CNC Custom Procurement Guide: Details to Include in Drawings for Accurate Honscn Quotes

Why Drawing Details Make or Break Your Quote

Let’s start with the basics: When we get a CNC drawing, we need to answer three big questions to quote accurately:

• How much will materials cost? (e.g., Is it 6061 aluminum or 7075? A 10mm thick sheet or 5mm?)

• How long will machining take? (e.g., Do we need to hit ±0.01mm tolerance, or is ±0.1mm okay? Are there undercuts that need a 5-axis machine?)

• What extra steps are needed? (e.g., Anodizing? Laser engraving? Compliance testing for medical parts?)

Without these details, we have to make assumptions—and assumptions almost always lead to wrong quotes. For example: If your drawing says “aluminum bracket” but no material grade, we might default to 7075 (stronger, but more expensive) when you actually need 6061 (cheaper, easier to machine). That alone could make your quote 20% higher than it needs to be.

Honscn doesn’t want to overquote (or underquote—we hate having to adjust prices later). The more details you give us, the more we can tailor the quote to your exact needs.

5 Key Details to Add to Your Drawing (And Why They Matter)

You don’t need to clutter your drawing with every possible spec—just these five things will make a huge difference. We’ll walk through each one, explain why it impacts cost, and show how Honscn uses it.

1. Material: Be Specific (Not Just “Aluminum” or “Steel”)

“Saying ‘stainless steel’ is like saying ‘a car’—there are dozens of types, and they all cost different amounts,” says Mike, our CNC material specialist. The material you choose affects everything from machining time to raw material costs, so specificity here is key.

What to include:

• Grade: e.g., 6061-T6 aluminum (not just “aluminum”), 304 stainless steel (not just “stainless”), or PEEK plastic (not just “plastic”).

• Size/Form: e.g., 100mm x 50mm x 5mm sheet, 15mm diameter rod, or 2mm thick tube.

• Any special requirements: e.g., “food-grade 316 stainless” (for kitchen equipment) or “FDA-approved ABS” (for medical parts).

Why it matters:

A 6061-T6 aluminum bracket costs ~30% less than the same bracket made from 7075-T6 (7075 is stronger but harder to machine, so it takes longer). For example, one client sent us a drawing for a drone frame that just said “aluminum.” We quoted based on 7075 (\(12 per unit), but when they clarified it was 6061, we dropped the quote to \)9—saving them 25%.

How Honscn uses this:

We source materials directly from trusted mills, so we have real-time pricing for every grade. Once you specify the material, we calculate exactly how much of it we’ll need (including scrap—we factor in 5-10% for machining waste) and add that to the quote. No guesses, just exact numbers.

2. Tolerances: Mark “Critical” vs. “Non-Critical” Dimensions

Tolerance is how much a dimension can vary (e.g., ±0.01mm means the part can be 0.01mm bigger or smaller than the design). Tighter tolerances = more time = higher cost—so there’s no need to over-specify.

What to include:

• Tolerance for every key dimension: e.g., “Hole diameter: 8mm ±0.03mm” or “Length: 50mm ±0.1mm.”

• Label critical vs. non-critical: Use a star (*) or note to say which dimensions matter most. For example, a hole that fits a bolt needs tight tolerance (*8mm ±0.02mm), but the overall length of a bracket might be non-critical (50mm ±0.1mm).

Why it matters:

Hitting ±0.01mm takes 2-3x longer than ±0.1mm—we have to use slower cutting speeds and check the part more often. One industrial client forgot to add tolerances to their sensor mount drawing. We assumed ±0.01mm (our default for precision parts) and quoted \(15 per unit. When they told us only the bolt hole needed ±0.02mm (the rest was ±0.1mm), we revised the quote to \)11.

How Honscn uses this:

We map out machining steps based on tolerances. Critical dimensions go on our high-precision 5-axis mills (slower, but more accurate), while non-critical ones use our standard 3-axis machines (faster, cheaper). This way, you only pay for precision where you need it.

3. Surface Finish: Define “Smooth” (With Numbers, Not Words)

“Smooth” means different things to different people. A finish that’s “smooth enough” for a hidden bracket might be too rough for a visible consumer part—and the cost difference can be huge.

What to include:

• Ra value: This is the industry standard for roughness (lower = smoother). For example:
  • Ra 6.3μm: Rough (hidden brackets, structural parts).
  • Ra 1.6μm: Smooth (most functional parts, like gears).
  • Ra 0.8μm: Very smooth (visible parts, like smartphone cases).

• Any post-machining treatments: e.g., “Anodize black (Type II),” “Powder coat red,” or “Passivate stainless steel (for corrosion resistance).”

Why it matters:

An Ra 0.8μm finish requires extra sanding or polishing—adding \(1-2 per part vs. Ra 6.3μm. A client making a custom grill for a restaurant sent us a drawing that said “smooth stainless steel.” We quoted \)20 per unit (assuming Ra 1.6μm + passivation), but they actually needed Ra 3.2μm (no extra polishing) and no passivation. The revised quote? $16 per unit.

How Honscn uses this:

We have in-house finishing teams for common treatments (anodizing, powder coating) and trusted partners for specialty ones (electroplating, laser marking). We calculate exact costs based on the finish type and part size—no markup for “mystery smoothness.”

4. Batch Size: Tell Us How Many You Need (Even If It’s a Prototype)

Batch size changes everything: Making 10 prototypes is cheaper per unit than 1 (we spread setup costs), but making 1,000 units is cheaper per unit than 100 (we use automated machines).

What to include:

• Exact quantity: e.g., “50 prototypes” or “1,200 production units.”

• Future volume (if you know it): e.g., “50 now, 500 next quarter.”

Why it matters:

Setup time for a CNC machine is ~1-2 hours (programming, tool changes). For 10 parts, that setup cost is spread over 10 units (\(10-20 per part). For 1,000 parts, it’s spread over 1,000 (\)0.10-0.20 per part). A startup making a prototype drone sent us a drawing for “1 part” and got a quote for \(50. When they said they’d need 20 more later, we gave them a “prototype + future” quote: \)40 for the first part, $25 each for the next 20.

How Honscn uses this:

For small batches (1-100 units), we use our quick-change 3-axis mills (fast setup, no automation). For large batches (100+), we switch to our automated lines (robotic part loaders, inline inspection) to cut labor time. We also offer volume discounts for future orders—if you tell us you’ll need more parts later, we can lock in a lower rate.

5. Special Requirements: Don’t Hide the “Odd Stuff”

Do you need the part to pass a salt spray test? Is there a logo you want laser-engraved? Does it need to comply with ISO 13485 (medical) or AS9100 (aerospace)? These “extra” requirements change the quote—but only if we know about them.

What to include:

• Compliance standards: e.g., “AS9100 certified (aerospace),” “FDA 21 CFR Part 177 (food contact).”

• Special tests: e.g., “Salt spray test (500 hours),” “Tensile strength testing.”

• Custom details: e.g., “Laser engrave part number on side,” “Deburr all edges (no sharp corners).”

Why it matters:

Compliance testing adds cost—but only if we plan for it. A medical client forgot to mention their sensor bracket needed ISO 13485 certification. Our initial quote was \(12 per unit, but adding the certification (document checks, material traceability) brought it to \)14. They were glad we caught it early—otherwise, the parts would have failed inspection later.

How Honscn uses this:

We have dedicated teams for compliant parts (medical, aerospace) who handle documentation and testing. We factor in test time and certification fees upfront, so you don’t get hit with surprise charges after the fact.

3 Common Drawing Mistakes (And How to Fix Them)

Even experienced buyers make these mistakes—but they’re easy to avoid. Here’s what to watch for:

Mistake 1: Leaving Tolerances Blank (Or Using “Standard”)

“Standard tolerance” means different things to different suppliers. Honscn’s “standard” for a bracket is ±0.1mm, but another supplier might use ±0.05mm—leading to price differences.

Fix: Add a tolerance block to your drawing (e.g., “All dimensions ±0.1mm unless marked *”). For critical dimensions, specify the exact tolerance (*8mm ±0.02mm).

Mistake 2: Forgetting to Note “Hidden” Features

Undercuts (recesses below the part’s surface), blind holes (holes that don’t go all the way through), or thin walls are easy to miss in a 2D drawing—but they change machining steps.

Fix: Use 3D CAD files (SolidWorks, STEP, or IGES) if you can—they show hidden features clearly. If you only have 2D, add a note: “Undercut: 2mm deep x 3mm wide (see detail A).”

Mistake 3: Assuming We Know Your “Why”

We don’t know if your part is for a kids’ toy (needs no sharp edges) or a jet engine (needs high-temperature steel) unless you tell us.

Fix: Add a 1-line note about the part’s use: “Sensor mount for industrial conveyor (exposed to dust, no corrosion needed).” This helps us flag issues (e.g., “Dust might clog that small hole—want to make it slightly bigger?”) before quoting.

How Honscn Turns Your Detailed Drawing Into a Fast, Accurate Quote

Once you send us a drawing with these details, here’s what happens next—we’ve streamlined the process to get you a quote in 24-48 hours:

• Our team reviews the drawing (1-2 hours): A CNC engineer and material specialist check for all the details we mentioned (material, tolerances, finish, batch size). If something’s missing, we email you one question (not 10) to fill the gap.

• We map machining steps: For example:

• • Material: 6061-T6 aluminum sheet (100x50x5mm) → cost $2 per part.

• • Machining: 3-axis mill for non-critical dimensions, 5-axis for the *8mm ±0.02mm hole → 15 minutes per part.

• • Finish: Anodize black (Type II) → $1.50 per part.

• • Batch size: 500 units → setup cost spread over 500 → $0.20 per part.

• We add transparency: Our quote includes a breakdown (material: \(2, machining: \)8, finish: \(1.50, setup: \)0.20) so you know exactly where your money goes. No hidden fees.

• We offer options: If there’s a cheaper way to make the part (e.g., “Switching to 6061 from 7075 saves $1.50 per unit”), we’ll include that as a note. We want you to get the best value, not just the first quote.

Real Example: How Details Cut a Client’s Quote by 18%

A small electronics firm sent us a drawing for a custom charging port bracket. Their initial drawing had:

• Material: “Aluminum”

• Dimensions: 40mm x 20mm x 3mm (no tolerances)

• Finish: “Smooth”

• Batch size: “100 units”

Our first quote (based on assumptions: 7075 aluminum, ±0.01mm tolerance, Ra 1.6μm finish) was $13 per unit.

They revised the drawing to add:

• Material: “6061-T6 aluminum (100x50x3mm sheet)”

• Tolerances: “*Hole: 5mm ±0.03mm; rest ±0.1mm”

• Finish: “Ra 3.2μm (no extra polishing)”

• Batch size: “100 now, 500 next month”

Our revised quote? \(10.75 per unit (18% cheaper). And we locked in the \)10.75 rate for their next 500 units—saving them even more later.

“The difference was just adding a few lines to our drawing,” said their purchasing manager (procurement manager). “We thought we were being clear, but Honscn showed us how small details make a big difference.”

Conclusion: Your Drawing = Your Cheat Code for Accurate Quotes

You don’t need to be a CNC expert to get a great quote from Honscn—you just need to give us the right details. Material grade, clear tolerances, Ra finish value, batch size, and special requirements: These five things will cut down on back-and-forth, speed up your quote, and ensure you’re not paying for things you don’t need.

And if you’re not sure what to include? We’re here to help. Honscn offers free drawing reviews—send us your draft, and we’ll point out missing details before you finalize it. We want your quote to be accurate, your project to run smoothly, and your partnership to be hassle-free.

Next time you’re ready to send a CNC drawing, remember: The more details you add, the more we can tailor the quote to your needs. Let’s get your part quoted right the first time.