GD&T

3 types of dimensions (based on tolerance)

Untoleranced, toleranced, and basic

4 types of dimensions (based on geometry)

External, internal, mixed, derived

Which projection is this

Third angle

Which projection is this

First angle

Nominal value

Corresponds to name. The first value usually idk depends on the tolerance style. (X.XX + .xx the bold is the nominal value)

What do untoleranced dimensions need/usually do?

Most often uses tables to specify tolerances

Upper deviation

(U). The greater tolerance value (NOT including the nominal value.)

Lower deviation

(L). Lesser tolerance value

What is Dnom

The nominal value

Dmax?

Dnom + U (nominal + upper deviation)

Dmin?

Dnom + L (nominal + lower deviation)

T?

Tolerance
= Dmax - Dmin = U - L (upper deviation - lower)

Tell me about basic dimensions idk

Enclosed in a rectangle. Theoretical/perfect dimension with 0 tolerance

What do basic dimensions need?

Feature control frame

What are basic dimensions also called

Gaging

What symbol is this?

Circularity

What symbol is this?

Flatness

What symbol is this?

Straightness

Symbol?

Cylindricity

What are the form tolerances?

Straightness, flatness, circularity, cylindricity

Symbol?

Angularity

Perpendicularity

Parallelism

What are the orientation tolerances?

Angularity, perpendicularity, parallelism

Circular runout

Total runout

What are the types of runout tolerances?

Circular and total

Line profile

Surface profile

What are the types of profile tolerances

Profile of a line, of a surface

Position

What category is the position tolerance in?

Its own category, position.

Modifier

Translation

What are the modifier symbols?

Modifier, translation

from-to

Between

Statistical tolerance

Continuous feature

Dynamic profile

All around

All over

diameter

spherical diameter

counterbore

spotface

Countersink

(symbol)

origin

square

arc length

reference

slope

depth

conical taper

What do taper and slope have different about their tolerancing?

They have a :1 after all their numbers. (.18 +- .02 : 1) which i think means per 1 unit?

Feature control frame

box that contains tolerance info

What are the 3 parts to a feature control frame?

Geometric characteristic symbol, tolerance, and datum feature references.

What is a leader

the line with an arrow on it

Leader ends?

Arrow for pointing to an edge, circle if pointing to surface

Datum features

Theoretically perfect datum planes, axes, and points

Datum symbol

see image. Has the letter identifying the datum inside

Datum identification?

Letters. A, B… AA, AB, AC… etc. Excluding I, O, Q

What letters are omitted for identifying datums

I, O, Q

Third angle projection

Like you are rotating the camera around the object. See img.

First angle projection

Like you are rolling the object around on the ground while looking at it.

Rule #1

At MMC parts must be at perfect form

Rule #2

Dimensioned assumed to be RFS unless stated otherwise (MMC or LMC)

Tell me about spotface

Mostly cleaning up surface, no depth specified usually.

Independency

What does independency symbol do?

States the independency of feature (of size usually) independent of form. Makes the dimension an exception to Rule #1

datum target

inch to mm conversion

1 in = 25.4 mm

Profile wave

waviness wave + roughness wave (wave superposition)

What is waviness usually due to?

Vibrations

What is roughness usually due to?

Tool marks

Errors of surface texture

Waviness and roughness

Errors of form

NOT an error of surface texture. Loss of form due to deflection, heat, loss of straightness, etc.

just the arrowed symbol

Surface lay parallel to plane symbol is projected on.

just the arrowed symbol

Surface lay perpendicular to plane symbol is projected on.

just arrowed symbol

crossed in 2 oblique directions relative to plane symbol is projected to

just arrowed symbol

Multi directional

just arrowed symbol

Approximately circular relative to center of surface

just arrowed symbol

Approx radial relative to center of surface

just arrowed symbol

Lay is particulate, protuberant, non-directional (like static, etc)

a and b?

a = max, b = min surface roughness

a?

surface roughness max. no min smoothness

surface obtained by any production process

surface obtained by removal of material by machining

no material removal

All around

all over

Everything is Ra 3.2 EXCEPT the Ra 3.2/1.6 and Ra 1.6 specifications. The parentheses mean except for

Difference between skid and skidless

Skid is usually more portable, uses a skid instead of a reference surface. Can only measure roughness
Skidless machines usually stationary/more expensive. Uses a very flat reference surface to compare. Can measure profile, waviness, rougheness.

Stylus methods

Metrology method using transducer (toucher, stylus) to convert the surface into an electronic signal to be processed.

Other names for Ra

AA (arithmetic average. US and Canada). CLA (centerline average, everyone other than US and Canada).

Ra

ABSOLUTE VALUE of difference between mean line and surface.

Ra equation

Ra = ( |y1| + |y2| + … |yn| ) / n
n = number of data points. This is approximate

Rq

Also called RMS (root mean square).

Rq equation

sqrt( (y1² + y2² + … yn² / n) ) approx

Ry

Maximum height of profile (from PEAK to VALLEY).
Ry = Rp + Rv = (Height of tallest peak from mean + height of lowest valley from mean)