C40 cabinets - correct wood screws

[Nordschleife]

I'm working on a pair of C40 Harkness cabinets and have noticed different wood screws on the backs and for mounting the crossover + baffle boards. Does anyone know what the correct wood screw size and type was for the mid/late 1950's JBL Signature cabinets?

The first C40 has 8 x 1/12 (my guess... could be size 9 or 10) steel wood screws with countersunk phillips heads.

The other C40 cabinet has 8 x 1 1/2" also, but these are slotted pan-head brass wood screws with additional grommet washers.

All of the screws are quite old, definitely at least 20-30 years based on their appearance. So it has me puzzled.

What were the correct original cabinet assembly screw sizes & types for the C-series cabs?

Thanks, Andy

[Wagner]

I'm working on a pair of C40 Harkness cabinets and have noticed different wood screws on the backs and for mounting the crossover + baffle boards. Does anyone know what the correct wood screw size and type was for the mid/late 1950's JBL Signature cabinets?

The first C40 has 8 x 1/12 (my guess... could be size 9 or 10) steel wood screws with countersunk phillips heads.

The other C40 cabinet has 8 x 1 1/2" also, but these are slotted pan-head brass wood screws with additional grommet washers.

All of the screws are quite old, definitely at least 20-30 years based on their appearance. So it has me puzzled.

What were the correct original cabinet assembly screw sizes & types for the C-series cabs?

Thanks, Andy

They changed over time
I restore them all to the fasteners used during the all plywood era *(with the exception of screw head type)
Use countersunk screws WITH the dress countersink finishing washers and you will be "correct"
There are also a few exceptions; some factory built C40 boxes allowed for the removal of BOTH back panels, some not (they were glued and then screwed)
On some of those examples (some, but not all), the screws used (on the NON-removable panel) were simply countersunk
If I am working on one of those types then I leave those particular screws "as is"

Bottom line? On anything removable, use the countersunk finishing washers; that is what was used before particle board and cost cutting came into the picture. And if you are so inclined, you can use the finishing washers on ALL screws and still be accurate (and it looks impressive/nice if you are an overly fastidious weirdo like me)

Only thing I change is, I will use brass where JBL used steel (and even that is not 100% of the time; I've had them come to me with both) as I also paint the backs of all my C40s flat black and always defer to the brass type

I do this, because on almost every example I have restored, the screws were extremely over tightened (especially on the plywood boxes) and the finishing washers practically flattened out, so I use fresh washers anyway for a clean consistent appearance

I've had many where the over torque had driven the washer almost completely into the panel. I would imagine that custom orders received a bit more finesse as for the final assembly

Original examples were built using 3 types: steel (color), black steel (anodized finish) and brass, so you'll be "OK" with any of them

*As for head types? Early boxes used slotted and later examples used Phillips (same as the rest of the industry) I always replace with fresh Phillips fasteners and save the original slotted ones for the same guys that want to save the old caps. That technically is a historical inaccuracy (a Phillips screw in an early 1950s box) but that is an anachronism I can live with for about 10 reasons but most importantly the ability to torque things down more accurately and with fewer blemishes.