Hypertherm HyPrecision 100D Instruction Manual page 45

Check Valve Lapping Instructions
During use, the check valve body face (1) becomes worn from the
action of the LP poppet. It may be indented from repeated poppet
impact or have erosion tracks. This deformation will affect the
sealing properties of this part. Periodically inspect this surface and
if necessary use the lapping procedure to return it to a flat and
near mirror finish. Proper lapping will help maintain the sealing
properties and increase the life of the part.
Repeated lapping may shorten the check valve dimensions and render it
unusable. If the sealing face is less than 0.385 in. from the body diameter area
(dimension X), it should be replaced.
This procedure is for a moderately worn check valve body face. Severe wear requires turning on a lathe
or grinding on a precision surface grinder prior to lapping.
If the sealing face (1) has slight indentations only, use 1500 grit paper. Lapping is complete when the
check valve body face is flat and has a near mirror finish.
Deeper indentations will need to be lapped with 600 grit SiC abrasive paper first. Lapping is complete
with this abrasive paper when the face has an even appearance and any indentations are removed.
The following items are required for the lapping procedure:
•
Granite inspection plate at least 9 in. x 12 in.
•
8.5 in. x 11 in. sheets of 600 and 1500 grit SiC abrasive paper
•
Lapping film
Lapping Procedure:
1. Place either the abrasive paper or lapping film on
the granite plate and secure the film in place with
masking tape around the edges.
2. Hold the check valve flat against the abrasive
surface to prevent any rocking of the part. Move
the check valve body (2) back and forth on the film
or paper. Rotate the valve 45 degrees after each
movement until the face of the body (1) is evenly
finished. Repeat this procedure for the poppet
face if needed.
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