Joyce MWJ2410 - Manual (Page 6)

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the lifting screw is removed from the jack. If the jack does not have stops, the lifting
screw can be removed by simply unthreading it from the wormgear.
3. Remove the thrust bearings (item # 4) and the wormgear (item # 5) from the sleeve.
The bearing cones may be pressed onto the wormgear.
4. Keyed jacks have a keyway cut the length of the lifting screw (item # 35). A keyed
sleeve cap (item # 17) has a key (item # 30), which travels in the keyway and prevents
rotation of the lifting screw. It is very important not to allow any side load on a keyed
jack, as the key can cut into the lifting screw, and severely affect the life of the jack.
5. Remove screws, (item # 10) from the bearing caps (item # 3). Remove the bearing
caps and seals (item # 7) carefully to avoid damaging seals. Make sure keys have been
removed first. Note: the MWJ51 and MWJ201 jacks have retaining clips instead of
bearing caps.
6. Carefully remove the shims (item # 8) from the jack sleeve or bearing cap. NOTE: there
will not necessarily be an equal quantity of shims per side. Keep track of the number
and order of shims on each side of the jack. The MWJ51 and MWJ201 jacks do not
have shims.
7. Remove the worm shaft bearings (item # 6). The cups may be press-fit and require the
use of a dead-blow, plastic or other non-marring mallet to remove the worm (item # 12).
2-4 Inspection of Components
1. Before any inspection, it will be necessary to completely clean all parts of the jack.
Use caution with any machined or fragile part.
2. Inspect the cleaned sleeve (item # 1) and sleeve cap (item # 2) for any signs of stress
or facture, especially around the mounting bolt locations.
3. Inspect the worm (item # 12) and thrust bearings (item # 4) for any signs of brinelling,
abrasive wear or spalling. Test for smooth, quiet operation of bearings.
4. Inspect bearing caps (item # 3) for any signs of stress.
5. Inspect the keyway on the worm (item # 12) and roll the worm on a flat surface to look
for wobble in the shaft. Threads on the worm should not show an excessive buildup of
bronze gear material.
6. Replace all seals when a complete disassembly is done.
7. Inspect Aluminum-Bronze wormgear (item # 5) for signs of excessive wear.
8. Check boots (item # 34) for wear or cracks
9. Inspect lifting screw (item # 14) or straightness.
2-5 Assembly of Machine Screw Jacks
1. Assure that all bearings are packed with grease. Coat seals with light oil and put
masking tape on keyways and other sharp surfaces to avoid seal damage.
2. Assembly of jack is reverse of the disassembly procedure. Make sure all bearings and
seals seat properly. The bearing cap screws and sleeve cap should only be hand
tightened initially. Some jacks may require the wormgear and thrust bearing be
installed first, as they will not pass the worm, if already installed.
3. Tighten bearing cap bolts. Check the input shaft for excessive axial or lateral
movement. If the input shaft feels loose remove shims, if it feels tight, add shims. Give
the input shaft a solid blow on each end (in axial direction) with a soft mallet and re-
check the feel. If it feels OK, continue to next step, otherwise continue adjusting the
shims. This is a trial and error operation. The correct set-up has a solid feel without
play (axial or lateral) and the input shaft rotates with an even, smooth but snug feel.
4. When jack is re-assembled, the thrust bearing pre-load needs to be set. Check by
rotating the input shaft, while tightening the sleeve cap. Continue to check the rotation
of the input shaft as the sleeve cap is tightened. Use a dead-blow hammer on top of
sleeve cap to help it seat. Tighten sleeve cap until it will not tighten further by hand.