Hello
I found this screw last week and became fascinated by its construction. Can someone explain the functions of the different parts to me?
What is the purpose of the notch at the bottom of the screw, which then goes through the threads with a rotating path?
What function do the threads with a different pitch in the middle serve?
What is the advantage of the lines on the underside of the head?
I found this screw last week and became fascinated by its construction. Can someone explain the functions of the different parts to me?
What is the purpose of the notch at the bottom of the screw, which then goes through the threads with a rotating path?
What function do the threads with a different pitch in the middle serve?
What is the advantage of the lines on the underside of the head?
The jacket at the tip of the screw is a drill bit so that the screw becomes self-drilling. This means you don't have to pre-drill or risk the wood splitting when you drive in the screw.
The same applies to the "lines" under the head. These are meant to allow the screw head to cut into the wood and disappear in a neat way. If these are missing, the head will instead press into the wood, which can cause splintering and create a large dent around the head instead of it being flush with the wood.
However, I don't know what the "extra" threads in the middle are good for, so I'm eagerly waiting for someone else's explanation.
The same applies to the "lines" under the head. These are meant to allow the screw head to cut into the wood and disappear in a neat way. If these are missing, the head will instead press into the wood, which can cause splintering and create a large dent around the head instead of it being flush with the wood.
However, I don't know what the "extra" threads in the middle are good for, so I'm eagerly waiting for someone else's explanation.
The threads in the middle are meant to help tighten the things you screw together without putting all the "force" on the screw head.
In other words, you don't need to screw it halfway into the decking board to get it to hold properly; the extra threading will grip the decking board and press it down.
However, it requires that the screw is suited for the thickness of the material you're fastening; if the extra threading is in the wrong place, it won't be effective.
In other words, you don't need to screw it halfway into the decking board to get it to hold properly; the extra threading will grip the decking board and press it down.
However, it requires that the screw is suited for the thickness of the material you're fastening; if the extra threading is in the wrong place, it won't be effective.
Looked at the picture again and think that "gängan" is a bit too flimsy, it might be intended to mill out the hole just to make more room for the screw head.
This is how a counter-thread usually looks otherwise:
http://www.bygghemma.se/utomhus/byg...uv/trallskruv-grabber-t-rex-black-c4/p-176236
This is how a counter-thread usually looks otherwise:
http://www.bygghemma.se/utomhus/byg...uv/trallskruv-grabber-t-rex-black-c4/p-176236
Or as PDF:Torpalainen said:A good guide in a twisted world
[link]
http://www.heco.se/trycksaker/PDFer/Pdf_katalog/Heco_kat_Skruvskolan.pdf