Creating draggable hinge joint

You can use the DragRigidBody2D script Here is my version of the script

 using UnityEngine;
 using System.Collections;
 
 public class DragRigidBody2D : MonoBehaviour
 {
     public float distance = 0.2f;
     public float dampingRatio = 1;
     public float frequency = 1.8f;
     public float linearDrag = 1.0f;
     public float angularDrag = 5.0f;
     private SpringJoint2D springJoint;
 
     void Start ()
     {
         if (!springJoint) {
             GameObject go = new GameObject ("Rigidbody2D Dragger");
             Rigidbody2D body = go.AddComponent ("Rigidbody2D") as Rigidbody2D;
             springJoint = go.AddComponent ("SpringJoint2D") as SpringJoint2D;
 
             body.isKinematic = true;
         }
     }
     
     // Update
     void Update ()
     {
         if (!Input.GetMouseButtonDown (0))
             return;
         
         Camera mainCamera = FindCamera ();
 
         int mask = (1 << 8);    
         RaycastHit2D hit = Physics2D.Raycast (mainCamera.ScreenToWorldPoint (Input.mousePosition), Vector2.zero, Mathf.Infinity, mask);
 
         // I have proxy collider objects (empty gameobjects with a 2D Collider) as a child of a 3D rigidbody - simulating collisions between 2D and 3D objects
         // I therefore set any 'touchable' object to layer 8 and use the layerMask above for all touchable items
 
         if (hit.rigidbody != null && hit.rigidbody.isKinematic == true) {
             return;
         } 
 
         if (hit.rigidbody != null && hit.rigidbody.isKinematic == false) {
 
             springJoint.transform.position = hit.point;
             
             springJoint.dampingRatio = dampingRatio;
             springJoint.frequency = frequency;
             springJoint.distance = distance;
 
             springJoint.connectedBody = hit.rigidbody;
             
             
             // maybe check if the 'fraction' is normalised. See http://docs.unity3d.com/Documentation/ScriptReference/RaycastHit2D-fraction.html
             StartCoroutine ("DragObject", hit.fraction);
             
             
             
         } // end of hit true condition
         
     } // end of update
     
     
     IEnumerator DragObject (float distance)
     {   
         
         float oldDrag = springJoint.connectedBody.drag;
         float oldAngularDrag = springJoint.connectedBody.angularDrag;
         
         springJoint.connectedBody.drag = linearDrag;
         springJoint.connectedBody.angularDrag = angularDrag;
         
         Camera mainCamera = FindCamera ();
         
         while (Input.GetMouseButton (0)) {
             Ray ray = mainCamera.ScreenPointToRay (Input.mousePosition);
             springJoint.transform.position = ray.GetPoint (distance);
             yield return null;
         }
         
         
         
         if (springJoint.connectedBody) {    
             springJoint.connectedBody.drag = oldDrag;
             springJoint.connectedBody.angularDrag = oldAngularDrag;
             springJoint.connectedBody = null;
         }
         
     }
     
     Camera FindCamera ()
     {
         if (camera)
             return camera;
         else
             return Camera.main;
     }
 }