Bolt Size Chart: Complete Metric & SAE Reference

Full bolt size chart with metric (M3–M36) and SAE (1/4"–1") dimensions, thread pitch, and wrench sizes.

Cornerstone Article #2: Complete Bolt Size Chart — Metric & SAE Reference (Free Download)

Target Keyword: "bolt size chart"

Search Intent: Informational + Transactional (user wants a reference, then buys tools)

Estimated Monthly Search Volume: 22,200+

Difficulty: Medium

Affiliate Revenue Potential: $80–$300/mo (high volume + tool/parts links)

Lead Magnet: Printable PDF version (email capture)

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SEO Metadata

Title Tag: Bolt Size Chart: Complete Metric & SAE Reference (Free PDF Download)
Meta Description: Full bolt size chart with metric (M3–M36) and SAE (1/4"–1") dimensions, thread pitch, and wrench sizes. Download free PDF.
H1: The Complete Bolt Size Chart — Metric & SAE Fastener Reference

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Content Structure

Introduction (200 words)

Comprehensive reference for all bolt sizes. Reference the frustration of being mid-project and needing to identify an unknown bolt. This chart covers everything.

Lead magnet CTA: "Download our free printable bolt size chart PDF to take to the shop."

Section 1: Metric Bolt Sizes (M3–M36)

Table: Size | Diameter | Thread Pitch | Wrench Size | Head Size
Common applications for each size
Affiliate placement #1: Digital caliper for measuring bolts — "Check Price on Amazon"

Section 2: SAE Bolt Sizes (1/4"–1")

Table: Size | Diameter | Thread Pitch (TPI) | Wrench Size | Head Size
UNF vs UNC coarse/fine thread explanation
Affiliate placement #2: Thread pitch gauge set — "Check Price on Amazon"

Section 3: Bolt Grade & Strength Markings

Grade 2, Grade 5, Grade 8 markings explained with images
When to use each grade
Affiliate placement #3: Grade identification card or bolt gauge tool — "Check Price on Amazon"

Section 4: Bolt Head Types & Wrench Sizes

Hex, square, Torx, Allen, flange head, carriage bolt
Comprehensive conversion table: bolt size → wrench/socket size
Affiliate placement #4: Socket set recommendation — "Check Price on Amazon"

Section 5: Printable Chart (Lead Magnet)

Clean, formatted table for printing
Email capture form: "Get the PDF version delivered to your inbox"
This is the email list builder — critical for Phase 3 monetization

Section 6: FAQ Schema

```json

{

"@context": "https://schema.org",

"@type": "FAQPage",

"mainEntity": [...]

}

```

Questions:

What's the difference between metric and SAE bolts?
How do I identify an unknown bolt?
What does M8x1.25 mean?
What wrench size for a 5/16" bolt?
What grade bolt should I use for a head gasket?

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Word Count: ~2,500 words

Internal Links

Link to vehicle database ("Find bolts for your specific vehicle")
Link to torque spec database
Link to HowSizeBolt homepage

External Links

6–8 Amazon affiliate links (calipers, gauges, socket sets, bolt assortments)
1–2 manufacturer websites

Expected Revenue Breakdown

Caliper links: 2% CTR × $45 avg × 4% commission = ~$2/mo per 1,000 visitors
Socket set links: 3% CTR × $55 avg × 4% commission = ~$4/mo per 1,000 visitors
At 10,000 monthly visitors: $60–$120/mo from this article alone
Plus email list captures → long-term recurring revenue