Can You Use a Smaller Circular Saw Blade?
This is one of the most frequently asked circular saw questions, and the answer is nuanced. Technically, a smaller blade may physically fit your saw (as long as the bore matches), but that doesn’t mean it’s safe or advisable. Here’s what actually happens, the risks involved, and the few situations where it might be acceptable.
Short Answer
Generally no — it’s not recommended. A smaller blade reduces your cutting depth, can prevent the blade guard from functioning properly, and may cause the blade to sit below the table on table saws. The only acceptable scenario is a very small difference (e.g., 160mm blade in a 165mm saw) where the guard still operates correctly.
What Happens When You Use a Smaller Blade
When you fit a blade that’s smaller than your saw’s rated diameter, several things change:
- Reduced cutting depth — Each 10mm smaller in diameter means roughly 5mm less maximum cutting depth. A 150mm blade in a 165mm saw loses about 7-8mm of cutting depth.
- Blade guard may not function — The lower blade guard on a circular saw is designed to retract as the blade meets the workpiece. With a smaller blade, the guard may not make proper contact and could jam or fail to retract.
- Different blade speed at the rim — A smaller blade has lower rim speed at the same RPM, which can affect cut quality and increase heat build-up.
- On table saws: blade may sit below the table surface — This is the most dangerous scenario. Never use a significantly smaller blade on a table saw.
When It Might Be Acceptable
There is one common scenario where a slightly smaller blade is widely accepted: using a 160mm blade in a 165mm saw. This is a very small difference (just 5mm in diameter, or 2.5mm less cutting depth) and the blade guard will still function normally on most saws. Many woodworkers do this with Festool TS 55 blades (which are 160mm) in standard 165mm cordless saws — the quality of Festool blades makes the tiny depth trade-off worthwhile.
Key rule: If the diameter difference is more than 5-10mm, don’t do it. If the blade guard doesn’t function properly with the smaller blade, don’t do it. And never use a smaller blade on a table saw or mitre saw.
Related guides: Circular Saw Blade Sizes | Bore Sizes Guide | Saw Blade Compatibility Guide
