Alex Black style window fixings - hole size

[ericbushby]

Hi All,
I intend to make some window cable fixing bolts for a Club members S4. They will be based on the excellent design by Alex Black, possibly with minor variations. I do have dimensioned drawings of various versions of this fitting.
They will be fitted during this winter so I do not have the glass to hand.
Has someone got a window glass out and if so will you measure the thickness and more importantly the diameter of the hole in the glass.
Is this hole drilled in which case it should be accurate or is it moulded and the size might vary.
On my S3 the glass is 4.9mm thick. I assume for now that the S4 is the same.
Hope you can help.
Eric in Burnley
1967 S3SE DHC

[oldelanman]

Hi Eric,
Not sure how critical the glass thickness is to your design but my S4 glass is only 3.95 mm thick. Can't help with the hole size as my glass is not out but hopefully someone else will be along shortly.

[ericbushby]

Thanks Roger,
There you go, another weight saving. I did not expect that.
My glass appears to be original as it has the dot under the `N` in TOUGHENED which is the date code for 7 (1967) Thanks again.
Eric

[oldelanman]

Hi Eric,
That's interesting, I didn't know you could date the glass. So I just checked mine and the etchings are different on the two windows and show different codes .... 1969 and 1971 ?? They both measure 3.95 mm thickness.
There is also a dot above the letters of "Triplex" .. any idea what that means ?

[RAJ2628]

My S4 Triplex glass measured 4.06mm. Given Eric's measurement of 3.95mm nearest imperial equivalent is 5/32"
Hole diameter is between 7mm and 7.5mm. Nearest Imperial equivalent is 9/32"

[ericbushby]

Thankyou for that. It may be a breakthrough for me.
Previous designs have used a 6mm or a 1/4" bolt to make the fastenings. If a size of 7mm is possible then I can confidently make the diameter of the bolt where it goes through the glass thick enough and strong enough to make it from brass. As I cannot machine stainless steel, prototypes so far have been 1/4" dia. steel.
Can someone else confirm the hole diameter please.
Eric

[RAJ2628]

I wrapped one piece of electricians tape around the shank of a brand new 7mm diameter drill.
It produced a lovely sliding fit in both holes.
Measured diameter 7.2mm.

[ericbushby]

That`s more like it, thankyou.
I didn`t like to be picky but I did need more accuracy, thanks
I can now allow a tolerance and turn a plain shank of maybe 6.8 mm. which will give me adequate strength in brass so that the internal grub screw cannot push the bolt head off at the cross drilled hole where the wire goes.
Prototype No 3 coming up. If this is a success I will post full details, but don`t hold your breath as I do not know when it will be tried out.
Eric

[Donels]

The 'dot' under the toughened lettering tells you the year the glass was manufactured. No dot would be 1970 and a dot under the T would be 1971, under the O 1972, etc.