Engineering knowledge base
Mechanical Engineering Guides
Practical explanations that connect DraftFit calculator results to the engineering decisions behind them.
Fits & tolerances
H7/g6 Fit Explained: Limits, Clearance and Typical Use
Understand how an H7/g6 ISO fit is built from hole and shaft tolerance zones, how clearance is calculated and when this fit is useful.
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Fits & tolerances
Clearance vs Transition vs Interference Fits
A practical guide to clearance, transition and interference fits, including how limit dimensions determine the actual fit class.
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Sealing
O-Ring Squeeze Explained: What the Percentage Means
Learn what O-ring squeeze means, how it is calculated and why groove geometry, duty and application type matter.
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Threads & fasteners
Bolt Preload vs Tightening Torque
Understand why tightening torque is only an indirect way to create bolt preload and why friction dominates many torque estimates.
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Shaft connections
Parallel Key Design: Shear Stress vs Bearing Pressure
See how torque creates tangential force in a parallel key and why both key shear and contact pressure should be checked.
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Search-intent guide
M10 Bolt Torque: Why There Is No Single Correct Value
A practical M10 bolt torque guide explaining the influence of property class, preload target, friction and bearing geometry.
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Search-intent guide
3.53 mm O-Ring Groove Dimensions: What Must Be Defined First
Why a 3.53 mm O-ring cross-section does not have one universal groove dimension and which application inputs determine the gland.
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Search-intent guide
DIN 6885 Key Size for a 35 mm Shaft
How to select the DIN 6885 parallel-key size for a 35 mm shaft and why length and strength still require engineering checks.
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GD&T
GD&T Position vs Concentricity: Practical Selection Notes
Understand why position and runout controls are often more practical than legacy concentricity concepts, especially when working across ISO and ASME conventions.
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