Mechanical Drawings Checklist

This checklist is prepared for preparing production-ready mechanical design drawings of the product, ensuring dimensional accuracy, and completely transferring material/workmanship information. The goal is to define production tolerances, verify assembly compatibility, and ensure traceability of each part.

Drawing Format and Title Information​

1. Is standard title block and border used?​

Each mechanical drawing should have a title block and drawing border compliant with corporate standards. The title block should contain at least the following information:

• Part name and code
• Revision number
• Date and preparer
• Checker
• Unit of measurement (mm / inch)
• Material type and surface treatment
• Page number (e.g., "1/3")

Without this information, a drawing is not considered valid as a production document. Title block is also mandatory for documentation traceability and revision tracking.

2. Is filename specified in each drawing file?​

Naming of drawing files should be standardized to prevent confusion during both production and archiving processes.

Filename should include part code, description, revision, and extension information. Consistency should be maintained between different formats (e.g., DWG, DXF, STEP, PDF), and only the final approved version should be sent to production. Archived old versions should be stored in "OBSOLETE" or "HISTORY" folders.

3. Are CAD layers used in the drawing visible and properly classified?​

In all CAD files, drawing layers should be organized by function and properly visible.

Incorrect layer management can lead to production errors especially in DXF or STEP export. Layer colors, thicknesses, and line types should comply with drawing standard document (e.g., "MECH_LAYER_STANDARD.pdf"). In files sent for production, only necessary layers should be open, reference lines should be closed.

Dimensioning and Geometric Consistency​

4. Are dimensions shown directly on material avoided?​

All dimensions should be shown only as notation on technical drawing plane (2D view), not on CAD model surface. Dimensions directly processed on model can cause incorrect information transfer to manufacturer. 2D technical drawing should be the only reference document for production approval. This rule ensures clean reading of drawings and correct interpretation of tolerances. "Model dimension display" should be turned off in CAD environment to ensure only approved dimensions are visible.

5. Are X and Y dimensions specified for each feature?​

Each feature like holes, slots, edge distances, and reference clearances should be positioned with X and Y coordinate dimensions. These dimensions should generally be given from reference corner (datum point) or centerlines.

Additionally:

• Diameter (Ø) for holes
• Radius (R) values for arcs or corner fillets must be specified

Details left without position dimension are left to production operator's estimation and increase assembly incompatibility risk.

6. Do all holes align with holes in mating parts?​

Mating hole alignment between multiple parts should be verified. This check should be verified in 3D in assembly model and noted in production drawing:

Production approval should not be given without this process. Incorrect alignment causes serious problems like screw not entering, forced pin insertion, or part cracking during assembly.

7. Is each hole diameter verified?​

Diameter control should be done separately according to hole function:

• Pilot hole
• Clearance hole
• Tapped hole

Each requires different tolerance and processing steps. Hole descriptions should be given in this format:

This information directly communicates process sequence and appropriate tool selection to manufacturer.

8. Are position tolerances defined for sheet metal parts?​

In sheet metal components, position tolerances of hole centers or bend points should be defined.

These tolerances should be determined according to laser cutting, punch, or CNC machining tolerance limits. Holes without tolerance cause post-bend alignment errors.

9. Are sheet metal hole diameter tolerances specified?​

Hole diameter tolerance should be clearly given in sheet materials.

This expression both informs manufacturer of allowed deviation limit and creates measurement criterion in quality control process. If general tolerance table exists, it should be indicated in drawing with note like "Tolerances unless otherwise specified: ISO 2768-mK".

10. Are all features fully dimensioned?​

All necessary dimensions should be given for each feature; no dimension should be left "derived" or "estimable". Missing dimension leads to operator's own interpretation in production and disrupts part standardization. Full dimensioning is a basic requirement for part compatibility, assembly ease, and measurement accuracy in quality control process.

Material, Coating, and Machining Instructions​

11. Is material type clearly specified?​

Material type of each part should be clearly defined in production document.

Material selection has direct impact on strength, weight, machinability, thermal expansion coefficient, and cost. Incorrect or missing material definition can cause post-production incompatibility and durability problems. Additionally, heat treatment (T6, Q+T) like material hardness classes must be specified for aluminum or steel parts. Color and density information should also be added for composite or plastic parts.

12. Is surface coating / finish information written?​

Surface coating or finish information should be specified for all mechanical parts.

Surface treatment is critically important for corrosion resistance, electrical insulation, heat distribution, and aesthetic appearance. Coating processes should be defined according to manufacturer standards (e.g., MIL-A-8625, ISO 2081, ASTM B633). If this information is missing, part may be rejected due to incorrect coating or color difference.

13. Are units specified (mm/inch)?​

Measurement unit used (e.g., mm or inch) in all drawings should be clearly written in title block.

Not specifying measurement system can cause scale errors or inappropriate part production during manufacturing. Additionally, mixed (metric + imperial) system should not be used; single system standard should be maintained throughout project. Ensure design team and manufacturer work in same measurement unit system.

14. Is chamfering, deburring, or brushing instruction added?​

Deburring instruction should be included in all mechanical drawings to remove sharp edges and burrs.

This process prevents both injuries during assembly and coating peeling. Additionally, processes like surface brushing (brushed finish) or edge rounding (R0.5 typical) should be clearly shown in drawing. This note is quality control criterion especially for CNC and laser cut parts.

15. Are detailed descriptions given for special processes?​

If welding, bending, heat treatment, surface hardening, laser engraving, marking, or post-assembly processing exists on part, these processes should be clearly specified. Each special process should be defined in detail in drawing notes section or referenced to relevant process document (e.g., "Process Spec PS-041").

These definitions provide clear instruction to manufacturer and determine which specification quality control will be based on. Missing process notes can cause serious deviations in part functional properties.

Hardware and Assembly Details​

16. Are all hardware components specified in BOM?​

All screws, nuts, washers, pins, rivets, pilot holes, and fasteners used in mechanical assembly should be defined as separate items in bill of materials (BOM). For each element, the following information should be present:

• Part type and standard (e.g., "M3x8 Socket Head Screw – ISO 4762")
• Material (e.g., "A2-70 Stainless Steel")
• Quantity (Qty)
• Reference position (e.g., HW-12)

When this information is missing, confusion or material shortage can occur on assembly line. Complete listing of hardware components is mandatory for both production planning and service spare parts management.

17. Are screw lengths verified?​

For each screw, total connection thickness (part + washer + nut) should be considered to verify screw length (L). Screw should engage at least 2 threads extra in threaded part.

Incorrect screw length causes either insufficient thread engagement or protrusion on opposite surface causing assembly error. In critical connections, "Thread engagement length ≥ 1.5 × nominal diameter" rule should be applied.

18. Is hole diameter checked for each hole according to appropriate screw diameter and type?​

All holes should be prepared at appropriate diameter according to screw type and diameter to be used.

Hole diameter and depth should comply with production standard (e.g., ISO 724 or ANSI B1.1). Incorrect hole dimension can lead to thread stripping, low tightening torque, or alignment error. Additionally, if insert (threaded bushing) is used for sheet metal or plastic parts, hole dimensions should be adjusted according to manufacturer recommendation.

19. Are tapped hole details specified in drawing?​

Tapped holes should be given in drawing with dimension, pitch, tolerance, and depth information.

These notations directly inform manufacturer about tool selection and machining depth. When tolerance class (e.g., 6H/6G) is not specified, machined holes may fit tight or loose during assembly. Additionally, in blind holes, minimum blind depth should be specified and bottom form (flat / cone) clearly expressed.

20. Are assembly screws, fittings, and fasteners compatible with each other?​

All fasteners should have same thread standard (metric / UNC / UNF) and same pitch value.

For example, M3 screw with M3 threaded hole, 4-40 UNC screw only with UNC hole.

This compatibility prevents production errors like:

• Thread stripping
• Forcing or jamming
• Torque imbalance

Screws, nuts, and washers used in assembly should have same mechanical class (e.g., A2-70, 8.8, 12.9), and galvanic corrosion risk should be evaluated in mixed material combinations (e.g., stainless screw – aluminum thread).

General Drawing and Production Controls​

21. Is file format saved appropriately for manufacturer?​

All mechanical drawings should be saved in file format requested by manufacturer or supplier.

Each file should be named to include project code, part name, revision, and version information.

Incorrect format or naming can cause incorrect data use in production process.

22. Is each drawing page numbered?​

In multi-page assembly or sub-part drawings, each page should be identified with page number and total page information.

This practice both facilitates production tracking and prevents errors like missing page submission. Page numbers should appear consistently in title block or page footer.

23. Do mechanical drawings contain revision code and date?​

Each drawing should include revision code (Rev), date, and drawer / checker information.

Revision information should match drawing filename and be consistent with documents sent to manufacturer. This check prevents old version drawings from being accidentally used during production. All changes should be stored in "Revision History" table with description and approval information.

24. Is there material and coating information for all screws and fasteners?​

Material type and surface coating (finish) information should be specified for all fasteners (screws, pins, nuts, washers) in drawings.

Coating type (e.g., galvanized, nickel, black oxide) is important not only aesthetically but also for corrosion resistance and non-conductivity. This information should appear exactly in quality control documents and supplier procurement lists.

25. Are explanatory notes on drawing simple, readable, and bilingual in English/Turkish?​

In projects working with international manufacturers and suppliers, notes on drawing should be prepared bilingually (Turkish/English).

This approach prevents interpretation errors and language-related misunderstandings on manufacturer side. Additionally, font selection should comply with technical drawing standard (e.g., ISO 3098).

26. Was tolerance stack-up analysis performed?​

Tolerance stack-up analysis should be performed for all dimensions affecting assembly. This analysis ensures deviations on each part do not accumulate in assembly causing excessive tightness or looseness.

Especially for:

• Case / cover joints
• PCB – mechanical mounting surfaces
• Gasket compression zones, this analysis is mandatory

Results should be archived as "Tolerance Analysis Report" and checked before production approval.

27. Is cover / gasket compression ratio verified according to IP target?​

In products targeting IP protection class, gasket compression ratio (% compression) should be calculated and tested.

Incorrect compression ratio negatively affects water or dust sealing. This verification should be done both in 3D CAD assembly and physical prototype tests. Gasket material (e.g., EPDM, Neoprene, Silicone) and Shore hardness should be in drawing notes.

28. Is assembly simulation (interference check) completed in 3D CAD?​

Interference check should be completed and reported in assembly file. This analysis is critically important in areas like hole alignment, cable passages, fan or heatsink clearances. Any interference or contact should be resolved before production. Simulation reports should be stored with design approval files.

29. Are assembly fixture and fixture details defined in drawings?​

If fixture, jig, or alignment apparatus to be used during assembly exists, their dimensions and positions should be defined as separate drawing or note.

This information ensures assembly repeatability in mass production and standardizes quality.

30. Is reference to packaging or assembly instruction (Packaging Spec No) added?​

Product packaging or pre-shipment protection instruction should be added to mechanical drawing as reference.

This reference prevents product from physical damage during post-production transportation or storage stages. Packaging instruction should be appropriate for product weight, surface coating type, and environmental protection requirements.