For railway track fasteners, the RDSO drawing is the specification. The Research Designs and Standards Organisation, under the Ministry of Railways, issues drawings that fix every dimension of items like fish bolts, track bolts and plate screws. When an order or tender quotes a drawing, the supplier manufactures exactly what that drawing shows.
The drawing number
Track drawings carry numbers such as RDSO/T-1899. The number identifies one specific item. Two bolts that look alike may have different drawing numbers because they fit different rail sections, plates or turnout positions — so always order by the number, not the description.
The alteration
Drawings are revised over time, and each revision is recorded as an alteration. The alteration can change a dimension, tolerance, material or note. Your tender or order should state which alteration applies; if it does not, ask before ordering. Quoting "RDSO/T-1899, Alt. X" removes any doubt.
What to read on the drawing
- Dimensions and tolerances — diameter, length, head and neck shape, thread length.
- Thread details — the thread form and size for the bolt and nut.
- Material and mechanical requirements — usually by reference to a specification.
- Notes — finish, marking, and any special requirement.
- Bill of material — whether the item includes a nut, washer or other parts.
What else your tender may add
Orders often add requirements that are not on the drawing itself: inspection agency, sampling, packing and marking. Include these in your enquiry so the quote reflects them.
Sending the enquiry
For each item, send the drawing number, alteration, quantity, inspection requirement and delivery details. S A Engineering manufactures fish bolts, track bolts for points and crossings and railway plate screws to RDSO drawings.
