Technologies
Knowing how to prepare a technical drawing for CNC quoting is the difference between getting an accurate quote in 24 hours and going back and forth with the machine shop for days. A well-prepared draw
Knowing how to prepare a technical drawing for CNC quoting is the difference between getting an accurate quote in 24 hours and going back and forth with the machine shop for days. A well-prepared drawing removes ambiguity, reduces risk of rework, and often results in a lower price — because the mach
Knowing how to prepare a technical drawing for CNC quoting is the difference between getting an accurate quote in 24 hours and going back and forth with the machine shop for days. A well-prepared drawing removes ambiguity, reduces risk of rework, and often results in a lower price — because the machinist can plan the job precisely instead of building in risk margins for unknown requirements.
This guide walks through every element your technical drawing needs to contain when requesting a CNC machining quote.
A CNC quote is only as accurate as the information provided. When a drawing is incomplete or ambiguous, machine shops do one of two things:
Both outcomes hurt you. A complete drawing is the most effective tool for getting competitive, reliable quotes and preventing cost surprises.
Your drawing needs enough views to fully define the part geometry. Standard practice:
For simple turned parts (shafts, pins, bushings), two views — front and right side — are often sufficient. For complex milled housings with features on multiple faces, you may need 4–6 views plus sections.
Every dimension that matters for function or assembly must be on the drawing. Don't rely on the machinist to scale dimensions from the view or calculate them from other dimensions.
Dimension guidelines: - Dimension from functional surfaces (the faces that contact mating parts), not from arbitrary reference points - Don't duplicate dimensions — each dimension should appear once - Chain dimensions only when the chain relationship is truly functional - Include overall dimensions (length, width, height) so the machinist can estimate material and setup
Without explicit tolerances, the machinist will apply whatever general standard they use — which may not match your requirements. Every critical dimension needs a tolerance:
If no tolerance is specified on a dimension, a competent shop will use the general block — but they'll also note this as a potential issue during review.
"Steel" is not a material specification. "Aluminum" is not a material specification. A complete material callout includes:
The clearer the material callout, the more accurate the material cost in your quote — and the lower the risk that the shop uses a cheaper substitute.
Surface finish affects functionality, appearance, and downstream processing. State it explicitly:
For parts where shape and position matter beyond basic dimensional tolerances, use Geometric Dimensioning and Tolerancing (GD&T):
Each GD&T callout requires a datum reference frame. Define your datums at functional surfaces — the same surfaces that contact mating parts or assembly fixtures.
Any threaded feature needs: - Thread standard: ISO metric (M6×1.0), UNC, UNF, BSPP - Thread class: 6H for standard metric, or state tolerance class - Thread depth: for blind holes, state minimum full thread depth - Threading direction: right-hand is standard, state if left-hand required
Don't just show a thread symbol — write it out: "M8×1.25 - 6H, 20 mm deep, through hole."
The title block is where basic job information lives:
The 3D model is not a substitute for a 2D drawing with tolerances. Send both: the STEP file for programming, the PDF drawing for tolerance, material, and finish requirements.
Missing tolerances on critical features: The machinist won't guess — they'll ask, and the quote will be delayed.
Unclear or missing material spec: Shops receiving "steel" will quote the cheapest option — you may get the wrong grade.
No surface finish callout: Machined surface finish varies by operation type and machine. Without Ra spec, you get whatever the default is.
Conflicting dimensions: When a dimension can be read two ways or one dimension contradicts another, the shop will stop and ask. Double-check your drawing math before sending.
DXF with construction geometry: If your DXF contains construction lines, reference geometry, or overlapping curves left over from the CAD design process, the laser or CNC programmer has to clean it up. This delays quoting and adds cost.
No revision control: If you send revisions, always increment the revision number and note what changed. Shops working from an outdated revision waste everyone's time.
To request a quote through Entag's CNC machining service:
For sheet metal parts requiring laser cutting, bending, and coating, see Entag's sheet metal fabrication page. For tube parts, see tube fabrication.
At minimum: a PDF drawing with all dimensions, at least a general tolerance block, and a material specification. Without these three, no machine shop can provide a reliable quote.
No — a well-dimensioned 2D drawing is sufficient for most parts. A 3D STEP file is useful for complex geometry because it helps the programmer verify the model matches the drawing, but the 2D drawing remains the authoritative document for tolerances and requirements.
Use ISO 2768-m (medium) as your general tolerance block — it covers ±0.1 mm for most common dimension ranges and is appropriate for general mechanical parts. Apply explicit tolerances only to features where function demands tighter control.
Entag accepts PDF (drawings), STEP or IGES (3D models), and DXF or DWG (2D CAD). Submit at app.entag.co.
A rough sketch can sometimes be enough for a preliminary estimate, but a formal quote with pricing you can rely on requires a complete dimensioned drawing. Invest the time in a proper drawing — it protects you and the supplier.
Notes should cover: any special processing requirements, marking or identification requirements (part number stamping, laser engraving), inspection requirements (CMM report, functional test), packaging or preservation requirements, and any customer-specific standards to follow.
Submit separate drawings for each manufacturing step (flat pattern for sheet metal, machined part drawing for CNC), plus an assembly drawing if the components interact. Note on each drawing which subsequent operations are required.
Entag manufactures precision machined parts for industrial clients across Egypt and the Middle East. Whether you need a single prototype or a full production run, our engineering team is ready to review your drawings and provide a quote.
