Start from the finished size. Add 0.25–0.5 in (6–13 mm) of ease on covers and 0.375–0.5 in (10–13 mm) of seam allowance on each sewn edge to get the cut panel. Stitch at 6–10 stitches per inch, use Tex 70 thread on light fabric and Tex 135 on 1000D, bartack every strap end, and expect ±0.125–0.25 in (±3–6 mm) on sewn dimensions.
SSG MFG · design guideDG-11 · 13 rules
13 rules, in the order you meet them on a model. Every value is typical; the principal quoting your part confirms its own limits.
| # | Rule | |
|---|---|---|
| 01 | Add ease to covers0.25–0.5 in (6–13 mm) over the equipment dimensions | 0.25–0.5 in (6–13 mm) over the equipment dimensions |
| 02 | Allow enough seam allowance0.375–0.5 in (10–13 mm) per sewn edge; 0.625 in (16 mm) on loosely woven fabric | 0.375–0.5 in (10–13 mm) per sewn edge; 0.625 in (16 mm) on loosely woven fabric |
| 03 | Cut load-bearing panels on grainMain load along the warp (roll length); avoid bias cuts on load-bearing panels | Main load along the warp (roll length); avoid bias cuts on load-bearing panels |
| 04 | Fit panels within the roll widthUsable width about 58 in (1.47 m) on a 60 in (1.5 m) roll | Usable width about 58 in (1.47 m) on a 60 in (1.5 m) roll |
| 05 | Set stitch density6–10 stitches per inch (about 2.5–4 per cm); lower end on coated fabric | 6–10 stitches per inch (about 2.5–4 per cm); lower end on coated fabric |
| 06 | Match thread to fabricAbout Tex 70 for light fabrics; Tex 135 for heavy webbing and 1000D; bonded nylon or polyester | About Tex 70 for light fabrics; Tex 135 for heavy webbing and 1000D; bonded nylon or polyester |
| 07 | Set stitch-to-edge distanceTopstitch 0.0625–0.125 in (1.5–3 mm) from the fold; 0.25 in (6 mm) gauge on twin-needle seams | Topstitch 0.0625–0.125 in (1.5–3 mm) from the fold; 0.25 in (6 mm) gauge on twin-needle seams |
| 08 | Reinforce load pointsBartack 0.375–1 in (10–25 mm) long, or a box-X, at every strap and handle end | Bartack 0.375–1 in (10–25 mm) long, or a box-X, at every strap and handle end |
| 09 | Seal cut edgesHot-cut nylon and polyester webbing; bind or overlock raw woven edges | Hot-cut nylon and polyester webbing; bind or overlock raw woven edges |
| 10 | Use standard hardwareStock #5, #8 or #10 zippers and 1–2 in (25–50 mm) webbing, buckles and D-rings | Stock #5, #8 or #10 zippers and 1–2 in (25–50 mm) webbing, buckles and D-rings |
| 11 | Weld or tape waterproof seamsRF welding or seam tape; no needle holes on the wet side | RF welding or seam tape; no needle holes on the wet side |
| 12 | Specify UV-resistant materials outdoorsUV-stabilized or solution-dyed polyester with polyester or PTFE thread | UV-stabilized or solution-dyed polyester with polyester or PTFE thread |
| 13 | Dimension the finished partMeasure flat and relaxed at named points; tolerance ±0.125–0.25 in (±3–6 mm) | Measure flat and relaxed at named points; tolerance ±0.125–0.25 in (±3–6 mm) |
These build on the short list on the soft goods process page, with the failure each rule prevents and a drawing for each.
Enter a finished size, then add ease and seam allowance to see the cut panel size and how a small error on each seam stacks up across a sewn part.
FINISHED 24.375 IN · 1 PANEL · CUT 25.375 IN EACH
Works: fits, and the seams hold
Each panel is cut 25.375 in wide and sews to 24.375 in finished, within typical tolerance.
Typical values: ±1/16 in of seam-allowance variation per sewn edge, and ±0.25 in on finished dimensions over about 24 in. Fabric shrink and stretch are extra; test-sew a sample.
Each rule with its typical value, the reason behind it and what happens on the floor when it's ignored. Switch any drawing between Do and Avoid; point at a callout to pick it out.
Rule 01
0.25–0.5 in (6–13 mm) over the equipment dimensions
Rule 02
0.375–0.5 in (10–13 mm) per sewn edge; 0.625 in (16 mm) on loosely woven fabric
Fig. 1Seam allowance
Do. A 3/8–1/2 in (10–13 mm) allowance leaves enough fabric beyond the stitches for the weave to hold under load and wash.
Avoid. Stitch too close to the raw edge and the yarns slip out from under the stitching: the seam frays open.
Rule 03
Main load along the warp (roll length); avoid bias cuts on load-bearing panels
Rule 04
Usable width about 58 in (1.47 m) on a 60 in (1.5 m) roll
Rule 05
6–10 stitches per inch (about 2.5–4 per cm); lower end on coated fabric
Rule 06
About Tex 70 for light fabrics; Tex 135 for heavy webbing and 1000D; bonded nylon or polyester
Rule 07
Topstitch 0.0625–0.125 in (1.5–3 mm) from the fold; 0.25 in (6 mm) gauge on twin-needle seams
Rule 08
Bartack 0.375–1 in (10–25 mm) long, or a box-X, at every strap and handle end
Fig. 2Reinforcing load points
Do. A box-X stitch or bartack spreads a strap's load over many stitches and both directions of the weave.
Avoid. A single stitch line puts the whole load on one row of needle holes, which perforate the fabric and tear along the line.
Rule 09
Hot-cut nylon and polyester webbing; bind or overlock raw woven edges
Rule 10
Stock #5, #8 or #10 zippers and 1–2 in (25–50 mm) webbing, buckles and D-rings
Rule 11
RF welding or seam tape; no needle holes on the wet side
Rule 12
UV-stabilized or solution-dyed polyester with polyester or PTFE thread
Rule 13
Measure flat and relaxed at named points; tolerance ±0.125–0.25 in (±3–6 mm)
Typical values for cut-and-sew products measured flat and relaxed. Tight values need die or laser cutting, sewing guides and jigs, or tighter AQL levels.
| Feature | Typical | Tight | Cost of tight |
|---|---|---|---|
| Finished sewn dimensionOver about 24 in (600 mm) | ±0.25 in (±6 mm) | ±0.125 in (±3 mm) | Moderate |
| Cut panel | ±0.0625 in (±1.5 mm), knife cut | ±0.03 in (±0.8 mm), die or laser cut | Low |
| Seam allowance | 0.375–0.5 in ±0.0625 in | ±0.03 in (±0.8 mm) with a guide | Low |
| Stitch distance from edge | ±0.0625 in (±1.5 mm) | ±0.03 in (±0.8 mm) | Low |
| Stitch density | Target ±1 stitch per inch | Target ±0.5 stitch per inch | Low |
| Hardware and strap locationTight values need a marking template or jig | ±0.25 in (±6 mm) | ±0.125 in (±3 mm) | Moderate |
| Webbing cut length | ±0.125 in (±3 mm) | ±0.0625 in (±1.5 mm) | Low |
| Inspection AQL, major / minor | 2.5 / 4.0 | 1.5 / 2.5 | Moderate |
Basis: Finished-goods spec sheet practice; ANSI/ASQ Z1.4 sampling. Put a general tolerance note on the drawing and tighten only the features that need it; every tight callout is priced. See the tolerance guide.
The same soft goods rules shift with the alloy or compound.
Heavy and abrasion resistant, so it needs Tex 135 thread and heavy needles. Nylon loses strength in sunlight faster than polyester, so pair it with UV-resistant thread outdoors.
Lighter, cheaper and more UV resistant than 1000D nylon. Tex 70–90 thread and 8–10 stitches per inch suit most bags and covers.
Stretches, so ease can be reduced or eliminated on fitted sleeves. Use a zigzag or flatlock stitch so the seam stretches with the foam.
Common as low-cost webbing. It is light and water resistant, but degrades in sunlight and holds less load than nylon or polyester webbing of the same width.
Used as stiffener panels and inserts in bags and cases. Allow about 0.125 in (3 mm) clearance per side in the sleeve so the insert slides in after sewing.
Run these against the model before it goes out for quote. The builder's DFM check catches most of them on an uploaded part.
0 of 12 checked
Most bags, covers and cases use 0.375–0.5 in (10–13 mm) per sewn edge. Loosely woven fabrics that fray need about 0.625 in (16 mm), and bound or welded edges can run smaller. Keep one allowance across a product where possible, so operators set the guide once and cut panels stay consistent.
Add about 0.25–0.5 in (6–13 mm) to each equipment dimension so the cover slides on and absorbs sewing tolerance. Use the upper end on stiff vinyl-coated fabric and on covers pulled on by hand. Stretch materials such as neoprene can need little or no ease. Fit-check the first sample on the real equipment.
A bartack is a dense zigzag stitch, typically 0.375–1 in (10–25 mm) long, sewn across a strap or seam end to lock it in place. It reinforces handles, belt loops, strap ends and zipper ends where load concentrates. For heavier loads, a box-X pattern spreads the force over a larger area of fabric.
Use about 6–8 stitches per inch (2.5–3 per cm) on heavy and coated fabrics such as 1000D nylon and vinyl-coated polyester, and 8–10 on lighter fabrics. Too many stitches in coated fabric perforate it like a tear line. Too few leave loose stitches that snag and open under load.
Bonded nylon or polyester in about Tex 70–90 suits 500D and 600D fabrics. Use Tex 135 for 1000D Cordura and heavy webbing, with a needle sized to match. Choose polyester or PTFE thread for outdoor products, since nylon thread loses strength faster in sunlight.
Dimension the finished part at named measuring points, measured flat and relaxed, and allow about ±0.125–0.25 in (±3–6 mm) on sewn dimensions. Cut panels hold tighter, around ±0.03–0.06 in (±0.8–1.5 mm). Add hardware locations, stitch density and an AQL sampling plan such as 2.5 major and 4.0 minor.
Check your part against these rules.
Drop a STEP file in the builder for an instant DFM check and a budgetary estimate, then send it to principals who run soft goods every day.
