CNC Machining Knowledge Base
The reference tables, calculators, material data and buying notes our own engineers use — grouped by topic so you can find the number or rule you need in one place. No download, no email gate, no "talk to sales."
Most machine-shop blogs are written to rank for a keyword. This page is written so that, when you are standing at a quote or a drawing, you can answer the question without leaving the tab. Start with the domain that matches your problem, or jump straight to the asset you already know you need.
Tolerances & GD&T
How much a part can deviate, and how to read what the drawing actually asks for. These are the tables our quoting engineers keep open.
CNC Machining Tolerance Chart
ISO 2768 numeric tables for all four tolerance classes, what each process can realistically hold, every GD&T symbol in one table, and the tolerance-cost curve that decides your quote.
GD&T True Position & Stack-Up Calculator
Convert measured X/Y deviation into true position in diametral and radial form, add the MMC bonus, and run the same dimensions through worst-case and RSS stack-up.
ISO 286 Fits & Tolerance Grades
Standard tolerance grades IT5 to IT14 for any nominal size, exact H and h limits, and a guide to which clearance, transition or interference fit suits which job.
Tolerance Stack-Up Calculator
Sum the ± tolerances on a chain of dimensions and see the worst-case and RSS spread at the gap before you machine — so an assembly that measures fine doesn't fail to fit.
GD&T for Buyers
The six GD&T symbols that decide price and fit — and the four mistakes that cost money on real drawings.
Materials & Machinability
What each metal and plastic actually does on the machine — grades, the tolerances they hold, and how to pick without over-specifying.
Aluminium vs Stainless vs Titanium
Six alloys compared on 13 properties, with specific strength, real machining-time ratios and a seven-question decision guide.
Aluminium Grade Selection Chart
6061, 7075, 5052, 2024, 6063 and 2A12 compared on strength, fatigue life, machinability, weldability, anodising response and cost — plus a seven-step decision tree.
Titanium Machining Guide
Why titanium destroys cutting tools, what speeds and feeds actually work, and the chip fire risk most guides omit.
Aluminum CNC Machining
Grades 6061, 7075, 6082 and more — how to choose, what tolerance to expect, and anodising rules that keep aluminum parts cheap and accurate.
Steel CNC Machining
1018, 1045, 4140 and more — how to hold tolerance on hardening-sensitive grades, and the pre- and post-heat-treatment sequencing that keeps parts dimensionally stable.
Stainless Steel CNC Machining
303, 304, 316 and 17-4 PH — work-hardening control, the feeds that stop smearing, and passivation rules that keep corrosion resistance intact.
Copper CNC Machining
C101, C110 and tellurium copper — why copper grabs the tool, the sharp-edge and low-speed setup that stops built-up edge, and where brass is the cheaper stand-in.
Material Weight Calculator
Blank weight for plate, round bar, tube and hex bar in aluminium, steel, stainless, titanium, brass and common engineering plastics.
Plastic CNC Machining Guide
POM, PEEK, PTFE, nylon and UHMW — grades, the quirks that make each one tricky, and a selection table.
CNC Material Selection Guide
Twelve materials on one matrix — machinability, cost, corrosion, strength-to-weight — plus a five-question selector for aluminium, stainless, steel, titanium, brass, copper and engineering plastics. With a printable PDF.
Passivation of Stainless Steel
Why machined stainless rusts, when passivation (ASTM A967 / AMS 2700) is actually needed, and citric vs nitric — plus how we handle it through our finishing partner.
Inconel & Hastelloy CNC Machining
Why nickel alloys fight the cutter, the low-speed / high-feed strategy that works, and the grades (718, 625, X, C-276) we run for aerospace, defense and energy.
Cost & Quoting
Where the money goes on a machining quote, and the levers that move it. Use these before you compare two shops' numbers.
CNC Cost Calculator
Pick material, quantity, size, complexity, tolerance and finish for an indicative per-part range in seconds — no email gate, no download.
How to Reduce CNC Machining Cost
Twelve design changes ranked by how much they actually move the quote — setups first, not materials. With the reasoning behind each one.
How CNC Machining Cost Is Calculated
What the hourly rate covers, the five lines on every quote, and the levers ranked by impact — including why 5-axis sometimes costs less overall.
We Quoted 5x Their Supplier. We Lost.
A US manufacturer's existing supplier beat us by five times. We dug into why, explained the arithmetic, and told them to stay put. What ten years of process optimisation actually buys.
Why 40 Parts Cost More Per Piece Than 4,000
Programming, setup and prove-out don't scale with quantity. The full cost breakdown, plus four questions to ask any shop quoting you a small batch.
We Redesigned a Competitor's Part and Cut Cost 40%
Copying a part isn't engineering it. When a customer asked us to replicate a rival component, we proposed a redesign that held the same fit for far less.
How We Built the Instant Quote Tool
Why we shipped a no-email-gate estimator, what it actually computes, and the trade-offs we made so a budget number appears in seconds.
When a China Quote Matched a US Shop
A buyer sent us a US shop's quote and we came in level — what actually drove the number, and where offshore still wins on price.
How to Read a CNC Quote
Every line on a machining quote decoded — setup, programming, material, finishing, inspection — so two quotes finally compare.
Instant Quote Tool
Upload your 2D drawing (PDF) and 3D STEP model and get an itemised reference quote in seconds — material cost from true model mass, machine time at a per-minute shop rate, setup and packaging free. Then send the files for a formal quote.
Surface Finish & Coating
Roughness, anodize, passivation and the rest — what each process changes, and where a finish quietly breaks a fit.
Surface Roughness Ra Chart
Ra values by process, what each step down costs, Ra vs Rz, and how to specify roughness without over-paying.
Surface Finish Comparison Chart
Nine finishes side by side — anodising Type II and hardcoat, passivation, black oxide, zinc, electroless nickel, powder coat, bead blast, polishing — with thickness, hardness and salt spray hours.
Surface Roughness Converter
Convert between Ra in micrometres and microinches, RMS, Rz and the ISO N-grade numbers, and see which process reaches which finish.
Anodizing CNC Aluminum Parts
Type II vs Type III thickness, the 50/50 dimensional-growth rule that breaks tight bores, colour limits by alloy, and the three questions that stop you over-specifying hardcoat.
Process & Machine Selection
CNC vs other processes, and which axis count or machine a part really needs. Stop paying for capability the drawing doesn't require.
Swiss Machining vs CNC Turning
How a sliding-headstock lathe beats a standard lathe on small, long and high-volume turned parts — what it suits, the tolerances it holds, and the DFM calls that keep Swiss runs cheap.
CNC Machining vs 3D Printing
Where the cost curves cross by quantity, material and tolerance — and a decision table for your own part.
CNC vs Injection Moulding
Where the cost curves cross by quantity, and the decision table for your own part — including when moulding wins and when it doesn't.
DFM & Buying Guides
The rules that keep a drawing cheap, fast and in tolerance — plus how to source from China without the usual pain.
Free NDA Template
A ready-to-use mutual non-disclosure agreement for sending drawings to a machining shop. Covers 3D models, specs, quotes and process know-how.
Why Source CNC Machining From Shenzhen?
A shop owner's honest take — what the city actually gives you, what it doesn't, and how to vet any Shenzhen supplier in one email.
CNC Machining Design Guide
Twelve DFM rules — wall thickness, corner radii, hole depth, threads, tolerances — that keep a machined part cheap, fast and in tolerance. With a quick-reference table.
Printable DFM Checklist
Twelve design-for-manufacture rules you can tick off before sending a drawing — with a one-page PDF to keep at your desk.
CNC Machining Glossary (A–Z)
Sixty-plus terms from anodising to 5-axis, written for buyers — every entry links to the deeper guide it relates to.
Real Parts We've Machined
Aluminium, stainless, brass and plastic parts off our floor, grouped by material — no stock photos, no fake customer names.
How to Work With a Chinese CNC Supplier
Seven checks before you send a drawing — real photos, quote reading, IP protection, inspection, lead times, Incoterms and after-sales.
Our ISO 9001-Aligned Quality System
How we run quality on the floor without holding the certificate — seven practices, and when a certified supplier is the safer route.
Industries & Applications
How the same machining fundamentals map onto aerospace, automotive, medical, robotics, automation and power-electronics programs.
CNC Machining Electronics Enclosures
Material choice, wall-thickness and warp rules, EMI gasket grooves, threaded inserts and the tolerances that keep a machined box from becoming a scrap bin.
CNC Machining for Medical Devices
Housings, instrument bodies, fixtures and prototypes — what to brief, which materials, and how tolerance and inspection are handled (including when a certified supplier is the safer route).
CNC Machining Automation Parts
Fixture plates, manifold blocks, end-effector brackets — materials, the tolerances that matter, and DFM calls that keep a line running.
CNC Machined Robotics Parts
Joint housings, harmonic-drive cases, linkages — lightweight materials, thin-wall strategy and bearing-seat tolerances for millions of cycles.
Machining for the Medical Industry
Where medical programs sit relative to our other industries — surgical instruments, diagnostic hardware and implants, and how inspection and traceability are handled.
CNC Machining for EV Components
How to brief machined EV parts — busbars, battery and inverter housings, liquid-cooling plates — with the material, flatness and DFM rules that keep a part from failing at the weld or the thermal interface.
CNC Machined Heat Sinks
Aluminium vs copper, fin geometry and the fin-spacing and base-flatness rules that keep a machined sink from chattering, warping or losing its thermal bond — plus the anodize trap.
Custom CNC Parts
Any part machined to your drawing — any quantity, any common engineering material, with ±0.01mm precision, CMM inspection and a 24-hour quote.
Notes from the Shop
Straight-talk stories from real quotes — the jobs we won, the ones we lost, and what the arithmetic actually showed.
Speeds & Feeds Calculator
Get spindle RPM and feed rate for milling and turning in seconds. Pick a material, enter tool diameter and chip load — reference values, no signup.
Thread & Tap Drill Chart
Metric and unified thread dimensions with tap drill sizes, computed from the ISO 68 and ASME B1.1 basic profile. The calculator handles any diameter and pitch you type in.
Drilling & Tapping Calculator
Spindle speed, feed rate, removal rate and cycle time for drilling and rigid tapping, including the retract overhead a peck cycle really costs.
Bend Allowance & Tonnage Calculator
Bend allowance, bend deduction, flat pattern length and the press brake tonnage the job will need, using the standard air-bend formulae.
Machining Time Estimator
Cutting time from toolpath length, plus tool changes, load and unload and setup, so you get a cycle time and a batch time rather than a cutting time.
Machine Selection by Part Features
Describe the envelope, how many directions carry features and how tight the tolerance is, and see whether the part needs 3-axis, 3+2, 5-axis or mill-turn.
CNC Unit Converter
Length and tolerance, surface roughness, cutting speed, feed, mass, pressure and temperature — the conversions that come up on drawings and inspection reports.
We Don't Hold ISO 13485. Here's How Medical Work Happens.
A veterinary device company needed a certificate we don't have. They visited our floor, and we built an arrangement inside their own certified supply chain instead.
A Drawing Missing 3 Dimensions? We Added a 30% Risk Premium.
What a shop should do when a print is incomplete — and why a transparent risk premium beats a low quote that hides the gap.
We Walked Away From a 10,000-Piece Order
When the print, the volume and the commercial terms didn't line up, we said no — and what that decision protects on every job after it.
CNC Machining Supplier & Manufacturer
One supplier for milling, turning, 5-axis, prototyping and low-volume production — made in our own Shenzhen workshop, inspected under a single quality system.
Found what you needed?
Brief the drawing using these references, then send it for a quote — we reply within 24 hours.