Manufacturer · Fashion & Home Accessories
A sweatshirt with a front zip uses an open-end YKK nylon coil zip – most often No. 5, and No. 3 for light knitted tops and children’s styles. The open-end zip opens fully at the bottom with a pin and box, and on long styles it can be two-way. A coil is preferred over a metal zip because it is light, flexible and follows the movement of the knit.
Which YKK zip to choose for a sweatshirt
The choice starts with three questions: how heavy the knit is, how long the top is and whether the zip will be visible as a design element. The answers determine the coil size, the type of bottom end and the slider.
| Style | Size | Construction |
|---|---|---|
| Light sports top, zip-neck T-shirt | No. 3 | Open-end or closed-end (for a half zip) |
| Classic sweatshirt / hoodie | No. 5 | Open-end, one slider |
| Long sweatshirt, tunic, sweatshirt dress | No. 5 | Two-way open-end |
| Heavy fleece, padded sweatshirt | No. 5 or No. 8 | Open-end |
| Children’s sweatshirt | No. 3 or No. 5 | Open-end, with an easy-grip puller |
If the top is more of an outdoor jacket and will carry a heavy load, compare it with YKK Vislon moulded zips, which look sportier and are stiffer.
Open-end, two-way or half zip
Open-end zip with one slider
The standard for hoodies and sweatshirts. At the bottom there is a pin on one side and a box on the other; when fastening, the pin is inserted into the box and the slider is pulled up.
Two-way open-end zip
It has two sliders and can also be opened from the bottom. It is useful on long styles when the wearer sits down or rides a bike. Two-way zips require slightly longer fitting and more careful stitching of the bottom part.
Closed-end half zip
Used on “half-zip” and “quarter-zip” tops that are pulled on over the head. An open-end mechanism is not needed here.
Length of the open-end zip
For an open-end zip, the length is measured from the top stop to the bottom end of the box. It must match the front seam from the hem or ribbed band to the top edge of the collar. An inaccurate length is the most common cause of a wavy front seam:
- if the zip is longer than the opening, the knit gathers and the zip “bulges”;
- if it is shorter, the knit stretches during sewing and then ripples around the tape.
That is why, for a new style, a sample is sewn in each key size and only then is the length table fixed. For size ranges, it is normal to have two or three different zip lengths.
Slider and puller
- Auto-lock – holds the zip closed at the desired height; suitable for sweatshirts worn half-open.
- Non-locking slider – moves more easily, but can slip down with movement.
- Double-sided puller – allows the zip to be opened from the inside as well; useful on jackets, rarely on sweatshirts.
- Puller with a cord or tape – makes gripping easier with gloves and for children; on children’s clothing, watch the length of dangling elements.
Sewing into knits without ripples
Knitted fabric stretches, while the zip tape does not. That is why the sewing technique is as important as the zip itself:
- Stabilise the front edge with interfacing tape or a binding so that it does not stretch.
- Use a walking foot or differential feed so that the tape and the knit move evenly.
- Tack the zip first with a temporary stitch and check the symmetry of the two sides, especially with stripes and prints that need to line up.
- Make sure the fabric is not too close to the coil so that the slider does not catch it.
- Iron through a cloth at a moderate temperature – the coil must not be pressed directly with a hot iron.
Zip colour
On sweatshirts, the zip is almost always visible, so its colour is part of the design. Two popular solutions: the zip matches the main fabric or is deliberately contrasting, for example white on a navy sweatshirt. In both cases, give a number from the YKK colour card so that the shade is the same across all sizes and on repeat orders. If the sweatshirt has coloured piping or stripes, match the zip to them, not just to the main fabric.
Men’s and women’s styles
Technologists often ask whether the same zip can be used for men’s and women’s styles. It can, but pay attention to the pin side: in some markets and brands, women’s styles have a mirrored orientation. Clarify your brand’s standard before ordering, because the difference only shows in the finished product.
Durability in washing
Sweatshirts are washed often and usually at a higher temperature than outerwear. A coil zip copes well with this if a few rules are followed, which are worth including on the care label or in the customer instructions:
- the zip is closed fully before washing so that it does not bend in the drum or catch other garments;
- the garment is turned inside out, which protects both the prints and the slider;
- tumble drying at high temperature is not recommended for knits and indirectly strains the zip if the fabric shrinks.
YKK zinc alloy sliders have a finish that withstands regular washing; with special finishes, for example coloured to match the zip, check a washed sample before series production.
Ordering through Polkom
Polkom is a Bulgarian manufacturer of accessories for fashion, furniture, footwear and bags that also supplies original YKK zips to brands and garment factories. Browse YKK nylon coil zips and send an inquiry with the style, fabric, lengths by size and colour. We will prepare samples and a quote; minimum quantities depend on the item.
