Marble and Natural Stone: What Can You Do on a CNC?
"Can marble be cut?" is one of the most frequently asked questions. The short answer: with a desktop CNC such as the Raptorex you can engrave/score marble; cutting or deeply carving marble is not the job of this class of machine. This guide explains what can and cannot be done, and the correct method.
📑 Table of Contents
1. Quick Summary
- Marble is not machined by "removing chips" but by "abrading/scoring". That is why you need diamond tools rather than normal carbide end mills.
- Can be done (Raptorex Pro/Pro V2): text, logo and pattern engraving on small marble plates/plaques — especially with the diamond drag method.
- Can't be done (on this class of machine): cutting a marble slab, deep carving/relief, and working granite or quartz. Those are jobs for special high-torque, water-cooled stone CNCs.
- Two critical requirements: a diamond tool + dust/water management. Marble dust wears down the machine's rails and leadscrews; don't try it without protecting the machine.
- Expectation: the engraving result is not "carving" but a fine/scored line. On white marble the score stays light-colored; paint/fill may be needed for contrast.
Know this first
Marble dust is abrasive and alkaline. Dust from dry engraving gets into the machine's ways and leadscrews, ruining its precision; inhaling it is also harmful to your health. Marble work makes machine-protection measures mandatory (see Section 5).
2. The Stone Family: Marble vs. Granite
Before discussing whether marble is machinable, we need to separate stones by hardness. When people say "stone CNC", they are actually dealing with materials of very different difficulty:
| Stone | Hardness | CNC machinability | Desktop CNC (Raptorex)? |
|---|---|---|---|
| Marble, limestone | Soft (~Mohs 3–4) | Engraving + light carving possible (diamond bit + water) | Engraving yes, carving limited |
| Slate, soapstone | Medium-soft | Engraving suitable; mind the layered structure | Engraving yes |
| Granite | Hard (~Mohs 6–7) | Requires an industrial stone CNC + water cooling | No |
| Quartz / quartzite, ceramic, tile | Very hard / abrasive | Industrial equipment required | No |
Why?
Granite and quartz are dense, abrasive materials that rapidly wear out even diamond abrasives; their cutting forces and vibration also demand special stone machines with cast-iron frames and 5–15 kW water-cooled spindles. The Raptorex spindle (180 W – 2.3 kW, air-cooled) and frame were not designed for this load — attempting it will damage the machine.
3. What Can / Can't Be Done on These Machines?
| Job | Result | Requirements |
|---|---|---|
| Text, logo and pattern engraving on small plates / plaques / tiles (diamond drag) | Doable | Diamond drag pen, fixed Z, dust control; Pro/Pro V2 recommended |
| Shallow rotary-bit engraving / fine scoring (diamond V/burr) | Limited, possible | Diamond bit, low spindle speed, very shallow passes, wet environment + machine protection |
| Cutting / drilling a marble slab | No | Requires a water jet, a diamond saw or a large stone CNC |
| Deep carving / 3D relief / embossing | No | Requires a special high-torque, water-cooled machine |
| Working granite, quartz or ceramic | No | Industrial-class equipment |
The Mini series?
The Mini V2/V3 (180–500 W) struggle with marble engraving; their low torque and light frame mean "wobbly lines" with a diamond drag pen and clogging risk with a rotary bit. If you are considering marble engraving, the Pro or Pro V2 is the right choice.
4. The Right Tool: Diamond Bits
Marble dulls carbide bits instantly. The tools used for stone work are diamond-abrasive tools. On a Raptorex there are two basic methods:
Method A — Diamond drag — Recommended
- It is not a rotating bit but a diamond point in a spring-loaded / adjustable-pressure pen. The spindle doesn't spin; the point engraves the marble by scoring it at a fixed depth/pressure.
- It is the safest and cleanest method: little dust, very low force, no strain on the machine.
- Ideal for fine text, logos and photo-scan (dot/line art) engraving. It is the standard for the desktop work of headstone and plaque workshops.
- The tool mounts not in the collet but in a separate drag pen holder (with a 90° conical diamond point).
Method B — Rotary diamond bits (V/burr) — cautious, limited
- Diamond-coated V-groove or ball bits; the spindle turns at a low speed and the tool abrades with very shallow passes.
- Force and dust are greater; a wet environment + machine protection are a must.
- On marble, limited use is recommended with passes no deeper than 0.1–0.5 mm. Going deeper = risk of breakage and machine wear.
Don't touch marble with a carbide bit
Normal end mills (including those intended for aluminum/wood) dull within seconds on marble and, by trying to "cut" the material, can chip the edge. Stone work is only done with diamond-abrasive tools.
5. Water and Dust Management
Marble work has two invisible dangers: abrasive dust and heat. If neither is controlled, both the job and the machine suffer.
- Why water? Water prevents the diamond bit from overheating, washes away the stone slurry and keeps the dust down. A diamond bit run dry "glazes" and dulls quickly.
- How to apply water on a Raptorex? The machine's spindle is air-cooled and its electronics are not sealed against water. So deliver the water to the cutting point as a fine drip/spray; don't splash water on the spindle, control board or motors. (The liquid cooling module's tank can be used for this; the spray nozzle is mounted next to the spindle.)
- Dust control: if you are not using water, at least remove the dust right away with vacuum / wet cleaning. Collect dry dust with a damp cloth rather than sweeping it (fine dust gets into the air).
- Protect the machine: cover the area around the engraving zone and under the table with plastic/protective sheeting; lubricate the rails and leadscrews frequently; after the job, clean the machine with air + a damp cloth.
Health
Marble dust (which may contain crystalline silica) is harmful to the lungs when inhaled. On dusty jobs, wear an FFP2/FFP3 mask, ventilate the workshop and wear safety glasses.
6. Parameters (Starting Points)
The values below are safe starting points for the Raptorex Pro/Pro V2. The rule in stone work is "little and slow"; don't make big changes all at once.
Diamond drag (scoring engraving)
| Parameter | Value |
|---|---|
| Spindle | Doesn't spin (M5 / off) — the pen works by pressure |
| Feed (F) | 300–800 mm/min (depending on machine rigidity; lower it if you see vibration) |
| Z depth / pressure | By the pen point's spring pressure; 0.1–0.3 mm in Z (adjusted according to the point) |
| Cooling | Usually dry is fine; light moisture on intensive work |
Rotary diamond bit (shallow scoring) — advanced
| Parameter | Value |
|---|---|
| Spindle speed (S) | 8,000–10,000 rpm (the machines' 18,000 max is too much for stone — lower the speed) |
| Feed (F) | 200–500 mm/min |
| Axial depth | 0.1–0.3 mm/pass (never go deeper) |
| Plunge | Very slow (50–100 mm/min) or with a ramp; a vertical plunge breaks the bit |
| Cooling | Required — a fine water spray at the cutting point |
For contrast
On marble, the scored line can stay light or the same color. To make the engraving stand out, fill the line with fill paint / a marble pen and wipe off the excess for contrast — the standard method of headstone workshops.
7. Workholding and Part Preparation
- Choose a small piece: the plaque/tile size must fit the machine's work area and the weight must not strain the table (e.g. small plates up to ~20×30 cm are ideal on the Pro).
- Flat and thick: use a piece with a level surface and full bottom contact. On curved/bowed marble the line depth will be inconsistent.
- Workholding: marble is heavy but can shift. Clamp it with double-sided tape + wooden wedges/clamps at the edges; the part must not be supported over a void (cracking risk).
- Surface cleaning: start on a dry surface free of dust and oil.
- Zeroing: set the surface correctly with a probe or a paper test; on stone a Z error means a broken bit or a deep scratch.
Part kick-out
A poorly secured piece of marble can kick out when the pen/bit catches, or break the bit. Never skip the workholding.
8. Your First Marble Engraving Trial
- Scrap piece: always do your first trial on a waste/cheap piece of marble.
- Set up the diamond drag: mount the diamond drag pen in the drag holder; switch the spindle off (M5). Set Z very close to the surface and start with light spring pressure.
- Draw a simple test: try a straight line + a piece of text (F ~500 mm/min). If the line is faint, increase the pressure; if it vibrates, reduce the feed.
- Lock in the depth: once you get a consistent line, note that Z/pressure value and use the same on the real job.
- Move to the real piece: secure the part, clean the surface, set the reference and start the engraving.
- Add contrast (optional): make the engraving stand out with paint/fill, then wipe off the excess once dry.
- Clean the machine: after the job, remove the dust with a damp cloth and lubricate the rails/screws.
Example G-code tip (diamond drag)
The spindle is off and the pen travels by pressure:
M5 · G0 Z0.2 · F500 · (engraving path) · raise Z when done
9. FAQ
- Can marble be cut on a CNC? With a desktop CNC, marble is not cut; it is engraved/scored. Cutting slabs requires a water jet or a special stone CNC.
- Can granite be machined? No — desktop CNCs, including the Raptorex, are not suitable for granite (hardness, vibration and cooling requirements).
- Can I engrave a name on a marble plaque? Yes — with the diamond drag method, text/logo engraving can be done on the Pro/Pro V2; small, flat plaques are ideal.
- Which bit? For diamond drag, a conical diamond drag pen; for rotary scoring, diamond-coated V/burr bits. Don't use carbide/HSS.
- What if I try a normal end mill? It won't work: carbide dulls instantly on marble, and if you force it to "cut", the edge chips. Stone work demands diamond abrasives.
- Does dust damage the machine? Yes — marble dust wears down the rails/leadscrews. Suppress the dust (moisture), and clean and lubricate the machine after the job.
- Can photo/portrait engraving be done? Grayscale (dot) photo engraving can be attempted with a diamond drag; the result depends on machine precision and the material. Start with a simple logo or text.
References
References and further reading
- CNCSourced — How to CNC Engrave on Granite, Marble, or Any Stone (diamond drag, bit and speed recommendations)
- AccTek CNC — How to Carve Stone with a CNC Router? (stone CNC requirements, water cooling)
- CNC Stone Routing Guide — Tools, Parameters & Workflow (marble/granite tool and spindle tables)
- Granite CNC Engraving Settings Guide — YIHAICNC (spindle/feed/plunge limits)
Note: The values here are safe starting points. Small adjustments may be needed depending on stone density, bit type and machine model. Always do your first trial on a scrap piece.
Related topics
🔗 Manual / Spray Cooling — for light moisture/cooling during engraving.
🔗 Preparing and Managing Cutting (Coolant) Fluid — if you will use a tank system.
Thinking about marble engraving?
Tell us which piece (plaque/tile) you will work on and at what size; our technical team will guide you to the right machine and diamond tool.