JSI Series (Inch)
Inch JSI / JSXInch male-male adjusters. Standard carbon steel (JSI, zinc-plated) or premium chromoly steel (JSX) for high-load or vibration applications.
Male-Male Threaded Adjusters for Rod End Linkage
Jack Screws
A jack screw is a double-male threaded adjuster — thread a rod end onto each end and turn the body to set length, turnbuckle-style. SYZ jack screws come in carbon steel (JSI / JSI-M) and chromoly (JSX / JSX-M), inch 10-32 to 1-12 and metric M5 to M16, with RH/LH thread options for on-assembly adjustment.
JSI / JSI-M
Inch + Metric
Carbon / Chromoly
JSI / JSX Options
RH & LH
Adjustable Thread
30 + 6
Configurations
ISO 9001:2015 Certified
Factory Direct Sourcing
15–30 Day Lead Time
26 Years Manufacturing
OEM-Grade Tolerances
Overview
What Is a Jack Screw?
A jack screw is a double-male threaded adjuster used to fine-tune the length of a rod-end linkage.
With a female-threaded rod end threaded onto each male end (and locked with jam nuts), turning the jack screw body lengthens or shortens the assembly — a compact alternative to a full turnbuckle for precise preload and alignment.
Turnbuckle Effect: By combining one right-hand (RH) and one left-hand (LH) threaded end, rotating the central jack screw body moves both ends inward or outward simultaneously. This allows rapid length adjustment while the linkage remains mounted on the machine or vehicle.
Product Specs
Product Series Breakdown
Available in carbon steel and high-strength alloy chromoly options in both inch and metric standards.
JSI-M Series (Metric)
Metric JSI-M / JSX-MMetric male-male adjusters. Available in zinc-plated carbon steel (JSI-M) or high-strength chromoly (JSX-M) for European metric assemblies.
Selection and Sizing Guide
- • Inch assemblies: Select JSI (carbon steel) or JSX (chromoly, higher strength).
- • Metric assemblies: Select JSI-M (carbon steel) or JSX-M (chromoly).
- • Threads & Jam Nuts: Match thread size and hand to your rod ends. Always add jam nuts to lock the settings securely against vibration.
Link Construction
Jack Screw vs. Turnbuckle vs. Tube Adapter
Three methods to make an adjustable linkage rod.
Jack Screw
A compact male-male threaded connector. Female-threaded rod ends screw onto the jack screw ends.
Best for: tight spaces, compact assembliesTurnbuckle
A female-female hollow adjuster body. Male-threaded rod ends thread into the turnbuckle body ends.
Best for: broader adjustment rangesTube Adapter
Welded inside structural tubing to build custom links from scratch. Allows standard male rod ends to thread directly in.
Best for: high-load fabricated linksApplications
Where Jack Screws Perform
Precision length fine-tuning for high-load linkage systems.
Alignment & Preload
Fine adjustment of sway bar linkages, agricultural implement linkages, and control linkages where geometry is critical.
Motorsport Suspension
Chromoly JSX series is ideal for race car suspension adjustment links, steering tie-rods, and adjustable control arms.
Machinery Controls
Actuator rod-length tuning and machinery linkage setting in conveyor setups and packaging machinery.
FAQ
Common Questions
What is a jack screw used for?
To adjust the length of a rod-end linkage: thread a female-threaded rod end onto each male end of the jack screw, and turn the central body to lengthen or shorten the assembly, then lock with jam nuts.
Carbon steel or chromoly jack screw?
We offer JSI/JSI-M in standard carbon steel (zinc-plated) for general industrial adjusters, or JSX/JSX-M in high-strength chromoly steel for higher-load suspension or steering applications.
How is a jack screw different from a turnbuckle?
A jack screw is a compact male-male adjuster (rod ends screw onto it); a turnbuckle is a female-female hollow body (rod ends screw into it). Both use opposing right-hand and left-hand threads for adjustments on the vehicle.
Are jack screws available in inch and metric?
Yes. Inch JSI covers thread sizes from #3 up to #16 UNF, while metric JSI-M covers M5 up to M20.
Do I need jam nuts with a jack screw?
Yes. Jam nuts are required on both ends to lock the rod ends against the jack screw body. Without them, vibration will back the threads out, changing the linkage length and weakening the joint.
Factory Direct
Request a Jack Screw Quote
Send us your thread specs, material selection, and quantity requirements. We will provide pricing within 24 hours.