Support Screw Jack

Support Screw Jack is an independent steel structural element widely used in building temporary scaffolding and concrete formwork shoring systems. It consists of threaded spindle, adjusting nut and load‑bearing end fitting. The end fitting can be flat base plate or U‑shaped cradle head, satisfying bottom foundation bearing and top beam propping separately. Each structural part performs discrete mechanical functions, and the whole assembly can complete height calibration and load‑bearing tasks independently without additional scaffolding accessories. Carbon structural steel serves as primary raw material. The threaded spindle is available in solid round steel bar and hollow seamless steel pipe. Solid spindle has compact metal texture, high compression and bending resistance, suitable for heavy‑load working conditions such as thick concrete slab shoring and large‑span temporary frame support. Hollow spindle cuts down overall self‑weight while meeting medium‑load bearing requirements, reducing physical burden for manual handling and on‑site installation. Thread sections are mostly processed by cold rolling technology, improving surface hardness of thread teeth and lowering wear caused by frequent nut rotation during cyclic turnover. Adjusting nuts are manufactured by forging or casting processes, and their structural completeness determines locking stability under sustained vertical compression load. The flat base plate enlarges contact area with supporting surface, disperses concentrated vertical pressure and reduces subsidence risk on soft ground. The U‑shaped cradle head forms a restraining groove to hold timber beams, H20 beams and steel beams, limiting lateral offset of horizontal load‑bearing members under concrete pouring loads. Welding joints between end fitting and spindle are key stress‑bearing positions, and welding continuity shall be guaranteed in production.

Various surface anti‑corrosion treatments adapt to different construction environments. Hot‑dip galvanizing forms dense zinc‑iron alloy protective layers covering spindle, thread teeth and all welding seams. This coating provides reliable resistance against rainwater, humid air and salt fog erosion, fit for long‑term outdoor exposure and marine transportation. Electro‑galvanizing produces relatively thin zinc layer on steel surface, applicable for short‑cycle construction projects with low corrosion risk. Paint finishing tends to peel off under thread friction and mechanical impact, so it is rarely adopted for construction hardware with high turnover frequency. According to installation positions, support screw jack can be divided into base type and U‑head type. Base type is arranged beneath vertical support uprights to bear overall vertical loads of shoring frames and compensate foundation elevation deviations. U‑head type is assembled at the top of upright members to constrain horizontal load‑bearing beams and withstand downward pressure transferred from formwork and fresh concrete.

Core dimensional parameters determine its practical mechanical performance. Spindle outer diameter is a critical indicator of load‑bearing grade, and larger diameter corresponds to higher ultimate compression capacity. Effective adjustment stroke defines valid height‑changing range. Excessively exposed threaded segments beyond effective stroke scope will reduce structural rigidity and raise bending deformation risk under load. The dimension of base plate or U‑shaped cradle shall match actual site bearing conditions. Undersized load‑bearing end will cause excessive local pressure, triggering settlement, beam slipping or component damage. This component is compatible with multiple mainstream shoring systems, including tube‑and‑coupler scaffolding, ringlock and cuplock shoring frames. Dimensional tolerances shall comply with corresponding international technical specifications to ensure reliable physical fitting during field assembly.

Prior to construction deployment, visual inspection and sampling mechanical tests shall be carried out as independent inspection workflows. Visual examination covers spindle bending deformation, surface cracks, welding discontinuity, thread tooth damage and anti‑corrosion layer peeling. Recycled support screw jacks require stricter inspection criteria. Even with intact outer appearance, invisible metal fatigue may accumulate after repeated load cycles and cannot be judged merely by surface observation. Sampling compression tests verify ultimate bearing capacity and anti‑deformation performance. Components with permanent bending, thread slipping and structural cracks must be screened out and scrapped, and shall not be mixed into construction usage. Secondary modification operations including cutting, welding and hole‑drilling on finished support screw jack are prohibited. Arbitrary alteration will change original steel section characteristics and weaken overall load‑bearing performance of the component.

Support Screw Jack is designed for cyclic reuse. After shoring frame dismantling, concrete mortar, dust and foreign residues attached to spindle and thread grooves need thorough cleaning. Impurities trapped inside thread gaps will cause nut jamming and interfere with normal height adjustment and locking effect in subsequent service cycles. Finished components shall be stored in dry and ventilated surroundings, sorted and stacked by specification, avoiding long‑term rain soaking and direct contact with damp soil. Improper on‑site operations include over‑extending threaded spindle, offset load placement on load‑bearing end, and applying load exceeding rated limit. These improper practices may result in component deformation and abnormal local stress distribution of shoring frames. As an independent adjustable load‑bearing unit for temporary construction support, its structural integrity and mechanical stability directly influence load transmission state of shoring structures, and constitute essential preconditions for safe concrete pouring and formwork dimension control.