I am starting an exhaust port project for my H2D and I see I need BT3-20 screws to attach to the back of the machine. I am unfamiliar with this thread call out.
They look to be metric screws (3mm by 20mm) but with a very course thread. Can anyone enlighten me on why these are not just normal M3 machine screws (.5mm pitch I think). are these the same thread and pitch as a 3mm wood screw, just with a flat end and no taper on the point?
Also, I see you can buy them from Bambu, but is there somewhere else I can source these that I don’t have to pay $7 in shipping for a $1 bag of screws?
As you said it’s metric, an M3 x 20mm machine screw should work. The cap might not match but if you’re just looking to save a couple bucks it should get the job done.
My research leads me to being that the BT is a type 25 screw, which is specifically designed for self tapping threads in plastic. The ridges might be a bit sharper on a normal machine screw but it should still fit I would think
So I guess that means the mounting holes in the back of the machine are just plastic holes that are to be tapped? that feels dicey for mounting permanent hardware pieces.
I guess if I decide to use machine screws (which I have plenty) I should run a tap in the opening first. but I think it makes sense to use a courser thread like the ones they recommend if I want good bite in a plastic hole.
Guess I will have to buy a roll of filament too to make it worthwhile on the shipping because I can’t seem to find these listed anywhere else.
No, the thread pitch is VERY different. More than 2x. They look a lot more like a wood screw with most of the pointed tip truncated. Other than being a nominal 3 mm in diameter, they have nothing to do with any metric machine screw.
Typically screws going into plastics are “thread-forming” type, Plastite style, triangular lobed so they roll their own thread (versus “self-tapping” screws).
Usually I’d order from McMaster when I need these, since they’re not commonly available at most local hardware vendors.
I finally found the “generic” term for these screws! Wanted to post it so others can independently source these as well.
1st of all:
BT = blind taper (I’m pretty sure)
3 = size (mm)
SHCS = socket head cap screw
What you’re looking for is “thread rolling screws”
If you type that into Amazon you will see the thread type that the BT3 screws have.
I have yet to find an assortment of these or a 1:1 replacement (SHCS thread rolling), but it’s a step in the right direction.
I’ve just measured the ones that came with my H2D Laser for the extraction hood and it looks like the screws are these ones from Bambu M3x4x14 (AA210). Although the thread itself is more like a wood screw on the ones I have so maybe not?
I know you mentioned about shipping etc but it wasn’t clear to me the exact screws needed.
Unfortunately the H2S doesn’t come with them if it’s not the laser version - trying to get confirmation of the size myself without removing the ones from my H2D!
