Matco Tools M148 Operator's Manual page 18

§5.3 Wire Feeding Maintenance
The welding wire must travel smoothly and freely from the spool all the way to the weld pool for
controlled welding. Poor welding performance is many times a result of mechanical feeding
problems with the wire through the torch. Check for smooth feeding without welding by holding
gun 1' from wood surface and feeding wire at 60-degree angle. It should feed smoothly as it
bows up from the surface. If not, maintenance needs to be performed.
1. Drive Roll: Check the wear of the feed roll "V" groove and clean the groove with wire
brush and/or compressed air.
2. Idle Roll: Check for signs of wear and good bearing support. Change is necessary.
3. Wire Guide: Pressure of the feed rolls removes copper plating from the welding wire's
surface which then finds its way to the wire guide. If the wire guide is not cleaned, it
gradually clogs up and causes wire feed malfunctions. Clean the wire guide in the
following manner：
a. Cut the wire and remove the welding gun from the feeder.
b. With a pneumatic pistol, blow compressed air through the wire guide.
c. Blow the wire feed mechanism and reel housing clean with compressed air.
d. Reattach the torch, install wire, feed wire, install and tighten the contact tip with
wrench and install nozzle.
4. Wire Liner Replacement: If the wire liner in the MIG gun cable is too worn or totally
clogged, change it to a new one according to the following instructions:
a. Remove MIG gun mounting nut which exposes the brass liner nut.
b. Remove liner nut and withdraw the wire conduit liner from the gun cable.
c. Push a new liner in to the gun making sure that it enters all the way to the contact
tip's base. Trim to length to lightly contact base of tip.
d. File the sharp edges of the cut-off end round for smooth feeding
e. Tighten the wire liner nut in place and reattach the gun to machine.
f. Feed wire through gun and reinstall contact tip, tighten with wrench.
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