Mechanical Engineering
Your ME Toolkit
Everything you need to ace ME interviews and sharpen your engineering skills β materials, tolerances, GD&T, DFM, and more.
0
Interviews done
40+
ME companies
30+
Engineering materials
9
Tools available
Interview Simulator
Mock ME interviews for Tesla, SpaceX, Apple, Dyson, Medtronic & 35+ more.
Material Explorer
Yield strength, UTS, modulus, density, thermal expansion for 30+ materials.
Process Guide
Compare injection molding, CNC, casting, forging, 3D printing, and more.
Surface Finishes
Anodizing (Type II / III), Alodine, black oxide, powder coat, plating, and heat treatments β materials, thickness, compatibility.
GD&T Reference
All 14 symbols with Datum Reference Frame, MMC/LMC bonus tolerance, and Feature Control Frame anatomy.
Tolerance Stack
Worst-case and RSS tolerance analysis for linear assemblies.
DFM Checklist
Process-specific DFM checklists β injection molding, CNC, sheet metal, casting.
Brief Generator
Generate realistic ME design briefs to practice your problem-solving process.
π οΈ
Ready for a real ME interview?
BrahmWorks connects you with senior mechanical engineers at top companies for live 1:1 mock interviews, design challenge walkthroughs, and portfolio reviews.
Interview Simulator
Choose a company
Select a company, configure your session, and start your mock ME interview.
Interview Config
β
No company selected
Pick one from the grid
Material Explorer
Engineering Materials
Browse 30+ engineering materials with mechanical and thermal properties. Click any card for full specs.
Process Guide
Manufacturing Processes
Compare manufacturing methods by volume, tolerance, material, and cost. Click for detailed guidelines.
Surface Finishes
CNC & Post-Process Finishes
Complete reference for metal finishing β anodizing types, platings, coatings, and heat treatments. Compatible materials, thickness, and design tips.
GD&T Reference
Geometric Dimensioning & Tolerancing
All 14 GD&T symbols, Datum Reference Frame, Feature Control Frame anatomy, and material condition modifiers (ASME Y14.5-2018).
π
Datum Reference Frame (DRF)
A 3D Cartesian coordinate system against which all tolerances are defined. The DRF constrains 6 degrees of freedom (3 translational, 3 rotational).
Datums are theoretical perfect points, axes, and planes.
Datum features are the actual (imperfect) physical surfaces on the part.
Primary datum: minimum 3 contact points. Secondary: 2 points. Tertiary: 1 point. Define datums that mimic how the part assembles.
Datums are theoretical perfect points, axes, and planes.
Datum features are the actual (imperfect) physical surfaces on the part.
Primary datum: minimum 3 contact points. Secondary: 2 points. Tertiary: 1 point. Define datums that mimic how the part assembles.
π²
Feature Control Frame
Each FCF carries one tolerance requirement. Reading left to right:
[Symbol] β geometric characteristic type
[β value] β shape + size of tolerance zone (β = cylindrical, no prefix = two parallel planes)
[M/L/S] β material condition modifier (optional)
[A] [B] [C] β datum references in order of precedence
Form tolerances (flatness, circularity) never reference datums. Location tolerances usually require all three.
[Symbol] β geometric characteristic type
[β value] β shape + size of tolerance zone (β = cylindrical, no prefix = two parallel planes)
[M/L/S] β material condition modifier (optional)
[A] [B] [C] β datum references in order of precedence
Form tolerances (flatness, circularity) never reference datums. Location tolerances usually require all three.
βοΈ
Material Condition Modifiers
MMC (β) β Maximum Material Condition: Feature has the most material β largest pin, smallest hole. Enables "bonus tolerance" as feature departs from MMC.
LMC (β) β Least Material Condition: Feature has the least material β smallest pin, largest hole.
RFS β Regardless of Feature Size: Default (no symbol). Tolerance applies at any feature size β no bonus tolerance.
Bonus tolerance example: Hole β20Β±0.5mm with position β0.6β. At MMC (β19.5), bonus=0. At β20.0, bonus=0.5, so position tolerance is β1.1mm.
LMC (β) β Least Material Condition: Feature has the least material β smallest pin, largest hole.
RFS β Regardless of Feature Size: Default (no symbol). Tolerance applies at any feature size β no bonus tolerance.
Bonus tolerance example: Hole β20Β±0.5mm with position β0.6β. At MMC (β19.5), bonus=0. At β20.0, bonus=0.5, so position tolerance is β1.1mm.
π
GD&T vs. Β± Tolerancing
Coordinate (Β±) tolerancing uses square tolerance zones. GD&T uses circular/cylindrical zones β providing 57% more usable tolerance area for the same design intent.
GD&T clearly defines inspection requirements. Β± tolerancing leaves ambiguity about how to measure. GD&T separates size, form, orientation, and location β each controlled independently.
Basic dimensions (boxed values) are theoretically exact. Title block tolerances do not apply to basic dims β tolerance is specified only in the FCF.
GD&T clearly defines inspection requirements. Β± tolerancing leaves ambiguity about how to measure. GD&T separates size, form, orientation, and location β each controlled independently.
Basic dimensions (boxed values) are theoretically exact. Title block tolerances do not apply to basic dims β tolerance is specified only in the FCF.
Symbol Reference
Tolerance Stack Calculator
Tolerance Analysis
Add parts to your assembly and compute worst-case and RSS (statistical) tolerance stacks. Reference process achievable tolerances below.
Tolerance Types
Bilateral: Β±0.05mm β variation allowed both above and below nominal. Most common.
Unilateral: +0.0 / β0.1mm β variation in one direction only. Used for interference fits, critical clearances.
Limit: 19.95 / 20.05 β direct upper and lower limits. Unambiguous for inspection.
Rule of thumb: Keep tolerances as large as function allows. Halving tolerance can 3β5Γ machining cost.
Unilateral: +0.0 / β0.1mm β variation in one direction only. Used for interference fits, critical clearances.
Limit: 19.95 / 20.05 β direct upper and lower limits. Unambiguous for inspection.
Rule of thumb: Keep tolerances as large as function allows. Halving tolerance can 3β5Γ machining cost.
Achievable Tolerances by Process
CNC Machining (standard)Β±0.05mm
CNC Machining (precision)Β±0.01mm
Grinding / LappingΒ±0.005mm
Injection Molding (commercial)Β±0.2mm
Injection Molding (fine)Β±0.05mm
Die CastingΒ±0.15mm
Sheet Metal bendingΒ±0.25mm
Investment CastingΒ±0.3mm
Worst-Case vs. RSS
Worst-Case (WC): Assumes all parts are simultaneously at their worst limit. Guarantees assembly β but very conservative. Use for safety-critical assemblies or when part count is low (β€4).
RSS (Root Sum Squared): Statistical method. Assumes variation is normally distributed. RSS tolerance = β(βtα΅’Β²). Allows ~99.73% yield (3Ο). Use when part count is large and yield loss is acceptable.
Cpk β₯ 1.33 is a common minimum process capability target for critical dimensions.
RSS (Root Sum Squared): Statistical method. Assumes variation is normally distributed. RSS tolerance = β(βtα΅’Β²). Allows ~99.73% yield (3Ο). Use when part count is large and yield loss is acceptable.
Cpk β₯ 1.33 is a common minimum process capability target for critical dimensions.
Assembly Parts
DFM Checklist
Design for Manufacturability
Process-specific guidelines to catch manufacturability issues before they reach production.
0 / 0 checked
Brief Generator
ME Design Brief
Generate realistic mechanical engineering design briefs to practice your process.