FAQ Section

CNC (Computer Numerical Control) machining is a subtractive manufacturing process in which computer-controlled cutting tools remove material from a solid workpiece to produce a finished part. The machine follows a programmed toolpath with extreme precision, allowing the same geometry to be reproduced consistently across hundreds or thousands of parts. CNC machining is used to produce components from metals, plastics, and composites for aerospace, defense, medical device, and industrial applications.

Standard CNC milling and turning routinely hold tolerances of ±0.005". High-precision CNC machining achieves ±0.0002" or tighter on critical features. Precision grinding can reach ±0.0001" on bearing journals and sealing surfaces. The achievable tolerance depends on part geometry, material, feature type, and surface finish requirements. Delta Machine & Tool machines to tolerances as tight as ±0.0001" depending on the process and application.

3-axis CNC machining moves the cutting tool along X, Y, and Z linear axes — effective for prismatic parts with features accessible from one or two directions. multi-axis machining adds two rotational axes, allowing the cutting tool to approach the workpiece from virtually any angle. Simultaneous multi-axis machining produces complex contoured surfaces, compound-angle bores, and undercut features in a single setup — eliminating re-fixturing and improving positional accuracy. Essential for aerospace structural components, turbine-related parts, and any geometry too complex for 3-axis platforms.

Swiss screw machining (sliding headstock turning) is a CNC turning process designed for small-diameter, high-complexity parts. A sliding headstock advances bar stock through a guide bushing that supports the material at the cutting zone — eliminating deflection on long, slender parts. This enables extremely tight tolerances (often ±0.0002") at high volumes. Widely used for medical implant screws, aerospace connector pins, hydraulic fittings, and small-diameter precision components.

Precision grinding is an abrasive machining process used when tighter tolerances and finer surface finishes are required than conventional CNC cutting can achieve. Surface grinding produces flat reference-quality planar surfaces. Cylindrical grinding produces precise outer diameters on shafts. Centerless grinding produces consistent diameters without requiring centers. Grinding can hold ±0.0001" and achieve surface finishes as fine as 8 Ra — essential for bearing journals, sealing surfaces, and hardened components processed after heat treatment.

Turn-mill machining (mill-turn or multitasking) combines CNC turning and CNC milling on a single machine platform. Live tooling allows milling, drilling, and tapping while the part is still in the lathe chuck — eliminating transfer to a separate mill, reducing setup time, minimizing positional error, and shortening total lead time. Particularly efficient for complex shaft components requiring both turned diameters and milled cross-features. See Delta's CNC turning page for details.

GD&T (Geometric Dimensioning and Tolerancing), governed by ASME Y14.5, is a standardized engineering drawing language defining allowable variation in the shape, size, orientation, and location of part features. GD&T symbols and feature control frames communicate design intent precisely — including flatness, cylindricity, true position, concentricity, and profile tolerances. It allows tightest tolerances only on functionally critical features while giving latitude on non-critical dimensions, improving manufacturability and reducing cost. Our DFM team reviews GD&T callouts on every new part number.

Ra (Roughness Average) is the arithmetic average of surface profile deviations — the most common surface finish parameter, measured in microinches (μin) or micrometers (μm). Lower Ra = smoother surface. Rz (Mean Roughness Depth) measures the average of the five highest peaks and five deepest valleys — more sensitive to extreme events like scratches or burrs. Ra is adequate for most specifications; Rz is used when maximum peak-to-valley height is functionally critical, such as on sealing surfaces or precision optical components.

AS9100 is the internationally recognized Quality Management System (QMS) standard for aerospace and defense manufacturing, based on ISO 9001 with additional requirements covering risk management, configuration control, key characteristics, and supply chain management. AS9100 Rev D is the current revision. Certified suppliers have demonstrated that their quality processes meet rigorous aerospace OEM requirements. Delta Machine & Tool is AS9100 Rev D certified.

A FAIR (First Article Inspection Report), governed by AS9102, is a complete documentation package produced for the first production part off a new setup. It provides objective evidence that the manufacturing process can produce a conforming part to all engineering drawing requirements. A FAIR includes a ballooned drawing with every dimension and callout assigned a balloon number, actual measured values for each characteristic, material certifications, process certifications, and applicable notes. Required by most aerospace and defense OEMs before a new part number enters production. See Delta's CMM inspection service.

A Certificate of Conformance (CoC) is a document affirming that the parts being shipped conform to all applicable engineering drawing requirements and quality standards. It references the part number, revision level, purchase order, lot number, quantity, and applicable material or process certifications. Delta Machine & Tool includes a Certificate of Conformance with every shipment as standard practice — no request required.

Material traceability links every finished component back to its original raw material lot — including the heat number, mill certificate, and chemical and mechanical test report (MTR). For aerospace and defense programs, full traceability is a contractual requirement: if a non-conformance is discovered in the field, traceability allows all parts from the same material lot to be identified and quarantined. Delta sources all materials from AS9100-approved suppliers, collects mill certs and MTRs on every order, and maintains these records for the life of each program.

DFM (Design for Manufacturability) is an engineering review of customer drawings before production to identify features that will be difficult, expensive, or risky to manufacture. It examines tolerance specifications (identifying any tighter than the process can reliably hold), feature accessibility (deep pockets, thin walls, undercuts), material and process compatibility, and inspection feasibility. Early DFM reduces first-article failure rates, lowers unit cost, and compresses program lead times. Delta performs DFM review on every new part number at no additional charge.

CNC machining processes a wide range of materials including aluminum alloys (2024, 6061, 7075), titanium alloys (Ti-6Al-4V), stainless steels (303, 304, 316L, 17-4 PH, 15-5 PH), nickel superalloys (Inconel 625, 718, Waspaloy, Hastelloy), alloy and tool steels (4130, 4140, 4340, H13, D2), brass and bronze (C360, C932), copper, and engineering plastics (PEEK, Delrin, Nylon, UHMW). Material selection is driven by strength, weight, corrosion resistance, and temperature requirements. See Delta's full materials page.

Inconel (most commonly 625 and 718) is a nickel-based superalloy known for exceptional strength, high-temperature performance, and corrosion resistance — widely used in aerospace propulsion and chemical processing. Inconel is notoriously difficult to machine because it work-hardens rapidly during cutting, has low thermal conductivity (concentrating heat at the cutting edge), and remains extremely strong at elevated temperatures. These properties accelerate tool wear and require specialized tooling, conservative cutting parameters, and aggressive coolant strategies. Delta has extensive experience machining Inconel 625 and 718. See the materials page.

Ti-6Al-4V (Grade 5 titanium) is the most widely used titanium alloy — approximately 50% of all titanium production. An alpha-beta alloy with ~6% aluminum and ~4% vanadium offering outstanding strength-to-weight ratio, excellent corrosion resistance, and good fatigue life to ~600°F. Used extensively in aerospace structural components, aircraft engine parts, and medical implants. Ti-6Al-4V ELI (Extra Low Interstitial) is a purer variant with improved fracture toughness specifically for medical implant applications. See Delta's materials page.

PEEK (Polyether ether ketone) is a high-performance thermoplastic with exceptional mechanical strength, chemical resistance, and biocompatibility. Its elastic modulus is close to cortical bone, reducing stress shielding in orthopedic implants. PEEK is radiolucent (invisible on X-rays), allowing physicians to monitor tissue healing without interference. It is sterilizable by autoclaving, gamma radiation, and ethylene oxide. Widely used for spinal fusion cages, orthopedic trials, dental implant components, and surgical instrument handles. CNC machining PEEK requires careful process control to manage heat buildup on tight-tolerance features.

Common surface finishes for CNC machined parts: aluminum — Type II anodizing (MIL-A-8625 Type II) for corrosion protection, Type III hard anodize for wear resistance, chromate conversion coating (Alodine, MIL-DTL-5541) for corrosion protection and paint adhesion. Stainless steel and titanium — passivation (ASTM A967 / AMS 2700). General — electroless nickel plating for a hard, uniform coating on ferrous and non-ferrous parts. Heat treatment (stress relief, aging, annealing) per AMS specifications. Delta coordinates all surface finishing through its AS9100-approved processor network.

Passivation is a chemical treatment applied to stainless steel components to remove free iron and surface contaminants introduced during machining, and to promote a dense, stable chromium oxide layer that maximizes corrosion resistance. Performed per ASTM A967 or AMS 2700. Required when stainless steel parts will be exposed to corrosive environments, when biocompatibility is needed (medical devices), or when machining may have compromised surface corrosion performance. It does not change part dimensions or appearance. See Delta's surface finishing service.

Anodizing converts aluminum's surface into a hard aluminum oxide layer. Type II (standard) anodizing per MIL-A-8625 produces a 0.0002–0.001" coating for corrosion protection and dyeing. Type III hard anodizing produces a much thicker, denser coating (0.001–0.002") that is significantly harder (~60–70 Rockwell C equivalent) and more wear-resistant. Type III is specified for parts subject to sliding wear, high contact loads, or abrasive environments — hydraulic actuator parts, valve bodies, aerospace structural joints. Delta coordinates anodizing through its AS9100-approved processor network.

Most CNC machining quotes are delivered within 24–48 business hours of receiving complete engineering drawings and program requirements. Complex multi-component assemblies may take slightly longer. Providing complete information upfront — engineering drawings (PDF, DWG, or STEP/IGES), material specification, quantity, target delivery date, and quality requirements (FAIR, CoC) — allows accurate, fast quoting without back-and-forth. Request a quote from Delta here.

The most useful file formats for CNC machining quotes are: PDF (2D engineering drawing with all dimensions, tolerances, and notes), DWG or DXF (2D CAD drawing files), and STEP (.stp/.step) or IGES (.igs/.iges) for 3D CAD models. STEP is preferred for 3D geometry due to universal CAD compatibility. Providing both a PDF drawing and a STEP file gives the most complete picture of your design intent, enabling more accurate quoting and better DFM feedback. Upload your files here.

Lead times vary based on part complexity, material availability, quantity, and quality documentation requirements. Prototype/first article parts typically require 2–4 weeks from drawing approval. Production orders for medium-complexity parts generally run 4–8 weeks. Programs requiring FAIR/AS9102 documentation may require longer lead times for the first article phase. Discussing delivery requirements early allows Delta's production scheduling team to plan material procurement, machine time, and secondary operations to meet your target dates. Delta sustains a On-time delivery rate across all programs.

Visit the Request a Quote page and upload your engineering drawings (PDF, DWG, STEP, or IGES) along with your material specification, quantity, target delivery date, and quality requirements. You can also email drawings directly to admin@deltamachineandtool.com. Delta's engineering team reviews every submission and responds with a detailed quote within 24–48 business hours. Delta Machine & Tool is located at 207 Carter Drive, Unit E, West Chester, PA 19382.

In aerospace and defense supply chains, a Tier-1 supplier sells directly to the OEM (Boeing, Lockheed Martin, Raytheon, etc.). A Tier-2 supplier sells to a Tier-1 supplier. Tier-1 status carries greater responsibility: managing its own supply chain, flowing down OEM quality requirements, and delivering dock-ready product meeting all engineering and documentation requirements. Delta Machine & Tool operates as a Tier-1 supplier to aerospace and defense OEMs, managing material, machining, finishing, and documentation under a single quality umbrella.

Single-source manufacturing means one supplier manages the complete workflow — from raw material procurement through machining, secondary operations, assembly, inspection, documentation, and delivery. For customers, single-source reduces purchase orders and supplier relationships, eliminates quality risk introduced when parts transfer between multiple suppliers, simplifies accountability, and compresses total program lead time. Delta Machine & Tool operates as a Tier-1 single-source partner, managing the entire supply chain under its AS9100 Rev D quality management system.

Delta Machine & Tool serves aerospace (structural, avionics, and propulsion components), defense (ground systems, naval, ordnance), medical device (implants, instruments, surgical robotics), industrial OEM (automation, fluid power, robotics), energy (nuclear, oil and gas, renewables), and automotive (performance, EV drivetrain, motorsport) programs. All programs are governed by Delta's AS9100 Rev D quality management system.