Which roughness conversions are valid? →
A change of units preserves the parameter. A change from Ra to Rz or Rq needs additional information about the profile and the definition.
Tolerances & finishes
Start with the requirement on your drawing.
Find the meaning, check the conditions, then calculate from known inputs.
I have hole and shaft limits
Calculate clearance or interference.
I have a surface marking
Read Ra, Rz, N grades and measurement conditions.
I have a geometric control
Read the feature, zone, modifiers and datum references.
I need an assembly dimension
Build a signed linear tolerance chain.
Find a reference
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Try a shorter term or reset the filters. Use the four task routes above if you do not know the term.
Read a surface-texture symbol in its edition →
First identify the drawing standard and edition. Then distinguish the manufacturing requirement, roughness parameter, texture direction and any additional fields.
Legacy N grades: find the nominal Ra value →
N7 corresponds to the nominal Ra reference value 1.6 µm in the documented comparator table. N grades do not specify a manufacturing process or replace measurement conditions.
Rz: check the definition before comparing values →
Rz is version-sensitive. The same label on two reports does not establish that the values describe the same profile characteristic.
Check coating thickness and dimensional growth →
Select the measurement method for the coating, substrate and state. A generic coating name does not establish its required thickness or the dimensional allowance.
Start with the fit you need to understand →
The hole and shaft limits determine a signed diametral-clearance interval. That interval describes a size relationship; it does not by itself approve an assembly or load capacity.
Calculate clearance from hole and shaft limits →
Use the actual minimum and maximum sizes from your drawing or applicable table. The result is signed diametral clearance, not radial eccentricity or an assembly approval.
Read an IT width and a tolerance-zone position →
The grade sets a tolerance width for a nominal-size interval. The letter locates that interval relative to the nominal size. You need both to obtain limits.
Read an ISO 2768 drawing note without mixing editions →
Identify the cited part, edition, class and feature type. There is no automatic default class for a drawing that does not specify one.
Specify plastic dimensions with a conditioning state →
A generic polymer name cannot guarantee an achievable machining tolerance. Define the exact material, geometry and inspection conditions with the supplier.
Find the applicable weld acceptance requirement →
Use the contract’s welding standard, edition, joint/material scope and inspection requirements. A generic defect table cannot determine acceptance for every weld.
Tolerance width versus allowance between mating parts →
A tolerance width belongs to one size interval. A clearance or interference value compares two mating sizes. Keep the sign convention visible.
Clearance fit: understand the zero boundary →
A non-negative signed clearance interval has no size-only interference. A zero minimum is a theoretical boundary, not proof that real parts slide together freely.
Interference fit: distinguish size overlap from capacity →
If the entire signed clearance interval is negative, the size limits imply interference. That does not calculate contact pressure, transmitted torque or a safe assembly method.
Bearing fit is different from internal clearance →
The shaft or housing fit describes the ring’s mounting interface. Bearing internal clearance describes relative movement within the bearing.
Read the letter: tolerance-zone position →
The letter identifies the zone position; the grade number describes its width for the applicable size interval. Uppercase and lowercase distinguish hole and shaft codes.
Read the number: IT tolerance width →
An IT grade is a tolerance-width designation. It is not a deviation from nominal and not a guaranteed machining capability.
Nominal size: identify which dimension it names →
For a hole/shaft fit, nominal size is the reference used with deviations. For some named products, the size designation must instead be looked up in that product system.
Thou and mil: convert the length, then read the tolerance →
One thou, or one mil in a length/thickness context, is 0.001 inch = 0.0254 mm = 25.4 µm exactly. A microinch is one thousandth of a mil.
Estimate free thermal expansion of a bore →
Estimate the bore temperature that would remove an assumed diametral interference and add a specified clearance. This is a linear expansion model, not a safe mounting temperature or joint-strength calculation.
Thread class: keep internal and external designations →
A thread class supplies tolerance context for a specified thread system. It does not by itself provide a tapping-drill size, torque or a universal fit clearance.
Find the geometric control on your drawing →
Read the full control and drawing edition. A symbol category alone does not determine all datum, size and boundary requirements.
A boxed basic dimension gives a theoretical target →
The boxed value identifies theoretically exact target geometry. It is not an ordinary ± size tolerance; the associated requirements establish permitted variation.
Separate the datum feature, simulator and datum →
The physical feature has imperfections. The datum is an ideal reference established from the specified features and rules; a simulator helps establish that reference in inspection.
Read a geometric tolerance as a complete requirement →
Start with the standard and edition, then identify the controlled feature, tolerance zone, modifiers and any required datum relationships.
MMC and LMC: identify the material-size boundary →
For a simple hole, MMC is its smallest permitted diameter; for a simple shaft, MMC is its largest. LMC is the opposite size limit.
Circular runout versus total runout →
Circular runout addresses individual circular sections during rotation about the specified datum axis. Total runout addresses the designated surface over its required extent.
True position is the target, not the tolerance zone →
Distinguish the theoretical location, the permitted zone and the measured feature. Not every position requirement can be reduced to a diameter or a pair of XY numbers.
Virtual condition: a boundary under stated rules →
A virtual-condition boundary combines size and the applicable geometric control. A single boundary value does not determine the acceptability of an entire assembly.
Build the dimensional chain before adding tolerances →
Define the functional output and the direction of each contributing dimension. Worst-case bounds and statistical spread answer different questions.
Calculate a one-dimensional tolerance stack →
Enter nominal dimensions, signs and symmetric tolerance half-widths in one unit. The default result is the worst-case interval for this linear chain.
Plan a Gauge R&R study around the measurement task →
A Gauge R&R study evaluates repeatability and reproducibility under a defined study design. It does not replace checks of bias, stability or the complete uncertainty budget.
Prepare a traceable first article inspection record →
Determine the applicable contract and revision, then plan traceable verification of design characteristics and required process/material evidence.
Surface quality: start with the marking →
Read the parameter, units and measurement conditions.
Ra: read the parameter and measurement conditions →
Read Ra 1.6 µm, its meaning and its measurement context.
Convert roughness units: µm ↔ µin →
Convert units for Ra or Rz without changing the parameter.
Thread tolerance classes →
Keep the system, size and internal/external designation together.
What changed in this reference section?
Unsupported generic values were replaced with source-scoped examples, explicit-input calculations and edition-aware guidance. Each existing URL remains reachable.
Read the page-by-page decisions →