Which screw for 45-timber - why is the unthreaded part of the screws so short?

[crazytok]

A fixed 50mm thread is unlikely to make a difference...

 

[ramafred]

But if you are going to join 2 studs 45 on the board and do not want any protrusion on the back, you need to have a 45mm thread or less just to get it to pinch properly. If you pull it 5mm extra, it will stick out 5mm.

 

[crazytok]

But it has to do with the length of the screw, not the length of the thread.

 

[ramafred]

Well, a 90mm screw is correct for two 45mm studs. If you use an 80mm screw, you will likely still have threads left in both studs unless you drive it too deep.

You want threads only in one stud to create a clamping effect. If the thread remains in both studs, they won't clamp together properly unless you use a clamp, which isn't very productive.

The cutting edge that is on most screws after the thread is meant to expose the shank (the unthreaded part) for the head, where the load should rest.

 

[Stickan56]

If you're going to screw together two pieces of timber, you buy screws like these, they pull nicely.
https://www.essve.se/essvese/sv/pro...01-46/konstrukt-skruv-6-5x90-cs-100-118102-46
There are also thicker and longer ones for thicker timbers.

Stickan

 

[fb35523]

Then you need to screw in, screw out, and screw in again.

Exactly. When you pull the screw, you notice it starts to gap. Screw it in a few more centimeters and then out so much that it leaves the other board completely. Then the gap closes up (and you can possibly press it together the last bit if needed). Then you screw it in again, and suddenly you have a pre-threaded hole in the other board that the screw grips directly without starting to gap.

If you have a 90 mm long screw and need to pull it a bit too much so it won't gap, you can screw it in slightly at an angle. Then you can get it in that little extra needed to break through the extra threads in the first board.

 

[Stickan56]

Exactly. When you tighten the screw, you notice that it starts to gap. Tighten the screw a few centimeters more and then loosen it enough so that it leaves the other stud completely. Then the gap closes (and you can possibly press the last bit together if needed). Then tighten the screw again, and suddenly you have a pre-threaded hole in the other stud that the screw grips directly without it starting to gap.

If you have a 90 mm long screw and have to tighten it a bit too much so that it doesn't gap, you can angle it slightly in. This way, you can get it in that extra bit needed for the extra threads in the first stud to be worn out.

You avoid this if you use the correct screw from the start. See my reply #20.

Stickan

 

[mattiasp]

After @Stickan56's tip, I looked for those screws, they weren't available at Bauhaus. Found them at XL. Good to have in the screw box! Unfortunately, they don't exist in the cheaper indoor version.

 

[ramafred]

Or you can buy a standard countersunk wood screw from another supplier that actually has the correct thread length. The construction screw is unnecessarily expensive.

 

[mattiasp]

Or you can buy a regular countersunk wood screw from another supplier that actually has the correct thread length. The construction screw is unnecessarily expensive.

Can you show where such a screw is available for purchase, or who manufactures one?

 

[ramafred]

Can you show where such a thing can be purchased, or who manufactures one?

Absolutely. Essve should be available at Bauhaus, I realized? Their old Cutters had crazy thread lengths, but the new Essdriven looks like it has thread lengths.


Essve
https://www.essve.se/essvese/sv/pro...huvud/träskruv-ess-5-0x90-fs-cs-100-137120-46

VSB
https://vsbyggskruv.se/produkt/traskruv-tft-utvandig/

Gunnebo Fastening
https://www.gunnebofastening.se/produkt/?product_id=174&family_slug=skruv

 

[tobbbias]

If you're going to join 2 pieces of 45, then an 80 mm screw should be perfect, and you countersink the screw about 5 mm into the upper 45. This compresses the wood fibers just enough at the surface, the thread length will be perfect if you have 40 mm unthreaded, and you have 5 mm to spare at the tip of the screw...?

 

[Gazpacho]

V/S/B Art: P4706085 is perfect for joining 2 45s.
6mm thick and 85mm long with a 42mm threaded part and a 43mm unthreaded part.
It tightens suitably when the head is countersunk.

 

[Stickan56]

For 2 pieces of 45s, I use Essve construction screw ET-T
https://www.essve.com/sv/produkter/...sskruv/et-t/konstruktionsskruv-et-t-corrseal/
There is a different pitch on the two threads, which causes the wooden parts to be pulled together.

Stickan

 

[RocketScienceSmurf]

I am planning to put up an interior wall and want to attach a 45x95 standing on its edge against the floor joists, so I would prefer a screw that is unthreaded 90-95mm. Is that available?