Restoration Tool/Part

[mdsalemi]

Hello All,

Earlier this year I posted a query on a variety of restoration forums regarding what to do when your sheet-metal screws enlarge the holes and no longer work.  This is specific to the screws that hold on the myriad amounts of trim on our doors.  Being aluminum (or aluminium for those on the other side...) there is only a limited number of times you can insert, remove and re-insert such a screw into soft sheet metal before it simply won't work.

When I had my doors apart last year getting the screws back in didn't work too well.  Now most are loose and won't tighten.

No good solution seemed to emerge; JB-Weld followed by re-drilling, or hammering the hole tighter with a dolly and ball pein hammer seem to be the solutions offered.  None of those seemed long term or particularly elegant to me.

I dug a little deeper and was surprised to find that the solution exists, and I'm astounded nobody pointed it out to me; I stumbled upon it from one of my fastener suppliers.  The solution is called a rivet nut:

Download Attachment: Rivet Nut.jpg
9.4 KB

Basically it is something like a pop-rivet, installed with a special tool.  Drill out the bad hole to a size dictated by the proper size rivet nut; insert the nut and the tool, and crimp in place.  Instead of an ever enlarging hole for sheet metal screws you now have a threaded hole.  Swap out the oval-head sheet metal screws for STAINLESS machine screws and you are set.

My local repair facility's body shop has these; apparently all late model Mercedes use something like this to install license plates on the rear.  They'll be happy to lend it to me when I get my door apart again.

These are available in a variety of sizes for a variety of materials.  They install blind (from one side) and are nearly flush with the surface.  They are made by a variety of manufacturers, some plain, some knurled, and some hex; the hex ones require a special punch to get the hex-hole in your sheet metal.  Riv-Nuts is a brand name but there are others.  And you can get them at Grainger's.  Do a search for "Rivet Nuts" and you'll see a variety. Emhart, Atlas, Marson all make them.

While I'm hesitant about drilling holes larger to accomodate these my holes are already too large.

When I get it done I'll report back.

Michael Salemi
1969 280SL
Signal Red 568G w/Black Leather (Restored)
President, International Stars Section
Mercedes-Benz Club of America

[Mike Hughes]

Good recommendation!  These things work wonderfully well.  Many factory supplied and aftermarket cosmetic kits (spoilers, ground effects kits, etc.) come with them.  Once properly installed they provide superior anchoring stability over a plain sheet metal screw.

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

[J. Huber]

Dang. Why couldn't I have invented that. I actually could have used it yesterday. The small screw assembly that holds down my driver's carpet started to wiggle. I determined that the screw hole in the floor had basically "grown" so the screw was not gripping. Because that screw is an odd little fellow and not available in a larger screw -- I decided to drill a new hole right next to the old one. (something us "driver" owners can get away with!) Anyway, the rivet nut would have been perfect. Thanks for sharing, Michael.

James
63 230SL

[gugel]

Michael,

What size rivet nut did you use for attaching the trim strips on the doors?  Or did it vary from hole to hole?

Chris Earnest

[TheEngineer]

Michael: You are so resourceful! Thanks!

[mdsalemi]

Chris and all,

I have not done it yet; I just "discovered" this part.  I then found someone (the body shop at Motorwerks, one of the local independent mechanical shops for Mercedes and BMW) who had the installation tool, and then asked (yes is the answer) if they'd lend it to me for a weekend when they were closed.  The rivet nuts are insignificant in cost; the installation tools start at about $65 and go up from there.

A quick investigation has yielded that the smallest sizes the rivet nuts come in in SAE threads is 6-32; in metric, M4.  This appears to be OK, but I need to actually get replacement screws and see how they fit in the trim.  The small oval-head screws that give me trouble are on the chrome trim that surround the door latch; and the vertical piece that kind of hold the door panel to the lower rear part of the door.  There are other parts that are giving me trouble too but these have larger sizes.

I need to get all the parts and see how everything might work prior to drilling the holes.  Even though the things install blind and are nearly flush with the surface they are being installed in, have to check for clearances in the back to ensure they don't interfere with anything.  There's one chance to get it right.

If I got the rivet nuts in Grade 8 (hardened), and the machine screws in the much softer stainless, it looks like it would last a very long time.

Attached are photos I took last year when I took the door apart; you can even see on the bottom of the vertical trim how the screw isn't tight.

Download Attachment: Door1.jpg
53.68 KB

Download Attachment: Door2.jpg
45.91 KB

Michael Salemi
1969 280SL
Signal Red 568G w/Black Leather (Restored)
President, International Stars Section
Mercedes-Benz Club of America

[Mike Hughes]

quote:Originally posted by mdsalemi

Even though the things install blind and are nearly flush with the surface they are being installed in, have to check for clearances in the back to ensure they don't interfere with anything.

Download Attachment: Door1.jpg
53.68 KB

Download Attachment: Door2.jpg
45.91 KB

Michael Salemi
1969 280SL
Signal Red 568G w/Black Leather (Restored)
President, International Stars Section
Mercedes-Benz Club of America

Mike -

Checking behind is only part of what you might want to check.  The operative word is "nearly" flush.  The lip will stand a little proud of the surface, which may interfere with the flush fitting of the trim pieces.  This only would become a problem if the clearances with the door aperature are tight enough that the chrome trim would scrape or rub against the lock plate or body while closing or when closed.  You don't want to ruin your chrome trim bits!

On normal sheet metal one could always use a punch to "dimple" the area to make the area more flush.  On a 113 door it *might* be possible to gently counter-sink the area with a flat tip bit if the casting is thick enough in the areas where you need to install the rivet-nuts.

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

[66andBlue]

Hello Michael,
did you ever finish this project and if so, how did the rivets work out?
I need to find a solution for the enlarged holes in the door also.
Thanks!

[mdsalemi]

Hello Alfred,

The Rivnut worked, but not for very long.  The problem might have been that it was being installed in the aluminum frame.  (Note: this is for the threaded hole to accept the screws that hold the large interior door handle on; the one you pull to close the door).

I had this done in early 2009, and in October 2009 as I was driving the car up north for winter hibernation, the door popped open on the highway, something it is tending to do while going over certain kinds of bumps in the road.  I grabbed the door handle while doing 70, and tried to quickly snap the door shut.  The handle--with screw and RivNut attached, pulled out on one side. (the rear screw was fine).

In early 2010 as soon as I got my car out of winter storage, back it went to Motorworks for "plan B".  Plan B was welding a nut onto the frame, which required a skilled aluminum welder (person, not machine), and that they did.  They had no issue doing it, no issue getting it back together.  It did not pull out this time, though I am a bit more careful when pulling on the door handle.

There are different types and kinds of rivnuts and perhaps a more careful installation would have done the trick.  I don't think most people know just how much tension force you exert on that handle when you close the door.

Now, if I can only fix that door popping open problem...

[dseretakis]

I have not encountered this problem yet and forgive me if the question is stupid but why can't larger screws be used?

[66andBlue]

Thanks Michael!
I want to fix the holes under the chrome covers and for that it should work since they'll not experience any pulling or pushing force.
Now I have to find a place where I can borrow the tool for it.
Or perhaps invest in a simple one sold by Maryland metrics: http://mdmetric.com/prod/rivetnuttool/rivetnuttool.htm

Dseretakis,
the reason is that then the larger lens head will not fit into the recess in the chrome cover shown in the photo in Michael's earlier post.
(http://www.sl113.org/forums/uploaded/mdsalemi/20078178426_Door1.jpg).

[mdsalemi]

I have not encountered this problem yet and forgive me if the question is stupid but why can't larger screws be used?

...while Alfred has a slight different location application, in my case (the door pull) the screws that hold the pull on were, I believe, machine-thread screws.  The next size up from whatever it was would have been a bit large (IMO) and would have made that one screw different from the rest.  That to me, is bogus work--precisely the kind of thing that we complain about here.

I may have gone through a lot of effort and learning but all my door handles are held on with the same screws now.

[Peter h]

the same problem at my car, i use bigger screw but it is not so nice

I want to try it with this  Loctite 29690 Flüssigmetall-5-Minuten-Epoxy LOCTITE® Hysol® 3450 25 ml shot it in the hole and drill a new hole later.
This is a 2 K metal filler, they say you can drill a hole in it.
I hope it works

Peter

[stickandrudderman]

Metal filler will not work.
The rivnut is a good solution for  panels, but for anything else (Aluminium or iron castings) a time-sert is the way to go; best tool in my workshop.

[66andBlue]

Hello Stick,
what is a "time-sert" ? Please translate, or better yet show a picture.

[mdsalemi]

Alfred--

http://www.timesert.com/

Looks like the equivalent of a "heli-coil" often used in stripped spark plug holes.  Did not come across this in my search two years ago, and alas I did not get a lot of help from anybody anywhere on the subject.

Do a search on Amazon or Google you'll find the kits available, something under $75.  I would have happily paid that.  You can use what you need and probably recover 60% or more by putting the tools/kits on Craigslist or eBay when done.

[J. Huber]

While we are on the subject -- anyone have the p/n for the screws? I have a potpourri of screws on the door chrome. Thx.

[hkollan]

The original part number for the screws holding the chrome plates is a DIN number N 007983 002203.
The problem with enlarged holes can be solved in different ways, some are mentioned in this thread already.
If the holes are not excessively enlarged Mercedes can probably offer the best solution.
Part number A 000 990 1036 is a larger replacement screw, but with a smaller lens head that will fit in the recess of the chrome cover.
They cost a couple of euros a piece, but they're worth every cent IMO.
Regards,

Hans

[ja17]

Hello,

Another quick fix I use all the time on the doors is to insert a piece of solid copper wire into the hole. Then start the screw. After the screw is started after the screw is started,  I break the cooper wire off so that it is flush, then finish turning the screw in. Works great.  The cooper is pliable and helps fill the oversize hole. The original screws are used. You can salvage solid strands of solid cooper wire from some heavy sections of electrical cable. Strands from some old battery cables work sometimes.

For doors skins, if you have  oversize holes for the exterior chrome trim, you can use the "loop"end  of a plastic wire ties as a plastic nut on the back side of the screws !  You must have the door panels off in this case but it works well also using the original screws.

[Raymond]

Another slick trick from the master!