ASVAB CampDrawings, Symbols and Shop Terminology flashcards
8 cards with the formulas, rules and traps from this lesson. Answer in your head, then flip to check.
Rule · 1/8
Drawing scale 2:1 vs 1:2: does scale change the written dimension?
No. At 2:1 the picture is twice actual size; at 1:2 it is half. The written dimension (e.g. 20 mm) is the true size regardless of scale, so never multiply a dimension by the scale.
Term · 2/8
Visible, hidden and center lines: what does each show?
Thick solid line: edge seen directly. Short dashes: edge hidden from that view. Long-short dash pattern: centerline marking an axis or symmetry, not solid material.
Common trap · 3/8
What does the callout 4X Ø6 THRU mean?
Four separate holes, each 6 mm in diameter, going all the way through. 4X is a count of features, not a multiplier on the diameter; hole locations come from separate dimensions.
Formula · 4/8
Diameter vs radius symbols: Ø and R
Ø is diameter (full distance across through the center); R is radius (center to arc). , so Ø18 means R = 9 mm. Do not confuse Ø18 with R18.
Fact · 5/8
Inch to millimeter conversion
exactly. Multiply inches by 25.4 to get mm (2.50 in = 63.5 mm); divide mm by 25.4 for inches. Note 1/4 in = 6.35 mm, not 6 mm.
Rule · 6/8
How do you find the limits of 20.0 ± 0.2 mm and 12.00 +0.10/−0.00 mm?
Bilateral ± varies both ways: 20.0 ± 0.2 means 19.8 to 20.2 mm. Unilateral varies one way: 12.00 +0.10/−0.00 means 12.00 to 12.10 mm. Endpoints are normally acceptable.
Formula · 7/8
Thread pitch from threads per inch; what do 1/4-20 and M8 × 1.25 mean?
. 1/4-20: 1/4 in major diameter, 20 threads per inch, so pitch 0.050 in. M8 × 1.25: 8 mm major diameter, 1.25 mm pitch.
Term · 8/8
Counterbore vs countersink
Counterbore: flat-bottomed cylindrical recess around a hole, for socket-head screws. Countersink: cone-shaped entry so a flat-head screw sits flush. They are not interchangeable.