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BACS21X4W — STUD ASSEMBLY,TURNLOCK FASTENER

✓ Government record, cited
— · BOLT SCREW
PRODUCT OVERVIEW

BACS21X4W: STUD ASSEMBLY,TURNLOCK FASTENER.

STUD ASSEMBLY,TURNLOCK FASTENER. Key specifications include material: STEEL PIN, head_length: 0.850 INCHES MINIMUM AND 0.890 INCHES MAXIMUM IN, eyelet_length: 0.257 INCHES NOMINAL IN, surface_treatment: CADMIUM AND CHROMATE OVERALL, stud_assembly_style: STUD ASSEMBLY, eyelet_outside_diameter: 0.341 INCHES MINIMUM AND 0.348 INCHES MAXIMUM IN. This part is cataloged in the U.S.

Government catalog under NSN 5325-00-489-0931, indicating validated use in U.S. government and defense logistics supply chains. Available through authorized enterprise resellers and TPM (Third Party Maintenance) channels.

Verify compatibility with your specific system configuration before ordering.

WHERE IT FITS
BACS21X4W
NSN: 5325-00-489-0931
FSC: 5325 — Fastening Devices
CAGE: 81205 — THE BOEING COMPANY DIV DEFENSE (USA)
SPECIFICATIONS
materialSTEEL PIN
head_length0.850 INCHES MINIMUM AND 0.890 INCHES MAXIMUM IN
eyelet_length0.257 INCHES NOMINAL IN
surface_treatmentCADMIUM AND CHROMATE OVERALL
stud_assembly_styleSTUD ASSEMBLY
eyelet_outside_diameter0.341 INCHES MINIMUM AND 0.348 INCHES MAXIMUM IN
turnlock_stud_head_styleFLAT COUNTERSUNK WING
material_accommodated_thickness0.141 INCHES MINIMUM AND 0.170 INCHES MAXIMUM IN
material_document_and_classificationQQ-W-470 FED SPEC SINGLE MATERIAL RESPONSE PIN
surface_treatment_document_and_classificationQQ-P-416,TY 2,CL 2 FED SPEC ALL TREATMENT RESPONSES OVERALL
distance_from_engaging_member_to_largest_bearing_surface_of_head0.513 INCHES MINIMUM AND 0.528 INCHES MAXIMUM IN
NSN5325-00-489-0931
COMPONENT DIAGRAM
BOLT / SCREW — THREAD VERIFICATION REQUIRED Hex HEAD LENGTH: — THREAD: — × — MATERIAL: — PN: BACS21X4W · OEM ⚠ VERIFY BEFORE ORDERING Verify thread pitch before ordering — metric (M8×1.25) ≠ imperial (5/16-18). Wrong thread = wrong part. Grade/class stamped on bolt head determines tensile strength ✓ BROKER TIP Grade/class stamped on head determines tensile strength. Grade 8 > Grade 5 > Grade 2. Always confirm head marking matches specification requirement PARTSTABLE TECHNICAL DRAWING — NOT TO SCALE
KEY FEATURES
•
SURFACE TREATMENT DOCUMENT AND CLASSIFICATION: QQ-P-416,TY 2,CL 2 FED SPEC ALL TREATMENT RESPONSES OVERALL
•
HEAD LENGTH: 0.850 INCHES MINIMUM AND 0.890 INCHES MAXIMUM IN
•
EYELET OUTSIDE DIAMETER: 0.341 INCHES MINIMUM AND 0.348 INCHES MAXIMUM IN
•
MATERIAL ACCOMMODATED THICKNESS: 0.141 INCHES MINIMUM AND 0.170 INCHES MAXIMUM IN
•
MATERIAL DOCUMENT AND CLASSIFICATION: QQ-W-470 FED SPEC SINGLE MATERIAL RESPONSE PIN
•
DISTANCE FROM ENGAGING MEMBER TO LARGEST BEARING SURFACE OF HEAD: 0.513 INCHES MINIMUM AND 0.528 INCHES MAXIMUM IN
•
TURNLOCK STUD HEAD STYLE: FLAT COUNTERSUNK WING
TECHNICAL CHARACTERISTICS
SURFACE TREATMENT DOCUMENT AND CLASSIFICATIONQQ-P-416,TY 2,CL 2 FED SPEC ALL TREATMENT RESPONSES OVERALL
HEAD LENGTH0.850 INCHES MINIMUM AND 0.890 INCHES MAXIMUM IN
EYELET OUTSIDE DIAMETER0.341 INCHES MINIMUM AND 0.348 INCHES MAXIMUM IN
MATERIAL ACCOMMODATED THICKNESS0.141 INCHES MINIMUM AND 0.170 INCHES MAXIMUM IN
MATERIAL DOCUMENT AND CLASSIFICATIONQQ-W-470 FED SPEC SINGLE MATERIAL RESPONSE PIN
MATERIAL DOCUMENT AND CLASSIFICATIONQQ-W-470 FED SPEC SINGLE MATERIAL RESPONSE EJECTOR SPRING
DISTANCE FROM ENGAGING MEMBER TO LARGEST BEARING SURFACE OF HEAD0.513 INCHES MINIMUM AND 0.528 INCHES MAXIMUM IN
TURNLOCK STUD HEAD STYLEFLAT COUNTERSUNK WING
SURFACE TREATMENTCADMIUM AND CHROMATE OVERALL
MATERIALSTEEL COMP 4037 STUD
SUBSTITUTES & CROSS-REFERENCES 4
BACS21ED4WSame NSN cross-reference
Same NSN cross-reference
Also cataloged under this NSN
4002-4WSame NSN cross-reference
Same NSN cross-reference
Also cataloged under this NSN
8804136Same NSN cross-reference
Same NSN cross-reference
Also cataloged under this NSN
944.48.77.919Same NSN cross-reference
Same NSN cross-reference
Also cataloged under this NSN
LIFECYCLE
NSN statusCancelled· U.S. Government catalog
Acquisition advice: Insurance item — stocked against contingency demandNo demilitarization required
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FREQUENTLY ASKED QUESTIONS
What is BACS21X4W?
BACS21X4W is a STUD ASSEMBLY,TURNLOCK FASTENER.
What parts can replace BACS21X4W?
There are 4 known substitutes for BACS21X4W: BACS21ED4W, 4002-4W, 8804136 and 1 more. Substitute compatibility should be verified for your specific system.
What is the NSN for BACS21X4W?
BACS21X4W is cataloged in the U.S. Government catalog under NSN 5325-00-489-0931. This indicates validated use in U.S. government and defense supply chains.
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✓ PartsTable — the parts reference. Every fact cited to its source.
PartsTable Design LLC · partstable.com
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-18.
PartsTable commercial catalog: edition Unified commercial catalog snapshot through 2026-09-28, edition date not on file, retrieved 2026-09-28.