Quick Answer

Cut curves and circles in concrete by first marking the line, then using a ring saw for tight radii, a walk-behind saw with a pivot for long arcs, or a diamond wire saw for large openings such as floor drains and manholes. Never force a circular saw around a curve — it binds, wanders, and chips the edge. A pilot hole at the start and a shallow starter cut keep the blade on line.

When You Need a Curved Concrete Cut

• Floor drains and sink openings: round or oval holes in slabs.
• Curbs and planters: arc-shaped joints in hardscape.
• Manhole and sewer access: removing circular covers in existing concrete.
• Decorative saw cuts: compass joints, curves in stamped or scored driveways.
• Stair openings and curved wall penetrations.

Pick the Right Tool for the Radius

Cut shape	Best tool	Why
Tight radius, small circle (10–40 cm)	Ring saw	Open center starts inside a hole; thin rim follows curves
Medium arc, straight start plus curve	Handheld saw with pivot guide	Cheaper; you control feed direction
Long shallow arc (joints, curbs)	Walk-behind floor saw	Weight and stability; good depth control
Large opening (60 cm+), rebar	Diamond wire saw	No blade-diameter limit; cuts rebar cleanly

The ARIX Ordered-Segment Diamond Ring Saw Blade (JOY-ARX-RS) is the go-to tool for interior circular work: its open center drops over a pilot hole, and the ordered segments keep it true on tight turns.

Step-by-Step: Cutting a Circle in a Slab

1. Mark it: trace the circle on the concrete; check dimensions against the fitting (drain, pipe, liner).
2. Drill a pilot hole: a core-bit or hammer-drill hole just inside the line gives the blade or wire a start.
3. Starter cut: plunge a shallow guide channel along the line, then follow it with the ring saw to full depth.
4. Cut the arc: feed slowly, let the blade follow the curve, and keep the saw base flat. Do not twist sideways — that is how segments crack.
5. Support the cut-out: the concrete disk inside the circle drops once free; support it or cut it into pieces before it falls.
6. Clean up: feather the edge with a grinder if needed; keep water running on wet cuts.

Long Arcs and Big Openings

For arcs longer than a meter, a walk-behind saw on a curved guide rail stays truer than a handheld tool. For large openings with rebar, a Diamond Wire Saw for Concrete — JOY-WS-C removes the section without the diameter limits of a circular blade and cuts through steel cleanly. On straight runs that turn into curves, keep a Concrete and Asphalt Saw Blade (Laser Welded) — JOY-CA-LW ready for the transition, and slow the feed as you enter the arc.

Common Mistakes

• Twisting the blade: a circular blade cuts in one plane; sideways pressure cracks segments and warps the core.
• No pilot hole: plunge-starting a circle wanders and chips.
• Too-deep first pass: shallow starter cuts, then follow at depth — full-depth plunge on a curve binds.
• Letting the cut-out drop: unsupported pieces crack the surrounding slab when they fall.

Frequently Asked Questions

Q: Can I cut a circle with a regular angle-grinder blade?

A: For small holes yes, but a ring saw is safer and cleaner: it starts inside the hole without plunge-cutting the whole disk from the surface, and its open center avoids trapping the blade.

Q: What size pilot hole do I need for a ring saw?

A: Just larger than the ring's inner diameter, usually 20–35 mm. Drill it inside the scored line so the blade follows your mark.

Q: How do I cut a curve through rebar?

A: A diamond wire saw is the practical answer for large reinforced openings. For small circles, a ring saw with welded segments will cut occasional rebar if you slow the feed and keep water on.

Q: Can I saw-cut a curve in fresh green concrete?

A: Yes, within the early-entry window — but use an early-entry saw and keep the arc shallow; green concrete is softer and the blade glazes if you force it.

Conclusion

Curved and circular cuts come down to matching the tool to the radius: ring saw for tight holes, pivot-guided saw for medium arcs, walk-behind for long curves, wire saw for large reinforced openings. Mark carefully, pilot the start, and never twist the blade. With the right setup, openings for drains, manholes, and decorative joints come out true and clean — and the segments keep their full life because the cut stayed in one plane.