Wednesday, 4 March 2009

Sewing-5



Needle Point

These are divided into two parts- Cutting points and cloth points.

Cutting Points: These are needed for fabrics like leather where there are no gaps in the structure.

Cloth Points: These are needed for those fabrics where there are gaps in the structure.

Cutting point Neeedles

a. Wedge Point: It produces most durable seam on leather. It resists great stress, the incision lie at right angle to the seam direction and high stitch density can be achieved.

b. Cross Point: Here strength is considerably weakened. The material is likely to tear if stress is at the right angle. The incisions lie parallel to the direction of the seam.

c. Twist Point: The strength is intermediate and the incisions like 45 deg. to the direction of the seam.


Cloth Point Needles

These are used for sewing textile materials rather than the sheet material already described. The points have a round cross section.

The needles are different for the various woven and knitted fabrics.

Knitted fabrics consist of yarns with spaces between them and if a yarn in a knitted fabric is broken the knitted structure may begin to unravel. The requirement in sewing knitted fabrics is :

a. A needle which will slightly deflate the yarns and enter the spaces.

b. A needle of as small a size as possible consistent with needle strength and sewing thread size.

c. A fabric which is sufficiently lubricated that it has flexibility in relation to the movement of the needle.

The shape of the tip of the neele point which best achieves this deflation is a ball shape and the needle is referred to as a ball point needle.

Woven fabric consist of yarns which can have greater or lesser amounts of twist, interlaced with each other at various degrees of density.

For that a needle is needed that goes between the fibres and does not strike and break them.

The shape of the tip of the needle point which best achieves this penetration between the fibres has the appearance of being slighly cone shaped. It is usually referred to as a set point needle.

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