The MGA With An Attitude
RUSTED SCREWS for Top Frame Attachment -- BD-104

At 07:13 PM 10/6/04 -0600, Jim Smolka wrote:
>"When going to re-attach the convertible top frame to the body, the "nuts" on the inside of the body are either not there, or are wobbly and not conducive to beginning a thread. Any suggestions?"

This is a very troublesome point. I believe it is the only place in the MGA where there are captive nuts enclosed inside of a box section where they are not accessible from the back of the panel. Other places, like for door hinges and striker plate, a removable tapping plate is used.

Those are cage nuts. It is a square nut floating in a small sheet metal box which has tabs spot welded to the parent panel on two ends only. It is common for these to rust solid to the fasteners and to be destroyed during disassembly. Either the screw breaks off, or the nut breaks loose and turns in the cage.

If the cage nuts are still there and in good condition, but you have a hard time starting the screw, you still have a chance. Run a tap through the nut to be sure the threads are clean and that the nut is still captive and does not turn. You can also grind a point on the screw tip to assist in centering the nut to get the thread started.

For a free turning nut you can use a ball grinder in a Dremel tool to grind the head off the countersunk screw to remove the bracket. For a broken screw you might be able to drill it out and clean out the thread in the nut with a tap. Otherwise it's a cut and weld operation to open the pillar for repair of the captive nut inside. Repair panels are available for this application with the captive nuts already installed.

For location of the screws when welding in a new panel, the nuts go in a vertical row 1-7/8" to 2" aft of the body edge where the weather strip mounts. Exact dimension here is not critical, as the legs of the top frame float in this direction to find their own center when erected. Distance from top of body aft of door opening down to the bottom nut is 4-3/4". If you must err in position here, give preference to being a little higher, definitely not lower. The fabric flange on the rag top overlaps the top of the side curtain frame considerably near the back. See photos here: mgtech/top/tt37.htm - mgtech/top/tt38.htm

After being frustrated by this more than once, the last time around I welded in a 5/16 inch thick steel plate with tapped holes in the appropriate locations. I also use stainless steel screws with hex socket drive so I can use an Allen wrench for good leverage (and lots of anti-seize compound). Having to remove the screws again four years later I was able to muscle them out without more cut and weld.

For more information on this particular problem (and rusted fasteners in general) see Removing a rusted bolt.

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