Resources
Engineering guides for designing, specifying, and sourcing CNC machined parts — written from the shop floor, not a marketing desk.
Engineering Guides
CNC Machining Knowledge Base
These CNC machining guides are the practical references our own engineers use when reviewing drawings and quotes: what drives cost, how to choose materials and tolerances, which process fits your geometry, and how lead time and MOQ really work. They are written from the shop floor, not a marketing desk — no fluff, no vendor pitch, just the decision logic. Use them before you send the RFQ — or send the files and get the same feedback with your quote.
Metal Pickling
How acid removes mill scale, rust, and oxides — acids, concentrations, pickling vs passivation, and safety.
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ISO 2768 Tolerances
General tolerance classes f/m/c/v for size, H/K/L for geometry, the actual tables, and when it is enough.
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Shot Peening
Compressive residual stress, Almen intensity and coverage, media selection, and fatigue life improvement.
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Stress-Strain Curve
Elastic region, yield point, necking, fracture — plus yield vs tensile strength and modulus.
Read the guide →Does Copper Rust?
No — rust is iron oxide. Copper corrodes into a green patina instead. Corrosion, patina chemistry, and prevention.
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1018 vs 1045 vs 4140 Steel
AISI grade numbers, carbon content, strength, hardness, heat treatment, machinability, and cost.
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Wire EDM Machining
How spark erosion cuts any conductive metal with no cutting force, wire vs sinker EDM, tolerances, and limits.
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Types of Fasteners
Bolts, screws, studs, nuts, washers, pins, rivets, and anchors — with strength grades and how to choose.
Read the guide →Hot Dip Galvanizing
The hot dip galvanizing process, ASTM A123/A153 coating grades, HDG vs electro-galvanized vs galvanneal, and machining rules.
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Chamfer vs Fillet
Chamfer vs fillet differences, drawing callouts (C x 45 deg vs R), stress and cost trade-offs, and DFM rules for edge features.
Read the guide →Case Hardening
Carburizing vs nitriding vs induction hardening: case depth, hardness, distortion, cost, and the machine-harden-grind sequence.
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G Code vs M Code
The two command families behind every CNC program — motion and geometry (G) vs machine functions (M) — with tables and examples.
Read the guide →Magnetic Metals Explained
Which metals are non magnetic? Full chart, why 304 stainless is non-magnetic, and when magnetism drives material selection.
Read the guide →Tolerance Stack Up
Worst case vs RSS stack-up math, a five-part worked example, GD&T bonus tolerance, and design fixes that shrink the chain.
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PTFE Machining
How to machine Teflon: creep, 10x thermal expansion, tooling, parameters, tolerances, filled grades, and selection tips.
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Xometry Alternatives
Xometry competitors compared: marketplace platforms vs Protolabs vs direct factory sourcing — pricing, QC, IP, and fit.
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NPT Thread Size Chart
All NPT dimensions 1/16–2 in: TPI, OD, tap drills, hand-tight and effective lengths, plus taper sealing and NPT vs BSP.
Read the guide →Types of Taps Explained
Taper, plug, and bottoming chamfers, spiral point vs spiral flute, cutting vs forming taps, pipe taps, coatings, and speeds.
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Square Thread
Why the 0-degree square thread is the most efficient power-screw form, how it compares with Acme and buttress, and when to specify it.
Read the guide →Acrylic vs Polycarbonate
PMMA vs PC compared: impact strength, clarity, scratch and UV resistance, heat limits, machinability, and cost.
Read the guide →PP vs Polyethylene
Polypropylene vs polyethylene compared with real data: stiffness, heat, cold toughness, chemical resistance, and cost.
Read the guide →Polycarbonate vs PVC
PC vs PVC compared — impact strength, transparency, heat and flame resistance, machinability, and cost.
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ABS vs HDPE
Stiffness, chemical resistance, machinability, and cost compared — pick the right plastic for your machined part.
Read the guide →Delrin vs HDPE
Stiff, precise Delrin vs tough, chemical-proof HDPE: property data, friction, machining, and cost.
Read the guide →Teflon vs Delrin
PTFE vs POM compared: friction, temperature, chemical resistance, strength, creep, machinability, and cost.
Read the guide →Counterbore vs Spotface
Counterbore vs spotface vs countersink: definitions, ASME Y14.5 symbols, metric counterbore size chart, and machining methods.
Read the guide →Blind vs Through Holes
Blind hole vs through hole: depth and THRU callouts, chip evacuation, bottoming taps, and why thru holes cost less.
Read the guide →Clearance Hole Chart
Metric and inch clearance holes for bolts — ISO 273 fine/medium/coarse sizes for M1.6–M30, and when to tap instead.
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GD&T Parallelism Explained
The parallelism symbol under ASME Y14.5: tolerance zones, datum rules, callout examples, and measurement.
Read the guide →GD&T Runout Explained
Circular vs total runout, FIM/TIR, dial-indicator measurement about a datum axis, and typical applications.
Read the guide →Cylindricity in GD&T
The strictest form control for cylinders: symbol, tolerance zone, measurement, and when to specify it.
Read the guide →Perpendicularity in GD&T
The perpendicularity symbol: surface vs axis control with the diameter modifier, datum rules, and measurement.
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Profile of a Surface
Profile of a surface vs line, bilateral and unilateral tolerance zones, and how CMM scanning verifies contours.
Read the guide →GD&T Straightness
Surface straightness vs axis straightness with the diameter modifier: symbols, MMC bonus, and measurement.
Read the guide →Circularity (Roundness)
Roundness under ASME Y14.5: the symbol, how it differs from cylindricity and runout, and how it is measured.
Read the guide →GD&T Datums Explained
Datum features, the 3-2-1 rule, datum reference frames, datum targets, and how to choose the right datums.
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Swiss Machining
Sliding headstock, guide bushing, and done-in-one turning — when long, slender parts belong on a Swiss lathe, and when they do not.
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Machining Brass
C360 vs C260 vs lead-free grades, milling and turning parameters that work, and when bronze is the better call.
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6061-T6 vs T651
Same strength on the datasheet, different behavior on the machine — what the stress-relieving stretch actually buys you.
Read the guide →Sandblasting vs Bead Blasting
Cutting vs peening: media, roughness, dimensional impact, and which blasting finish to specify.
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Ra vs Rz
What each roughness parameter measures, why there is no fixed conversion, and which one to call out.
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PEEK Machining
Unfilled vs glass- vs carbon-filled grades, the annealing rule, and tooling that survives filled PEEK.
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Stainless Steel Milling
303 vs 304 vs 316 machinability (78/45/40%), carbide speeds and chip loads by grade, and the work-hardening rules that protect tools and finish.
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Aluminum Milling: Feeds & Speeds
Feeds and speeds by operation (800–3,000 SFM carbide), chip load starting points, 6061 vs 7075 vs 5052 behavior, and how to beat built-up edge.
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Free-Machining Steel
12L14 vs 1215, how lead and sulfur break chips, the weldability and corrosion trade-offs, and when free-machining grades cut unit cost.
Read the guide →Cast Iron Machining
Gray vs ductile iron machinability, carbide speeds by grade, why graphite makes chips easy, and the casting-quality traps to catch early.
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Machining Magnesium
AZ31B vs AZ91D, why magnesium is the easiest structural metal to cut, the chip fire rules, and when it beats aluminum on weight.
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Inconel Machining Guide
Why Inconel 718 rates 12% machinability, annealed vs aged condition, carbide speeds and feeds by operation, and the work-hardening rules that scrap parts.
Read the guide →Machining Copper
C110 vs C145 tellurium copper, why pure copper is gummy, the tooling that beats built-up edge, and when brass is the cheaper answer.
Read the guide →Metal Materials Guide
Aluminum, steel, stainless, titanium, copper alloys — the five families and how to choose.
Read the guide →Metal Machining
The subtractive processes — milling, turning, drilling, grinding, EDM — with tolerances, finishes, and materials.
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Custom Machining
Custom vs off-the-shelf parts, the CAD-to-inspection process, materials, cost factors, and lead times.
Read the guide →Press Fit
The interference fit that locks parts without fasteners: how much interference, press vs shrink vs slip, and how to specify it.
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Engineering Fits
Clearance, transition, and interference fits: hole vs shaft basis, H7/g6 and H7/p6, and how to read a fit callout.
Read the guide →Engineering Drawing Symbols
Surface finish marks and Ra, hole and thread callouts, and GD&T — the symbols on a machining drawing, decoded.
Read the guide →CNC Grinding
Surface, cylindrical, and centerless grinding: tolerances, surface finish, when grinding beats milling, and its cost.
Read the guide →Countersink Holes
The conical recess for flat-head screws: angles (82/90/100), countersink vs counterbore vs spotface, and how they are machined.
Read the guide →Thread Sizes & Chart
Metric (M) and Unified (UNC/UNF) designations, common sizes, tolerance classes, and thread milling vs tapping.
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Bead Blasting Finish
The uniform matte surface: process, Ra, bead blasting vs sand blasting vs brushed vs anodizing, and cost.
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Cast Iron vs Steel
The 2% carbon line, strength and brittleness, machinability, vibration damping, cost, and machine bases vs shafts.
Read the guide →What Is Reaming?
The finishing pass after drilling: tolerance (H7), surface finish, stock allowance, reamer types, and reaming vs boring vs honing.
Read the guide →Unilateral vs Bilateral Tolerance
What each tolerance type means, worked examples, when to use each, GD&T equivalents, and why unilateral costs more to hold.
Read the guide →Alloy Steel vs Carbon Steel
Composition, strength, machinability, weldability, hardenability, and cost — 1018, 1045, 4140, and 4340 compared.
Read the guide →Brushed Metal Finish
The directional satin surface: process, Ra, brushed vs polished vs bead blasted, which metals it suits, and cost.
Read the guide →Roughing vs Finishing
Depth of cut, feed, speed, stock allowance, and why roughing and finishing are separate passes — with real parameter ranges.
Read the guide →CNC Quality Control Process
Incoming material, in-process and final inspection, CMM and other equipment, first article inspection, PPAP, SPC, and the documentation buyers should ask for.
Read the guide →303 vs 304 Stainless Steel
The sulfur difference, machinability, corrosion resistance, weldability, mechanical properties, and when to choose each — for CNC machined parts.
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Automotive CNC Parts
Materials (6061/7075, steel, stainless, POM), common parts, prototype vs production (PPAP), tolerances, finishes, and why automotive work is won on repeatability.
Read the guide →GD&T Symbols Explained
True position and MMC bonus tolerance, flatness, parallelism, perpendicularity, runout vs concentricity, profile, and datums — each symbol explained for machined parts.
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How to Vet a Chinese CNC Shop
Verify certifications, audit equipment and inspection over live video, gate production behind first article inspection, and spot trading-company red flags.
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IP Protection & NDA for China
NNN agreements vs plain NDAs, practical protection steps (split suppliers, own tooling, limit drawings), and the mistakes that leak your design.
Read the guide →PEEK vs Delrin
Strength, service temperature, chemical resistance, machinability, cost, wear, and water absorption — PEEK vs Delrin (acetal) compared for machined plastic parts.
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Medical Device Machining
Medical-grade alloys (316L, Ti-6Al-4V ELI, PEEK, cobalt-chrome), surface finish Ra targets, ISO 13485 vs 21 CFR 820, and why medical parts cost more.
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Aerospace Machined Parts
Materials (6061/7075, Ti-6Al-4V, Inconel 718, 17-4), tolerance bands, AS9100D/NADCAP/ITAR certifications, cost, and lead times — for aerospace components.
Read the guide →Electropolishing vs Passivation
What each process does, surface roughness, corrosion resistance, specs (ASTM B912 vs A967/AMS 2700), cost, and which industries need which — for stainless machined parts.
Read the guide →Black Oxide vs Zinc Plating
Corrosion resistance, cost, dimensional change, appearance, and hydrogen embrittlement — black oxide, zinc plating, and black zinc compared for machined steel parts.
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Shipping & Tariffs from China
Freight costs, transit times, FOB vs DDP, the 2026 tariff reality, and how customs clears your parts — everything between order placed and parts on your dock.
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Inconel vs Titanium
Density, strength, service temperature, corrosion, machinability, and cost — Inconel 718, Inconel 625, and Ti-6Al-4V compared with real data for machined parts.
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Titanium vs Steel
Density, strength, strength-to-weight, stiffness, machinability, corrosion, and cost — Ti-6Al-4V, Grade 2, 4140, 1018, and 316 compared with real data for machined parts.
Read the guide →Steel vs Aluminum
Strength, stiffness, weight, machinability, corrosion, and real cost — 1018, 4140, and 304 stainless versus 6061 and 7075, with grade data.
Read the guide →Titanium vs Aluminum
Density, strength, strength-to-weight, machinability, corrosion, and cost — Grade 5, Grade 2, 6061, and 7075 compared with real data for machined parts.
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Brass vs Bronze vs Copper
Composition, machinability ratings, conductivity, strength, corrosion behavior, and cost — how to pick the right copper alloy for your machined parts.
Read the guide →5-Axis vs 3-Axis CNC
3+2 vs simultaneous, done-in-one economics, and the accuracy argument — plus a three-question test to pick the right process for your part.
Read the guide →Get an Accurate CNC Quote
The complete RFQ package, why supplier prices diverge 3×, quantity-break strategy, and the red flags that predict a bad order.
Read the guide →6061 vs 6063 Aluminum
Strength, machinability, extrudability, and anodizing — why machined parts want 6061 and extrusions want 6063, with the numbers to prove it.
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AS9100 vs ISO 9001
What AS9100 actually adds, AS9102 FAI, who requires it, and when ISO 9001 is enough — a buyer’s guide to machining supplier certification.
Read the guide →GD&T Basics for Machined Parts
The 14 symbols explained, feature control frames, datums, MMC bonus tolerance, and why true position beats ± tolerancing — from the shop side.
Read the guide →Delrin vs Nylon
Moisture absorption, strength, machinability, wear, temperature, and cost — the engineering-plastics decision, plus where PEEK fits.
Read the guide →Passivation of Stainless Steel
What passivation actually does, ASTM A967 and AMS 2700 methods, nitric vs citric, and the verification tests that prove it worked — written for machined parts.
Read the guide →Surface Finish Chart (Ra)
Ra values in μm and μin, N1–N12 grades, what each process achieves, and what finer finishes cost — plus how to specify finish on drawings without overpaying.
Read the guide →6061 vs 5052 Aluminum
Strength, machinability, bending, welding, corrosion, anodizing, and 2026 prices — the machining alloy vs the forming alloy, and how to specify the right one.
Read the guide →304 vs 316 Stainless Steel
Composition, corrosion resistance (PREN), machinability, and the 2026 price gap — plus the selection rules for when 304 is enough and when you must pay for 316 or 316L.
Read the guide →China CNC Machining Cost
The full 2026 price breakdown: machine-hour rates, real part price examples, material, finishing, freight and duty — what a China machining quote is actually made of.
Read the guide →CNC Machining: China vs USA
An honest comparison on landed cost (including the 2026 tariff reality), lead time, and quality — plus a decision framework for when domestic sourcing wins and when China wins.
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Outsource CNC Machining to China
The step-by-step playbook: RFQ preparation, supplier vetting, landed-cost math, remote quality control with first article inspection, and shipping. Written for buyers who want factory-direct sourcing without the usual risks.
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What Is CNC Machining?
The plain-English starting point: how subtractive machining works, the main process types, the materials it cuts, the tolerances it holds, and where machined parts are actually used. If you are new to sourcing machined parts — or briefing a colleague who is — start here.
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Types of CNC Machining
3-, 4-, and 5-axis milling, turning, mill-turn, Swiss machining, EDM, and grinding, compared by the geometry each one handles best. The useful takeaway: most parts have one obviously right process, and choosing it early saves real money.
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How Does CNC Machining Work?
Follow a part from CAD to CAM, setup, machining, inspection, and shipping — and see where cost and lead time actually build up along the way.
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What Is Precision Machining?
Tolerance bands from general to ultra-precision, what enables them, what drives cost up, and how to specify precision without over-tolerancing your parts.
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CNC Machining Materials
A six-factor selection framework (strength, weight, corrosion, temperature, machinability, cost), a full metal-and-plastic comparison table, and the five material mistakes we see most often in RFQs — like specifying 316 where 304 would do, or Delrin where moisture rules it out.
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6061 vs 7075 Aluminum
Strength, weldability, machinability, corrosion resistance, and cost compared — plus what happens when you substitute one alloy for the other.
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Nylon CNC Machining
PA6 vs PA66, cast vs extruded stock, moisture absorption and tolerance planning, nylon vs Delrin, and drawing tips for machined PA parts.
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CNC Machining Tolerances
ISO 2768 classes, GD&T basics, achievable tolerances by process, and the tolerance-cost relationship. The core lesson: tolerance only the features that need it, because every tightened callout is paid for in cycle time and inspection.
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DFM: CNC Design Guide
Corner radii, wall thickness, thread depth, tolerancing strategy, and the top 10 drawing mistakes we see in RFQs. This is the guide that pays for itself: most DFM fixes cost nothing at the design stage and hundreds of dollars at the machine.
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CNC Machining Cost
The five cost buckets behind every quote (material, setup, cycle time, finishing, inspection), the quantity-price curve, and the DFM levers that actually move unit cost. Read this before negotiating price — you will know which lever to pull instead.
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Lead Time & MOQ
Where lead time actually goes between PO and delivery, why small batches cost more per part, what MOQ really means from a machine shop, and the specific moves that shorten delivery: standard materials, relaxed cosmetic callouts, and consolidated orders.
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Anodizing Aluminum
Type I/II/III per MIL-A-8625, process steps, dye colors, dimensional effects, masking, and how to write the drawing callout.
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Hard Coat Anodizing
Type III hardcoat: thickness, hardness, when to specify it, dimensional planning, color limits, and drawing callout examples.
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First Article Inspection (FAI)
What an FAI report contains, when one is required, how AS9102 formats it, and how FAI differs from a C of C or full inspection.
Read the guide →Head-to-Head
Process & Finish Comparisons
Engineer's comparisons of the decisions that come up on real RFQs — process against process, finish against finish.
CNC Machining vs 3D Printing
An engineer's comparison of the two processes on tolerance, strength, materials, cost, and lead time — plus the hybrid route (print to validate, machine to produce) that most real product programs end up using.
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Anodizing vs Powder Coating
Durability, thickness, tolerances, corrosion behavior, and cost — how to pick the right finish for machined aluminum parts.
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Milling vs Turning
How each CNC process works, which part geometries fit each, cost and tolerance differences, and when mill-turn wins.
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