Mae trwch gwe- y rhan fertigol sy'n cysylltu'r fflansau- yn amrywio yn ôl cyfres UB a dyfnder, gydag amrediadau o 4.0 mm (HEA 80) i 25.0 mm (HEM 1000):
Cyfres AAU: Trwch gwe 4.0–20.0 mm (ee, HEA 100: 5.0 mm, HEA 300: 10.5 mm).
Cyfres HEB: Trwch we 4.5–22.0 mm (ee, HEB 120: 6.5 mm, HEB 400: 13.5 mm) (trwchus nag AAU ar gyfer capasiti cneifio uwch).
Cyfres HEM: Web thickness 5.0–25.0 mm (e.g., HEM 140: 8.0 mm, HEM 500: 18.0 mm) (thickest webs for heavy shear loads).The web's primary role is to resist shear forces (e.g., wind, seismic loads). Thicker webs handle higher shear, making HEM series UB steel suitable for short-span, heavy-load applications (e.g., industrial crane girders). EN 10025-2 specifies web thickness tolerances: ±0.4 mm for thicknesses ≤10 mm, ±0.5 mm for 10.1–20 mm, and ±0.6 mm for >20 mm. Mae'r goddefiannau hyn yn sicrhau perfformiad cneifio cyson ar draws sypiau.