Circular Saw Blade Bore Sizes Guide
The bore size (also called the arbor hole) is the centre hole in a circular saw blade that fits over your saw’s spindle. If the bore size doesn’t match your saw’s arbor, the blade won’t fit — or worse, it’ll wobble dangerously. This is the most critical compatibility measurement for circular saw blades, and getting it wrong is one of the most common mistakes.
Quick Answer
Most cordless circular saws in the UK use a 20mm bore. Most mitre saws and table saws use a 30mm bore. Some cordless saws use a 16mm bore (e.g. Ryobi 18V ONE+); Milwaukee M18 saws use 15.87mm. Older corded saws may use 25.4mm (1″). Many blades include reduction rings so a 30mm bore blade can fit a 20mm arbor.
Common Bore Sizes in the UK
| Bore Size | Common Saw Types | Example Saws |
|---|---|---|
| 16mm | Cordless and mini circular saws | Ryobi 18V ONE+ (R18CS), some mini circular saws |
| 20mm | Most cordless circular saws (18V/20V Max) | DeWalt DCS391, Makita DSS611, Bosch GKS 18V, Festool TS 55 |
| 25.4mm (1″) | Some older corded circular saws | Older Bosch and Black & Decker corded models |
| 30mm | Mitre saws, table saws, larger corded saws | DeWalt DWS774, Makita LS1019, Bosch GCM series |
Recommended Circular Saw Blades
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What Are Reduction Rings?
Reduction rings (also called bore bushings or reducing washers) are thin metal rings that sit inside the bore hole to reduce it to a smaller size. For example, a blade with a 30mm bore can include a 30mm-to-20mm reduction ring, allowing it to fit a saw with a 20mm arbor. Many blades sold in the UK include one or more reduction rings in the pack.
Key rule: Always ensure the reduction ring sits flush and secure. A loose reduction ring can cause the blade to wobble, which is both dangerous and produces poor cuts. If a reduction ring doesn’t fit tightly, don’t use it — buy a blade with the correct bore size instead.
How to Measure Your Saw’s Bore Size
The easiest way to find your saw’s bore size is to check the existing blade — the bore size is usually printed or stamped on the blade itself (e.g., “165 x 20mm” means 165mm diameter, 20mm bore). You can also check your saw’s manual or the specification sticker on the saw body. If in doubt, measure the arbor spindle diameter with a ruler or callipers.
Bore Size by Brand and Model
| Brand | Cordless Circular Saws | Mitre Saws |
|---|---|---|
| DeWalt | 20mm (DCS391, DCS570, DCS565) | 30mm (DWS774, DWS778, DWS780) |
| Makita | 20mm (DSS611, DHS680, DSS610) | 30mm (LS1019, LS0815, LS1018) |
| Bosch | 20mm (GKS 18V-57, GKS 18V-68) | 30mm (GCM 8 SJL, GCM 12 GDL) |
| Milwaukee | 15.87mm (M18 CCS55, M18 FCSRH) | 30mm (M18 FMS254, M18 FMS305) |
| Ryobi | 16mm (R18CS-0) | 30mm (EMS216) |
| Festool | 20mm (TS 55, TSC 55) | 30mm (KS 120, Kapex KS 60) |
Recommended Circular Saw Blades
| Blade | Size | Bore | Best For | Link |
|---|---|---|---|---|
| Saxton TCT 165mm 80T Fine Cut | 165mm | 20mm | Fine cuts in wood — cordless saws | View on Amazon |
| Trend CSB/16560 60T | 165mm | 20mm | Extra-fine finish — professional | View on Amazon |
| Saxton Multi-Purpose 165mm 40T | 165mm | 20mm | General purpose — wood and metal | View on Amazon |
| Saxton TCT 216mm 100T | 216mm | 30mm | Fine crosscuts — mitre saws | View on Amazon |
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Related guides: Circular Saw Blade Sizes | Can You Use a Smaller Blade? | Saw Blade Compatibility Guide
How we compile this guide
We cross-reference compatibility details against manufacturer specifications where available, official tool manuals, and the physical standards that govern fitment (bore sizes, arbor diameters, voltage platforms, connector types). We prioritise primary sources over retailer listings, flag anything we can’t confirm, and re-verify the data on a regular cycle. Where we give a buying recommendation, we tell you the reasoning — not just the link. More on our method →