The Problem
A plant in western India ran a process positioner driven by an imported worm gear screw jack. After years of intermittent duty, axial backlash at the load nut had grown past the plant’s acceptance limit. The bronze nut was worn; the trapezoidal screw showed polished flanks. The housing and foundation were still sound.
The original overseas channel quoted a long lead time for a matching nut and screw kit — and preferred a full-unit order. The positioner could not wait on import logistics while a catalogue code worked its way through shipping and customs. A “nearest Indian catalogue jack” would have forced foundation rework: the imported unit had a non-standard mounting footprint and a specific screw-end connection to the load plate.
Maintenance needed a drop-in replacement — same bolt pattern, same travel, same input shaft position for the existing motor coupling — not a brand-name part number.
The Solution
The worn jack was shipped to Anand Gears in Bhayander East. We treated it as a reverse-engineering sample:
- Mounting footprint — hole centres and housing base outline in millimetres; upright orientation confirmed.
- Screw — trapezoidal (Tr) major diameter, pitch, free length, usable stroke, and load-end detail for the plate connection.
- Drive — worm ratio from worm starts and wheel tooth count; input shaft diameter, length, and keyway for the existing coupling.
- Accessories — bellows length for the exposed screw; provision for limit-switch cams if the plant reuses existing switches.
Load and duty put the unit in the 100 kN catalogue class (AG-SJ-100), which sits inside our published machine screw jack range of 5 kN to 350 kN. We built a complete drop-in jack — translating screw (TP), trapezoidal thread for self-locking hold under intermittent duty — rather than only a nut, because screw and nut wear together and should return as a matched pair.
The new unit reused the existing foundation bolts and motor coupling without field machining of the base. Spares policy going forward: the plant can order bronze nuts, safety nuts, bellows boots, and worm sets locally from the same manufacturer instead of reopening an import file for every wear item. See screw jack replacement & spares and catalogue machine screw jacks.
The Result
| Item | Original constraint | Delivered approach |
|---|---|---|
| Mounting | Fixed imported footprint | Matched hole pattern & base outline (mm) |
| Screw | Worn Tr lifting screw + bronze nut | New Tr screw + load nut (matched pair) |
| Travel | Existing stroke envelope | Usable stroke matched to sample |
| Drive interface | Existing motor coupling | Input shaft steps matched; same worm ratio class |
| Capacity class | Within mid-range industrial duty | AG-SJ-100 class (100 kN; range 5–350 kN) |
| Future spares | Import kit / long lead | Local nut, screw, worm set, bellows path |
Representative replacement job — the outcome that matters: a geometric drop-in fit, and every future spare available locally instead of on an import lead time.
Photos from the Job
Facing a similar replacement?
Send the sample or photos plus load (kN), stroke (mm), and mounting sketch. We quote a drop-in jack or spares only when the housing is still good.
Talk to an Engineeror call +91 98203 83719 • anandgears@gmail.com