Quartz Cold Processing for Custom Fused Silica Components

Quartz cold processing (also called cold working or CNC diamond machining) is a specialized manufacturing method that removes material from high-purity fused silica at room temperature using diamond-impregnated tools on precision CNC equipment. Because fused silica is extremely hard and brittle, conventional cutting tools cannot be used. Material is removed by controlled abrasive grinding, producing accurate geometries, sharp features and high surface quality without the thermal stresses associated with flame working.
Unlike thermal processing, which softens and reshapes the quartz structure through heat, cold processing is a subtractive method. It is ideal for creating holes, slots, threads, stepped diameters, flat surfaces, precise lengths and complex milled features that cannot be achieved by flame forming alone. After machining, parts may undergo mechanical polishing, lapping or optical finishing, and stress-relief annealing when required to ensure long-term dimensional stability.

FGQuartz provides a full range of quartz cold processing services. Each process is performed on precision CNC equipment using diamond tooling, controlled coolant systems and experienced technicians to ensure purity, dimensional accuracy and structural integrity.

CNC turning and cylindrical grinding are used to produce accurate outer and inner diameters, stepped profiles, tapers and precise lengths on quartz tubes and rods.
Processing Capabilities:
• Outer diameter (OD) grinding and turning
• Inner diameter (ID) grinding
• Stepped diameters and shoulders
• Tapers and conical sections
• Precision length cutting and facing
• Chamfering and edge finishing
How It Works:
1. The quartz tube or rod is mounted on a precision CNC lathe or cylindrical grinder.
2. Diamond wheels or tools remove material under controlled feed rates and coolant flow.
3. Multiple passes ensure dimensional accuracy while minimizing subsurface damage.
4. Final inspection verifies OD, ID, concentricity and surface finish.
This process is essential for creating precision process tubes, support rods, push paddles and any component requiring tight diameter control.
Typical Applications:
Precision furnace tubes, wafer handling rods, optical support elements and custom cylindrical fixtures used in semiconductor and laboratory equipment.

Multi-axis CNC milling creates complex features such as slots, pockets, grooves, freeform surfaces and contoured geometries that cannot be produced by simple turning or grinding.
Capabilities:
• Slots and keyways
• Pockets and recessed areas
• Freeform and contoured surfaces
• Grooves and channels
• Complex 3D profiles
• Edge profiling and chamfers
Process Advantages:
• High geometric flexibility for non-rotational features
• Consistent accuracy across multiple identical parts
• Ability to machine both flat plates and cylindrical components
• Suitable for wafer boats, fixtures and optical mounts
Milling is performed with diamond-impregnated tools on multi-axis CNC centers. Careful parameter control prevents cracking and maintains surface integrity.
Typical Applications:
Wafer boats with precise slot geometry, custom furnace fixtures, optical mounts, gas injectors and any part requiring complex non-cylindrical features.

Diamond core drilling produces clean through-holes and blind holes in fused silica with controlled diameter, depth and edge quality.
Drilling Capabilities:
• Through holes
• Blind holes
• Countersinks and counterbores
• Multiple hole patterns
• Small-diameter and large-diameter holes
Detailed Process:
1. The component is securely fixtured.
2. A diamond core drill advances under controlled feed and coolant.
3. Hole diameter, depth and position are maintained to tight tolerances.
4. Edges are deburred or chamfered as required.
Proper drilling produces holes free of cracks and chips, essential for vacuum ports, sensor openings and assembly features.
Typical Applications:
Process tubes with side ports, vacuum flanges, optical windows with mounting holes, sensor housings and multi-port chambers. For complex assemblies combining drilled features with welded ports, see our Custom Quartz Glass page.

Precision cutting produces accurate lengths and clean edges on tubes, rods and plates. Edge finishing removes chips and prepares surfaces for assembly or further processing.
Capabilities:
• Straight cutting to precise lengths
• Angle cutting and mitering
• Chamfering and beveling
• Edge rounding and deburring
• Slotting and notching
Cutting is performed with diamond saws or CNC-controlled tools. Proper cooling and feed control minimize micro-cracks and ensure clean edges suitable for sealing or welding.
Typical Applications:
Cut-to-length process tubes, plate blanks, optical substrates and any component requiring accurate overall dimensions and clean edges.

Surface grinding, lapping and optical polishing produce flat, parallel and optically smooth surfaces required for windows, plates and precision interfaces.
Capabilities:
• Surface grinding for thickness and flatness control
• Double-sided grinding and lapping
• Optical polishing to low surface roughness
• Parallelism and flatness improvement
• Removal of machining marks
Process Advantages:
• Achieves tight thickness tolerances
• Produces high optical transparency and low scatter
• Reduces particle generation in clean processes
• Prepares surfaces for coating or sealing
These finishing steps are essential when surface quality directly affects optical performance or process cleanliness.
Typical Applications:
Optical windows, viewports, wafer inspection plates, laser components and any quartz surface requiring optical-grade finish.

Although cold processing generates less residual stress than thermal forming, significant material removal or complex geometries may still require controlled annealing to ensure long-term dimensional stability.
Annealing Process:
1. The component is slowly heated to a carefully controlled temperature below the softening point.
2. The temperature is held for a defined period to allow residual stresses to relax.
3. The part is then cooled at a controlled, slow rate.
Key Benefits:
• Reduced residual stress from machining
• Improved resistance to cracking under thermal cycling
• Enhanced dimensional stability in service
Annealing is applied selectively to heavily machined or large components that will experience temperature cycling in the customer’s process.
Typical Applications:
Precision optical components, large plates, complex milled fixtures and any cold-processed part intended for high-temperature service.

1. Drawing Review — We analyze customer drawings and confirm process feasibility and achievable tolerances
2. Material Selection — Appropriate high-purity fused silica is selected
3. CNC Programming & Setup — Toolpaths are generated and machines are prepared with diamond tooling
4. Cold Processing — Turning, grinding, milling, drilling or cutting is performed
5. Surface Finishing — Grinding, lapping or optical polishing is applied where required
6. Annealing (if needed) — Controlled stress relief is carried out
7. Inspection — Dimensional, visual and surface quality inspection
8. Cleaning & Packaging — Final cleaning and secure packaging for shipment
This workflow ensures consistent quality from prototype to production quantities.

What is quartz cold processing?
It is a room-temperature manufacturing method that removes material from fused silica using diamond tooling on CNC equipment to achieve precise dimensions and complex features.
What is CNC diamond machining used for?
It produces holes, slots, threads, stepped diameters, flat surfaces and tight-tolerance geometries that cannot be created by flame forming alone.
Can fused silica be machined to tight tolerances?
Yes. It depends on the geometry, dimensions, and surface finish requirements. For critical features, tighter tolerances can be achieved.
What is the difference between cold processing and thermal processing?
Cold processing removes material mechanically. Thermal processing softens and reshapes or joins the quartz with heat. Most complex parts use both methods.
Why are diamond tools required for quartz machining?
Fused silica is extremely hard and brittle. Only diamond-impregnated tools can effectively remove material without rapid tool failure or excessive cracking.
Can you manufacture quartz components from drawings?
Yes. We regularly manufacture according to customer drawings (DXF, STEP, PDF) and provide feasibility feedback before production.

Submit your drawings and requirements. FGQuartz provides complete quartz fabrication solutions — from material preparation through CNC diamond machining, precision finishing and final inspection.
Whether you need precision tubes with complex features, optical windows, wafer boats, machined plates or multi-feature fixtures, we can manufacture them according to your specifications.