Cutting porcelain and sintered stone on a CNC bridge saw

Material properties that matter for cutting

Porcelain slabs and sintered stone are fired, not bonded with resin. They are hard, dense, almost non-absorbent and brittle. Large-format slabs are made from about 3 mm to 30 mm thick; 6 mm and 12 mm are common for cladding and countertops, 20 mm for countertops without a mitered build-up. Many products have a printed or glazed decoration that does not run through the body, so a chipped edge or miter shows the base color.

Two properties drive the cutting method:

• Residual tension. Slabs carry stress from firing. A cut that releases it unevenly can crack the slab or bend the kerf, and the crack often appears near the end of a cut or at an inside corner.
• Brittleness. Porcelain does not deform before it fails. Vibration, an unsupported section or a fast exit chips the edge or breaks the piece.

Blade selection

Use a continuous rim blade made for porcelain or sintered stone. The Della Terra fabrication manual states that granite, marble or quartz blades are not suitable. Segmented granite blades hammer the edge at each gap and chip the surface. Porcelain blades use a thin rim and a bond made for hard ceramic: the Nikon BMF is a 10 mm continuous rim, and the Weha sintered stone blade uses very closely spaced segments on a 10 mm rim to the same effect.

For a 12 mm slab, Della Terra gives a blade diameter of 300–500 mm (12–20 in), depending on the machine. Smaller blades are stiffer and are often preferred for miters on thin slabs.

Blade speed and feed rate

Peripheral speed for porcelain is lower than for marble. Amastone gives 40–50 m/s for porcelain stoneware; Alpha gives 32–45 m/s. Typical rpm: 1,700–2,500 for a Ø350 mm (14 in) blade, lower for larger blades. Tenax gives 2,150–2,500 rpm on Ø360 mm and 1,900–2,200 rpm on Ø410 mm.

Feed rate depends mainly on slab thickness:

Slab thickness	Tenax (straight)	Alpha (straight / miter)	Weha sintered (straight)
3–4.9 mm	1.5–1.8 m/min
5–9 mm	1.2–1.5 m/min
10–12 mm	1.0–1.2 m/min	1.7 / 0.85 m/min	1.0–1.4 m/min (10–15 mm)
13–20 mm	0.8–1.0 m/min	1.0 / 0.5 m/min (20 mm)	0.6–0.8 m/min (20 mm)
30 mm		0.7 / 0.35 m/min	0.5–0.6 m/min

The sources broadly agree: about 1.0–1.7 m/min for 12 mm and 0.6–1.0 m/min for 20 mm. The right figure depends on the blade, the product (sintered stone is often harder than porcelain) and machine rigidity. Start at the low end and increase by test cut.

Entry and exit feed reduction

Most chipping happens where the blade enters and leaves the slab. Tenax recommends reducing feed by 40–50% at entry and exit. Della Terra recommends starting at 50% feed, running 100% through the middle and exiting at 50%. On a CNC bridge saw, program this as a ramp on every cut. Set blade depth so the blade only just breaks through the bottom of the slab.

Detensioning cuts

Before cutting parts, trim 10–20 mm (3/8–3/4 in) from every edge: both long sides first, cut in the same direction, then both short sides. This releases residual tension and squares the slab. Della Terra makes this the first step of fabrication. Skipping it is a common cause of cracks during later cuts.

Water and support

Cut wet with water on the leading edge, on both sides of the blade. Support the slab flat; Della Terra recommends a dense foam backer between slab and worktable to damp vibration, and suction cups placed evenly under the slab around cutouts.

Miter cuts

Porcelain miters are in demand because a 12 mm slab with a mitered apron looks like a 40–60 mm stone top. They are also where porcelain fails most often. Tenax recommends 40% lower feed at 45°; Alpha halves straight-cut feed. Della Terra suggests cutting just over 45° to leave room for adhesive at the back of the joint. On a 5-axis CNC bridge saw the A-axis head tilt cuts the miter with the slab flat and supported, and a rigid head prevents the blade wobble that causes a chipped miter tip. See mitered edges.

Sink cutouts and core drilling

Never cut sharp inside corners in porcelain. Della Terra’s procedure:

• Core drill each corner with a wet diamond core bit, minimum 6 mm (1/4 in) radius.
• Core bit speed 2,000–3,000 rpm, feed 20–30 mm/min, dropping to 5 mm/min for the first and last 2 mm.
• Join the holes with a finger bit along a smooth path.
• Keep cutouts at least 50 mm (2 in) from the slab edge and from each other.

On a bridge saw this needs the electrospindle option; without it, core drill and finish the cutout on a separate machine.

How machine features reduce defects

• Rigidity and smooth axis motion: Porcelain shows every vibration as edge chipping. A heavy monoblock frame and servo drives that ramp feed smoothly matter more here than on any other material.
• Programmed feed ramps: The CNC applies entry and exit reduction on every cut, which manual saws depend on the operator to do.
• Vacuum manipulator: Lifts thin, brittle pieces evenly instead of sliding them across the worktable.
• Slab thickness reader: Sets blade depth to just break through.

Silica and regulation

Porcelain contains crystalline silica; WorkSafe Victoria lists it at 14–18%. Cut wet. In Australia, sintered stone and porcelain products without resin are excluded from the engineered stone ban that took effect on 1 July 2024. In California, Section 5204 states that fired ceramic and porcelain tiles and panels are not “artificial stone”, but cutting any silica-containing product above 10% crystalline silica is still a high-exposure trigger task under the same rule. Plan for wet methods and the full set of controls.

Next step

Send us your porcelain or sintered stone slabs and edge details and we will run a straight and miter cutting test, with entry and exit feeds recorded. Request it through request a configuration or see it on a factory visit.