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Work-Holding for Surface Grinding
Workpieces of different sizes and shapes can be ground
on a surface grinder by using a variety of work holding accessories. Some
of these work-holding accessories will be described in this information
sheet.
| Two Sided Tape
Two-sided tape is often used for holding thin workpieces when
trying to grind out the warpage. Thin, warped, workpieces will be
pulled flat by the power of the magnet. After the part is ground and
the magnet released, the part resumes it’s original twisted shape.
By using two-sided tape you can grind the warpage out of the part,
permanently. One side of the tape is applied to the chuck while the
other side holds the work (Figure 1). No magnetic power is used.
When using tape you will need to take extremely light cuts, without
the use of coolant. Two-sided tape can also be used for holding
thin, non-magnetic, pieces on the chuck when grinding. |
Figure 1. Two-sided tape is being
used to hold a thin, warped, workpiece.
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| Magna-lock Clamps.
Magna-lock clamps, shown in Figure 2, are used to firmly grip the
sides of a non-magnetic work- piece. |
Figure 2. Magna-Lock Clamps
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Figure 3. Magna-Lock Clamps |
These clamps consist of two heat-treated steel strips, with comb
like teeth, which are held together by a thin piece of spring steel
located in the center (Figure 3). |
| The spring steel is slightly bent along the entire length of the
clamp. The spring steel strips hold the comb like clamp strips at an
angle with respect to each other and thereby form a concave and
convex side. When the locks are placed on a magnetic chuck with the
concave faces down and the chuck turned on, the magnetic field will
flatten the magna-lock clamps, thus causing the comb like teeth to
grip the workpiece firmly (Figure 4). |
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Figure 4. The magna-lock clamps can
assist in holding steel work pieces that have very little bearing
surface and workpieces that are non-magnetic.
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Precision Angle Plate
| Precision angle plates are used extensively for doing surface
grinding work (Figure 5). The vertical face of the angle plate forms
a second reference and locating surface that is perpendicular to the
surface of the magnetic chuck.
The work pieces are located and clamped to the face of the angle
plate in order to grind surfaces perpendicular to each other. Angle
plates are also used for holding non-magnetic parts for surface
grinding. |
Figure 5. Precision angle plate used in Surface Grinding.
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Magnetic Parallels
| Magnetic parallels have alternate laminations of brass
and soft iron (Figure 6). The soft iron allows the magnetic force of
the chuck to be drawn through the parallels, allowing the parallels
to act as magnets although they are not truly magnetic. Magnetic
parallels are used to hold workpieces that have bosses or other
projecting surfaces on the side of the workpiece to be chucked
(Figure 7). As precision tools, magnetic parallels should be handled
with care to avoid nicks and scratches that raise burrs.
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Figure 7. Magnetic Parallels hold work pieces with
projections on the side facing the chuck.
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Figure 6. Magnetic Parallels.
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Precision V-Blocks
| The precision V-block, which is made to a very high standard of
accuracy, is another very useful surface grinding work holding
accessory (Figure 8). Precision magnetic V-blocks are often made in
matched pairs. Figure 9 shows a typical application of V-blocks
being used on surface grinding work. |
Figure 8. Magnetic V-block
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| The standard application of a V-block is for holding
and locating a cylindrical part, although magnetic V-blocks can be
used for holding and grinding parts at 45-degree angles as seen in
Figure 10. |
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Figure 9. Magnetic V-blocks being used
to hold cylindrically shaped workpieces for grinding.
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Figure 10. Magnetic V-blocks can
hold round, square, or irregularly shaped parts.
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Complex shaped punches, used in dies, are often held in
magnetic v-blocks that are specially machined and ground to hold these
parts in correct alignment on the surface grinder.
Magnetic Adjustable
V-Blocks
| A precision magnetic adjustable V-block, as shown in Figure 11,
can be swiveled through a total angle of 90 degrees. There are
angular gradations in degrees, and a vernier scale graduated to 5
minutes located at the end of the V-block. The magnetic adjustable
V-block can be used to grind angles as well as to hold cylindrical
parts. An advantage of the magnetic adjustable V-block in grinding
angles is that two locating surfaces are available for positioning
the work; therefore: the workpiece can be accurately located along
two planes. |
Figure 11. A magnetic adjustable
V-block used for grinding an angular surface.
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| Sine Plate
Sine plates (Figure 12) are used to hold the workpiece for
grinding angles to precise tolerances. Two very accurate rolls are
attached to the bottom of the sine plate an exact distance apart.
They are generally placed with their centers 10 inches apart,
although on very small plates this distance might be only 5 inches.
Placing precision gage blocks below the roll raises one end of the
sine plate to an exact angle. The gage blocks can be stacked to any
height desired with great accuracy. The height at which the gage
blocks must be stacked can be determined by looking up the sine of
the angle desired in the Machinery’s Handbook. |
Figure 12. A precision angle
is ground using a magnetic sine plate.
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| Compound Angle Sine Plate
The compound sine plate shown in figure 13 is used
for grinding compound angles. In principle, it is the same as the
sine plate shown in Figure 12 except that two individual sine plates
are used in order to get the required compound angle. This compound
sine plate can also be used to set up for ordinary angles by using
only one of the two plates. The Workpiece is held on the
work-holding surface of the sine plate by a permanent magnet chuck. |
Figure 13. Compound Angle Sine Plate
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