Thirty millimeters on most European table saws, miter saws and stationary machines, often 20 mm on plunge and track saws. American saws use 5/8 inch, and the two are not interchangeable.
What the bore is
The bore is the hole in the middle of the blade. It has to match the saw’s arbor exactly, because any play becomes runout: the blade wobbles a fraction of a millimeter on every revolution, which shows up as a kerf wider than the blade, burn marks and a rougher cut.
The common sizes
- 30 mm (1.18 in): most European table saws, miter saws, panel saws and stationary machines.
- 20 mm (0.79 in): many European plunge and track saws and small circular saws, such as Festool’s and Makita’s.
- 5/8 in (15.9 mm): the standard on American 10 in and 12 in table and miter saws and 7-1/4 in circular saws.
- 1 in (25.4 mm): some large blades for 14 in and bigger saws.
Which way a mismatch goes
A blade whose bore is smaller than the arbor simply will not go on. A blade whose bore is larger fits loosely and runs off center unless a machined reducer ring fills the gap. A ring always adapts a larger bore down to a smaller arbor, never the other way.
Reducer rings work, with a caveat
A properly machined ring, sized exactly to both diameters and thinner than the blade body, is a legitimate fix; our answer on whether a reducer ring is safe covers the details. But every ring is one more interface that can sit a hair off center. If a blade exists in the bore your saw uses, buy that one.
Where it catches people
Imported blades, blades bought abroad, and European machines brought to the US. A 30 mm blade on a 5/8 in arbor would need a ring that fills more than 14 mm of gap: avoid it. On a US saw, buy a 5/8 in blade, such as the WEN BL1060 10 in, 60-tooth blade.
Check before ordering, every time
The bore is printed on the blade body next to the diameter, for example 254 × 30 mm or 10 in × 5/8 in, and your saw’s manual gives the arbor size. All the blades we cover are on our circular saw blade page, and choosing a blade for the material explains tooth counts.
What comes up most often
Can I put a European 30 mm blade on my US table saw?
Only with a machined 30 mm to 5/8 in reducer ring, and it is not a good idea: the gap is large, and every interface is a chance for runout. Blades in 5/8 in bore are widely sold in the US; buy one of those instead.
Why do some blades have a diamond-shaped knockout?
Many 7-1/4 in circular saw blades sold in the US have a 5/8 in round bore with a diamond knockout around it. Saws with a diamond arbor, mostly older worm-drive models, take the knockout out; everything else uses the round hole.
Where do I find the bore on a blade?
It is printed on the blade body next to the diameter and tooth count, for example 254 × 30 mm or 10 in × 5/8 in, and it should be on any listing worth buying from. Your saw’s manual gives the arbor size.
What happens if the bore is too large?
The blade sits off center on the arbor. That runout shows up as a wider kerf than the blade, burn marks, vibration and a rougher cut, and at worst the blade can shift under the flange. Never run a loose blade.
Last reviewed October 28, 2026