Basic Terminology of Machine Drawings (aka Manufacturing Drawings)
At Restoric®, we specialise in utilising our CAD services to create, interpret, and modernise machine drawings for restoration, prototyping, and manufacturing projects. Understanding the terminology used in these drawings is essential for any engineer, draughtsman, or technician working with precision parts.
🧾 What Are Machine Drawings?
Machine drawings are detailed 2D representations of components, assemblies, and features. They include the necessary specifications to manufacture, inspect, and assemble parts correctly. These specifications often follow standards like BS 8888 and include information such as:
- Dimensions and tolerances
- Surface finishes
- Thread types and fitment
- Machining symbols
- Section views and enlarged details
Below is a complete glossary of 40 essential machine drawing terms used in professional drafting practices.
Manufacturing Drawing
📘 Glossary: 40 Key Terms used in Machine/Manufacturing Drawings
| No. | Term | Definition |
|---|---|---|
| 1 | Angular Dimension | Measurement of angles between features. |
| 2 | Arrowheads | Tips on dimension lines to indicate limits. |
| 3 | Auxiliary Dimension | Reference-only dimensions not used in manufacturing. |
| 4 | Boss | Protruding feature, typically circular, for reinforcement or assembly. |
| 5 | Centre Line | Dashed line marking the axis of symmetry. |
| 6 | Long Dashed Dotted Wide Line | Indicates a special surface specification. |
| 7 | Chamfer | Beveled edge (often 45°) for easier assembly. |
| 8 | Circlip Groove | Groove that accommodates a retaining ring. |
| 9 | Clearance Hole | Hole larger than the fastener for free passage. |
| 10 | Counterbore | Cylindrical recess for bolt or nut to sit flush. |
| 11 | Countersink | Conical recess for screw heads to lie flush. |
| 12 | Section Plane | Line indicating where a sectional view is taken. |
| 13 | Dimension Line | Line used to indicate measurements with values. |
| 14 | Enlarged View | Zoomed-in section of the drawing for clarity. |
| 15 | Round | Describes an external corner radius. |
| 16 | Fillet | Internal radius to eliminate sharp internal corners. |
| 17 | Flange | Projecting rim used for strength or mounting. |
| 18 | Hatching | Lines used in section views to indicate material cut-through. |
| 19 | Hidden Detail | Dashed lines representing non-visible features. |
| 20 | Knurl | Patterned surface for grip, often decorative. |
| 21 | Leader Line | Connects annotations or dimensions to features. |
| 22 | Local Section | Partial section view showing detail without cutting the whole part. |
| 23 | Machining Centre | Precision hole used for aligning the workpiece. |
| 24 | Machining Symbol | Indicates a surface must be machined to a standard finish. |
| 25 | Surface Finish | Numerical roughness specification (e.g., Ra value). |
| 26 | Surface Finish (Min/Max) | Defines allowable surface roughness range. |
| 27 | Pitch Circle Diameter (PCD) | Circle that passes through equally spaced holes. |
| 28 | Recess | Cutout area to reduce mass or accommodate other parts. |
| 29 | Slot | Narrow groove or channel feature. |
| 30 | Spigot | Male projection used to locate parts together. |
| 31 | Splined Shaft | Shaft with longitudinal grooves for torque transmission. |
| 32 | Square | Symbol or profile indicating a square shape. |
| 33 | Taper | Gradual change in diameter or thickness. |
| 34 | Taper Symbol | Box that describes taper dimensions and angle. |
| 35 | External Thread | Male thread used on bolts or studs. |
| 36 | Internal Thread | Female thread for nuts or tapped holes. |
| 37 | Undercut | Relief groove near a shoulder for easier fit or finish. |
| 38 | Woodruff Key | Half-moon key seated in curved shaft slot for torque transfer. |
| 39 | Key | Rectangular/square block used to lock rotation. |
| 40 | Keyway | Groove that houses the key in shaft or hub. |
📌 Conclusion
Machine drawings are essential tools for transforming ideas into accurate, manufacturable products. Knowing the language they use—dimensions, features, finishes—empowers you to read, create, and communicate with precision.
Need help converting legacy drawings or creating new ones? Contact Restoric® today for expert assistance in 2D detailing, 3D modeling, and manufacturing documentation.
