- A light duty loading of 220 N/m (light access stairs, gangways and the like not more than 600 mm wide).
- A medium duty loading of 360 N/m (Light access stairs gangways and the like more than 600 mm wide, stairways, landings, balconies, private and domestic).
- A heavy duty loading of 740 N/m (All other stairways, landing and balconies and all parapets and handrails to roof). This greater loading should also be observed when there is any possibility of the handrail being leant on by a crowd of people using the stair or gangway as an observation platform
| Loading class |
Nominal ball dia |
Shank size | Maximum pitch | Solid or tubular | Rail size | screw Grub size |
| 1 | 70 | 25 N.B. (M) | 1480 | T | 25 N.B. (M) | A |
| 1 | 70 | 32 N.B. (M) | 1800 | T | 25 N.B. (M) | A |
| 1 | 60 | 32 O.D. | 1800 | S | 25 N.B. (M) | C |
| 1 | 60 | 38 O.D. | 1800 | S | 25 N.B. (M) | C |
| 1 | 70 | 38 O.D. | 1800 | S | 32 N.B. (M) | C |
| 2 | 70 | 25 N.B. (M) | 900 | T | 25 N.B. (M) | A |
| 2 | 60 | 32 O.D. | 1222 | S | 25 N.B. (M) | C |
| 2 | 70 | 32 N.B. (M) | 1550 | T | 25 N.B. (M) | A |
| 2 | 70 | 32 N.B. (H) | 1750 | T | 25 N.B. (M) | A |
| 2 | 60 | 38 O.D. | 1800 | S | 25 N.B. (M) | C |
| 2 | 70 | 38 O.D. | 1800 | S | 32 N.B. (M) | C |
| 3 | 80 | 32 N.B. (M) | 750 | T | 32 N.B. (M) | B |
| 3 | 80 | 32 N.B. (H) | 850 | T | 32 N.B. (M) | B |
| 3 | 80 | 40 N.B. (M) | 970 | T | 32 N.B. (M) | B |
| 3 | 60 | 38 O.D. | 1092 | S | 25 N.B. (M) | C |
| 3 | 70 | 38 O.D. | 1092 | S | 32 N.B. (M) | C |
| 3 | 80 | 40 N.B. (H) | 1150 | T | 32 N.B. (M) | B |
- M Denotes medium quality tube and ‚H‘ denotes heavy quality tube.
- A Denotes M6 x 16 zinc plated cone pointed socket set screws.
- B Denotes M6 x 20 zinc plated cone pointed socket set screws.
- C Denotes M10 x 16 zinc plated cone pointed socket set screws
Socket set screws or grub screws only fitted to balls of one standard per run where there is possibility of rail movement, unless noted otherwise.
