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4.5 Inch Flap Disc (115mm): The Standard for Weld Grinding & Finishing
The 4.5 inch flap disc (115 mm) matches the world's most popular angle grinder size, making it the default choice for weld dressing, deburring and metal finishing across fabrication shops and job sites.
Specifications
- Diameter: 115 mm (4-1/2") — Max RPM 13,300
- Bore: 22.2 mm (7/8")
- Abrasives: aluminum oxide, zirconia, ceramic
- Shapes: T27 flat, T29 angled, curved
- Grits: 40–600 (common working range 36–120)
Quick Selection Guide
| Job | Shape | Grit | Abrasive |
|---|---|---|---|
| Weld seam removal | T29 | 36/40 | Zirconia or ceramic |
| Chamfering | T29 | 50/60 | Zirconia |
| Deburring | T27 or T29 | 60/80 | Aluminum oxide+ |
| Surface finishing & cleaning | T27 | 80/120 | Any |
| Stainless finishing | T27 | 80/120 | Ceramic (cool cut) |
Why 4.5 Inch Dominates
- Tool availability: every shop runs 4-1/2" grinders — discs are always in stock.
- Control: small disc, light tool — easy one-hand finishing on assemblies.
- Economy: lowest price per disc of all sizes; ideal for high-consumption shops.
Technique
- T27: work at 0–15° to the surface for flat finishing.
- T29: work at 15–25° for aggressive grinding on welds and edges.
- Let the disc's weight do the work — pressure glazes the flaps and overheats the workpiece.
FAQ
What grit flap disc for removing welds?
Start 36–40 grit zirconia T29 to level the weld, then 80–120 grit to blend and finish.
How many flap discs per weld job?
A zirconia 4.5" flap disc typically dresses 10–20 m of weld depending on bead size — far more than a fiber disc.
Plastic or fiberglass backing?
Fiberglass backing is rigid and standard; plastic (trim-able) backing lets you consume more flap material; metal backing suits heavy edge work.
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