Switch setting practice: A kink is made in stock rails ahead of the toe of switch at what standard distance?

Introduction / Context:
Accurate switch geometry ensures smooth entry to the turnout, proper contact between switch and stock rail, and minimized wear. A small intentional kink in the stock rail ahead of the toe helps achieve the desired fit and gauge through the switch zone.

Given Data / Assumptions:

• Standard practice for conventional turnouts.
• Distance is measured along the stock rail ahead of the toe of switch.

Concept / Approach:
The kink location is chosen to provide a subtle alignment change that assists the switchblade in closing properly, maintaining gauge and contact without creating abrupt geometry. The commonly adopted nominal distance in many standard drawings for conventional turnouts is about 20 cm ahead of the toe.

Step-by-Step Solution:

Verification / Alternative check:
Turnout assembly and inspection manuals indicate a short, controlled kink ahead of the toe near 200 mm to assure seating and running quality.

Why Other Options Are Wrong:

• 10 or 15 cm: Too close; may not provide adequate alignment transition.
• 30 or more: Excessive; risks disturbing approach geometry and wheel guidance.

Common Pitfalls:

• Treating the kink as a sharp bend; it is a subtle, controlled change to aid switch closure.

Final Answer:
20 cm