# What Should Be on a CNC Machining Drawing? A Complete Checklist > A CNC drawing has to answer twelve questions before the shop can quote you. Here is the complete list, what happens when you skip each item, and the ten-point pre-send check. https://www.sinbo-machining.com/blog/cnc-drawing-checklist/ --- ## On This Page - What Should Be on a CNC Machining Drawing? A Complete Checklist - The Twelve Items Every RFQ Needs - Tier 1, Tier 2 and Tier 3: What to Send Now - Material: Never Write "Aluminum" - Tolerances: State the Default Class or Get the Wrong Part - Surface Finish: By Feature, Not by Part - Inspection, Lead Time and Delivery - The Ten-Point Pre-Send Check - Sources - Frequently Asked Questions - Related Articles - Send Us a Drawing and Get a Quote in Days DFM # What Should Be on a CNC Machining Drawing? A Complete Checklist October 28, 2026 | 11 min read ## What Should Be on a CNC Machining Drawing? A Complete Checklist A CNC drawing has to answer twelve questions before a shop can quote you without guessing, and every one of them costs you money if it is left unanswered. The list is shorter than it sounds: a part name and drawing number, a material standard with grade and temper, a quantity, the drawing or model itself, the critical tolerances, the surface finish by feature, the secondary processes, the inspection scope, the lead time, the Incoterms and the payment terms. Nine of those twelve take less than five minutes to write down, and a complete RFQ is the difference between a quote you can act on and a range you have to renegotiate. ## The Twelve Items Every RFQ Needs | # | Item | Why it matters | 1 | Part name, drawing number and revision | A reference for every email that follows. Without a drawing number, every quote revision is a different document. | 2 | Material designation with full standard code and temper | “Aluminum” is not a material. 6061-T6 and 7075-T7351 differ by 2× in cost and 3× in machinability. EN AW-6082 T6 or ASTM B211 7075-T7351 removes the ambiguity. | 3 | Quantity: target, minimum order, annual forecast if known | 1 piece, 5 pieces, 50 pieces, 500 pieces and 5,000 pieces are quoted on completely different cost stacks. Honest quantity beats inflated quantity — the factory will re-price if you lied. | 4 | Drawing or 3D model with GD&T | If you have a drawing, send it as PDF plus native CAD if you can. If you only have STEP, that is fine — say so explicitly so the factory knows to flag tolerance ambiguity. | 5 | Critical tolerances, the ±0.0X mm ones | Mark them on the drawing or call them out in writing. “Tight tolerances” is not a specification. If the part has 3 features at ±0.01 mm and 30 features at ±0.1 mm, the factory needs to know which is which. | 6 | Surface finish requirements, Ra value by feature | Ra 1.6 as-milled is essentially free. Ra 0.4 ground is 30–80% added cost. Ra 0.05 mirror-polished is a different process entirely. | 7 | Secondary processes: heat treat, anodize, plating, passivation, painting, laser marking | Each one is a separate supplier and adds lead time. A 5-day part with a 10-day anodize and 5-day shipping is 20 days, not 5. | 8 | Inspection requirements: FAI report, CMM, key characteristics, material cert | EN 10204 3.1 mill cert is the baseline, AS9102 FAI is the aerospace baseline, and medical work has its own FAI variations. | 9 | Quantity of parts to inspect: 100%, AQL sampling, or first-article only | “Inspect every part to ±0.01 mm” is an entirely different cost line from “FAI only”. The factory needs to know which. | 10 | Lead time: standard or expedite, with a target date | “ASAP” is not a lead time. “Need parts in our Munich warehouse by 2026-09-15 for a trade show” is. | 11 | Incoterms (EXW, FOB, CIF, DAP, DDP) and target country | EXW is the cheapest to quote but pushes all logistics onto you. DDP is the easiest for you but requires the factory to know your import rules. Pick one and tell the factory. | 12 | Payment terms and RFQ response deadline | Net 30 versus Net 60 versus a 50% deposit affects which factories will even respond. A 7-day response deadline is reasonable for a complete RFQ; 3 days is rude unless you offer a paid rush. [CNC machined 3-axis parts with pockets, holes and 2D profiles] A machined part with pockets, holes and profiles: every one of these features is an instruction the drawing has to give clearly. ## Tier 1, Tier 2 and Tier 3: What to Send Now Not everything has to go in the first email. Splitting the RFQ into three tiers keeps it short without leaving the gaps that cause late-stage surprises. | Tier | What belongs here | If you skip it | Must-have (Tier 1) | Material designation and temper, quantity, drawing or STEP with GD&T, key tolerances, surface finish, lead time, target country for shipment | The factory will not quote, or will quote with assumptions you have to correct later | Important (Tier 2) | Critical features called out, inspection requirements, secondary processes, Incoterms, payment terms, RFQ response deadline | The quote will be a rough range only, with major exclusions to be negotiated later — this is where 80% of late-stage surprises come from | Optional (Tier 3) | Acceptable alternates, preferred material brand, packaging requirements, target price, NDA, audit rights, sample policy | Negotiations start from defaults that may not match your needs; a small loss of control, not a deal-breaker The stage of the project also changes what matters. A prototype is about form, fit and function, and its cost is often 5–10× the production unit price because setup and programming are amortized over very few parts. A production run is about cost, capacity, on-time delivery and quality consistency. [Bar chart of the unit cost multiplier at prototype, pilot and production stages] [Swiss-type precision turned components] Relative unit cost by stage: prototype 5–10× the production price, pilot 2–3×, production 1.0×. Precision turned components: the same drawing rules apply whether the part is milled or turned. ## Material: Never Write "Aluminum" This is the single most expensive ambiguity on a drawing. A shop that receives “stainless steel” or “aluminum” picks the cheapest grade that fits, and you get 303 instead of 17-4 PH, or 6063 instead of 6061-T6. Always specify the standard plus the grade plus the temper: AISI 316L, ASTM B211 7075-T7351, EN AW-6082 T6. [Machined 6061-T651 aluminium bracket] 6061-T651 machined bracket: alloy, temper and standard designation together make the material unambiguous. If you want a fallback, say so explicitly — “6061-T6 or equivalent to ASTM B211” is a usable sentence. If you do not want a fallback, say that too: “no substitution without written approval” takes one line and closes the argument. ## Tolerances: State the Default Class or Get the Wrong Part If the drawing has 30 dimensions and no GD&T and no default-tolerance callout, the factory will pick ISO 2768 medium (m) by default. If you expected ISO 2768 fine (f), the parts arrive 2× looser than expected and nobody can tell whose fault it was. Two ways to close it, and you only need one: - Put a default tolerance class in the title block, such as ISO 2768-mK or ASME Y14.5-2018, with explicit GD&T on the critical features. - Or tolerance every dimension individually, which is legal but slow for both sides. [4140 alloy steel CNC machined parts] 4140 alloy steel machined parts: an explicit default tolerance class keeps a 30-dimension drawing unambiguous. Marking the critical features matters just as much as stating the class. A feature list of “3 features at ±0.01 mm, 30 features at ±0.1 mm” tells the shop exactly where the inspection time and the scrap risk are. ## Surface Finish: By Feature, Not by Part A single Ra number for the whole part is a specification that guarantees you will over-pay for most of it or under-finish the one surface that matters. List the finish by feature or zone instead. A sealing face at Ra 0.4 and all other external surfaces at Ra 1.6 is a complete and cheap specification. [Surface finished CNC machined parts] Finished machined parts: a sealing face and a cosmetic face need different finishes, and one number cannot cover both. The same zone-by-zone logic applies to the coating, the masking, and the edges. And remember that the finish and the dimension are independent specifications — a tight dimension does not require a smooth surface. ## Inspection, Lead Time and Delivery These three lines are where a cheap quote becomes an expensive order. [CMM inspection of a CNC machined part] CMM inspection: defining the inspection scope up front decides whether the quote includes a CMM line or not. Inspection scope has to be quantified. Specify what “critical” means: 100% on which features, measured with a CMM, a height gauge or a micrometer, and for everything else an AQL sampling plan or first-article-only. Full CMM inspection on a part with 50 dimensions takes 30–60 minutes per part; FAI only takes minutes. Lead time has to be a date with a reason. “Need by 2026-09-15 for a trade show” is a lead time. “ASAP” is a feeling, and every factory reads it differently. If you do need a real expedite, say so and budget for the 30–100% expedite premium. Delivery has to be a mode. Sea freight is the cheapest at 25–40 days, air freight is 5–10 days at 4–8× the cost, and a courier is 3–7 days and the most expensive. For prototypes air is almost always the answer; for production it is sea. [Horizontal range chart of transit time by shipping mode] [Horizontal stacked chart of a 20-day total lead time from three sequential stages] Transit time by shipping mode: sea 25–40 days, air 5–10 days at 4–8× the cost, courier 3–7 days at the highest cost. Total lead time: 5 days of machining plus 10 days of anodizing plus 5 days of shipping gives 20 days, not 5. One more cross-border item deserves its own line: ask for a DDP quote when you want a true landed cost, or at minimum CIF plus estimated duties. Do not accept EXW if you do not know the tariff schedule for your HS code. Section 232 applies 25% to steel and 10% to aluminum articles in the US, with the scope expanded in 2020 to many derivative products. ## The Ten-Point Pre-Send Check Run this list before you hit send. Every item on it costs about a minute, and every one of them has a fix. | # | Check | If no, fix before sending | 1 | Material is specified to standard plus grade plus temper, not trade name? | Add the standard designation: ASTM B211 7075-T7351, EN AW-6082 T6, AISI 316L. | 2 | Drawing has either explicit GD&T or a stated default-tolerance class such as ISO 2768-mK? | Add the default callout in the title block. | 3 | Critical tolerances of ±0.0X mm are flagged on the drawing or in text? | Mark them with notes or a critical-features callout. | 4 | Surface finish is specified per feature, not per part? | Break the callout into zones such as sealing face versus body. | 5 | Quantity is honest, not inflated? | Tell the truth. Inflated quantities cost you trust and money later. | 6 | Lead time is a date, not a feeling? | “By 2026-09-15” is a lead time. “ASAP” is not. | 7 | Inspection scope is defined: 100%, AQL or FAI-only? | Add the line: Inspection: FAI on the first 5 parts, AQL 1.0 on dimensions per ISO 2859-1 normal inspection for the rest. | 8 | Material cert type is named: EN 10204 3.1, 3.2 or ASTM mill cert? | For EU pressure equipment use EN 10204 3.1 or 3.2; for others the factory's standard mill cert is usually fine. | 9 | Incoterms are picked: EXW, FOB, CIF, DAP or DDP? | For first-time suppliers DDP is the cleanest; for ongoing relationships FOB or EXW. | 10 | Payment terms are explicit: deposit percentage and balance trigger? | For first orders 30/70 T/T is the default; for ongoing relationships Net 30 once the relationship is established. And one last item that is not on the drawing at all but should be in the RFQ: the shipping mode and the target landed date. The factory can offer a sea or an air quote, but they need to know the constraint. “Cheapest” is not a logistics specification. ## Sources Every number on this page comes from our engineering wiki. - [How to RFQ CNC Machined Parts Without Wasting Three Months on Basic Questions ](https://www.sinbo-machining.com/wiki/dfm/how-to-rfq-cnc-parts/) ## Frequently Asked Questions Five items, no fewer: (1) material to standard plus grade plus temper, such as ASTM B211 6061-T6 and not just “aluminum”; (2) quantity with target and minimum; (3) drawing or 3D model with GD&T or a stated default-tolerance class; (4) critical tolerances and surface finish called out per feature; (5) lead time as a specific date, not “ASAP”. Without any of these, the factory will either refuse to quote or will quote with assumptions you will have to correct later. The full 12-item list in this page is what separates an “accurate quote” from a “rough range”. Because the RFQ is rarely as complete as the buyer thinks. The most common reasons a factory asks 10 follow-up questions: (1) the drawing has a tolerance or feature the buyer did not notice; (2) the default-tolerance class is not stated, so the factory has to ask which one applies; (3) the material is named in trade form such as “stainless” without a standard designation; (4) the surface finish is a single number for a part that clearly has multiple functional zones; (5) the lead time is “ASAP” and the factory needs a real date to plan capacity. None of these is the factory being slow — they are the factory refusing to guess. A good factory will ask 3–5 clarifying questions and then quote in 3–7 business days. Do not argue the number — ask for the math. A good response is: “Our target was $X per piece. Your quote is $Y. Can you share the cycle time you assumed, the material cost per piece, the setup hours, and any line items we might have missed?” Three things usually come back: (1) the factory interpreted the drawing differently than you intended, so fix the spec and re-quote; (2) the factory included secondary operations such as heat treat, surface finish or FAI that you did not explicitly exclude, so confirm scope and re-quote; (3) the factory’s capacity and cost base really are higher than the market, which is information rather than a negotiation starting point. If the quote is more than 40% above the median of your other quotes after the first round, the work is probably not interesting to the factory or there is a capability gap — walk away and use a different supplier rather than run a second round of negotiation. A standard NDA is not enough for Chinese OEM manufacturing. An NDA prevents the factory from telling others about your IP, but does not stop the factory from using your IP itself, or from selling your product to your customers. Use an NNN agreement (Non-Use, Non-Disclosure, Non-Circumvention) instead. The three clauses cover: (1) Non-Use — the factory cannot use your IP to make parts for competitors; (2) Non-Disclosure — the factory cannot share your IP with third parties; (3) Non-Circumvention — the factory cannot sell to your customers or channels. The NNN must be bilingual Chinese-English, governed by Chinese law, enforceable in a Chinese court, and include explicit per-breach monetary damages. A US or EU NDA has essentially no enforcement value in a Chinese court. ## Related Articles [What Is DFM in CNC Machining? A Buyer's Guide Read more → ](https://www.sinbo-machining.com/blog/dfm-guide/)[How to Reduce CNC Machining Costs Without Changing the Design Read more → ](https://www.sinbo-machining.com/blog/reduce-cnc-costs/)[CNC Tolerance Stack-Up: Why Your Part Did Not Fit Read more → ](https://www.sinbo-machining.com/blog/tolerance-stack-up/)#drawing #RFQ #GD&T #tolerance #quoting [Back to Blog ](https://www.sinbo-machining.com/blog/) ## Send Us a Drawing and Get a Quote in Days Upload the 2D drawing and the 3D model, tell us the quantity and the finish, and our engineers will come back with a line-item quote. [Get Quote ](https://www.sinbo-machining.com/quote/)[Contact Us ](https://www.sinbo-machining.com/contact/)