Drawing Completeness
A complete drawing speeds up quoting. Missing info causes delays. Check each item before you submit.
- All dimensions shown. Every feature needs a dimension. Do not rely on the CAD model alone.
- General tolerance block. Add a default tolerance (like ±0.005") in the title block.
- Material called out. List the material and temper. Example: 6061-T6 Aluminum.
- Finish specified. Call out surface finish or coating. Example: Anodize Type II, Black.
- Part number and revision. Every drawing needs a unique part number and revision letter.
- Scale and units. Show the drawing scale and whether units are inches or millimeters.
- Third-angle projection. Use third-angle projection for US shops. Mark it on the drawing.
Send both a 2D PDF drawing and a 3D STEP file. The drawing controls dimensions. The STEP file lets the shop program the CNC machine.
Feature Review
Check each feature in your design against these rules.
- Inside corner radii. Every inside corner has a radius ≥ 1/3 the pocket depth.
- Wall thickness. Aluminum walls ≥ 0.040". Steel walls ≥ 0.060".
- Pocket depth. No deeper than 4x the pocket width.
- Hole depth. No deeper than 4x the hole diameter for standard drills.
- Hole sizes. Use standard drill sizes when possible.
- Undercuts. Avoid undercuts unless the part truly needs them.
- Thin, tall features. Add ribs or widen the base to prevent vibration.
- Thread depth. Thread engagement of 1.5x to 2x the diameter is enough.
Tolerance Review
Over-tolerancing is the top cost driver. Review every tolerance on your drawing.
- General tolerance set. ±0.005" for most features is standard.
- Tight tolerances justified. Each ±0.001" or tighter feature has a real reason.
- No stacked tolerances. Dimensions come from a single datum.
- Surface finish called out. Only specify Ra values where the surface matters.
- GD&T used correctly. Datums are defined. Feature control frames are complete.
Count how many features have tolerances tighter than ±0.005". If more than 20% do, you are likely over-tolerancing. Each tight tolerance adds cost.
Material & Finish
- Material grade specified. Not just "aluminum" but "6061-T6 aluminum."
- Finish type named. Anodize, powder coat, passivate, or as-machined.
- Finish spec referenced. Example: MIL-A-8625 Type II for anodizing.
- Color specified. If finish is dyed, list the color.
- Masking areas marked. Show which areas should NOT be coated.
- Hardware called out. List any inserts, pins, or press-fit hardware.
File Prep
- STEP file exported. STEP (.stp) is the most universal 3D format.
- PDF drawing attached. A 2D PDF drawing with all dimensions and notes.
- File names match. The file name matches the part number on the drawing.
- Latest revision. Double-check you are sending the latest version.
- No broken references. Open the STEP file in a viewer before sending.
Print this page and check off each item before you upload your files. It takes 5 minutes and prevents days of delays.
Ready to submit your design?
Upload your CAD file for an instant quote. Free DFM review included with every order.
Upload CAD for Instant QuoteReady to submit your design?
Upload your CAD file for an instant quote. Free DFM review included with every order.
Upload CAD for Instant QuoteFrequently Asked Questions
Do I need a 2D drawing if I have a 3D model?
Yes. A 2D drawing is the legal document that controls your part. It defines tolerances, finishes, and notes that a 3D model cannot carry. Always send both a STEP file and a PDF drawing.
What if I am not sure about tolerances?
Use ±0.005" as your default. Tell the shop which features mate with other parts. They can suggest the right tolerance for those features.
Can I skip the finish specification?
If you want as-machined finish, say so on the drawing. If you leave it blank, the shop will ask and delay your quote. Always specify the finish.
What file format should I send?
Send a STEP (.stp) file for 3D geometry and a PDF for the 2D drawing. STEP is the most universal format. Avoid native CAD files unless the shop requests them.
