Complete Guide to Pins & Clips

Understanding fastening pins, retaining clips, and securing hardware for mechanical assemblies and equipment

What You'll Learn

Pin Types

Cotter, clevis, spring, dowel, roll, and taper pins

Clip Types

Retaining rings, E-clips, C-clips, and snap rings

Sizing & Selection

How to measure and choose the right size

Downloadable Reference Guides

Quick access to all pin and clip specification charts and guides

Pin Types & Styles

Pins are cylindrical fasteners used for alignment, pivoting, retention, and securing components. Understanding the different types ensures proper selection for load requirements, precision, and ease of assembly.

Split & Securing Pins

Cotter Pins

Features: Split pin with two legs, secured by bending legs apart

Semi-circular cross-section split down middle
Legs bend outward after insertion to lock
Easy to install and remove
Sizes: 1/32" to 3/4" diameter
Materials: Steel, stainless, brass

Best For: Securing clevis pins, castle nuts, preventing nut loosening, linkages

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Clevis Pins

Features: Smooth cylindrical pin with head and hole for cotter pin

Flat or domed head for bearing surface
Hole through shank for cotter pin retention
Precision ground for smooth pivoting
Sizes: 1/8" to 1" diameter
Standard and heavy-duty versions

Best For: Linkages, yokes, pivoting connections, agricultural equipment, trailers

Hitch Pins

Features: Large pin with clip or ball lock for quick coupling

Heavy-duty construction for towing
Quick-release clip or lynch pin
Sizes: 1/4" to 1" diameter
Various lengths for different applications
Zinc plated or stainless steel

Best For: Trailer hitches, implements, quick-disconnect applications, towing equipment

Lynch Pins

Features: Wire pin with looped handle and bent leg

Quick-release design with pull ring
Bent leg prevents accidental removal
Easy single-handed operation
Sizes: 1/8" to 1/2" wire diameter
Galvanized or stainless options

Best For: Agricultural equipment, trailers, implements, frequent assembly/disassembly

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Precision & Spring Pins

Dowel Pins

Features: Precision ground solid cylindrical pin

Tight tolerance for precise alignment
Hardened steel for strength
Chamfered or radiused ends
Standard tolerance: ±0.0001"
Sizes: 1/16" to 2" diameter

Best For: Precision alignment, dies, molds, jigs, fixtures, machinery positioning

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Spring Pins (Coiled)

Features: Rolled spring steel coil with gap along length

Compresses radially when inserted
Spring tension holds pin in place
Compensates for hole variation
Standard, heavy, and light duty
Reusable - can be removed/installed multiple times

Best For: Shafts, linkages, quick-change applications, moderate shear loads

Roll Pins (Slotted)

Features: Tubular pin with single slot along length

Single slot allows compression during insertion
Spring force holds pin in hole
Lighter duty than coiled spring pins
Sizes: 1/32" to 1" diameter
Carbon or stainless steel

Best For: Light shear loads, handles, knobs, lever attachments, shaft retention

Taper Pins

Features: Precision ground with 1/4" per foot taper

Standardized 1:48 taper ratio
Self-locking when driven in
Requires reamed tapered hole
Very high shear strength
Numbered sizes: 7/0 to 10

Best For: Pulleys, gears, couplings, permanent/semi-permanent shaft connections

Grooved Pins

Features: Solid pin with longitudinal grooves

Three longitudinal grooves along length
Grooves compress during insertion
No hole enlargement or fretting
Higher shear strength than spring pins
Pilot or full-length grooves

Best For: High-shear applications, machinery, automotive, permanent installations

Quick-Release Pins

Features: Pin with button, ball lock, or wire ring release

Push-button or pull-ring mechanisms
No tools required for removal
Single or double-acting designs
Stainless for corrosion resistance
Various grip lengths available

Best For: Frequent assembly/disassembly, adjustable equipment, exercise machines

Pin Selection Quick Guide

For Pivoting/Linkages: Clevis pins with cotter pins - allow rotation while secured

For Precision Alignment: Dowel pins - tight tolerances prevent movement

For Shafts/Axles: Spring pins or roll pins - radial compression holds in place

For Permanent Connections: Taper pins or grooved pins - high shear strength

For Quick Release: Hitch pins, lynch pins, or quick-release pins - easy removal

Clip & Retaining Ring Types

Clips and retaining rings secure components on shafts or in housings without threading. They provide axial positioning and prevent parts from sliding or separating.

Retaining Rings & Circlips

Internal Retaining Rings

Features: Ring fits inside bore/housing with ears pointing inward

Installed in grooved bore or housing
Expands during installation with special pliers
Holds bearings, bushings in housings
Two lugs for plier installation
Sizes: 3/16" to 12" bore diameter

Best For: Retaining bearings in housings, securing components inside bores

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External Retaining Rings

Features: Ring fits over shaft with ears pointing outward

Installed in grooved shaft
Compresses during installation with pliers
Most common retaining ring type
Standard duty and heavy duty versions
Sizes: 1/8" to 12" shaft diameter

Best For: Shaft assemblies, securing gears/pulleys, axial positioning on shafts

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E-Clips (External)

Features: E-shaped ring that slides onto shaft or rod

No groove required - fits on plain shaft
Easy installation - push on with screwdriver
Lower load capacity than grooved rings
Three contact points grip shaft
Sizes: 1/16" to 2" shaft diameter

Best For: Light-duty shaft retention, preventing component slide, simple assemblies

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C-Clips

Features: C-shaped ring that snaps into groove

Open C shape allows easy installation
Can be installed/removed without shaft removal
Lower thrust capacity than closed rings
Good for frequent assembly/disassembly
Also called crescent clips

Best For: Applications requiring frequent removal, light thrust loads, maintenance

Specialty Clips & Fasteners

Push-On Retainers

Features: Starlock or curved washer that pushes onto shaft

No groove required
Teeth bite into shaft for retention
Quick push-on installation
One-time use (not reusable)
Light to medium duty loads

Best For: Knobs, handles, wheels, one-time assembly, production applications

Snap Rings (Spiral)

Features: Multi-turn spiral ring that winds onto shaft

No groove required - grips by friction
Easy installation by screwing on
Reusable and adjustable
360° contact with shaft
Light duty applications

Best For: Shaft end retention, temporary securing, prototyping, adjustable positions

Bow Tie Clips

Features: Flat spring steel clip with two prongs

Push-on installation into hole
Spring prongs grip hole sides
Used for panel retention
Automotive and electronic applications
Various sizes for different hole diameters

Best For: Panel fastening, automotive trim, enclosures, light retention

Retaining Ring Material Selection

Carbon Steel: Standard choice, cost-effective, good for most applications. Phosphate coating for corrosion resistance.

Stainless Steel (302/304): Excellent corrosion resistance, non-magnetic, food service and marine applications.

Beryllium Copper: Non-magnetic, non-sparking, excellent spring properties, electronic and aerospace applications.

Spring Steel (Music Wire): High strength, maximum spring properties, heavy-duty applications.

Download Retaining Ring Guide

Complete guide to retaining ring types, sizing, and installation

Retaining Ring Guide

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Sizing & Measurement Guide

Proper sizing is critical for pins and clips to function correctly. Understanding measurement methods ensures proper fit and performance.

Pin Sizing Reference

Pin Type	Diameter Sizes	Length Range	Tolerance	Measurement Notes
Cotter Pins	1/32" to 3/4"	1/2" to 6"	±0.005"	Diameter measured before splitting
Clevis Pins	1/8" to 1"	1/2" to 8"	±0.001"	Grip length is usable shaft length
Dowel Pins	1/16" to 2"	1/4" to 12"	±0.0001"	Precision ground, standard sizes only
Spring Pins (Coiled)	1/16" to 1"	1/4" to 6"	±0.002"	Nominal diameter, compresses when inserted
Roll Pins	1/32" to 1"	1/4" to 6"	±0.003"	Nominal diameter of finished pin
Taper Pins	Size 7/0 to 10	1/2" to 8"	±0.0005"	Numbered sizes, 1/4" per foot taper
Grooved Pins	1/16" to 1/2"	1/4" to 6"	±0.0005"	Measured at largest diameter
Quick-Release Pins	1/8" to 3/4"	1/2" to 12"	±0.002"	Grip length is material thickness capacity

Retaining Ring Sizing

Ring Type	Size Range	Groove Required	Key Measurements
External Retaining Ring	1/8" to 12" shaft dia.	Yes	Shaft diameter, groove width, groove diameter
Internal Retaining Ring	3/16" to 12" bore dia.	Yes	Bore diameter, groove width, groove diameter
E-Clip (External)	1/16" to 2" shaft dia.	No	Shaft diameter only
C-Clip	1/4" to 4" shaft dia.	Yes	Shaft diameter, groove diameter
Push-On Retainer	1/16" to 2" shaft dia.	No	Shaft diameter, smooth finish required
Spiral Ring	1/8" to 3" shaft dia.	No	Shaft diameter, turns required

Hole Size Recommendations

Spring Pins & Roll Pins

Hole Sizing Formula:

Standard duty: Hole = Pin nominal diameter
Heavy duty: Hole = Pin diameter - 0.002"
Light duty: Hole = Pin diameter + 0.002"
Chamfer hole entrance 30° to 45°
Hole depth = Pin length + 0.010" minimum

Dowel Pins & Grooved Pins

Hole Sizing Formula:

Press fit: Hole = Pin diameter - 0.0002"
Light drive: Hole = Pin diameter - 0.0001"
Slip fit: Hole = Pin diameter + 0.0002"
Ream holes for precision
Chamfer entrance for easier installation

Important: Retaining Ring Groove Specifications

Retaining rings require precisely machined grooves to function properly. Incorrect groove dimensions can cause ring failure or part damage. Always consult groove dimension charts for your specific ring size and type. Standard groove dimensions are published by manufacturers and must be followed exactly.

Download Sizing Charts

Complete sizing references for pins and retaining rings

Pin Size Chart Retaining Ring Grooves

Applications & Installation Guide

Selecting and installing pins and clips correctly ensures reliable performance and safety in mechanical assemblies.

Application-Specific Recommendations

Linkages & Pivots

Recommended: Clevis pins with cotter pins

Selection: Pin diameter per load chart, grip length = total thickness
Cotter pin size: Largest that fits through hole
Installation: Insert clevis pin, add washer, insert cotter pin
Securing: Bend cotter pin legs 45° away from each other
Inspection: Check for wear annually in high-cycle applications

Shaft Assemblies

Recommended: External retaining rings or spring pins

Retaining rings: For axial loads, requires machined groove
Spring pins: For shear loads, no groove needed
Ring installation: Use snap ring pliers, compress ring evenly
Pin installation: Drive from chamfered end until flush
Inspection: Ensure ring fully seats in groove

Precision Alignment

Recommended: Dowel pins

Hole preparation: Must be reamed to precision tolerance
Installation: Press fit, use arbor press for control
Depth: Pin should extend 60% into second part minimum
Material: Hardened alloy steel for permanent installations
Removal: Drill and use pin extractor if needed

Bearing Retention

Recommended: Internal retaining rings

Groove location: Per bearing manufacturer specifications
Ring type: Standard or heavy duty based on thrust load
Installation: Expand ring with internal pliers, seat in groove
Inspection: Ring must be fully seated 360°
Safety: Wear eye protection - rings can slip during install

Hitch & Towing

Recommended: Hitch pins with clips or lynch pins

Sizing: Pin diameter must match hitch receiver
Length: Long enough to clear both sides plus clip
Material: Grade 5 or better steel, zinc plated
Clip installation: Ensure positive engagement
Inspection: Check for wear or bending before each use

Quick-Change Systems

Recommended: Quick-release pins or lynch pins

Button pins: For frequent adjustment, tool-free operation
Lynch pins: For agricultural and trailer applications
Grip length: Must accommodate total material thickness
Load rating: Check manufacturer specifications
Maintenance: Keep mechanism clean and lubricated

Installation Tips & Best Practices

Pin Installation

Always chamfer hole entrance for easier insertion
Use proper drivers - never hammer directly on pins
For spring pins, drive from chamfered end
Support workpiece to prevent damage
Clean holes before installation
Check alignment before driving pins

Retaining Ring Installation

Use proper snap ring pliers (internal or external)
Wear safety glasses - rings can slip
Expand/compress evenly to avoid twisting
Ensure ring fully seats in groove 360°
Rotate ring in groove to verify proper seat
Inspect for burrs or damage before use

Removal Techniques

Spring pins: Punch out from opposite end
Dowel pins: Drill and use pin extractor
Retaining rings: Use proper pliers, wear safety glasses
Cotter pins: Straighten legs, pull with pliers
Taper pins: Drive out from large end
Replace damaged pins - do not reuse

Common Mistakes to Avoid

Wrong hole size: Too tight causes pin or hole damage; too loose reduces holding power
Missing chamfer: Makes installation difficult and damages pin
Undersized pins: Inadequate shear strength for load - can fail catastrophically
Improper groove depth: Retaining ring won't seat or will pop out under load
Reusing damaged parts: Bent cotter pins or damaged retaining rings can fail
No safety glasses: Retaining rings can slip during installation - eye hazard
Force misalignment: Forcing pins into misaligned holes damages parts

Download Installation Guide

Complete installation procedures for all pin and clip types

Installation Guide

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Cotter Pins Dowel Pins Retaining Rings E-Clips Snap Ring Pliers