Cutting quartzite on a CNC bridge saw

Quartzite properties that matter for cutting

Quartzite is metamorphosed sandstone: quartz grains recrystallized into a dense, interlocked rock. It is harder than glass and does not etch in acid. For the saw, that means the highest blade wear and the lowest feed rates of any natural stone in the shop.

Slabs are usually 20 mm or 30 mm (3/4 in or 1 1/4 in) thick, often resin-treated on the face and mesh-backed where the stone has fissures.

The first problem is the label. Building Stone Magazine reports that marbles and sandstones are regularly sold as quartzite. A stone sold as “soft quartzite” is usually a marble. Test before you program the job: a true quartzite scratches a glass tile, and a knife point leaves no scratch you can feel with a fingernail. If the stone fails the glass test, cut it with marble or granite parameters. If it passes, use quartzite parameters, or you will glaze blades and burn edges.

Blade selection

Use a blade made for quartzite. Quartz wears the diamond flat instead of exposing new crystals, so quartzite blades use a soft bond that wears away and keeps fresh diamond at the cutting face. A granite blade with a harder bond will glaze on true quartzite: the segments go shiny, feed drops, motor load rises and the cut starts to wander. Dressing the blade on an abrasive block reopens a glazed segment, but a correctly bonded blade needs it less often.

Smaller blades are the norm. Ø350–400 mm (14–16 in) blades are stiffer and load the motor less than larger blades at the same cutting depth. That matters because hard stone deflects a blade more.

Blade speed and feed rate

Quartzite runs at the lowest peripheral speed of the common stones. Alpha gives 25–28 m/s and recommends the low end of the range if the saw has variable speed:

Blade diameter	Quartzite rpm (Alpha)
350 mm (14 in)	1,400–1,500
400 mm (16 in)	1,200–1,300
450 mm (18 in)	1,100–1,200
500 mm (20 in)	1,000–1,100

Published feed rates:

• Alpha chart: 1.8 m/min in 12 mm, 1.0 m/min in 20 mm and 0.66 m/min in 30 mm straight cuts.
• Spider II: 0.9–1.5 m/min (3–5 ft/min) on quartzite, against 1.8–3.7 m/min on granite with the same blade.
• DIABU Red Eagle: 0.8–1.8 m/min (30–70 in/min) on quartzite, against 2.5–4.1 m/min on granite.
• ZENESIS quartzite blade: the seller reports 1.8 m/min (6 ft/min) on Taj Mahal, a claim for one stone, not a general spec.

The figures agree on one point: quartzite cuts at roughly one third to one half of granite feed. Plan on 0.7–1.8 m/min, set by slab thickness, blade and machine, and confirm by test cut. Budget the job accordingly: a quartzite kitchen takes noticeably longer on the saw than the same kitchen in granite.

Entry, exit and water

Hard stone chips at the exit when the blade pushes through the last few millimeters. Reduce feed at entry and exit, then hold steady feed through the slab. Water flow is critical: quartzite generates more heat per meter of cut than granite, and a short water supply glazes the blade quickly.

Miter cuts

Miters in quartzite are slow but clean if the blade stays true. Alpha halves feed for 45° cuts: 0.5 m/min in 20 mm slabs. Blade deflection shows up as a curved or uneven miter face, which makes a visible glue line. On a 5-axis CNC bridge saw the A-axis head tilt and a rigid bridge keep the miter angle consistent along the full length. See mitered edges.

Sink cutouts and core drilling

Core bits wear fast in quartzite. Run the core bit with full water and moderate down-feed, and check the bit for glazing between holes. Cutouts with radius corners are slow work for a finger bit; many shops cut the straight sides with the blade, core drill the corners, and finish the radius by hand or on a CNC work center.

How machine features reduce defects

• Rigidity: Hard stone exposes any flex in the bridge or head. A heavy monoblock frame and backlash-free drives keep the cut straight at low feed.
• Load-based feed control: A CNC that reads spindle load can slow down when the blade starts to glaze, before the cut wanders.
• Slab thickness reader: Sets depth per slab, so the blade does not cut deeper into the worktable than needed, which saves blade wear on an expensive stone.
• Vacuum manipulator: Moves heavy 30 mm pieces between cuts without hand handling.

Silica and wet cutting

Quartzite is close to pure crystalline silica. The OSHA and NIOSH hazard alert lists quartzite at 95% or more and names quartzite and certain engineered stones as having the highest silica levels. Quartzite dust is as hazardous as engineered quartz dust. Under Cal/OSHA Section 5204 it is natural stone above 10% silica, so cutting is a high-exposure trigger task. Wet methods are mandatory and dry cutting and dry sweeping are prohibited. California also requires respirators (a PAPR, with some exceptions) and air monitoring against an action level of 25 µg/m³. Use the same controls for quartzite as for engineered quartz.

Next step

Send us a slab of the quartzite you cut most and we will run a feed-rate and blade-wear test on it. Request it through request a configuration or watch it on a factory visit.