Joyce Machine Screw Jacks - Manual (Page 6)

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stops on the screw, these will need to be removed before 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). The steel
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 to prevent 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 WJ250, WJ500, WJ1000 and WJ51 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 WJ250 thru WJ51 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. Insure 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 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.