Sheet Metal Screw Guide

Type A (Thread Forming - Coarse)

Thread Design: Spaced threads, sharp point

• Coarse, widely-spaced threads
• Sharp gimlet point
• Forms threads by displacing material
• Creates high thread engagement
• Sizes: #2 through #14
• Best for: Thin sheet metal (up to 18 gauge), resinous wood, asbestos, plastic
• NOT for: Thick metals, brittle plastics

Type AB (Thread Forming - Combination)

Thread Design: Combination point, versatile

• Combines features of Type A and B
• Intermediate thread pitch
• Sharp point for easy starting
• Most versatile self-tapping screw
• Sizes: #2 through #14
• Best for: Light gauge sheet metal, plastics, plywood, asbestos, resinous wood
• Advantage: Works in wider range of materials than A or B alone

Type B (Thread Forming - Fine)

Thread Design: Fine threads, blunt point

• Finer, closer-spaced threads than Type A
• Blunt point for pilot holes
• Forms threads by displacing material
• Requires pre-drilled pilot hole
• Sizes: #2 through #14
• Best for: Heavier gauge metal (18-24 gauge), plastics, plywood, harder woods
• Advantage: Finer threads provide better holding in thicker materials

Type 17 (Thread Cutting)

Thread Design: Fine threads with cutting slot

• Machine screw threads with cutting slot
• Cuts threads rather than forming them
• Six longitudinal cutting edges at point
• Chip cavity to collect cut material
• Sizes: #4 through 5/16"
• Best for: Stainless steel, non-ferrous metals, plastics
• Advantage: Reduces stress on material, less chance of cracking

Type 23 (Thread Cutting - Extended)

Thread Design: Fine threads, extended cutting slot

• Similar to Type 17 but cutting edges extend higher
• Longer chip cavity
• Cuts cleaner threads
• Better for thicker materials
• Sizes: #4 through 3/8"
• Best for: Thick sheet metal, castings, plastics
• Advantage: Superior performance in thick materials

Type 25 (Thread Cutting - Tri-slot)

Thread Design: Three cutting edges

• Three cutting edges instead of six
• Large chip cavity
• Reduced driving torque
• Less material stress
• Sizes: #6 through 1/4"
• Best for: Plastics, composites, brittle materials
• Advantage: Minimizes cracking in brittle materials

Point #1 (Tek 1)

Material Thickness: Up to 0.015" (29-20 gauge)

• Shortest drill point
• Very thin materials only
• Fastest drilling action
• Applications: HVAC ductwork, thin sheet metal, light steel framing

Point #2 (Tek 2)

Material Thickness: Up to 0.060" (16-14 gauge)

• Short drill point
• Light to medium gauge metal
• Most common drill point
• Applications: Metal roofing, siding, light structural steel

Point #3 (Tek 3)

Material Thickness: Up to 0.125" (11-7 gauge)

• Medium drill point
• Medium to heavy gauge steel
• Commercial construction standard
• Applications: Steel framing, commercial roofing, heavy HVAC

Point #4 (Tek 4)

Material Thickness: Up to 0.187" (7-3 gauge)

• Long drill point
• Heavy gauge steel
• Slower but more powerful drilling
• Applications: Structural steel, heavy equipment, industrial applications

Point #5 (Tek 5)

Material Thickness: Up to 0.500" (1/2" thick)

• Longest drill point
• Very heavy gauge materials
• Most aggressive drilling
• Applications: Thick steel beams, structural connections, heavy machinery

Stitch Screws

Purpose: Metal-to-metal joining

• Self-drilling or self-piercing
• Joins overlapping metal sheets
• No exposed fastener head
• Applications: HVAC duct connections, joining sheet metal

Pan Head

• Low rounded top
• Large bearing surface
• Most common head style
• Use: General purpose sheet metal work

Flat Head (Countersunk)

• 82° countersunk angle
• Sits flush or below surface
• Smooth finished appearance
• Use: When flush surface required

Hex Head

• Six-sided head
• Wrench or socket drive
• High torque capability
• Use: Heavy-duty applications, high torque

Hex Washer Head

• Hex head with integrated washer
• Large bearing surface
• Weather sealing capability
• Use: Metal roofing, siding, outdoor

Truss Head

• Extra-wide, low-profile head
• Maximum bearing surface
• Won't pull through thin metal
• Use: Very thin materials, HVAC

Oval Head

• Countersunk with rounded top
• Decorative appearance
• Partially recessed
• Use: Decorative applications

Phillips Drive

• Cross-shaped recess
• Most common drive type
• Self-centering
• Cams out at high torque (prevents over-tightening)
• Best for: General purpose, hand tools

Square Drive (Robertson)

• Square recess
• Superior bit engagement
• Won't cam out
• One-hand operation possible
• Best for: Production work, power tools

Star/Torx Drive

• Six-pointed star recess
• Maximum torque transfer
• No cam-out
• Long bit life
• Best for: High-torque applications, production

Hex Socket Drive

• Hexagonal recess
• Very high torque capability
• Requires hex key or bit
• Won't cam out
• Best for: Heavy-duty, high-torque needs

External Hex Drive

• Hex-shaped head
• Wrench or socket driven
• Highest torque capability
• Very secure grip
• Best for: Structural, extreme torque

Slotted Drive

• Single slot
• Traditional style
• Easy to strip
• Decorative use
• Best for: Light duty, decorative applications only

Light Gauge Sheet Metal (18-26 ga)

• Recommended: Type A, Type AB, Tek 1, Tek 2
• Use coarse threads for better grip
• Sharp point for easy penetration
• Pan or truss head prevents pull-through
• Applications: HVAC, ductwork, metal panels, appliances

Medium to Heavy Gauge (14-18 ga)

• Recommended: Type B, Type AB, Tek 2, Tek 3
• Finer threads for better holding power
• May require pilot hole for Type B
• Self-drilling eliminates pre-drilling
• Applications: Steel studs, metal framing, roofing

Structural Steel (7-11 ga)

• Recommended: Type 17, Type 23, Tek 3, Tek 4
• Thread cutting reduces material stress
• Longer drill points required
• Hex head for high torque
• Applications: Steel framing, structural connections

Stainless Steel

• Recommended: Type 17, Type 23, stainless steel screws
• Use stainless screws to prevent galvanic corrosion
• Thread cutting prevents galling
• Slower drilling speed required
• Applications: Food service, marine, corrosive environments

Aluminum & Soft Metals

• Recommended: Type A, Type AB, aluminum or stainless screws
• Avoid galvanic corrosion with proper screw material
• Coarse threads work well
• Easy to strip - don't over-tighten
• Applications: Aluminum siding, trim, enclosures

Plastics & Composites

• Recommended: Type AB, Type 25 (for brittle plastics)
• Thread cutting for brittle plastics to prevent cracking
• Coarse threads for soft plastics
• Don't over-tighten - plastics crack easily
• Applications: Plastic enclosures, composite panels

Pilot Holes

• Type A/AB: Often no pilot hole needed in thin materials
• Type B: Always use pilot hole
• Pilot hole size: 70-75% of screw major diameter
• Thick materials: Pilot hole reduces splitting and stress
• Stainless/hard metals: Always pre-drill

Driving Technique

• Use correct bit size - loose fit causes cam-out
• Start slowly to establish thread
• Apply steady, even pressure
• Let drill point do the work (self-drilling)
• Don't over-tighten - causes stripping

Tool Selection

• Light duty: Cordless drill/driver sufficient
• Medium duty: Impact driver recommended
• Heavy duty: High-torque impact driver required
• Production: Screw gun with adjustable clutch
• Use magnetic bit holders for easier handling

Zinc Plated

• Standard indoor protection
• Economical
• Clear or yellow chromate
• Best for: Interior applications, dry environments

Stainless Steel (304, 410)

• Excellent corrosion resistance
• No coating needed
• 304 for marine, 410 for general
• Best for: Exterior, marine, food service

Dacromet/Geomet Coating

• Superior corrosion protection
• No hydrogen embrittlement
• Gray appearance
• Best for: Automotive, extreme environments

Painted/Colored

• Matches panel colors
• Corrosion protection + aesthetics
• Common in roofing screws
• Best for: Metal roofing, siding, visible fasteners