5/16-18 Hex Bolts Cap Screws Partially Threaded 18-8 304 Stainless All Lengths for Sale

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5/16-18 Hex Bolts Cap Screws Partially Threaded 18-8 304 Stainless All Lengths For Sale

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5/16-18 Hex Bolts Cap Screws Partially Threaded 18-8 304 Stainless All Lengths:
$12.75

5/16\"-18 Stainless Steel Hex Head Bolts 18-8 (304)

Partial Thread • 1-1/2\" to 7\" Lengths • UNC • Bulk

At a Glance 5/16\"-18 hex head bolts in 18-8 (304) stainless steel, partially threaded: 16 lengths from 1-1/2\" to 7\", packs of 5 to 2,500.

Plain shank under the head for shear and pivot joints
Thread: 5/16\"-18 coarse (UNC)
Wrench size 1/2\"
Plain finish
Choose length and pack size above

Description

Fastenio 5/16\"-18 hex head bolts in 18-8 (304) stainless steel, partial thread (PT). The hex head accepts a 1/2\" wrench or socket and the partial-thread shank provides a smooth bearing surface where the bolt passes through the work piece — ideal for shear-loaded connections and pivot/clevis applications.

This listing covers 5/16\"-18 UNC Coarse only, in sixteen lengths from 1-1/2\" through 7\", in pack quantities from 5 (sample) up to 2,500 (production bulk). Manufactured to ASME B18.2.1 hex bolt dimensions.

Partial Thread vs Full Thread

Partial Thread (this listing) — threaded portion at the tip with a smooth shank above it. Smooth shank carries shear load cleanly and reduces wear in pivot/clevis applications.
Full Thread — threaded the entire length. Use when grip thickness varies, when you need maximum thread engagement, or when the bolt also serves as a stud. See the Fastenio 5/16-18 fully-threaded sibling listing (cross-linked below).
Length convention — bolt length is measured from under the head to the tip (not including the head).

Material

Grade: 18-8 Stainless Steel (Type 304 / A2-70 equivalent) — 18% chromium, 8% nickel austenitic alloy. Excellent corrosion resistance in atmospheric, freshwater, and most chemical environments. For salt-water or splash-zone exposure, specify 316 stainless.

Finish: Plain (no plating). 18-8\'s self-renewing passive oxide layer provides natural corrosion protection.

Specification: ASME B18.2.1 Hex Bolt, partial thread per spec.

How to Order

Select your variation by Length and Unit Quantity:

Length — measured under-head to tip. Choose based on your grip thickness plus enough thread engagement for the nut (typically at least 1.5x the bolt diameter, so ~1/2\" minimum thread engagement for 5/16\").
Thread per spec — partial thread length scales with bolt length per ASME B18.2.1. Shorter bolts may be effectively fully threaded; longer bolts have proportionally more smooth shank.
Unit Quantity — 5 and 10 are sample/repair packs. 25–100 cover small projects. 250–2,500 are production-volume bulk.

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Need it faster? UPS 2nd Day Air and Next Day Air are available by request — message us with your ZIP code before purchase for a quote.

Need a larger quantity? Volume pricing is available beyond the listed pack sizes — message us with your target qty and we\'ll quote.

Available Lengths & Thread Coverage

All bolts in this listing are Partially Threaded. The unthreaded body length under the head provides shear strength and clean alignment through clamped parts.

Total LengthThread LengthBody (Grip) Length 1-1/2\"7/8\"5/8\" 1-3/4\"7/8\"7/8\" 2\"7/8\"1-1/8\" 2-1/4\"7/8\"1-3/8\" 2-1/2\"7/8\"1-5/8\" 2-3/4\"7/8\"1-7/8\" 3\"7/8\"2-1/8\" 3-1/4\"7/8\"2-3/8\" 3-1/2\"7/8\"2-5/8\" 3-3/4\"7/8\"2-7/8\" 4\"7/8\"3-1/8\" 4-1/4\"7/8\"3-3/8\" 4-1/2\"7/8\"3-5/8\" 5\"7/8\"4-1/8\" 6\"7/8\"5-1/8\" 7\"1-1/8\"5-7/8\"

Applications

HVAC — equipment mounts, frames, condensation-exposed connections.
Industrial — machinery assembly, motor mounts, conveyor frames, structural connections.
Automotive — chassis, body work, brackets, suspension hardware.
Construction — structural connections, brackets, anchoring, signage.
Signs & Outdoor — lighting, signage, fencing, weather-exposed assemblies.

Notes

Torque: follow standard torque specs for 18-8 stainless 5/16\"-18 (typically ~13 ft-lb dry, lower if lubricated). Do not over-torque — 18-8 is softer than alloy steel and can gall.
Galling prevention: use stainless-safe anti-seize on the threads for repeated assembly or large clamp lengths.
Galvanic compatibility: use 18-8 bolts with 18-8 nuts and washers. Pairing stainless bolts with carbon-steel nuts in wet environments accelerates corrosion of the carbon-steel part.
Pair with the right hardware: 5/16\"-18 finished hex nut + 5/16\" flat washer (+ optional split lock washer or Nylock nut for vibration).

Related Fastenio Products

5/16-18 SS Hex Bolts (Fully Threaded)

Same bolt, threaded the entire length.

View →

SS Finished Hex Nuts (Multi-Size)

5/16-18 hex nuts in this multi-size listing.

View →

SS Flat Washers 18-8

5/16\" flat washer for load distribution.

View → Visit the Fastenio Store for More Fasteners → FASTENIO – Industrial-grade fasteners engineered for strength, precision, and lasting performance.