M4 M5 Small Head Square Bolt — 304 Stainless Steel, Multiple Lengths

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M4 M5 Small Head Square Bolt — 304 Stainless Steel, Multiple Lengths

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Size: M4x12

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M4 M5 Small Head Square Bolts in 304 Stainless Steel — Secure Grip Where Space Is Tight

Machinists, fabricators, and hands-on DIYers regularly run into the same problem: a standard bolt head is too large for the clearance available, or a Phillips drive strips before the joint is fully torqued. These 304 stainless steel small-head square bolts solve both issues — the reduced head profile clears tight enclosures and extrusion channels, while the four-flat square geometry gives a positive wrench grip that won't cam out under load.

Each bolt is machined from 304 stainless steel with ISO metric coarse threads. The M4 series covers lengths from 12mm (≈1/2") to 30mm (≈1-3/16"), and the M5 series spans 8mm (≈5/16") to 40mm (≈1-9/16"). Available in pack quantities of 1, 5, 10, 20, 30, 50, or 100 pieces — order a single bolt to test fit, or stock up with a 100-piece bulk pack for ongoing production.

Common use cases include electronics enclosure assembly, aluminum extrusion frames, robotics and small-engine brackets, furniture hardware, and any application requiring a metric square head machine screw with corrosion resistance. The small-head geometry also suits flush-clearance installations in sheet-metal panels and T-slot profiles where a full-size head would interfere.

🔩 Thread Compatibility: ISO metric coarse — M4 (0.7mm pitch) and M5 (0.8mm pitch). Fits any standard metric M4 or M5 nut, threaded insert, or tapped hole per ISO 68-1. Not compatible with UNC or UNF inch-thread hardware.

✅ Key Features of These M4 M5 Small Head Square Bolts

🟦 Reduced Square Head Profile — The compact head footprint fits confined clearances in enclosures, T-slot extrusions, and sheet-metal assemblies where a full-size square head would foul surrounding components or require oversized counterbores.
🛡️ 304 Stainless Steel Body — Resists rust, oxidation, and mild chemical exposure without additional coating, making these bolts a dependable choice for indoor, outdoor, and light coastal installations.
🔧 Positive Wrench Engagement — Four flat sides provide a secure grip for open-end or box wrenches, eliminating the cam-out risk common with Phillips or Pozidriv drives in tight-access metric square head machine screw applications.
📐 Wide Length Selection — M4 from 12–30mm and M5 from 8–40mm in a single listing, covering the most common grip lengths for electronics, robotics, and light structural brackets without sourcing from multiple suppliers.
📦 Flexible Pack Quantities — Choose 1 to 100 pieces per order. Single-piece and 5-piece options suit prototyping and repair; 50-piece and 100-piece bulk packs lower the per-unit cost for production use.
⚙️ ISO Metric Coarse Thread — M4×0.7 and M5×0.8 threads are interchangeable with standard metric nuts, lock nuts, and washers, keeping your fastener inventory simple and sourcing straightforward.

📐 Technical Specifications — Small Head Square Bolt M4 M5

Material	304 Stainless Steel (A2 equivalent)
Head Style	Square Head — Small / Reduced Head Profile
Drive Method	Open-end wrench or box wrench on square head (no special bit required)
Thread Standard	ISO Metric Coarse — M4×0.7mm pitch, M5×0.8mm pitch
Available Sizes — M4	M4×12mm (≈1/2"), M4×16mm (≈5/8"), M4×20mm (≈25/32"), M4×25mm (≈1"), M4×30mm (≈1-3/16")
Available Sizes — M5	M5×8mm (≈5/16"), M5×10mm (≈25/64"), M5×12mm (≈1/2"), M5×16mm (≈5/8"), M5×20mm (≈25/32"), M5×25mm (≈1"), M5×30mm (≈1-3/16"), M5×35mm (≈1-3/8"), M5×40mm (≈1-9/16")
Pack Quantities	1, 5, 10, 20, 30, 50, 100 pcs (select above)
Surface Finish	Natural stainless — uncoated, brushed mill finish
Tensile Strength (typical)	Typically 500–700 MPa (72,000–101,000 psi) for 304 SS
Corrosion Resistance	Good — outdoor and light coastal use; not rated for direct saltwater immersion
Compatible Hardware	Standard ISO metric M4 / M5 hex nuts, lock nuts, flat washers, threaded inserts
Country of Origin	See variant options

⚠️ Sizing Tip: Measure total grip length (all clamped material thickness) and add 1–1.5× the bolt diameter for adequate thread engagement. If you are unsure, contact us to confirm before placing a bulk order.

❓ Frequently Asked Questions

How do I choose the right bolt length for my application?

A reliable starting point is to add the total grip length (thickness of all clamped materials) plus at least 1–1.5× the bolt diameter for thread engagement. For example, clamping two 6mm aluminum plates with an M4 bolt typically calls for 12–16mm (about 1/2" to 5/8"). When uncertain, go slightly longer — excess thread can be accommodated with a standard nut.

What tensile strength can I expect from these 304 stainless steel bolts?

304 stainless steel fasteners generally achieve a tensile strength of approximately 500–700 MPa (72,000–101,000 psi), which is typically sufficient for light-to-medium structural and mechanical assemblies. For safety-critical or high-vibration joints, consult an engineer and consider a higher-grade alloy such as A4-80 (316 SS).

Are these bolts suitable for outdoor or marine use?

304 stainless steel provides good corrosion resistance in most outdoor conditions — rain, humidity, and mild coastal exposure. For direct saltwater immersion, splash zones, or highly chlorinated environments, 316 stainless steel (A4 grade) is generally recommended instead.

What thread standard do these bolts follow, and will they fit standard metric nuts?

These bolts use ISO metric coarse threads — M4 at 0.7mm pitch and M5 at 0.8mm pitch. They are fully compatible with any standard metric M4 or M5 hex nut, nylon lock nut, flat washer, or tapped hole per ISO 68-1. They are not compatible with UNC or UNF inch-thread hardware.

What tool do I need to install a small-head square bolt?

Small-head square bolts are driven with an open-end wrench, box wrench, or adjustable wrench gripping the four flat sides of the head. No special socket or bit is required. The reduced head profile is specifically designed for confined spaces where a full-size square head would foul adjacent components.

Can I pair these bolts with standard metric washers and lock nuts?

Yes. The M4 and M5 threads are fully compatible with standard ISO metric flat washers, split lock washers, and nylon insert lock nuts of the corresponding size. Always verify thread pitch when mixing fastener brands to avoid cross-threading.

How many pieces should I order for a repair job versus a production run?

For a single repair or prototype, the 1-piece or 5-piece options let you verify fit before committing. For workshop stocking or production runs, the 50-piece or 100-piece packs offer a lower per-unit cost. Quantity pricing is applied automatically when you select your pack size above.

🛒 Select your size and quantity above, then add to cart — ships from our US warehouse.

M4 M5 Small Head Square Bolt — 304 Stainless Steel, Multiple Lengths

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Description

M4 M5 Small Head Square Bolts in 304 Stainless Steel — Secure Grip Where Space Is Tight

✅ Key Features of These M4 M5 Small Head Square Bolts

📐 Technical Specifications — Small Head Square Bolt M4 M5

❓ Frequently Asked Questions

M4 M5 Small Head Square Bolt — 304 Stainless Steel, Multiple Lengths

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