1. Surface Grinding Operations

2. Introduction, Safety, and Mounting the Grinding Wheel
Surface grinders machine flat surfaces, like milling
Safety: see cautions in text
Mounting:
Remove spindle nuts to release old wheel
Perform ring test
Use blotter and clean, burr-free washer
Jog spindle and run to test

3. FIGURE 7.3.1 Loosening the spindle nut on most grinders requires two wrenches.
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FIGURE Wheels should always be ring tested before they are installed. Ring testing checks the wheel for soundness.
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4. A B
FIGURE (A) A permanent magnet and (B) an electromagnet. The control for the electromagnet offers the ability to vary the magnetic force exerted on a workpiece which can limit distortion of thin workpieces.
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5. Workholding Devices Magnetic devices
Permanent magnet vs. electromagnet
Magnetic parallels, V-blocks, angle plates, sine chucks
Angle plates, V-blocks, and collet blocks for milling can be used for grinding
Grinding vises different from milling vises

6. FIGURE The gold lines on the chuck represent the lines of magnetism. The workpiece should span 3 or more of these lines to be safely secured. Notice the back rail on this chuck. It is used to help align a workpiece on the chuck.
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7. FIGURE 7.3.6 Magnetic parallels extend the magnetic field
FIGURE Blocking consists of placing pieces of ferromagnetic metal around the workpiece. This is done to help hold the workpiece secure during the grinding operation. When using this method it is important to make sure the blocking material is shorter than the actual workpiece.
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FIGURE Magnetic parallels extend the magnetic field
of the magnetic chuck.
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8. FIGURE 7.3.8 Magnetic sine chucks can be used to hold a
Magnetic V-blocks.
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FIGURE Magnetic sine chucks can be used to hold a
workpiece at a preset angle. The angle is set by using a gage block build as with a sine bar.
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9. FIGURE 7.3.9 A workpiece is often passed over a demagnetizer after grinding.
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FIGURE Grinding vises are very accurately ground and can be used to quickly and accurately secure workpieces.
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10. Wheel Dressing Dress and true wheel before use
Dressing sharpens, truing stops runout
Dress/true aluminum oxide/silicon carbide wheels: with diamond dressing tools
Superabrasive wheels: true first with brake truing device, then dress with dressing stick
FIGURE Truing makes the wheel face run true to its axis and dressing sharpens the wheel.
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11. A B
FIGURE “A” shows a single point dresser. “B” shows a cluster point dresser.
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12. FIGURE 7.3.13 Preferred location of the diamond dresser on the left edge of the chuck.
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FIGURE Proper dresser position is an important safety consideration. The diamond should be offset to the left of the wheel centerline. If the diamond is angled in its holder, the angle should be placed as shown.
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13. FIGURE 7.3.15 The dresser is being positioned near the edge of the wheel.
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FIGURE The dresser is fed across the face of the wheel to perform the dressing operation. Feeding the dresser slowly will result in a wheel having a slightly more closed structure while feeding faster will produce a slightly more open structure.
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14. FIGURE 7.3.17 Illustration of brake truing.
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15. Grinding Parallel Surfaces
Most basic/common operation
Often best to start with largest surface
Secure workpiece and clean before grinding
Grind magnetic chuck periodically to keep surface flat
FIGURE The grinding wheel should travel all the way off the work piece at the end of each longitudinal pass.
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16. FIGURE The table should be cross-fed far enough so that the wheel travels off the front and rear of the part.
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17. FIGURE When touching off, the grinding wheel is positioned so that only about 1/8" of its width is over the work. Layout fluid can make it easier to see when the wheel touches since the dark blue provides a good visual contrast to the workpiece.
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FIGURE The arrows show the direction of feed as a surface is ground.
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18. Grinding Perpendicular Surfaces and Angles
Perpendicular surfaces: set parallel to magnetic chuck or use angle plate or grinding vise
Angles: use magnetic V-block, sine bar and angle plate, or magnetic sine chuck
FIGURE Angle plates are often used to grind a workpiece square. If setup properly, two perpendicular surfaces of the workpiece can be ground without repositioning the work on the angle plate. Here the part is positioned so that the left side extends past the angle plate while the side facing up is ground.
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19. FIGURE Without repositioning the work on the angle plate, it is turned on its side for grinding the adjacent side. Clamps must be repositioned for clearance with the grinding wheel.
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FIGURE A precision grinding vise can be used in place of an angle plate when grinding perpendicular surfaces.
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20. FIGURE Two surfaces of the workpiece can be ground without reclamping the work by turning the grinding vise on its side.
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21. FIGURE 7.3.26 Magnetic V-blocks are helpful when grinding 45-degree angles.
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FIGURE Using a sine bar and gage blocks to position the workpiece on an angle plate.
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22. FIGURE Magnetic sine plates can also be used with gage blocks to set up angles. This method is very accurate.
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FIGURE The vertical walls of the step and the slot of this workpiece have been finished using side grinding techniques.
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23. Side Grinding
Use periphery of wheel to grind surface parallel to magnetic chuck and side to grind vertical surface
Dress side before grinding
Mount work parallel to table travel
FIGURE The dresser should be positioned on end and aligned with the centerline of the wheel for side dressing.
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24. FIGURE 7.3.31 Dresser being used to dress the side of the wheel.
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25. FIGURE Dressing a small undercut into the wheel can help reduce the amount of surface-to-surface contact between the workpiece and the wheel.
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FIGURE Dressing a small undercut can also be performed by hand using a dressing stick.
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26. FIGURE 7.3.35 Positioning of the wheel near the surfaces to be ground.
FIGURE A dial indicator being used to align the workpiece with the longitudinal travel.
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FIGURE Positioning of the wheel near the surfaces to
be ground.
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27. FIGURE 7.3.36 Grinding horizontal and vertical surfaces.
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FIGURE A collet type fixture can be used to produce cylindrical or angular surfaces.
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28. Grinding Cylindrical Work and Grinding Problems
Grind cylindrical features, radii, and angles using indexing feature
Grinding problems
Burning work surface
Scratches on work surface
Waviness/chatter on work surface

29. Grinding Cylindrical Work and Grinding Problems (cont’d.)
FIGURE (A) The center of the workpiece should be in line with the center of the wheel when using a spin fixture. (B) Lower the wheel head while rotating the fixture handwheel to grind the cylindrical surface.
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30. FIGURE 7.3.39 Angular graduations or an indexing ring can be used to set up angles for grinding.
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FIGURE A V-block fixture can align the workpiece by moving the V-block from the centerline of the fixture. A dial indicator can be used to ensure that the cylindrical surface is running true.
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31. A wavy surface may indicate a loose or out-of-round grinding wheel.
FIGURE Burn marks appear as dark streaks in the surface of the workpiece.
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FIGURE
A wavy surface may indicate a loose or out-of-round grinding wheel.
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