MIL-B-857
Close Tolerance Bolts
Mumbai · India
Why the Shank Fit Genuinely Matters
A general-purpose bolt in a clearance-fit hole relies almost entirely on friction between the clamped plates to resist a joint sliding sideways under shear load — the bolt’s own shank barely touches the sides of the hole at all. That’s perfectly fine for most structural connections, but it leaves the joint vulnerable to slip if the clamping force ever relaxes, and it means the bolt itself does very little to directly resist shear.
A close tolerance bolt changes that relationship entirely. The shank is ground to a precise diameter matched to a reamed hole with only a few thousandths of an inch of clearance — sometimes an interference fit — so the bolt shank itself bears directly against the hole wall and carries shear load structurally, independent of how much clamping friction exists. That’s exactly why these bolts matter in precision aerospace and structural joints where slip simply isn’t acceptable, and why the reamed-hole tolerance has to be controlled just as tightly as the bolt’s own ground shank diameter.
Akbar Fasteners Pvt. Ltd. exports to over 50 countries, and our close tolerance bolt range is manufactured with precision-ground shank diameter control, verified by dimensional and shear testing under our ISO 9001:2015 quality system.
Where This Specification Genuinely Applies
Direct Shear Load Transfer
Ground shank bears directly against the reamed hole wall, carrying shear structurally rather than through friction alone.
Eliminates Joint Slip
Near-zero shank clearance prevents lateral movement even if clamping tension relaxes over time.
Precise, Repeatable Alignment
Controlled shank diameter locates mating parts consistently every time the joint is assembled.
Verified Shank Tolerance & Shear Strength
Batch dimensional and shear testing confirms genuine ground-shank precision, not just correct thread fit.
MIL-B-857 Options Explained
Alloy Steel Close Tolerance Bolt
Heat-treated alloy steel for high-strength precision structural connections requiring maximum shear capacity.
CRES Close Tolerance Bolt
Stainless or corrosion-resistant alloy option for precision joints exposed to a corrosive environment.
Hex Head / Protruding Head
Standard head style options matched to the wrenching access available at the joint.
Close Tolerance Bolts vs FF-B-588 General Hex Bolts
Confirming whether the joint genuinely needs precision shear-load transfer determines whether a close tolerance bolt is worth the added cost and reaming requirement. This table is the quick reference we use with buyers before quoting.
| Aspect | MIL-B-857 Close Tolerance | FF-B-588 General Hex Bolt |
|---|---|---|
| Shank Fit | Ground, near-zero clearance | Standard clearance fit |
| Hole Preparation | Reamed to precise tolerance | Standard drilled hole |
| Shear Load Path | Direct through the shank | Primarily through clamping friction |
| Best Suited For | Precision, shear-critical joints | General structural/mechanical assembly |
MIL-B-857 Specification Details
Materials We Manufacture In
- Alloy Steel Heat Treated
- Corrosion-Resistant Steel 300 Series CRES
- Finish Cadmium / Zinc-Nickel / Passivated
- Coating Per Environment Requirement
How Close Tolerance Bolts Are Made
- Process Forged & Ground
- Shank Tolerance Precision Controlled
- Testing Dimensional / Shear
- Quality Batch Sampled
Available Dimensions
- Nominal Size 1/4″ – 1.5″ (Inch Series)
- Metric Equivalent Available to Drawing
- Shank Length Custom to Grip Range
- Custom Sizes On Request
Application Areas
Wherever a shear-critical joint genuinely cannot tolerate slip or misalignment.
Aircraft Structural Joints
frame precision connections
Precision Machine Tool Assembly
in machine tool structure
Defense & Military Structure
precision shear connections
Bridge & Structural Steel Connections
structural joints
Fixture & Jig Location
location in fixturing
Marine Structural Assembly
joints in marine structure
Robotics & Automation Frames
automated equipment structure
General Precision Structural Fastening
needing near-zero slip
Standard Export Documentation
Prepared as standard practice for every MIL-B-857 close tolerance bolt shipment.
Mill Test Certificate (MTC)
Heat number, chemical composition, and mechanical property verification for every lot.
Shank Diameter Inspection Report
Batch-level dimensional testing confirming genuine precision shank tolerance for the ordered size.
Certificate of Conformance
Confirms the shipment matches the purchase order material/tolerance specification in full.
Certificate of Origin (COO)
Confirms India as country of manufacture for destination customs purposes.
NABL Accredited Test Reports
Independent mechanical and dimensional testing available on request for critical applications.
Commercial Invoice & Packing List
Itemized value, Incoterm, and detailed carton/weight breakdown for customs clearance.
Internationally Recognised Standards Coverage
Related Fastener Grades & Materials
FF-B-588 Hex Bolts
Our general-purpose hex bolt specification for standard clearance-fit assembly.
View FF-B-588 →MIL-DTL-1222 Studs & Bolts
Our alloy steel and corrosion-resistant stud/bolt family specification for related material grades.
View MIL-DTL-1222 →FF-P-386 Straight Pins
Our precision locating pin specification, sharing the same precision-fit philosophy.
View FF-P-386 →Fasteners Manufacturer & Exporter to the USA
Our broader capability manufacturing to ASTM/ASME and US federal/military standards.
View USA Export Guide →Need a Joint That
Genuinely Can’t Slip?
Tell us your reamed hole tolerance, material requirement, and shear load — we’ll confirm specification match and quote across our full close tolerance bolt range. Akbar Fasteners Pvt. Ltd. responds within 24 hours.
Sales: +91 724 0000 733 · Support: +91 800 9315 333 · sales@akbarfasteners.in