Thread And Seam Construction

BY MACKENZIE WALTON
MARCH 2012

• Thread sizing conventions

• Common types of sewing thread

Thread size is determined the same way that yarn size is determined for
textiles. While there are different systems, they are all based on weight
and length specifications, and not by diameter as might be assumed.

• METRIC TICKET (Nm)
# of 1,000 metre lengths in 1,000 grams

• COTTON COUNT (Ne)
# of 840 yard hanks in 1 pound
• TEX
grams per 10,000 metres

• DENIER
grams per 9,000 metres

GENERAL GUIDELINES FOR THREAD SIZE SELECTION
SEWING THREAD SIZES BY FABRIC WEIGHT FABRIC WEIGHT
GARMENT EXAMPLES
TEX (GSM) (oz/yd2)

18, 24 65 - 140 2-4 T-shirts, Lingerie

24, 27, 30 140 - 200 4-6 Shirts, Dresses

30, 40 200 - 275 6-8 Light-Weight Bottoms

40, 60 275 - 400 8 - 12 Light-Weight Denim

60, 80, 105 400 - 500 12 - 15 Heavy-Weight Denim

COTTON THREAD

Generally provides good sewing performance but strength and abrasion
resistance is inferior to synthetic threads of equal thickness

• Mostly used for piece-dye items
• Shrinkage may cause puckering after wash/dye
• Can be mercerized – reduces shrinkage, increases strength and luster,
improves dye up-take

SPUN POLYESTER THREAD

Made with staple polyester fibers. Provides good sewing
performance, good dimensional stability and good stitch locking
properties due to the fibrous surface.
• Resistant to sunlight and chemicals
• Stronger than cotton, including 4X better abrasion resistance
• Ideal for light to medium weight fabrics

CORESPUN POLYESTER THREAD

Made by spinning staple polyester or cotton fibers around a continuous
filament polyester core. Provides enhanced strength and elongation while
maintaining stitch locking ability and can be run at higher speeds without
breakages.
• Higher machine speeds mean an increase in productivity by up to 21%
• Best thread for heavy fabrics, like denim and outerwear
• More consistent sewing quality due to better loop formation and
resistance to damage
• Most expensive general purpose sewing thread

TEXTURED FILAMENT THREAD

Continuous filaments of polyester or nylon are entangled by various
methods to create softness and bulk. Ideal for overlocking and the looper
of coverseams, these threads provide excellent coverage for raw edges
• Most economical thread
• Softness makes it ideal for lopping threads that sit close to the skin
• Excellent elasticity for stretch fabric applications
• Often found in intimates, baby clothes, and athletic wear

OTHER THREAD TYPES

• Mono-filament ‘Invisible’ Thread
• Embroidery Thread
• Elastic Thread
• Specialty – Lurex, Indigo
• Locked Filament Thread
• Glow in the Dark

LUBRICATION

Regardless of construction, all threads are finished with a lubricating
coating. This facilitates the passage of the thread through the machine and
needles, reducing friction and heat that can cause damage.

LIFE SPAN

Under optimal conditions, thread will last about 18 months before the
lubricants start to break down and thread quality starts to deteriorate.
Unsurprisingly, most factories do not store thread in optimal conditions
and so this period is usually much shorter.

• Needle sizing conventions

• Different Needle Types

Most sewing is done with rounded-point
needles. Actual cutting points are only
used for leather and similar fabrics. ‘Set
Points’ are normal, lightly rounded points
used for wovens, while knits demand
more rounded needles, referred to as ‘ball points’

Different levels of roundness are identified with letter markers

R = Normal round
• for light woven fabrics

SPI = Acute round
• For densely woven fabrics

SES = Light Ball
• Fine to medium knits, fine denim, medium to heavy wovens

SUK = Medium Ball
• Stonewashed denims, corsetry

SKF = Heavy Ball
• Fine elastic materials, coarse knits

SKL = Special Ball
• Medium to coarse elastic materials, coarse knits, lycra

The fabric and end use will determine the thread size and type, and needle
type that you will use. The chosen thread will determine the needle size.
There will be a range of possible thread sizes and types that can be used
with any given fabric, depending on the application.

• Seam Types
• Stitch Types
• Applications
• What makes a good seam

• Superimposed Seams (basic simple seam)
• Lapped Seams
• Lapped felled seams

• Flat Seams
• Bound seams
• Edge finishing

SUPERIMPOSED SEAMS

STANDARD SEAM FRENCH SEAM

LAPPED SEAMS
LAPPED SEAM

FELLED SEAM

301 - LOCKSTITCH

• Basic 1-needle straight stitch
• Uses least amount of thread
• Tightest and most secure stitch
• High abrasion resistance due to low profile on the fabric
• No stretch

304 - ZIGZAG

• 1-needle zigzag lockstitch
• Can stretch, and can provide edge coverage
• Used to apply lace or appliques
• Used for bar tacks and button holes

101 - CHAINSTITCH

• Formed using 1 thread only – no bobbin or looper
• On its own it is only suitable as a basting stitch
• Blind hemming is a variation of this stitch

401 - CHAINSTITCH

• Formed using 2 threads – needle and looper
• Appears the same as 401, but is much more secure and
durable
• Ability to stretch
• Excellent for setting elastic
• Frequently used for topstitching and for lapped seams on
high-wear garments like denim
• Less thread passes through the fabric than on a
lockstitch, which can reduce seam pucker
• 404 – Zigzag chainstitch

406 and 407 – COVER STITCH

• 406 uses 3 threads, 407 uses 4
• Excellent stretch. 407 has the most stretch
• Excellent strength
• Looper stitches are more efficient because you don’t have
to change a bobbin
• Less thread passes through the fabric than on a lockstitch,
which can reduce seam pucker
• Increased seam bulk
• Increased cost

503 – 2-THREAD OVEREDGE SERGE

• Formed using 1 needle and 1 looper thread
• No structural strength – only suitable for coverage of inner
seam allowances

504 – 3-THREAD OVEREDGE SERGE (OVERLOCK)

• Formed using 1 needle thread, 1 looper thread, and 1 cover
thread
• Most common for overlocking, and often used for sewing
seams on knit fabric

512 and 514 – MOCK SAFETY STITCH

• Formed using 2 needle threads, 1 looper, and 1 cover
thread
• Common for seaming knits, and can be used for wovens as
well
• Only 514 should be used on knits as it has better stretch

515, 516 – SAFETY STITCHES

• A combination of an overedge stitch with a 401 chainstitch
• 515: 4-thread safety uses a 503 overedge serge
• 516: 5-thread safety uses a 504 overlock stitch

FLATLOCK – 600 CLASS

• Formed using 2 – 4 needle threads plus 1 looper thread and
1 cover thread
• Fabric edges butt together but do not overlap
• Highly elastic seams with very low profile for maximum
comfort
• Efficient to sew
• Very high thread consumption
• Common for performance and scuba wear

SPECIALTY STITCHES

• Pick Stitch - classic
• Pick Stitch – on knits

SPECIALTY STITCHES

• Whip Stitch
• Blanket Stitch (single buttonhole)

• Tension
• SPI
• Thread Choice
• Stitch Choice
• Needle Type
• Needle Condition
• Seam Width
• Additional Elements

SEAM PROBLEMS

• Seam Pucker
• Grinning
• Skipped Stitches
• Broken Needle Threads
• Broken Bobbin Threads
• Needle Damage on Fabric
• Seam Slippage

SEAM PUCKER

• Bad tension
• Bad feed
• Fabric-Thread instability
• Uneven shrinkage during finishing
• Thread-bloat from washing
• Structural jamming/Inherent pucker
• Tight weaving does not have enough room between yarns
for thread
• Sewing caused yarns to be pushed out of place

Grinning

• Loose tension
• Incorrect stitch choice
• Lockstitch is the tightest stitch and will grin less than other
stitches

SKIPPED STITCHES

• Bad tension
• Machine timing is off
• Bobbin hook or looper is not entering needle thread loop
at correct time
• Incorrect needle choice
• The wrong needle can cause problems in creating the
needle thread loop
• Damaged needle
• If the needle is bent, or is striking the throat plate, it may
not create the loop in the right place for the hook to
catch

NEEDLE THREAD BREAKAGE

• Tight tension
• Trapping at package base
• Snarling before tension disc
• Poor needle choice
• If eye is too small, there will be increased friction
• Excessive heat
• Poor quality thread

BOBBIN/LOOPER THREAD BREAKAGE

• Tight tension
• Badly wound bobbin
• Incorrect fit of bobbin case
• Trapping at package base (for loopers)

NEEDLE DAMAGE

• Incorrect needle/thread choice
• Damaged needle

SEAM SLIPPAGE

• Problem is with the fabric – not the stitch
• Low yarn count, and continuous filament yarns that don’t grip
each other well are to blame
• Very minimal improvement can be achieved through
increasing seam allowance, adding topstitching, or changing
to a lapped felled seam
• When possible, seams can be fused
• Best option – Change fabric

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