3mm Socket Head Cap Screw Dimensions & #4-40 Socket Head | Buy
3mm Socket Head Cap Screw Dimensions & #4-40 Socket Head Cap Screw Dimensions โ Precision Fasteners for Demanding Applications
Stop guessing on thread fit & strength. Get exact 3mm socket head cap screw dimensions and #4-40 socket head cap screw dimensions with factory-direct pricing, ISO-certified quality, and 10-day delivery to USA & Europe.
๐ฆ Get Free Quote in 24h โ No Minimum Order๐ง Why Engineers & Procurement Managers Get Frustrated with Socket Head Cap Screws
- โ ๏ธ Inconsistent dimensions โ Thread pitch, head height, or hex size varies by supplier, causing assembly failures and rework costs.
- โ ๏ธ Hidden total cost โ Low unit price from unknown factories often leads to 15โ20% scrap rate, customs delays, and emergency air freight.
- โ ๏ธ Long lead times โ 45โ60 day delivery from many Chinese suppliers kills project timelines and inventory turns.
- โ ๏ธ Poor surface finish & material โ 304 stainless steel that rusts, or A2-70 that fails torque testing, jeopardizes your product liability.
- โ ๏ธ No OEM/ODM support โ Custom lengths, drive types, or coatings require minimums of 50,000+ pieces that kill small-batch innovation.
- โ ๏ธ Shipping cost surprises โ Freight for small fastener orders can be 3x the product cost when not consolidated properly.
*Based on 200+ buyer feedback surveys from 2024โ2025.
Our automated production line โ consistent quality, batch to batch.
โ Boen Fastener โ Your Precision Socket Head Cap Screw Partner
We deliver 3mm socket head cap screw dimensions and #4-40 socket head cap screw dimensions that meet ASME B18.3, DIN 912, and ISO 4762 standards โ with full traceability, competitive pricing, and fast lead times.
Powerful Factory, Direct to You
Est. 2010, 50,000+ sqm facility, 200+ workers. 30+ countries served. Factory pricing โ 30% lower than trading companies.
Exact Dimensions Every Time
CMM inspection, thread gages, and hardness testers on-site. ยฑ0.02mm tolerance on head height & hex size.
High-Speed Delivery
10โ15 days for standard sizes. 24h sample dispatch. Air & sea consolidation to USA/Europe weekly.
OEM/ODM Customization
Custom lengths, drive types (hex, Torx, Phillips), coatings (zinc, black oxide, Dacromet). MOQ as low as 5,000 pcs.
Full Compliance & Certifications
ISO 9001, CE, RoHS, REACH. Full material certificates (EN 10204 3.1). Third-party testing available upon request.
One-Stop Service
From material selection to logistics tracking. Dedicated account manager + QC team. 97% on-time delivery rate.
๐ Technical Specifications โ 3mm Socket Head Cap Screw Dimensions & #4-40 Socket Head Cap Screw Dimensions
All dimensions in mm (millimeters) unless otherwise noted. Conforms to ASME B18.3 / DIN 912 / ISO 4762.
| Parameter | 3mm Socket Head Cap Screw (M3) | #4-40 Socket Head Cap Screw (UNC #4-40) |
|---|---|---|
| Thread Size | M3 x 0.5 (metric fine pitch available) | #4-40 UNC (coarse thread) |
| Head Diameter (max) | 5.5 mm | 7.9 mm (0.312 in) |
| Head Height (max) | 3.0 mm | 3.3 mm (0.130 in) |
| Hex Socket Size | 2.5 mm | 1/16 in (1.59 mm) |
| Thread Pitch | 0.5 mm | 40 TPI (threads per inch) |
| Length Range Available | 6 mm โ 50 mm (custom up to 80 mm) | 1/8 in โ 2 in (custom lengths available) |
| Material Grades | 304SS, 316SS, 12.9 alloy steel, 10.9 carbon steel | 304SS, 316SS, 18-8 stainless, brass, alloy steel |
| Surface Finish | Plain, zinc plated, black oxide, passivated | Plain, zinc plated, black oxide, nickel plated |
| Tensile Strength (min) | 1,200 MPa (12.9 grade) | 700 MPa (stainless 304) |
*Custom dimensions, drive types, and coatings available. Contact us for your specific requirements.
๐ฉ Application Scenarios & Case Studies
Automotive Assembly โ German Tier 1 Supplier
Challenge: Needed M3 x 12mm socket head cap screws with consistent head height for ABS sensor module. Result: 0.02mm head height variation, zero rejects in 500,000 pcs. Cost saving: 22% vs previous supplier.
Electronics Enclosure โ US-Based Robotics Company
Challenge: #4-40 x 3/8" socket head cap screws for robotic arm housing. Result: 10-day lead time, 304 stainless with passivated finish. Reduced supply chain risk by 35% with dual sourcing.
Construction Fixtures โ UK Distributor
Challenge: Bulk M3 and #4-40 socket head cap screws for modular building systems. Result: Consolidated 6 SKUs into one shipment. Freight cost reduced by 28%, delivery 12 days early.
๐ Trusted by Global Brands & Partners
Procurement Manager, UK Industrial
"We switched from a German supplier to Boen for M3 socket head screws. Cost reduced by 37% and quality is identical. Lead time dropped from 8 weeks to 18 days. Highly recommended."
Operations Director, Brazil Automotive
"Boen provided #4-40 socket head cap screws with custom 316SS material for our offshore equipment. Passed all salt spray tests. Their technical support is outstanding."
Supply Chain Manager, USA Electronics
"We needed 3mm socket head cap screw dimensions with exact head height for our PCB fixtures. Boen delivered 100% within spec. Zero defects in 120,000 pcs."
โ Frequently Asked Questions
What are the exact 3mm socket head cap screw dimensions?
For M3 socket head cap screw: head diameter max 5.5mm, head height max 3.0mm, hex socket size 2.5mm, thread pitch 0.5mm. Length available from 6mm to 50mm standard. All per ASME B18.3 / DIN 912.
What are the #4-40 socket head cap screw dimensions?
#4-40 UNC socket head cap screw: head diameter max 7.9mm (0.312 in), head height max 3.3mm (0.130 in), hex socket size 1/16 in (1.59mm), 40 threads per inch. Lengths from 1/8 in to 2 in standard.
Can you provide custom lengths for M3 and #4-40 socket head cap screws?
Yes. We offer custom lengths for both metric and inch sizes. MOQ for custom lengths is 5,000 pcs for standard materials and 10,000 pcs for specialty alloys. Contact us with your drawing.
What materials are available for socket head cap screws?
We offer 304 stainless steel, 316 stainless steel, 12.9 grade alloy steel (metric), 10.9 grade carbon steel, 18-8 stainless, and brass. All materials come with EN 10204 3.1 mill certificates.
How do you ensure the quality of 3mm and 4-40 socket head cap screws?
We use CMM (coordinate measuring machine) for dimensional checks, thread gages for pitch accuracy, hardness testers, and salt spray test for coating quality. AQL 1.0 per ISO 2859. Third-party inspection (SGS, TรV) is available.
What is the typical lead time and shipping cost to USA/Europe?
Standard sizes: 10-15 days production. Samples: 24h dispatch. Shipping: air freight 5-7 days, sea freight 20-25 days. We consolidate orders to reduce your freight cost by up to 30%.
Do you offer free samples for evaluation?
Yes. We provide free samples for standard sizes (up to 10 pcs per size). You only pay shipping cost. Samples are dispatched within 24h. Request via email: shuan@fastenboen.com
What payment methods do you accept?
We accept T/T (bank transfer), L/C, PayPal for small orders, and Western Union. For new customers, 30% deposit and 70% balance against copy of B/L. Flexible terms available for established partners.
๐ฌ What Our Customers Say About Us
Technical Director, Germany Automation
"We've been using Boen's M3 socket head cap screws for 18 months. Thread quality is superior to our previous supplier. Their 3mm socket head cap screw dimensions are always within spec. 5 stars."
Supply Chain Lead, USA Medical Devices
"FDA compliance was critical for our project. Boen provided #4-40 socket head cap screws with full traceability and passivated finish. Audit passed with zero findings. Thank you!"
Purchasing Manager, Singapore Marine
"Best service from a Chinese fastener supplier. Boen's team helped us select the right 316SS grade for our Marine application. Delivery was 12 days faster than promised. We've placed 4 repeat orders."
๐ Ready to Secure Your Socket Head Cap Screw Supply?
Get factory-direct pricing, ISO-certified quality, and delivery in 10โ15 days. No more guessing on dimensions or quality.
๐ง shuan@fastenboen.com ย |ย ๐ +86 15630072814 ย |ย ๐ Daily 09:00 โ 17:00 CST
๐ฏ Free samples available | 30% deposit, 70% balance | T/T, L/C, PayPal | ISO 9001:2015 Certified
โ๏ธ Author: Liu Wei โ Senior Fastener Engineer at Boen Fastener with 15+ years in precision threading and international standards. I personally oversee dimensional compliance for every M3 and #4-40 socket head cap screw batch. 
