What material is best for making a part that is fastened with screws?
Depends.
What other requirements does the material need to fulfill?
You can use a thread-cutter in any plastic to make a perfect spiral and compress the material at the same time.
It has 4 pegs about a centimeter long that must not break off. Two pegs are hollow for screws to fasten it. The pegs go through a hole to align the part. Not much stress is put on the part
Ive been having issues with screws seperating layers
I like using brass inserts that can be put in with a soldering iron.
Brass inserts as already mentioned work extremely well. Good thread and sunk into the body of the print for incredible hold. No need to worry about layer separation if you melt them in. McMaster Carr is your supplier.
Nuts and an iron will do in a pinch.
@Keith_Applegarth i am starting a print as we speak to try that. I may try to fuse each part with acetone to help even more. Its an order of 50 pieces so that is going to hard to smooth them all
Plastite screws work well in plastic. You still have to size the hole correctly.
Are you wanting to use a self tapping screw like a wood screw or a fine thread like a bolt and nut. You can resess a nut into the far side and the bolt will then hold to a nut. If you want to tap into the plastic print with additional shell thikness to give the bolt or screw something to bite into. Larger threads are better but even a m3 bolt will hold prety tight. I print everything in pla
The business i am making these for uses self tapping screws
I would do it 0.1 -0.2 mm radius bigger than the shaft down the middle of the screw so the plastic wont split and do extra shells that will be like a fisher plug. If you can print the hole vertically.
I would, make sure I have about 3-5 shells of material of choice, or do both pla and abs as a sample and give the choice to client. Make the holes .1-.2mm bigger then the shank of the screw, and use a start and finish tap to cut threads in to holes. The more shells the stronger the part will be. Print a few test at different temps to make sure you have the best temp. Reinforce any items you can, no right angle edges if possible at points that are weaker. Look to reinforce high stress points with more shells or material. Highest strength check nylon, tglass or other material.