Technical guide
Bag sewing and closure types: a guide to choosing
A practical guide for plant managers and purchasing: which closure types exist, which bag each one is for, and what information you need to choose the equipment.
Closure types
Six ways to close a bag
Stitch types
401 stitch and 101 stitch: the difference that matters
Two-thread chain stitch (type 401)
It uses a needle thread and a looper thread that interlock. It is the stitch of industrial heads: strong, does not unravel by itself and withstands handling and stacking. It is the standard for almost all bags.
Single-thread chain stitch (type 101)
It uses a single thread. It opens easily by pulling the end, which is why it is used on bags the end user needs to open quickly. It is less secure if the thread breaks at one point.
Stitches per inch
The typical range is 2 to 3.25 stitches per inch; the factory standard is 2.5. More stitches close fine products better, but reduce speed.
Free space at the bag mouth
Pedestal systems need about 15 cm of free bag above the product. An overfilled bag cannot be sewn properly.
Bag thickness
Most heads sew up to 8 mm thick. Thicker bags require heads such as the Megatex (Yaohan) U700C (11 mm).
Bag types
Most common materials and formats
Recommendations by product
Which closure should you use for your product?
| Product | Typical bag | Recommended closure | Filling equipment |
|---|---|---|---|
| Salt | Woven or laminated PP with liner | Sewing with corrosion-resistant equipment | Stainless steel gross weight |
| Sugar | Woven PP or multiwall paper | Tape sewing or double needle | Digital gross weight or net weight |
| Animal feed | Woven PP | Single stitch or fold-over | Digital gross weight |
| Fertilizer | Woven PP with liner | Sealed liner + corrosion-resistant outer seam | Gross or net weight, corrosion-resistant |
| Flour and powders | Multiwall paper or valve bag | Crepe tape, pinch or valve | Auger net weight |
| Grains and seeds | Woven PP or jute | Single stitch | Digital gross-weight scale |
Already know which closure you need?
Send us a photo of your bag, the product and the daily output, and we will quote the right equipment.
Brands we represent
Seproma is the sole authorized Hamer-Fischbein representative in Costa Rica. Learn about the company.