Denim hardware is two different parts that happen to share a press. A jeans button (tack button, 工字扣) closes the waistband. A rivet (撞钉) reinforces a pocket corner. Swapping them, or setting them with the wrong die, is the classic laundry-return: spinning caps, burst faces, rust stains on stonewash.
TrimGem University teaches tack buttons next to zippers and pocket hardware because they share a wash, a plate and a die. The Guangzhou one-stop catalogue will keep adding denim closures; the clench geometry does not change.
The tack button
Two pieces: cap (A) and tack / nail (B). The tack is driven through the stack and rolled into the cap. The side view looks a little like the Chinese character 工, hence the mill name. Materials: brass, zinc alloy, steel, sometimes aluminium. Finishes: the usual antique coppers, nickels, imitation gold, plus resin drops and stones on fashion denim.
Ligne sizes mills actually stock (conversions vary slightly by house):
| Ligne | Approx. diameter |
|---|---|
| 16 L | 10 mm |
| 18 L | 11.5 mm |
| 20 L | 12.5 mm |
| 24 L | 15 mm |
| 27 L | 17 mm |
| 32 L | 20 mm |
Hollow caps are light. Resin-core (胶心) caps fill the shell so the tack has something to bite; cheap regrind cores split when the tack hits, and the button opens in wear. Double-prong tacks hold harder than single-prong on thick stacks — mill talk often quotes a higher pull for double-prong. Threaded tacks versus spike tacks are a holding-versus-piercing choice.
Also used on leather coats, down, boots and bags when the stack is thick.
The rivet
Again two pieces: cap and tack, clenched through several layers (denim mills often talk 4–7 layers at a pocket). Brass, zinc or aluminium faces; the job is abrasion and a visual “jean.” It is not a closure. Hole size in the cloth must be tight enough that the set cannot pull out as a unit.
Setting is the product
The die must match the cap’s relief (a logo needs a matching “cover die” or the mark crushes). Roll the tack enough to lock, not enough to burst the face. After a run, re-check shut height: fabric thickness changes, dies wear. Shop-floor rule of thumb when there is no gauge: a fingernail should not slip under the set, and a hard pull should not pop it — then confirm with the brand’s newton spec.
Stonewash and bleach punish thin plates and un-lacquered antiques. Specify wash route with the hardware, not after.
Fashion rhinestone and two-tone caps are extra processes on the same tack geometry. They still have to survive the wash. Hollow caps on a heavy stack are how faces burst; resin-core on a light fashion jean can be overkill — match the stack.
Pocket rivets that sit on a seam allowance need the die to miss the seam lump or the cap will sit drunk. That is a marker problem as much as a hardware problem.
TrimGem quotes tack buttons and rivets as matched sets with dies. A cap photo is not enough.