ITI/NCVT Sewing Technology (AITT Theory) flashcards

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

Needle size Nm 90

Metric needle size where Nm equals the blade diameter in hundredths of a millimetre; Nm 90 means a 0.90 mm blade, suitable for medium woven fabrics such as shirting and light denim.

Ball-point needle

A needle with a rounded point that pushes between knit yarn loops instead of cutting them; it prevents laddering and needle holes in jersey, rib and interlock fabrics.

Lockstitch class 300

A two-thread stitch where the upper and lower threads interlock inside the fabric; it is strong and non-stretch, needs a bobbin, and is the standard stitch for woven garments.

Four-thread overlock

A safety stitch using two needle threads and two looper threads that sews a seam and neatens the edge in one pass; commonly used for knit garment side seams.

French seam

A self-enclosing seam made by stitching wrong sides together, trimming, turning right sides out and stitching again; it hides all raw edges and suits sheer, light fabrics.

Flat-felled seam

A strong lapped seam where both raw edges are enclosed inside a fold and two parallel rows of stitching show; typical of jeans and shirt side seams.

Seam class 1

In ISO 4916, the superimposed seam class where two or more pieces are joined with edges aligned; the plain seam and French seam belong to this class.

Warp and weft

Warp yarns run lengthwise and have higher strength and less stretch; weft yarns run crosswise with more stretch. Bias is 45 degrees to warp and stretches most.

Tex yarn count

A direct yarn numbering system giving the mass in grams of 1,000 metres of yarn; a higher Tex value means a coarser, heavier yarn, unlike cotton count.

GSM fabric weight

Grams per square metre, the standard measure of fabric mass; light shirting is 80-150 GSM, medium 150-250 GSM, and heavy denim or coating 250-400 GSM and above.

Grain line marking

A pattern arrow that must be placed parallel to the warp; any deviation causes twisting, garment spirality after washing, and poor drape.

Marker efficiency

The percentage of marker area actually covered by pattern pieces; calculated as piece area divided by marker area times 100, with 80-90% typical for woven fabric.

Shrinkage allowance formula

Cut length equals finished length divided by one minus the shrinkage fraction; for 2% shrinkage on a 100 cm finished length, cut 100 divided by 0.98, about 102 cm.

Takt time

Available production time divided by customer demand; it sets the pace each workstation must meet and is the basis for balancing a sewing line.

Standard minute value

SMV equals basic time multiplied by performance rating plus allowances; it is the standard time allowed to complete one operation and is used for costing and efficiency.

Line efficiency formula

Efficiency percentage equals standard minutes produced divided by minutes attended, times 100; standard minutes produced equals pieces made times the SMV of the operation.

AQL 2.5 inspection

Acceptable Quality Limit sampling under ISO 2859-1; for major defects an AQL of 2.5 is common, and the sample size and accept/reject numbers are read from the table.

Four-point fabric system

A fabric inspection scoring method giving 1 to 4 points per defect by length; points per 100 square yards are compared with an agreed limit to accept or reject the roll.

Critical defect

A defect that poses a safety or legal risk, such as a needle fragment in a garment or a wrong fibre content label; it causes rejection of the whole lot.

Fusible interlining fusing

A resin-coated interlining bonded to the shell by heat, pressure and time, typically 130-160 degrees Celsius for 10-15 seconds; under-fusing causes bubbling.

Welt pocket construction

A pocket made by stitching a fabric strip over the opening; the welt is usually 2-3 cm wide, the opening 12-16 cm long, with both ends reinforced by bartacks.

Sleeve cap ease

The extra length of the sleeve cap over the armhole, usually 1.5-3 cm; it is distributed between notches and shrunk with steam before the sleeve is set in.

Iron temperature dots

Care label ironing symbols use dots: one dot means 110 degrees Celsius, two dots 150 degrees, and three dots 200 degrees maximum soleplate temperature.

Crocking fastness

Colour fastness to rubbing, rated 1 to 5; it is tested dry and wet, and a rating of 4 or above is normally required for apparel fabrics.

Break-even point

The sales volume at which total revenue equals total cost; it is calculated as fixed cost divided by selling price per unit minus variable cost per unit.

CMT costing

Cut, make and trim price covers labour, factory overhead and profit but excludes fabric and trims; the FOB price adds fabric, trims, packing and export costs.

Differential feed setting

An overlock feed adjustment: 1.0 for normal, 1.2-1.5 to stretch knits and prevent wavy seams, and 0.7-0.9 to gather lightweight woven fabric.

Skipped stitch cause

A missed stitch usually caused by a blunt or wrong-point needle, a needle too fine for the thread, incorrect needle bar height, or bad timing between needle and looper.

Lockout tagout procedure

Isolate the machine at the isolator, apply a personal lock and tag, and verify zero energy before threading, changing the knife, or clearing a jam.

Cotton dust hazard

Airborne lint and cotton dust from cutting and overlocking irritate the respiratory tract; local exhaust ventilation and face masks are the standard controls.

Button ligne size

The button diameter unit where one ligne equals 0.635 mm; a 20 ligne button measures about 12.7 mm and is a common shirt size.

Seam strength test

A test that pulls a seam perpendicular to its stitch line until rupture; a balanced seam should fail in the fabric rather than at the stitching.