related-product-inchJSI-6-21 JSX-6-21 Jack Screw JSI
JACK SCREW JSI Product Overview
JSI-6-21 / JSX-6-21 is a male-male inch jack screw adjuster with 3/8-24 threads at both ends. Thread length = 0.868″, hex size = 0.563″ across flats, total length = 2.125″, hex height = 0.219″.
The JSI (carbon steel, zinc plated) and JSX (4130 chromoly steel) jack screws thread into rod end bodies at both ends with a central hex for length adjustment. One end has right-hand thread; the other is left-hand — turning the hex extends or shortens the assembly without removing either end. Used in toe links, push rods, throttle rods, and any linkage requiring fine-increment length adjustment without disassembly.
Carbon steel version: JSI-6-21. 4130 chromoly version: JSX-6-21. Special lengths and thread combinations available in volume. Metric equivalent is the JSIM series.
JACK SCREW JSI Series — Full Size Range
All available sizes in the JACK SCREW JSI series. Can’t find your size? Contact us for custom dimensions.
| Carbon Steel | Chromoly Steel | Thread Right/Left | Thread Length | Hex Size | Total Length | Hex Height |
|---|---|---|---|---|---|---|
| JSI-3-14 | JSX-3-14 | 10-32 | 0.563 | 0.313 | 1.402 | 0.156 |
| JSI-3-19 | JSX-3-19 | 10-32 | 0.750 | 0.375 | 1.940 | 0.190 |
| JSI-4-18 | JSX-4-18 | 1/4-28 | 0.750 | 0.438 | 1.776 | 0.156 |
| JSI-4-26 | JSX-4-26 | 1/4-28 | 1.000 | 0.438 | 2.550 | 0.250 |
| JSI-5-23 | JSX-5-23 | 5/16-18 | 1.000 | 0.500 | 2.309 | 0.189 |
| JSI-5-27 | JSX-5-27 | 5/16-18 | 1.000 | 0.500 | 2.673 | 0.313 |
| JSI-6-21 | JSX-6-21 | 3/8-24 | 0.868 | 0.563 | 2.125 | 0.219 |
| JSI-6-26 | JSX-6-26 | 3/8-24 | 1.125 | 0.563 | 2.589 | 0.219 |
| JSI-6-27 | JSX-6-27 | 3/8-24 | 1.100 | 0.563 | 2.680 | 0.219 |
| JSI-6-33 | JSX-6-33 | 3/8-24 | 1.250 | 0.563 | 3.250 | 0.375 |
| JSI-7-29 | JSX-7-29 | 7/16-20 | 1.250 | 0.563 | 2.870 | 0.250 |
| JSI-7-37 | JSX-7-37 | 7/16-20 | 1.375 | 0.688 | 3.688 | 0.438 |
| JSI-8-29 | JSX-8-29 | 1/2-20 | 1.252 | 0.750 | 2.938 | 0.313 |
| JSI-8-34 | JSX-8-34 | 1/2-20 | 1.500 | 0.750 | 3.433 | 0.313 |
| JSI-8-40 | JSX-8-40 | 1/2-20 | 1.500 | 0.750 | 4.000 | 0.500 |
| JSI-10-37 | JSX-10-37 | 5/8-18 | 1.625 | 0.750 | 3.745 | 0.375 |
| JSI-10-41 | JSX-10-41 | 5/8-18 | 1.750 | 0.750 | 4.075 | 0.375 |
| JSI-10-50 | JSX-10-50 | 5/8-18 | 1.875 | 0.938 | 4.985 | 0.625 |
| JSI-12-40 | JSX-12-40 | 3/4-16 | 1.750 | 0.875 | 4.042 | 0.422 |
| JSI-12-46 | JSX-12-46 | 3/4-16 | 2.000 | 0.875 | 4.638 | 0.422 |
| JSI-12-55 | JSX-12-55 | 3/4-16 | 2.250 | 1.125 | 5.500 | 0.500 |
| JSI-12-60 | JSX-12-60 | 3/4-16 | 2.250 | 1.125 | 6.000 | 0.750 |
| JSI-12-65 | JSX-12-65 | 3/4-16 | 2.250 | 1.125 | 6.500 | 1.250 |
| JSI-12-75 | JSX-12-75 | 3/4-16 | 2.250 | 1.125 | 7.500 | 2.250 |
| JSI-12-86 | JSX-12-86 | 3/4-16 | 4.000 | 0.875 | 8.638 | 0.422 |
| JSI-14-66 | JSX-14-66 | 7/8-14 | 2.375 | 1.313 | 6.625 | 0.875 |
| JSI-16-80 | JSX-16-80 | 1 1/4-12 | 2.875 | 1.875 | 8.000 | 1.000 |
| JSI-16-1-80 | JSX-16-1-80 | 1-14 | 2.875 | 1.500 | 8.000 | 1.000 |
| JSI-16-2-58 | JSX-16-2-58 | 1-12 | 2.500 | 1.500 | 5.750 | 0.750 |
| JSI-16-2-80 | JSX-16-2-80 | 1-12 | 2.875 | 1.500 | 8.000 | 1.000 |
Every Unit Inspected Before Shipment
Raw Material Inspection
Material certifications verified. Composition confirmed by spectrometer before machining begins.
Thread Gauge Inspection
100% go/no-go gauge check on all threaded sections. Zero tolerance on dimensional non-conformance.
Load Capacity Test
Static and dynamic load tests run on representative samples from each production batch.
Dimensional Measurement
CMM verification of critical dimensions — ball diameter, bore, thread pitch, and body length.
Surface Inspection
Visual and tactile inspection for burrs, scratches, surface cracks, and plating defects.
Articulation Test
Misalignment angle and torque measured to confirm liner performance meets specification.
Heat Treatment Verify
Hardness tests confirm proper heat treatment on chromoly steel bodies and bearing balls.
Batch Documentation
Full traceability from raw material heat number to finished part. COC and inspection reports available.
Where JACK SCREW JSI Are Used
More from the JACK SCREW JSI Series
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JACK SCREW JSI Frequently Asked Questions
What is a JSI jack screw used for?
A JSI jack screw is a male-male adjuster used to fine-tune length or preload in linkage and threaded control assemblies.
What materials are available in this series?
Standard materials include carbon steel with zinc plating and chromoly steel for heavier-duty fabrication requirements.
How do I choose the right thread size?
Start with the required thread size, then confirm thread length, total length, hex size, and hex height for the assembly.
Are left-hand versions available?
Yes. The series supports right-hand and left-hand thread patterns depending on application requirements.
What dimensions matter most for fitment?
Thread size, thread length, total length, and the wrench hex dimensions are the primary fitment points for jack screw selection.
Can SYZ make special sizes?
Yes. Special sizes are available in production volume for OEM or repeat fabrication programs.