Sheet metal screws apparently used in tapped holes in my hardtop window frame.

[Tomnistuff]

I'm preparing to start the restoration reassembly of my hardtop.  My painter didn't plug the tiny holes in the hardtop before painting it.  The EPC calls for using N 007982 002222 screws to attach the hardtop exploded view inner and outer rails #25 and #26 to the hardtop "B" pillar (the one behind the door side window).  I cannot find any description of those screws so I'm not sure exactly what they look like.  There is a tiny tiny picture on the web site of Authentic Classics where the screws are a part of a hardtop screw kit, but no description or specification.
When I examined the hardtop, hanging from the garage ceiling, it looks like a #4 Phillips flat head screw which would be 2.9mm diameter x about 9.5mm long.  HOWEVER, the holes look like they are tapped and, to make matters worse, the threads are filled with paint and the screws won't go in with those tiny Phillips head crosses.

I didn't know at the time that  i should have told my restorer to plug the screw holes before painting.  Anyway, are the holes in the "B" pillar tapped (the metal is about 1/8 inch thick)?  I think that's too thick for a 3 mm sheet metal screw.  At this point, I don't know how to clean the paint out of the threads of the holes, and even if I do, what kind of screw do I use?  At this point, I'm about ready to try to drill and tap and use tiny countersunk machine screws to do the job.

Would someone who has restored a hardtop please advise?  The more suggestions the better.

Tom Kizer

[DaveB]

My 230SL parts book lists these as 'countersunk screw, sheet metal', with the number you describe (007982 002222, 16 required), superseded by 000000 004391. They are apparently the same as the four screws that secure the chrome instrument binnacle trim. Here's a photo from the Mercedesclubs.de site which indicates 2.9 x 6.5 mm length.
It may be prudent to practice on some scrap metal to find the right drill bit for a snug fit, before drilling out your painted-over holes. And of course having the correct driver bit.

[450sl]

Tom, for what it's worth: I seem to remember vaguely screws been used with 3 or 4 axial grooves in them, just like a screw tap, so I think you would call them self cutting screws...

Regards Mark

[Tomnistuff]

Hello 450sl and DaveB.

I appreciate your quick responses.  Dave, there was something that didn't seem right about the photo of the screws.  The length/diameter ratio didn't seem right.  I scaled the screw photo and if the screw is 2.9 dia, then the length is more like 9.5 than 6.5.  However, when I tried a 2.9 x 6.5 screw with the chrome rail on the "B" pillar, I was surprised to find that, although the screw seemed to bind up in the hole, it did so at exactly the same time that it held the chrome rail to the "B" pillar very firmly.  I also tried a longer (9.5 mm) screw and found that I could not drive it into the screw hole far enough to firmly hold the chrome rail before the screw thread bound in the "B" pillar hole thread.  The screw head stood off from the rail and the rail was still loose.

Based on a 1 screw test, I might be able to get the 16 screws to work by "fiddling" a little with the holes using a tool maker's file.

Alternatively, 450sl, I also may try to "Dremel" grind a groove in a long screw of the 2.9 mm diameter in an attempt to chase the ID of the holes.  I don't remember what it's called but I read last night of a type of screw that doesn't just start a hole, but cuts its own thread as it is screwed in.  It sounds like wishful thinking to imagine that a screw as small as 2.9 mm diameter could handle that much stress without breaking.  Anyway, I appreciate both your replies and will come back here to post my progress or failure in a few days.

Thanks again.

Tom Kizer
Quebec

[66andBlue]

Tom,
in the early 230SL cars the rail was fixed to the frame with a metric countersunk tapping screws DIN 7516 type D, M3 x 6 mm.
In later cars - I don't know the exact switch date but probably at the end of 1964 - a sheet metal screw DIN 7982 2.9 x 6.5mm was used as Dave B described. Did the hardtop come with your car, that is, it was made after 1964?
The attached copy shows a description of the DIN 7516 tapping screw.

[Sead]

Tom,
in the early 230SL cars the rail was fixed to the frame with a metric countersunk tapping screws DIN 7516 type D, M3 x 6 mm.
In later cars - I don't know the exact switch date but probably at the end of 1964 - a sheet metal screw DIN 7982 2.9 x 6.5mm was used as Dave B described. Did the hardtop come with your car, that is, it was made after 1964?
The attached copy shows a description of the DIN 7516 tapping screw.

Correct. See pic of my 03/64 HT attached.

[Tomnistuff]

Please pardon my delayed response.
    Alfred, my car was built on 11 August 1966, which I assume makes it a late 1966 model (if Daimler Benz used that terminology).  The thread cutting machine screws you show in your chart are much like the ones that hold the seal rail to the "B" pillar, trapping the inner and outer chrome rails between the seal rail and the "B" pillar itself.  I suspect that my hardtop came with the car, since it is specified on the Data Card that I got from Tom Hanson.
    Sead, the screws visible in your photos are those that I also have on my hardtop, the machine screws that I just mentioned above to Alfred.  The seal retainer rail in your photos are the ones held by those machine screws and trap the inner and outer "B" pillar rails against the hardtop "B" pillars.  The screws in your photos actually screw into the "B" pillar by passing between the inner and outer rails, that are themselves screwed to the "B" pillar by the screws being questioned by this thread.  The ones I am questioning are definitely smaller than the ones in your photos.  The ones in your photos are 4mm diameter machine screws.  The ones that hold the inner and outer rails are "approximately" 3 mm, either sheet metal or self tapping machine screws. 
     To all of you, I also tried this evening to screw into the "B" pillar holes for the inner and outer rails, a long (maybe 20mm) 3mm diameter machine screw (2.88mm O.D. by caliper measurement).  It would start in all holes but jammed about 1-2 turns into the holes.  None would go through.  That tells me that if I use a 3mm tap on those holes, I can use the 3mm machine screws to hold the inner and outer rails to the "B" pillars.  The head is the same as the 2.9mm x 9.5mm sheet metal screw.  I am reasonably sure that I will achieve a perfect attachment of the rails to the "B" pillar before I follow up with the seal rail and the 4mm machine screws that are specified by the EPC for the seal rail.  It will be impossible to know the difference without disassembling the hardtop "B" pillar chrome trim behind the door windows.  I have a metric tap kit, so it's only labor to tap already drilled holes that are almost exactly the right diameter.  The ones I tried are, but I'll try them all before doing it.

Tom Kizer

[Sead]

As I have changed probably almost every screw on my car ( sheeet metal screws, for trims etc.) I have made a huge list by checking in EPC, converting into DIN norm using "Schlüsselliste" and comparing then with a original example from car. I ordered them all from www.onlineschrauben.de.
Seee attached pdf document, scroll down to "Gruppe 77 Coupedach"
There are listed all screws used on Hardtop.
It is all in German, but you can see DIN norm and size. Quantity nr on left is not the actual needed number of screws as I ordered more.
Maybe this can help you (and others).

[GM]

Sead,
Might you have this list for the 280SL?
By the way, the link requires a username and password.
Thanks!

[Sead]

Sorry wrong link.
https://online-schrauben.de/shop/
I guess u can use this list also for 250 and 280. 99% at least shall be same.
Regards
Sead

[GM]

Thanks!

[Leester]

Hi Tom,

On my car (1970) both the inner and outer rails are held in place by Phillips flathead countersunk sheetmetal screws (pointed). The screws are 2.9mm diameter (most likely next to the head) and 6.5mm long. FWIW the head diameter is 5.36mm. So I concur with DaveB on the screw type and size.

3 of these hold the outer rail and 4 hold the inner rail.

For you and anyone else, I have a pretty good record of each piece of trim and the screws that secure it in a word document. Would be happy to post but I don't think I can post a word doc. Happy to provide the list on request.

Seems like an M3 tap might result in too big a hole so suggest you try on a piece of scrap metal.

Hope this helps.

On a related issue, I had a lot of trouble removing the outer rails. They seemed to be hooked onto the B-pillar - sorry not a very good description but if you look at the profile of the outer rail and the hardtop where it fits you might see what I mean. When you install the outer rails I would be curious to know if that presents any problems for you. I had pretty much decided that when I reassemble, I won't worry about trying to "hook" the back side of the rail to the hardtop since its held in place with the 3 screws mentioned above.

Good luck.