Pancyprian Machine Elements T.S. (Practical) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

First-angle projection

Object between observer and plane. Front view placed below the top view, left-side view on the right. Standard in ISO-E countries including Cyprus, marked by the truncated-cone symbol.

Hidden edge line

Dashed line of medium thickness showing edges not visible in the view. Omitted when it would clutter the drawing; a section view is then preferred to show internal detail.

Section hatching

Thin lines at 45 degrees filling cut material. Adjacent parts get opposite or differently spaced hatching. Shafts, bolts and ribs cut lengthwise are drawn unsectioned by convention.

ISO 286 tolerance class

Combination of a letter and IT grade, e.g. H7. Uppercase letters denote holes, lowercase shafts. The letter sets the fundamental deviation, the number sets the tolerance zone width.

Clearance fit calculation

Maximum clearance equals hole upper deviation minus shaft lower deviation. Minimum clearance equals hole lower deviation minus shaft upper deviation. Positive values at both limits mean a clearance fit.

Maximum material condition

State where the hole is smallest or the shaft is largest. Geometric tolerances with the MMC modifier gain bonus tolerance as the actual size departs from MMC toward LMC.

42CrMo4

Quenched and tempered alloy steel with about 0.42 % carbon, 1 % chromium and 0.2 % molybdenum. Used for high-strength shafts, gears and nitrided parts needing good toughness.

Case hardening

Carburise low-carbon steel such as 16MnCr5 at 900–930 °C to a 0.6–1.0 mm case, quench and temper. Produces a hard wear-resistant surface with a tough core, typical for gears.

Nitriding

Surface hardening at 500–550 °C in ammonia without quenching. Case depth 0.2–0.5 mm, very high hardness, minimal distortion. Suited to 42CrMo4 and dedicated nitriding steels.

Anodising

Electrochemical process forming a hard oxide layer on aluminium for corrosion and wear resistance. Can be dyed and sealed. Does not add significant thickness to the part.

Micrometer reading

Sleeve shows whole and half millimetres; thimble has 50 divisions giving 0.01 mm. Add sleeve value to thimble value times 0.01. Use the ratchet to limit measuring force.

Vernier caliper resolution

A 50-division vernier on a 1 mm main scale reads 0.02 mm; a 20-division vernier reads 0.05 mm. Read the main scale before zero, then the matching vernier line.

Gauge block wringing

Joining gauge blocks by pressing their lapped faces together so they adhere. Sets build any size from stacked blocks; used to calibrate micrometers and calipers at 20 °C.

Cutting speed formula

vc equals pi times diameter in millimetres times spindle speed in rpm, divided by 1000, giving metres per minute. Used to set lathe and milling speeds for a given tool and material.

Tapping drill size

Nominal thread diameter minus pitch. For M10 with 1.5 mm pitch the tapping drill is 8.5 mm. For M8 with 1.25 mm pitch it is 6.75 mm, usually rounded to 6.8 mm.

Climb versus conventional milling

Climb milling has cutter rotation with the feed, giving better finish but needing backlash-free machines. Conventional milling opposes the feed and is safer on older machines with worn leadscrews.

Bearing life L10

L10 equals the dynamic load rating divided by the equivalent load, raised to the power 3 for ball bearings or 10/3 for roller bearings, in millions of revolutions.

Bearing bore code

For bore codes 04 to 96, multiply by 5 to get the bore in millimetres. Code 04 is 20 mm, 05 is 25 mm, 06 is 30 mm. Codes 00, 01, 02, 03 mean 10, 12, 15, 17 mm.

Radial lip seal orientation

The sealing lip faces the medium being retained so pressure helps the lip contact the shaft. The shaft seat should be ground to Ra 0.2–0.8 µm and the lip lightly greased at fitting.

Grease fill quantity

Sealed bearings are filled for life. In open housings fill about one third of the free space; overfilling causes churning, overheating and grease breakdown, especially at high speed.

Gear module

Module equals pitch diameter divided by number of teeth, in millimetres. Two meshing gears must share the same module. Centre distance equals module times the sum of teeth divided by two.

V-belt tension check

Apply force at the middle of the span and measure deflection, typically about 16 mm per metre of span. Re-tension new belts after the first running hours and replace belts in matched sets.

Flexible coupling purpose

Transmits torque while accommodating small parallel, angular and axial misalignment plus shock loads. Types include jaw, tyre and disc couplings. Alignment is still required before running.

Soft foot correction

One machine foot does not sit flat, distorting the frame when bolted. Detect with a dial indicator while loosening each bolt in turn, then shim the foot before aligning shafts.

Lockout tagout

Isolate energy, lock the isolator, attach a tag with the fitter's name, and verify zero energy before maintenance. Only the person who applied the lock removes it.

Process capability Cpk

Measures how well a process fits the tolerance band, accounting for centring. A common minimum for critical dimensions is 1.33; below 1.0 the process produces rejects.

Waste coolant disposal

Coolant and waste oil are hazardous waste. Store in labelled containers, never pour to drain, and hand to a licensed collector. Metal swarf is segregated and drained before recycling.

First-off inspection

Inspect the first part produced after a setup against all drawing requirements before running the batch. Prevents producing a full batch to a wrong setting.

Torque wrench use

Set the required value, tighten steadily until the click or break, then release the spring to zero after use. Never use it to loosen fasteners or as a breaker bar.

Dial indicator alignment

Mount the indicator on a magnetic base, rotate the shaft and read parallel offset at the coupling rim and angular error at the face. Correct soft foot before shimming.

Brinelling failure

Permanent indentations in bearing races caused by shock loading or fitting force transmitted through the balls. Shows as evenly spaced marks; prevented by correct mounting and handling.

Induction hardening

Local surface hardening of medium-carbon steel by eddy-current heating followed by quenching and low-temperature tempering. Used for journals and gear teeth with controlled depth.