Edge Trim Sizing Guide

Edge Trim Sizing Guide

How to measure and select the right edge trim

Edge trim (also called edge protection, edge seal, or U-channel trim) protects and finishes exposed panel edges. Selecting the correct size ensures secure fitting and proper protection.

Understanding Edge Trim Dimensions

Edge Trim Anatomy

        ┌──── Bulb Width ────┐
        │                    │
    ╭───────────────────────────╮  ← Bulb Height
    │       ○ ○ ○ ○ ○ ○ ○       │    (protection)
    ╰───────────────────────────╯
        │ ┌────────────┐ │
        │ │            │ │  ← Grip Height
        │ │   PANEL    │ │
        │ │            │ │
        │ └────────────┘ │
        │◄──Grip Range──►│
        
    Grip Range: Panel thickness the trim accepts
    Bulb: The protective cushion section

How to Measure

Step 1: Measure Your Panel Thickness

Use a vernier calliper or accurate ruler to measure the exact thickness of the panel edge in millimetres.

  • Measure at several points—panels may vary
  • Include any coatings, paint, or finishes
  • Round up if between sizes

Step 2: Check Grip Range

Edge trim is specified by grip range. Your panel thickness must fall within this range:

  • 0.5-1.5mm grip: Sheet metal, thin panels
  • 1-2mm grip: Standard sheet metal
  • 1-3mm grip: Most common, versatile
  • 2-4mm grip: Thicker panels, composite
  • 3-6mm grip: Thick panels, marine ply

Step 3: Choose Bulb Size

The bulb provides protection and aesthetics. Consider:

  • Small bulb (8-10mm): Neat finish, light protection
  • Medium bulb (12-15mm): Good all-round protection
  • Large bulb (18-25mm): Maximum impact protection

Common Sizes & Applications

Grip Range Bulb Size Typical Applications
0.5-1.5mm 8mm × 6mm Thin sheet metal, access panels, electronics enclosures
1-2mm 10mm × 7mm Vehicle body panels, machine guards, cabinet edges
1-3mm 12mm × 10mm Most common—car doors, industrial panels, shopfitting
2-4mm 15mm × 12mm Thicker panels, composite materials, caravans
3-6mm 18mm × 14mm Marine ply, thick composites, heavy-duty applications
4-8mm 22mm × 18mm Thick panels, glass edges (with care), boat hatches

Material Selection

Material Best For Temperature Flexibility
PVC Indoor, cost-effective, general use -10°C to +60°C Moderate
EPDM Rubber Outdoor, UV exposure, weathersealing -40°C to +120°C Excellent
TPE Flexible, good all-round choice -30°C to +80°C Excellent
Silicone High temp, food-safe applications -60°C to +200°C Excellent

💡 Pro Tip: Steel Wire Core

Most edge trim contains a steel wire core that grips the panel edge. This provides secure fitting without adhesive. For smooth or irregular edges, choose adhesive-backed versions instead.

Application Examples

🚗 Vehicle Doors

1-3mm grip
EPDM material
12mm bulb

🚐 Caravan Panels

2-4mm grip
EPDM material
15mm bulb

⚙️ Machine Guards

1-2mm grip
PVC material
10mm bulb

🚢 Boat Hatches

3-6mm grip
EPDM material
18mm bulb

Installation Tips

  • Use soapy water as lubricant for long runs
  • Start at one end and push on progressively
  • For corners: Cut V-notches on inside of bend, mitre external corners
  • Butt joints: Cut ends square for tight fit, add adhesive if needed
  • Check grip: Trim should be snug but not splitting

Frequently Asked Questions

How do I measure for edge trim?

Measure the panel thickness in millimetres using a vernier calliper or accurate ruler. This is the key measurement—edge trim is sized by the "grip range" it accepts. For example, a "1-3mm grip" edge trim will fit panels between 1mm and 3mm thick. Your panel must fall within this range for proper fitting.

What is the bulb on edge trim?

The bulb is the rounded protective section that sits on top of or alongside the panel edge once fitted. It provides cushioning against impacts and creates a finished appearance. Larger bulbs offer more protection against knocks; smaller bulbs give a neater, less prominent finish. Choose based on whether protection or aesthetics is the priority.

Can edge trim go around corners?

Yes, flexible edge trim can bend around gentle curves without modification. For tight internal corners, cut V-notches on the inside of the bend to allow the trim to fold. External (outside) corners typically need mitre cuts at 45° angles. EPDM rubber and TPE trims are more flexible than rigid PVC, making them better for curved applications.

Does edge trim need adhesive?

Standard edge trim grips the panel mechanically via an internal steel wire core—no adhesive is required for most applications. The wire core pinches the panel edge to hold the trim in place. For very smooth panels, irregular edges, or high-vibration applications, adhesive-backed edge trim is available and may provide a more secure fit.

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Last updated: March 2026