SEMS - An Acronym/Name for Parts Geeks to Use

[ctaylor738]

Today I was trying to find an original-like replacement for the cap screw-and-washer combination used for 113 bumpers and their brackets.  I found out that such an assemblies are called "SEMS," which is a generic term for fasteners that come pre-assembled with washers.  The washers are put on before the threads are rolled so that they won't come off.  There are all sorts of bolts and screws with different types of washers made as SEMS.

SEMS is not really an acronym, though.  It is a registered trademark of Illinois Tool Works (ITW). They were originally developed and patented by E.C. Crowther in the 1930's for the company. The name comes from "pre-asSEMbled washers and screws." The last 's' is added at the end to denote the plural version (since these are commonly purchased in bulk).

Anyway, I did find out that the Aetna Screw Products Co. in Niles, IL makes metric SEMS, specifically a M10x25 cap screw with a free-spinning flat washer, which should solve my problem.

http://www.aetnascrew.com/cap_screws.htm

[mbzse]

Today I was trying to find an original-like replacement for the cap screw-and-washer combination used for 113 bumpers and their brackets

In the M-B Parts book (like 10 202; pertaining to 250-280SL, section 88) these bolts are certainly listed as separate M10 bolts with Hex head, flat thick washers and spring washers
Eight bolts at the front and eight at the rear
/Hans in Sweden

.

[mdsalemi]

these bolts are certainly listed as separate M10 bolts, flat thick washers and spring washers

...and being somewhat non-structural (such as bolts holding the head onto the engine, for example) and not needing a strength specification (such as hardened or Grade 8 or whatever) I simply went to a local fastener place and bought stainless steel metric components--nuts, bolts, washers and lock washers when I re-assembled mine years ago.  I suspect if they ever have to come off again, I'll be happy I chose stainless.  No paraffin candle or inductive bolt heaters will be necessary!  

[ctaylor738]

Well, it certainly wasn't my intent to start a discussion about bumper fasteners, but rather to introduce a term used in the trade. 

But since it went there, this seems to be another case where the replacement parts from MB are not what came on the car.  Most of the orginal cars that I have looked at have the SEMS, although there are at least two flavors: one with just a flat washer, and one wth a flat washer and a lock washer.  I confirmed with Gernold that this is the way they came.  Hence my search for something more "authentic."

Anyway, here's a picture of what I am trying to find seven more of.

Happy to buy some used ones if anyone has them.

Cheers,

[Jordan]

Chuck, if you find any can you let me know.  I just removed my front bumper to get it rechromed.  My bolts, which also have a flat and lock washer on them, as listed in the parts book, are badly rusted.  Tried cleaning and removing the rust but now they are badly pitted where the rust was removed.    I will probably go Michaels root if replacements cannot be found.

[mdsalemi]

Chuck,

That photo you posted--that washer is captive on the bolt?  Hard to tell from the photo.

http://www.aaronssemsmachinescrews.com  Read carefully; they say they'll MAKE what you NEED!
http://www.beaconfasteners.com/catalog/catalog.asp?groupid=5

If these guys can't help, there are quite a few specialty houses that supply automotive fasteners.  Might want to do a quick google search for automotive fasteners, metric sems, etc. and make some phone calls.

Good luck and I know you'll report back!!

[ctaylor738]

Yes, believe they are captive.  They did not answer my email, but I will give them a call tomorrow.

[Jordan]

My bolts have both a lock washer and flat washer captive.  The flat washers on the 4 bolts holding the bumper bracket to the frame are a larger diameter than the washers on the four bolts into the bumper.  I guess they are referred to as double SEM bolts.