large surface area of the wheel being engaged. Blanchard grinding can also result in a cross hatched pattern on the surface finish. Cross hatching is cosmetically desirable and provides improved wear characteristics where two parts have movement between them.

An example of cross-hatching on the face of a part.
Figure 11.6. An example of cross hatching on the face of a part. / Image Credit: Nicholas Malara, CC BY 4.0

Cylindrical

Cylindrical grinding on a tapered part.
Figure 11.7. Cylindrical grinding on a tapered part. / Image Credit: Nicholas Malara, CC BY 4.0

The picture above shows an operation on a cylindrical grinder.

On the left-hand side it is labeled, Outside Diameter Grinding, Cylindrical grinding a cylinder. Labeled are the grinding wheel, center, and workpiece. On the right-hand side, it is labeled Inside Diameter Grinding. Labeled are Work speed, Grinding wheel, Infeed, traverse feed motion, freshly ground surfaces, original work source, and workpiece.
Figure 11.8. Image Credit: Nicholas Malara, CC BY 4.0

Cylindrical grinders can be either external (a), or internal (b).

Cylindrical grinders are used to grind diameters, shoulders, and faces much like the features that are cut on a lathe. The workpiece is rotated against the surface of the grinding wheel as it turns. A hand wheel is used to make precise movements of the wheel head to set the cut depth. A power table moves the grinding wheel along the axis of the part’s rotation.

If a grinder is configured to cut only the outside diameter of the part, the OD, it is referred to as an OD Grinder. The same can be said for a machine set up to grind internal diameters, or ID. Faces and shoulders can also be ground with the side of the wheel on either style of machine mentioned previously. An ID grinder uses a wheel mounted on an arbor. The arbor is a shaft that supports the grinding wheel as it removes material in a cylindrical shape inside a part.

Attributions

  1. Figure 11.1: Horizontal surface grinder by T Bacon, courtesy Bates Technical College, for WA Open ProfTech, © SBCTC, CC BY 4.0
  2. Figure 11.2: Main parts of a surface grinder by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
  3. Figure 11.3: Directions by T Bacon, courtesy of Bates Technical College, for WA Open ProfTech, © SBCTC, CC BY 4.0
  4. Figure 11.4: Blanchard grinding by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
  5. Figure 11.5: Flywheel by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
  6. Figure 11.6: Cross hatch texture on surface by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
  7. Figure 11.7: Cylindrical grinding by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
  8. Figure 11.8: Cylindrical grinding by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
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Introduction to Machining Copyright © by SBCTC is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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