Rocker Panel Cover Screws

[Tomnistuff]

I am installing my freshly painted rocker panel covers on my freshly rotisseried 230SL and find I have a problem.  I would like to know how others have solved it.

When I started my restoration, my rocker panel covers were attached with 1/8 inch pop rivets, not screws, so they were obviously not the ones installed by the factory.  The EPC calls for N07982-002211 screws to attach the upper edge to the sill (under the glued-down ribbed rubber strip).  That number would be a #4 phillips flat head sheet metal tapping screw (length unknown).  I cannot determine what SLS calls for but it looks pretty much like a #4 (?) x 3/8" phillips flat head sheet metal screw.  #4 is smaller diameter than the 1/8 inch pop rivets that I removed, so #4 won't work in those holes.  In fact, when I tried #6, they wouldn't grip either.  #8 holds fine but they are so large that they stand off from the surface so much that they will cause bumps in the rubber strips.  See the photo.

I tried countersinking the holes but there is not enough thickness in the rocker panels for the screw to grip once it is countersunk.

I have concluded that I will have to drill new holes for #4 screws adjacent to the existing holes and plug the existing holes with something like RTV rubber.  If I still need to countersink the holes, then at least the small head of the #4 screws will require only a "touch" with the countersink bit to allow them to be flush.  If anyone has a similar experience, I would really like to hear your story.  Please share your experience and your opinion of my plan.  I'm getting paranoid.

Tom Kizer

[Larry & Norma]

I drilled new holes like you suggest.

[IXLR8]

I drilled new holes also.

the other Joe

[Tomnistuff]

Did you use #4 flat head screws?  I broke a couple of #4 stainless steel screws.  That is a PITA.  Maybe my drill bit is too small.  I think I'll go buy the "correct" drill bit and tap for #4 screw threads.  We're supposed to use sheet metal tapping screws, but the rocker panel sill material is structural and too thick to be called "sheet metal".  I think it needs tapping as well, not just drilling. 
We will see.  I'll report back when I have succeeded.  I am beginning to understand why the previous owner, or one of them, used pop rivets.

Tom Kizer

[Larry & Norma]

The secret is to get the holes the correct size, try different sizes on a scrap piece of metal first.
I think pop rivets were used by restorers to save time. I have removed most from my car.

[hkollan]

I used the original holes with DIN 7982 zink plated steel  screws, 2,9mm width and 9,5mm or if needed 13mm length(if my memory serves me right). If the holes are original size, this will work fine and leave no "bumps" in the rubber. Next width is 3,2 mm if some holes are enlarged.
The 7982 DIN screws can be had from several sources in Germany, here is one who offers these screws in SS (not quite correct, butvwill work) on eBay with WW shipping.

http://www.ebay.de/itm/50-Senk-Blechschrauben-2-9x9-5-DIN-7982-V2A-2-9-X-9-5-/110546476837?pt=DE_Haus_Garten_Heimwerker_Eisenwaren&hash=item19bd155f25

Hans

[wwheeler]

One thing you have to consider when it comes to using sheet screws into thick metal is the thread pitch of the screw. If the thread pitch is more narrow than the thickness of the metal, you will make threads in the metal. Sheet screws don't typically like to do this and two things will happen 1) break the screw 2) the threads on the screw will flatten out. If you make the hole so large that a too fine threaded sheet screw threads in, it will usually strip if you retry it.

A very course thread pitch would work if you can find it. My W111 has a similar trim panel that screws into the very thick rocker panel. Many of the old original screws broke off and I had to drill them out with a carbide drill. Those screws were very hard and maybe they are heat treaded when supplied from the factory. 

I ended up using Stainless MACHINE screws with a fine thread. I drilled the existing holes and then tapped it. I used antiseize to prevent them from corroding. They worked great and snugged up well.