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On many occassions I see well restored cars with ratty old fasteners on tail light and front indicator lenses. This small detail really bugs me. The screws used on the lenses are next to impossible to find. They are not a traditional pan head phillips. They are called fillister head screws. Pan head screws have a a rounded head with rounded sides. Fillister screws have a rounded head with straight sides. The head also is a little less than 7mm in diameter and has a little taller profile than a pan head. Another characteristic of the screws Alfa used is that they are partially threaded. This allows them to stay with the lens when the lens is removed.

It's very easy to make your own fillister head screw from a pan head. I used fully threaded pan head phillips screws and turned down the head. It's best to used stainless screws as they will not corrode. If you use a plated screw, the new surface that is created during the turning process will corrode.

I used a drill and dremel to make the new screws. I started by double nutting (is that a real word?) the screw and placing it in the drill chuck. I placed a sanding disk on the dremel. If you have a reversable drill, make sure that it is spinning in the opposite direction or the dremel. This method ensures getting a nicely rounded head. The diameter of the head needs to be turned down to something less than 7mm. I used another attachment on the dremel to turn down the threads nearest the screw head. This will ensure that the screw won't bind on the small lip in the lens screw hole. An option to doing this is to carefully file the lip off the hole.
 

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Great write-up!

You're correct about fasteners, too many otherwise well restored cars are let down by the use of fasteners with the 'wrong' heads (e.g. modern posidrive etc) although I suppose that many have to use what they can find. This is why I'm always on the hunt for old fasteners that could be used again if replated successfully. I believe there is a guy in the US who makes period-correct fasteners for Ferraris, but I forget his name.

The Carello/Altissimo rear lenses for the GT/GTA/GTV use these fillister head screws (thanks for that - never knew they had a different name!) and have tiny hard plastic washers to cushion them against the lens body. I turned a big batch of these on the lathe at home by stamping out blanks from plain sheet, packing them tightly along the length of a bolt with a nut on the end, then turning them down to the correct diameter. The photo of my rear lenses might just show what I mean. The fasteners are original to the lenses and were replated in satin zinc - but after seeing your idea I might just be tempted to make better ones!

Alex.
 

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Osso -

What a write-up! You may end up with the first 101 point original ever! Your photo collection alone is worth extra credit.....

;)

Robert
 

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that's a great idea! Looks awesome Osso!!
 

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Hi Alex,
could you be so kind as to let me know what the dimensions are for the bolts for the Carello lenses for a the bertone coupe? I' like to fabricate some as mentioned above (I don't have any...). It seems to me that all 4 fasteners are not all the same length, is that correct?
Thanks in advance
andrew
 

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Andrew,

I've taken apart several rear lenses now and you're right, the lengths of the fasteners do seem to be different but I haven't made any notes (yet). I'm also unsure which kind of rear light unit you have - mine has a cast mazac (pot metal) body, whereas the later cars had a white plastic backing with a lens unit which had a 'chromed' outer lip. The fasteners used might therefore be different, too.

In any case, it should not be hard to fabricate the fillister screws as per the instructions given above, and cutting off some of the thread if it consequently proves to be too long?

Alex.
 

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Hello Ossodiseppia - can you tell me please what the screw thread is?
I tried a couple of metric nuts on one fillister screw that I managed to get out but the one that I thought was the right size wouldnt go over the turned down end of the screw and the others diameter was obviously too big. My local 'nuts and bolts' shop couldnt identify what the screw thread was and the Alfa parts manual just tells me that its a Carello part number 11.632.435? I would appreciate any help/information you could possibly supply.

Many thanks
Bob
North Yorkshire
UK
 

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almost all are 5mm x 0.8..SS is the way to go..rules of thumb--use a rubber o ring in place of the washer---Never over tighten-- just BARELY snug or the lens will crack from expansion and contraction in the heat and cold...grind off the threads on the upper part of the shank toward the head to allow the lens to float on the screw
 
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