Complete Guide to Threaded Inserts

Helical Coil Inserts (HeliCoil)

Features: Coiled wire insert forming internal threads

• Diamond-shaped wire coil with tang for installation
• Provides stronger threads than parent material
• Distributes stress over larger area
• Thread sizes: M2 to M24, #2 to 1-1/4"
• Stainless steel wire construction

Best For: Thread repair, aluminum/magnesium, high-strength applications, aerospace

Key-Locking Inserts (Keenserts)

Features: Solid threaded bushing with external keys

• Precision internal and external threads
• Keys lock into broached hole
• Cannot rotate once installed
• Higher strength than helical coils
• Carbon steel or stainless steel

Best For: High-torque applications, heavy loads, permanent installations, machined parts

Tangless Inserts

Features: Helical coil without removal tang

• No tang to break off during installation
• Full thread engagement at bottom
• Requires special installation tool
• Easier to install than standard HeliCoil
• Aerospace and military applications

Best For: Blind holes, aerospace, automotive, high-reliability applications

Self-Tapping Inserts (E-Z Lok)

Features: External cutting threads for metal

• Taps own hole during installation
• No tapping or broaching required
• External hex for wrench installation
• For use in soft metals (aluminum, brass)
• Brass or stainless steel construction

Best For: Soft metals, field repairs, quick installations, cast aluminum

Threaded Inserts for Wood

Features: External wood threads, internal machine threads

• Coarse external threads for wood
• Fine internal machine threads
• Hex drive or slotted installation
• Brass, steel, or stainless options
• Sizes: #6 to 1/2" internal thread

Best For: Furniture, jigs, fixtures, repeated assembly, knockdown furniture

Heat-Set Inserts (Plastic)

Features: Brass insert heated and melted into plastic

• Knurled or undercut exterior grips plastic
• Heated with soldering iron
• Strong permanent installation
• Brass construction (good heat transfer)
• Common in 3D printed parts

Best For: Thermoplastics, 3D printed parts, injection molded parts, electronics

Ultrasonic Inserts

Features: Installed with ultrasonic welding equipment

• Ultrasonics melt plastic for installation
• Very fast installation (1-2 seconds)
• Requires ultrasonic equipment
• Production volumes only
• Strongest plastic installation method

Best For: High-volume production, injection molding, automotive, consumer electronics

Press-Fit Inserts (Plastic)

Features: Knurled body pressed into molded hole

• Knurls or ribs grip plastic
• Installed with arbor press
• Can be designed into mold
• Brass or stainless steel
• Good for moderate loads

Best For: Molded plastics, moderate loads, field installation, prototypes

Expansion Inserts for Wood

Features: Split body expands when screw inserted

• Slotted body expands in hole
• No external wood threads
• Can be installed/removed multiple times
• Good for particleboard and MDF
• Zinc or brass finish

Best For: Particleboard, MDF, plywood, cabinet hardware, soft woods

Rampa Nuts (Pronged)

Features: Four sharp prongs embed in wood

• Prongs hammer into wood surface
• Flush or projecting installation
• Very quick installation
• Moderate holding power
• Economical for high volumes

Best For: Light-duty wood assemblies, crates, pallets, quick knockdown furniture

Aluminum & Magnesium

Recommended Inserts: HeliCoil, tangless, or key-locking

• Soft material prone to thread stripping
• HeliCoil provides 2-3x thread strength
• Stainless inserts prevent galvanic corrosion
• Common in aerospace and automotive
• Excellent for thread repair after damage

Cast Iron & Steel

Recommended Inserts: HeliCoil or key-locking for repairs

• Typically for thread repair only
• Cast iron threads easily damaged
• Key-locking for high-torque applications
• Can salvage expensive castings
• Common in engine blocks and housings

Hardwood (Oak, Maple, Walnut)

• Best: Threaded inserts with coarse wood threads
• Brass inserts easier to install than steel
• Pre-drill hole to exact size
• Use wax or soap as lubricant
• Excellent holding power in hardwoods

Softwood (Pine, Fir, Cedar)

• Best: Expansion inserts or threaded inserts
• Avoid over-tightening during installation
• Slightly smaller hole than hardwood
• Expansion inserts work well in soft species
• Consider epoxy for extra strength

Particleboard & MDF

• Best: Expansion inserts (E-Z Anchor style)
• Standard wood inserts don't hold well
• Expansion action critical for grip
• Pre-drill accurate size hole
• Common in flat-pack furniture

Thermoplastics (ABS, Nylon, Acetal)

Recommended Inserts: Heat-set or ultrasonic

• Heat-set: Use soldering iron (prototypes)
• Ultrasonic: Production volumes (automated)
• Knurled exterior grips melted plastic
• Very strong permanent installation
• Common in 3D printed parts
• Temperature rating depends on plastic type

Thermosets & Composites

Recommended Inserts: Press-fit or bonded

• Cannot melt for heat-set installation
• Press-fit with knurled exterior
• Often bonded with epoxy
• Design bosses for insert during molding
• Used in fiberglass and carbon fiber parts
• Marine and aerospace applications

HeliCoil Installation

Tools Required: STI tap, installation mandrel, tang break-off tool

• Step 1: Drill hole to specified size
• Step 2: Tap hole with STI tap (NOT standard tap)
• Step 3: Thread coil onto mandrel
• Step 4: Screw coil into tapped hole
• Step 5: Break off tang below surface
• Verify: Coil is 1/4 to 1/2 turn below surface

Key-Locking Installation

Tools Required: Drill, broach, installation driver

• Step 1: Drill hole to exact size
• Step 2: Broach keyways (2 or 4 depending on insert)
• Step 3: Align insert keys with keyways
• Step 4: Drive insert in using installation tool
• Step 5: Verify flush installation
• Check: Insert cannot rotate in hole

Wood Insert Installation

Tools Required: Drill, hex key or screwdriver, optional wax

• Step 1: Drill straight hole to specified depth
• Step 2: Apply wax or soap to threads (brass only)
• Step 3: Start insert straight in hole
• Step 4: Drive in with hex key or slotted driver
• Step 5: Stop when flush or 1/16" below surface
• Caution: Don't over-tighten or strip wood threads

Heat-Set Insert Installation

Tools Required: Soldering iron, tip for insert size

• Step 1: Drill hole to exact specification
• Step 2: Heat soldering iron to 400-500°F
• Step 3: Place insert on hole, start straight
• Step 4: Press insert with hot tip - melts in
• Step 5: Hold 2-3 seconds, remove iron
• Cool: Let plastic cool 30 seconds before use

Self-Tapping Insert Installation

Tools Required: Drill, hex key or wrench

• Step 1: Drill hole per specifications
• Step 2: Chamfer hole entrance slightly
• Step 3: Start insert with hex driver
• Step 4: Drive in - insert cuts own threads
• Step 5: Stop when insert is flush
• Note: Requires significant torque in hard materials

Press-Fit Installation

Tools Required: Arbor press or installation tool

• Step 1: Drill or mold hole to size
• Step 2: Place insert in hole, check alignment
• Step 3: Press insert using steady force
• Step 4: Press until flush with surface
• Step 5: Verify insert doesn't rotate
• Tip: Add drop of epoxy for permanent installation

Hole Preparation

• Use sharp drill bits for clean holes
• Drill perpendicular to surface - no angle
• Deburr hole entrance after drilling
• Verify hole depth before installation
• Clean chips and debris from hole
• Use cutting fluid for metal holes

Installation Technique

• Start inserts straight - critical for success
• Use proper installation tools - not pliers
• Apply steady, even pressure
• Don't rush - take time to align properly
• Stop at correct depth - don't overdrive
• Verify full seating after installation

Quality Verification

• Test with mating screw after install
• Verify insert doesn't rotate
• Check for proper depth and flush fit
• Inspect for damaged threads
• Perform pull-out test on samples
• Document installation parameters