Question Apeks WTX-D30 screw size for attaching the backplate to the wing?

[Karlovsky120]

As I was rinsing my B&W set yesterday, I noticed one of the screws that connects the backplate to wing was missing. I only used the B&W several times and haven't messed with it since I got it, I have no idea how it got unscrewed. Unlike the screw, I'm screwed until I get a replacement.

I have quicky learned that this is the screw I need:

Apeks Book Screw Kit 2-Pack (Apeks BT115118 or BT115119)

However, I cannot figure out if I need the 3/4" or 3/8" version. I've measured the diameter of the flat part of the screw I had left and it was ~1.9cm which should be roughly 3/4". I figured that must be the dimenison they are talking about, but then I looked around some more and I found this brochure:

https://www.easywatersports.com/brochures/Apeks_Catalogue_Thailand.pdf

The screws in question are listed, but the description says you can pick between 3/4" or 3/8", depending on the length you want. So I don't know anymore. It might just be a bad translation.
If the damn kit wasn't 60EUR, I'd just buy both and see which one fits, but the damn kit is 60EUR.

Does anyone know which size I need?
Also, is there kind of tool you can tightent these with? Other than a giant screwdriver? What do you normally use?

Here are a few pictures of the one I have left:

 

[grantctobin]

Please don't pay $50 for those.

DGX Assembly Screws, Metal, Set of TWO

These metal assembly screws (aka book screws, aka sex bolts) are used for attaching various accessories, such as lift bag pouches, suit inflation mounting systems and sidemount buttplates, to a TransPac harness or to a hard backplate.

www.divegearexpress.com

Screwdriver the best option. You could loctite the threads if you find them slipping frequently. Make sure to look under them every now and again for corrosion.

 

[Karlovsky120]

Yeah, the price is ridiculous. Thanks!

So, the right size is 3/8"?

 

[runsongas]

assuming you have the cam bands going through both the plate and wing slots, you only need the screws if your cam bands aren't wide enough to keep the alignment themselves

 

[The Chairman]

Those are called sex bolts. They are available from Dive Gear Express for $7.

DGX Assembly Screws, Metal, Set of TWO

These metal assembly screws (aka book screws, aka sex bolts) are used for attaching various accessories, such as lift bag pouches, suit inflation mounting systems and sidemount buttplates, to a TransPac harness or to a hard backplate.

www.divegearexpress.com

 

[Badger7]

Also called book screws. And yes, for some reason the Apeks versions are outrageously expensive and totally unnecessary for you to find a match, just get new screws. I'm pretty sure the size you're seeing is length, not diameter. The longer book screw would be used up top, and go through the grommet in the wing, the backplate, and also the grommet in a harness, while the shorter screw would be used in the lower mounting hole, and only need to go through the only the bottom wing grommet and the back plate.

They don't need to be metal (I use these cheap plastic ones from DRIS instead, and keep a few spares in my kit), and if your backplate is aluminum, using metal screws is actually counterproductive as it may cause galvanic corrosion. That's why you see those embedded o-rings on one side, but if you compress them enough you can still sometimes get metal on metal contact

Seeing you're from Croatia, us over here in the US linking DRIS and DGX items probably isn't very helpful, but the usual retailers over in the EU carry book/sex/assembly screws in various materials in prices ranging from $6 to $60. Shoot for cheaper versions, if you replace them at all. Take a look at the Tek Tip in the link that Mr Chairman linked for you above for another viewpoint. Personally, I like my wing position locked and not flopping around on the cam bands during tank changes, but that is worth exactly $8 to me, not a penny more.

 

[Endler's]

Look for OMS 12mm:

They also have the o-ring in gland. 'Come three different lengths. Your ruler looks to measure 12mm.