Mystery screw identification - Page 1
Forum section: electronics / projects

author: rs20
author_rank: Super Contributor
timestamp: January 15, 2020, 09:15:45 pm
content: Folks,I need more copies of the screw which I have described/photographed below. Any info, from identifying the basic thread type standard right up to a specific part number, would be most greatly appreciated.Information #1The screw is one of the ones used to affix a PDL DBF30 faceplate (i.e., the only four screws that you can see simply by opening up the switchboard doors.)Information #2A photo is attached. I used a long lens and the image is heavily cropped, so I think it's fair to assume the image is more-or-less orthographic. The background is, of course, 0.1-inch spaced breadboard. My attempts at extracting distances from the photo are given below (with far too many significant figures).1351.1 px = 1 inchHead: PozidriveScrew length (excluding head)1014.9 px = 0.751" / 19.1 mmScrew pitch460.3 px / 6 = 0.05678" / 1.442 mm (17.6 TPI?)Screw minor dia (root)161.4 px = 0.119" / 3.03 mmScrew major dia (outer threads)214.2 px = 0.1585" / 4.03 mmHead dia423.3 px = 0.3133" / 7.95 mmHead depth152.6 px = 0.113" / 2.86 mm

author: Vgkid
author_rank: Super Contributor
timestamp: January 15, 2020, 09:24:42 pm
content: Looks like a self tapping sheet metal screw.Have a hardware store near by? Even better, have a local fastener dealer?

author: Whales
author_rank: Super Contributor
timestamp: January 15, 2020, 10:20:11 pm
content: Yep, I'll double the sheet metal self-tapper.Best thing to do is walk to Bunnings and compare it with what's on the racks. Even if you don't want to pay their prices it will let you find the model. Measuring thread pitches is useless if you don't already know what series the thread is in.EDIT: also, based solely on that photo, looks like it could be stainless. Can't be sure from here; but if it's anywhere near water then it might be worth it.

author: bill_c
author_rank: Regular Contributor
timestamp: January 16, 2020, 01:44:32 am
content: Take a look atwww.mcmaster.comfor any kind of screw, bolt, bearing, fitting, etc. Many items they carry have CAD drawing that may help you identify those items.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: January 16, 2020, 03:59:40 am
content: Dimensions are very close to a US #8, type A pitch self tapping sheet metal screw. Don't know how likely that size would be for use in your equipment.Sheet metal screws are really only intended to be driven once into a given hole. They often work for multiple insertions but often you need to go up a size to get the same clamping force. Unless you are going for a museum level restoration I wouldn't worry about exactly duplicating this screw, just get one with a head that fits and is same or slightly larger major diameter and similar pitch.

author: Stray Electron
author_rank: Super Contributor
timestamp: January 16, 2020, 05:12:42 am
content: Notice the slot cut lengthwise in the threads? That's there so that it will cut it's own threads into soft material like plastic and in thin sheet metal. They're typically made to be extremely low cost and for use in low cost products that don't have pre-threaded holes and they aren't really intended to be removed and reused more than a FEW times. The biggest problem with reusing them is that they work exactly as intended and cut new threads in the hole every time that you use then and after a removing and reinstalling them a few times, the material around the hole is soon all cut away and the screws will no longer hold. However if you're careful to get the threads in the hole and on the screw matched up they can be used many times. When you go to reinstall the screw, put it in the hole and turn it backwards (usually counter clockwise) until you feel it drop into the hole slightly as the threads in each part line up with each other. Then you can safely tighten it without cutting new threads in the hole and wearing away more material.Surprised that you didn't know what it was, those are EXTREMELY common in the US.

author: KeepItSimpleStupid
author_rank: Regular Contributor
timestamp: January 17, 2020, 04:13:34 pm
content: You might find something here:https://us.screwerk.com/enor at least something close. They specialize exclusively in screws for plastic. I did see Pozidrive heads.To avoid trouble buying from them, don't try to buy just 10 screws. Buy a 100.