bolt for the seats

[jan lauwers]

Gentlemen,

My theory is that everything in our car has a function or a reason for being the way it is...

Nevertheless, I am wondering why the bolts that hold the seats have a split.
If I am remember correctly, only the front bolts are like this.
In my car such a special bolt is missing and I would like to replace it with a normal bolt that I have in my drawer. Is that OK? What is that split for?

Thanks guys!
Jan

[Jonny B]

An excellent question, I did some searching and the only thing I could find was that these bolts are mainly used in electrical service for making connections. There was also a reference or two for their use in holding a cable or wire. Not much that would answer a question for use in holding the seat in place.

[jan lauwers]

Thanks Jonny.
Who knows... perhaps the bolts for the seats are NOT to be of this type at all?
Jan

[Pawel66]

I see 4 same kind screws seat to bracket and other 4 same kind screws to, I think floor. This is the one to hold bracket to floor?

No idea. For easier unscrewing in case it gets rusty where thread sticks out beneath floor?

[jan lauwers]

Yes these were sitting in the floor. Well it sounds like I can replace the missing one with an ordinary bolt then.

Thanks again guys,

Jan

[GM]

I just removed and replaced my driver seat this weekend and found the same bolt - used only for the front of the brackets that attach to the floor. Don't get me started about removing and replacing the front bolt next to the transmission hump...

[wwheeler]

It has a taper to help guide the bolt into the nut. That part is easy enough.

You see screws similar to this that are for thread cutting and cleaning, but the slot is not the same as this. Those are typically used where heavy coats of paint or other materials may have made their way into the threads of welded nuts during the manufacturing process. The slot in the screw provides a cutter and a place for the debris to collect that was in the threads of the nut.

On my W111, the front inner mounting is a weld nut to the body, but the rest are cage nuts. Wouldn't need them on a cage nut because those are added much later. But maybe for the one welded nut to the floor....Maybe the W113 arrangement is different?   

[66andBlue]

Thanks Jonny.
Who knows... perhaps the bolts for the seats are NOT to be of this type at all?
Jan

That is correct, they are not original. Take a look here, they are this type: https://www.sl113.org/wiki/Interior/Seats
Also note that there are two different sizes, M6 and M8.

{corrected May, 26}

[GM]

Looks like the Tech Manual covers up to early 280SL only? Maybe later is different? It seems extremely unlikely that Jan and I would have the same configuration for bolts? The adventure continues...

[rbouch8828]

After redoing the interior of my car I read through that section of the manual and since my car was built in August of 1969 I thought that it might take the newer screws, so I bought those. Unfortunately, without the taper and split, I could not get the bolts to start to thread into the hold-downs. So, I went back to the originals that I had and they went in like a charm. Those hold-downs with the sliding clips that the bolts thread into are not the greatest bit of engineering in our cars. There seem to be two clips in each bracket and I think they slide in opposite directions. So, I had to take a screwdriver to get the holes to all align, from the seat track through the two clips and then I could start threading the bolt. However, only the tapered and split bolt worked for me.

Best,
Roland

[jan lauwers]

Interesting... It sounds like these type of bolts are there for a reason. I will have to find out for myself... but that will not be soon; since my car is away for a bare metal repaint. It will be a few months before I am putting back the seats.

Jan

[wwheeler]

I just looked and I have the screws with the taper and split as well. Mine is an early '68 280SE W111. Pretty sure they came with the car. The head is exactly the same as the ones in the tech manual.

Another mystery......

[450sl]

if memory serves me well,  these are M8 bolts with - unusual-  10mm hex. heads..

[66andBlue]

Wallace,
thanks for looking because that solved the puzzle. The bolt (p/n 108 990 03 22) is correct for your W111 and for the W113 cars and it does have a split tip! I checked the W111 spare parts list (10212) which has a larger drawing of this bolt (#67 in the table) that shows clearly the slit in the tip.

So, Jan, relax you do have a bolt that looks correct and I apologize for the confusion. I have also corrected the tech. manual article.

This is for those who want to know more about these thread cutting point styles:
https://www.eaglefastener.net/technical/screw-point-styles.html

[jan lauwers]

Problem solved... and I have learned something new.

So, it is a matter of production efficiency. By using this type of bolts they could tap and fix in one movement. And, since the thread is now available in the chassis, it should be Ok to use a normal bolt when the original one is missing. I can not try it, I don't have my car here with me...

Thanks again guys,

Jan 

[wwheeler]

Thanks for posting the chart Alfred. I have been told I have a few screws loose, and now I can replace them with the correct type tip.

The tapered type tip will always be easier to install (with or without the thread cutter) because it helps guide the screw into the mating threads where alignment may be difficult.

[Benz Dr.]

I kind of thought that they may also be stronger but maybe not grade 8 screws.  I'd be inclined to use something better than a normal cap screw. 

[66andBlue]

...
The tapered type tip will always be easier to install (with or without the thread cutter) because it helps guide the screw into the mating threads where alignment may be difficult.

Wallace,
for that you need to find either a DIN 561B or DIN 564B screw. Difficult to find here but if you know a shop that buys from Würth then perhaps you can get a few. They have the smaller head, that is, a M8 bolt will have a 10mm head size, and they are rated 8.8.
https://eshop.wuerth.de/Product-categories/DIN-561-plain-steel-8.8/14013511110902.cyid/1401.cgid/en/US/EUR/

[swood1]

All,

The split is in the bolt for the first few threads as it acts as a simple tap and clears any paint from the welded on nuts.  It would only be required on the front seat brace as I believe the back ones use clips within the brackets.

We still use similar now on modern cars.

Hope this helps.

Steven