CAD & Drafting: interview questions and learning guide

2D drafting & drawing standards

A drawing is a contract between the designer and the person who makes the part.

Technical drawings show an object in orthographic views such as front, top and side, with sections where the inside must be shown. Dimensions, tolerances, notes and a title block with revision control tell the maker exactly what to build.

Interview tip: Explain how you check a drawing before release.

3D modeling & assemblies

Parametric models are smart: change one number and the whole design should follow.

In feature-based CAD you draw a constrained sketch, create features such as extrude and fillet, and then join parts in an assembly with mates. Fully defined sketches and clear references keep models stable. Interference checks and a bill of materials prepare the assembly for release.

Interview tip: Say which CAD tools you used and for what kind of parts.

GD&T, fits & manufacturing handoff

Tolerance is where design meets reality.

Geometric dimensioning and tolerancing uses datums and symbols to control form, orientation and position. The fit between mating parts can be a clearance, transition or interference fit. A tolerance stack-up adds up variation in an assembly, and design for manufacturing keeps parts easy to make.

Interview tip: Talk about how you work with the shop floor.

Sketch constraints and parametric modelling

A good sketch is a set of rules, not a drawing: change one number and the whole part follows.

Parametric CAD stores a model as sketches, dimensions, relations and features in an ordered tree. Constraints such as parallel, tangent and equal fix shape, and dimensions fix size. A fully defined sketch behaves predictably. Design intent means building so the model changes the way the designer wants, for example holes staying centred when width changes. Clean order and simple references keep the tree stable.

Interview tip: Explain design intent with an example and say you avoid referencing unstable edges.

Sheet metal and surfacing

A flat sheet folded like a paper box is simple, but the folds only work if the paper has room to bend.

Sheet metal parts are made by cutting and bending flat material, so the model needs thickness, bend radius and a bend rule. The flat pattern gives the cut size and must account for bend allowance. Reliefs prevent tearing at corners and minimum flange lengths keep bends practical. Surface modelling builds shapes from curves and patches for styled or complex forms, where smooth continuity between faces matters.

Interview tip: Mention the material thickness and bend radius your shop uses, because the flat size depends on them.

Assembly design and BOM

An assembly is a team photo: each part must stand in the right place and have a clear name tag.

An assembly puts parts and subassemblies together with mates that remove movement. Bottom-up design builds parts first and then joins them, while top-down design shapes parts from a layout. A clean structure with logical subassemblies keeps files light. The BOM lists every item with number, description, quantity and material, and balloons on the drawing link each part to it. Interference and motion checks come before release.

Interview tip: Show that you check mates and interference before releasing, and that part numbers follow a rule.

Drawing review, standards and PLM

A drawing is a contract with the workshop: one wrong number and the wrong part gets made on time.

Before release, every drawing is reviewed for views, dimensions, tolerances, notes, title block data and standard compliance. A checker also confirms the model matches the drawing. PLM or PDM systems store files with controlled states, versions and access. Changes follow a formal request and approval so everyone uses the latest revision, and old drawings are marked obsolete. Good control prevents wrong parts reaching the shop floor.

Interview tip: Say that you never edit released drawings directly, and always route changes through the change process.

AutoCAD commands, layers and blocks

Layers are tracing paper sheets stacked on one table. Keep each kind of line on its own sheet.

AutoCAD draws in 2D with lines, circles, arcs and polylines. Precision comes from object snaps, coordinate entry and commands such as offset, trim, fillet and array. Layers separate object types, such as centre lines, dimensions and hidden lines, each with a colour, linetype and lineweight. Blocks are reusable symbols so one change can update many copies. A tidy drawing uses named layers, correct units and clean, closed geometry.

Interview tip: Say that you work in layers and blocks, not with loose lines. It shows you can hand over a clean file.

Layouts, scale and plotting

Draw life size in model space. Put it on paper in layout space.

In AutoCAD you draw at full size in model space and arrange sheets in layouts, also called paper space. A viewport is a window on the model with its own scale, so one model can appear on many sheets at different scales. Text, dimensions and symbols must stay readable at the plot scale, which annotative styles help with. Plot style tables control line thickness and colour on paper. A good sheet has the right size, title block, scale note and revision table, and is checked in a PDF before release.

Interview tip: Always say you check the scale and print a test PDF before sending drawings out.

AutoCAD productivity: xrefs, dynamic blocks, templates and LISP

Do the boring part once. Then let the template, block or script repeat it.

Speed in AutoCAD comes from reusing work. External references let several drawings share one base drawing, so changes flow to all. Dynamic blocks hold many sizes in one symbol. Templates start every drawing with the right units, layers, text styles and title block. Attributes store text in blocks so schedules can be extracted. Small LISP routines and scripts automate repeated steps. A team agrees on layer names and standards so files from different people match.

Interview tip: Mention one time you saved effort with a template, block or script, with a number.

AutoCAD for civil, electrical and architectural drafting

Same tool, different language: a plan is read by a site engineer, a schematic by an electrician.

Drafting in AutoCAD differs by trade. Architectural and civil drawings use plans, sections, elevations and site plans with grids, levels, and symbols. Electrical drawings use schematics, single line diagrams, panel layouts and cable schedules with standard symbols. Mechanical, piping and HVAC drawings add routing, tags and bills of material. Each trade has symbols, layer conventions and approval steps. Many firms also use Revit or Civil 3D, so knowing how 2D drawings connect to a model is valuable.

Interview tip: Name the trade you draw for and the symbol standards you follow. Employers hire for the trade, not only the software.

Check views and dimensions, tolerances and notes, the standard used and the revision, then have a second person review it.

Use fully defined sketches, a clean feature order, clear names and stable references so parametric changes update correctly.

A clearance fit always leaves a gap between shaft and hole, while an interference fit has a shaft larger than the hole and is pressed together.

Shaping a design around the manufacturing process, material and tolerances so it is simple and low cost to make.

Use native files inside the team, STEP as a neutral 3D format, DWG or DXF for 2D exchange and PDF for review copies.

Use named layers, closed polylines, blocks for repeated parts, a company template and standards, and purge unused items before sending the file.

Model space is where you draw at full size. Paper space is the layout where viewports show the model at chosen scales with the title block.

Set and lock the viewport scale, plot at the right ratio, check text height and measure a known dimension on a test PDF.

An external reference links another drawing into the current one, used for shared base plans so updates flow to all sheets.

Work on a copy, sort objects into layers, convert repeated shapes into blocks, purge unused items and check units and dimensions before using it.

Company and national standards such as ISO or IS, ASME Y14.5 style GD&T and tolerances, and the layer and title block rules of the team.

Update the source drawing first, refresh linked drawings and schedules, check tags and numbers, mark the revision and tell everyone who uses the drawings.

Define templates, layers, text and dimension styles, file naming and review checklists.

Use a revision table, a change log, controlled folders and a review before release.

Use a checklist, cross-check dimensions, standards and BOM, and have a second person review.

Start with templates and simple parts, review often, share shortcuts and increase complexity.

Use blocks, templates, scripts and standard parts, and avoid rework with clear inputs.

Share early drafts, confirm inputs in writing and update quickly after changes.

Assess impact on schedule and cost, update drawings with revision control and communicate clearly.