Zipper Size Chart: Tape Width, Teeth Height and Slider Match

A zipper size chart is the working document a factory keeps beside a specification, and it carries the figures a designer needs to fit a chain to a garment. The chart lists the size number, the tape width, the tooth height and the pitch, and it pairs each row with the slider that fits. Read this way, it answers the three questions that decide a fit.

This article sets out the columns a zipper size chart should carry, explains how a tape width specification is matched to a fabric, and shows how a slider size match is confirmed before a run is released.

1. What a Zipper Size Chart Records

A zipper size chart records the dimensions of a chain by size number, with each size on its own row. The columns are the closed chain width, the tape width, the tooth height, the pitch and the slider code, and a metal chart adds a weight figure per metre. The chart is the reference the technician reads before setting a machine.

The purpose of the chart is to remove the size number as a single point of failure. A designer who writes a number 5 on a drawing has not said which tape width or which slider goes with it, and a supplier may fill the gap with a part that fits the number but not the garment. The chart turns the number into a set of dimensions that can be quoted.

The chart is also the record of what was approved. When a repeat order arrives, the four figures are checked against the chart rather than against memory. Difei Button (Guangzhou) Co Ltd keeps the chart with the retained sample, and Difei checks each new batch against the same figures so the fit does not drift between orders.

2. Tape Width Specification for Each Size

A tape width specification fixes the flat band on which the teeth are set, and it moves with the size number. A size 3 chain takes a tape from 12 to 14 mm wide, a size 5 from 20 to 25 mm, a size 8 from 30 to 33 mm and a size 10 from 35 to 40 mm. The band has to be wide enough to carry the chain seam and the flap seam on separate lines.

Within a size number the tape width is not fixed, which is why the specification matters. A size 5 chain can be supplied on a 20 mm tape or on a 25 mm tape, and the two fit different panels. A buyer replacing a chain has to match the tape as well as the number, or the seam allowance will not line up.

The bead profile belongs in the same row. The bead is the raised edge the teeth are anchored to, and its thickness is quoted with the tape width. A tape from a different weaver with a bead 0.2 mm thinner produces a tooth with a visible flash line, so the bead figure is part of the tape width specification rather than a detail of it.

The table shows the four columns that belong on a chart and the way they move together. A slider code that does not belong to the size number on the same row is the most common error on a hand-built chart, which is why the code is printed beside the size and never left to be looked up later.

3. Slider Size Match and Chain Geometry

A slider size match is confirmed by the channel rather than by the number alone. A size 5 slider will span a size 5 chain when the channel depth suits the tooth profile, and a metal chain needs a slightly deeper channel than a coil of the same number. The match is therefore a question of the tooth block as well as the size.

The puller bridge is the second part of the match. The bridge width is set to the chain width, so a slider built for a 20 mm tape chain will not sit correctly on a 25 mm tape chain of the same size number. The two are quoted together so that a mismatched pair is not assembled by accident.

The locking pawl is the third part. On a metal chain the tooth face gives the pawl a positive seat, so the locked part should resist a pull of 40 to 60 newtons without creeping. A slider size match that ignores the pawl may close cleanly and still release under a side load, which is why the assembled part is tested rather than the slider alone.

4. A Zipper Size Chart for Metal Chains

A zipper size chart for a metal chain carries one column that a coil chart does not, which is the tooth material. Brass, aluminium and nickel teeth share the size and the pitch but differ in weight and in finish, so a chart that lists the number alone is incomplete. The material is written against the size rather than assumed.

The weight figure is the second addition. A brass chain in size 5 is roughly 30 percent heavier than the aluminium one of the same length, and the difference matters on a light garment. A chart that carries a weight per metre lets a buyer compare two materials on the same line rather than in two separate documents.

The finish is the third addition. An antique brass and a bright nickel finish of the same size read very differently on a garment, so the approved finish is recorded on the chart beside the size. Difei keeps the approved finish swatch with the chart so a repeat order is checked against the same reference.

5. Tape Width Specification and Fabric Weight

A tape width specification should be matched to the fabric weight, because a heavy chain on a light cloth tears the seam. A size 5 chain on a light blouse pulls the seam out under its own weight, while a size 3 chain on a denim fly will not survive the wear. The tape width is the figure that decides how the load spreads across the seam.

The fabric weight is quoted in grams per square metre, and it is the figure to read beside the tape width. A shell above about 200 grams per square metre carries a size 5 tape without trouble, while a light cloth below 120 grams per square metre needs a narrower chain. The two figures belong on the same line of the specification.

The stitch line is the second consideration. A wider tape lets the chain seam and the flap seam sit on separate lines, which keeps the two from cutting each other. A narrow tape forces them onto one line and risks a leak and a tear at the same point. The tape width specification is therefore a design decision rather than a purchasing one.

6. Slider Size Match Across Size Numbers

A slider size match has to hold across the whole range rather than at one size. A supplier that runs a size 3, a size 5 and a size 8 needs a slider for each, and the three sliders are not interchangeable. A size 5 slider on a size 8 chain will not span the teeth, and a size 8 slider on a size 5 chain will not grip.

The channel depth differs across the range as well. A larger chain takes a deeper channel to cover the taller tooth, so a slider built for a size 3 will not seat on a size 5 chain even if the width were altered. The code is the safe reference, because it carries the size and the profile together.

The puller is the third part to hold across the range. A size 8 slider usually takes a longer puller than a size 5, because the chain is used on a heavier bag where a gloved hand is common. Difei keeps the slider codes and the puller options on one chart so a range can be quoted without a second lookup, and Difei notes on the chart which puller belongs to which code.

7. Reading a Zipper Size Chart for Coil Chains

Reading a zipper size chart for a coil chain follows the same columns, with two differences. A coil tooth is a flexible spiral rather than a solid block, so the tooth height is measured across the closed spiral and the channel is shallower. A size 5 coil runs at about 3.5 mm pitch against 4.5 mm on the metal chain of the same number.

The second difference is the tape. A coil chain is stitched to the tape after winding, so the bead profile is simpler than on a molded or a metal chain. A tape width quoted for a coil can therefore be narrower at the same size number without losing grip on the teeth.

The third difference is the weight. A coil chain is lighter than a metal chain of the same size number, which is why it appears on a light garment where a metal chain would feel heavy. A chart read side by side makes the difference visible, and it is the reason the two are quoted on separate rows rather than on one.

8. Tape Width Specification in a Purchase Order

A tape width specification should be written into the purchase order rather than left to the drawing, because the order is the document the factory works to. The order should carry the size number, the tape width, the tooth height, the pitch, the slider code and the finished length, and it should name the approved chart as a reference.

The order should also state the tolerance on the tape width, which is normally plus or minus 0.5 mm on a woven band. A tolerance that is not stated is filled by the supplier, and a band at the edge of a wide tolerance can fail to fit a seam allowance. Writing the figure removes the gap.

The third line is the approved sample. A purchase order that names the retained sample beside the chart gives the factory a physical reference as well as a written one. Difei writes the chart number and the sample date onto the order so the two can be matched, and Difei keeps both on file for the life of the part.

9. Frequently Asked Questions

9.1 What should a zipper size chart include?

A zipper size chart should carry one row per size number, with the closed chain width, the tape width, the tooth height, the pitch and the slider code in separate columns. A metal chart should add a weight figure per metre, because brass, aluminium and nickel teeth of the same size differ in weight. The chart should also record the approved finish and the retained sample date, so a repeat order is checked against the same reference rather than against memory. Write the chart number onto the purchase order so the factory works to the same document.

9.2 How is a tape width specification chosen?

A tape width specification is chosen to match the chain size and the fabric weight together. A size 3 chain takes a tape from 12 to 14 mm, a size 5 from 20 to 25 mm, a size 8 from 30 to 33 mm and a size 10 from 35 to 40 mm. The band has to be wide enough to carry the chain seam and the flap seam on separate lines, because two seams on one line risk a leak and a tear at the same point. A shell above about 200 grams per square metre carries a size 5 tape without trouble.

9.3 How do you confirm a slider size match?

A slider size match is confirmed by the channel rather than by the size number alone. A size 5 slider spans a size 5 chain when the channel depth suits the tooth profile, and a metal chain needs a slightly deeper channel than a coil of the same number. The puller bridge is set to the chain width, so a slider built for a 20 mm tape chain will not sit correctly on a 25 mm tape chain of the same size. The assembled part is tested, because a slider can close cleanly and still release under a side load.

9.4 What changes on a chart for a coil chain?

A chart for a coil chain follows the same columns as a metal one, with three differences. A coil tooth is a flexible spiral rather than a solid block, so the channel is shallower and the tooth height is read across the closed spiral. A size 5 coil runs at about 3.5 mm pitch against 4.5 mm on the metal chain of the same number, so the same opening takes more coil teeth. A coil chain is also lighter than a metal chain of the same size, and its tape can be narrower at the same number.