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41 shop-floor terms showing
The instructions showing what a part should be and how it must turn out.
“It is a recipe for metal. Skipping steps usually gets expensive.”
A controlled engineering drawing can include dimensions, notes, tolerances, material and revision information.
The version of a drawing you are supposed to use.
“Making the old version perfectly is still making the wrong part.”
The revision identifies changes made to controlled design documentation.
The information box on a print that tells you what drawing you are looking at.
“Check the name tag before introducing a chunk of metal to a cutter.”
Typically contains the drawing number, revision, units, scale and other administrative details.
How big the picture is compared with the actual part.
“A drawing is not permission to grab a ruler off your desk.”
A drawing scale is a ratio between represented and actual size; use stated dimensions to manufacture.
A number that tells you the size or location of something on a part.
“The print is telling you a number, not asking for your opinion.”
A specified numerical value associated with a feature or distance.
The distance straight across a circle, passing through its center.
“All the way across the donut. Not halfway.”
If a round hole is called out as Ø.500, the .500 refers to its diameter—not its radius.
Shown with Ø and measured through a circular feature’s center.
The distance from the center of a circle to its edge.
“Half the diameter. That tiny difference can ruin your whole afternoon.”
A 0.125 radius rounds a corner using part of a circle with a 0.125 radius.
Radius is half the diameter for a circle and is typically prefixed R.
A hole goes all the way through the part.
“Not a little pocket. All the way out the other side.”
A through-feature designation on a drawing.
There are four features covered by that callout.
“One note. Four holes. Do not drill a bonus fifth.”
The quantity prefix applies the specified requirement to four features.
An imaginary circle that the centers of bolt holes sit on.
“The holes are supposed to line up with the bolts. Novel concept.”
A pattern-defining circle, usually dimensioned by diameter; additional information controls count and angular locations.
The symbol ± is read “plus or minus.” It means a size can be a little bigger or a little smaller than the target number.
“A little wiggle room in both directions. Not an all-access pass to guess.”
The target is 1.000. The minus side takes away .005, giving .995. The plus side adds .005, giving 1.005. Both endpoints count in this example.
When used as 1.000 ± .005, the ± symbol indicates an equal bilateral dimensional tolerance: the upper deviation is +.005 and the lower deviation is −.005 relative to nominal 1.000.
How far a measurement can vary and still be accepted.
““Close enough” finally has actual numbers attached.”
Before this example: ± is read “plus or minus.” If that symbol is new, start with the Plus or minus entry just above.
From 1.000, subtract .005 to get .995, or add .005 to get 1.005. That is the allowed size range for this example.
The permitted variation of a dimension or characteristic.
A size can be above or below its target by amounts shown on the drawing. When you see ±, read it as “plus or minus.”
“The part gets a little wiggle room—on both sides.”
A tolerance expressed as upper and lower deviations around a nominal value.
The largest and smallest allowed sizes are written directly.
“Stay between these numbers and nobody needs a dramatic meeting.”
A dimensioning method stating maximum and minimum acceptable limits.
A sloped, flat cut across a sharp edge.
“We knocked off the corner so it stops picking fights with fingers.”
A chamfer is an intentional beveled edge, not a random deburring mark.
A beveled edge, often called out by size and angle.
A rounded inside corner between two surfaces.
“An inside corner that took the gentle route.”
A concave transition radius between intersecting surfaces.
Unwanted sharp material left at an edge after cutting.
“The tiny metal troublemaker waiting to bite your finger.”
Raised residual material created by processes such as drilling, milling or turning.
Remove those unwanted sharp edges and leftover bits.
“Make the part less interested in drawing blood.”
An operation to remove burrs without violating drawing requirements.
How fast the tool moves into or along the material.
“The cutter’s walking speed. Sprinting is not always smart.”
The programmed or applied rate of tool advancement relative to the workpiece.
How fast the rotating tool or workpiece spins.
“That is the spin dial—not the “make it better” dial.”
Usually expressed in revolutions per minute (RPM).
A larger flat-bottomed hole above a smaller hole, often for a bolt head.
“A little parking spot so the bolt head can sit down.”
Notice the larger cylindrical recess at the top and the smaller hole beneath it.
A cylindrical enlargement with a flat bottom, concentric with another hole.
A cone-shaped opening that lets a flat-head screw sit flush or below the surface.
“A funnel-shaped seat for a screw that wants to keep a low profile.”
The angled opening fits the tapered underside of a countersunk screw head.
A conical enlargement at the mouth of a hole, specified by diameter and angle or other applicable requirements.
A reference used to set up where and how a part gets measured.
“Everybody needs to agree where “here” is before arguing about “over there.””
Datum A establishes a reference; the actual inspection setup depends on the drawing’s datum features and controls.
A theoretically exact point, axis, plane, or combination derived from a datum feature to establish a datum reference frame.
A real surface or feature on the part used to establish a measurement reference.
“The actual part feature that helps us find “here.””
A physical feature identified to establish a datum during inspection or manufacturing.
A system of symbols that tells you how a feature is allowed to vary in shape, direction, or location.
“The print’s way of explaining what “in the right place” actually means.”
Geometric dimensioning and tolerancing communicates allowable geometric variation using standardized symbols and rules.
Usually called position: it controls where a feature is allowed to be, based on its intended location.
“That hole needs to be the right size AND in the right damn place.”
This sketch shows the idea only. A real position requirement controls a feature’s location using its specified tolerance zone and any datum references.
Position is a geometric tolerance controlling feature location relative to its theoretically exact position, as specified by its feature control frame.
A boxed set of symbols and numbers describing a geometric requirement.
“The tiny rectangle full of instructions everybody pretends they read.”
A compartmented frame containing a geometric characteristic, tolerance value/modifiers and datum references when required.
A boxed dimension showing the exact target location or geometry; its allowed variation is controlled elsewhere.
“The target on the map. The rules for missing it are in another box.”
A theoretically exact dimension, often shown boxed in ASME drawings.
How much a surface is allowed to wiggle away from being flat.
“A table that rocks is annoying. A part that rocks may be scrap.”
The entire controlled surface must lie within two parallel planes spaced by the specified flatness tolerance.
A form control defining the allowed separation between two parallel planes containing a surface.
How closely a feature must line up parallel to a reference.
“Two things can be neighbors without leaning into each other.”
An orientation control relative to a specified datum.
How closely a surface or axis must be at a right angle to a reference.
“Ninety degrees. Not “that looks pretty upright.””
A perpendicularity control establishes a tolerance zone oriented 90° to the referenced datum, with zone shape depending on the feature.
An orientation control relative to a specified datum.
How much a measured surface changes as a part rotates around a datum axis.
“Spin it. Watch the needle. Try not to panic.”
Circular or total runout controls variation of a surface relative to a datum axis, as specified.
Maximum material condition: the size at which a feature contains the most material.
“Biggest shaft, smallest hole. That is the most metal you can pack in.”
For an external feature MMC is its largest allowable size; for an internal feature MMC is its smallest allowable size.
A measuring machine that checks a part by locating points in 3D space.
“An incredibly accurate way to discover the part had other plans.”
Coordinate Measuring Machine used to determine feature geometry and dimensions.
A handheld tool used to measure outside sizes, inside sizes, and depths when appropriate.
“Great tool. Still not a magic wand.”
A comparative dimensional measuring instrument whose suitability depends on tolerance and measurement method.
A precision measuring tool commonly used for sizes like thicknesses and diameters.
“When “pretty close” is not close enough.”
A screw-based measuring instrument for precision dimensional measurements.
A tool that shows small movement or variation as a needle changes position.
“The needle tells on the part. Every. Single. Time.”
A displacement indicator often used for alignment, comparison and runout checks.
A part that cannot be accepted or economically fixed to meet requirements.
“Congratulations on your new premium-priced paperweight.”
Nonconforming material designated for disposal or recycling according to company procedures.
Fixing a nonconforming part so it meets the original requirements.
“The part gets a second chance. Your schedule might not.”
Action taken to make a nonconforming product conform to its original requirements.
A careful check that the first production result meets the drawing and process requirements.
“Check one properly before making fifty wrong ones.”
A documented verification of a representative initial production item, with scope defined by customer or industry requirements.
The texture or roughness a surface is required to have.
“A shiny-looking part can still be rough in all the wrong ways.”
Drawing requirements may specify surface texture parameters, processes or other finish criteria.