Joint.breakForce
var breakForce: float;
float breakForce;
breakForce as float
Description

The force that needs to be applied for this joint to break.

The force might come from collisions with other objects, forces applied with rigidbody.AddTorque or from other joints. See Also: Joint.OnJointBreak.
	// Makes the joint break when a force larger than 10 is applied
	hingeJoint.breakForce = 10;
	// Makes the joint unbreakable
	hingeJoint.breakForce = Mathf.Infinity;
using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void Example() {
        hingeJoint.breakForce = 10;
        hingeJoint.breakForce = Mathf.Infinity;
    }
}
import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def Example() as void:
		hingeJoint.breakForce = 10
		hingeJoint.breakForce = Mathf.Infinity