Very small screws. Replacing or fixing - Page 1
Forum section: electronics / general

author: ThunderZed
author_rank: Regular Contributor
timestamp: April 04, 2022, 06:45:02 pm
content: I've an electronic device closed by 4 very small screws. My problem is they're very worn and I've to replace them or try to fix them.I took some measures and the diameter (just the body, not the head) is 1mm (= 0,0394in) and the length is 12mm (= 0,4724in) but only the last 4mm (= 0,1575in) are threaded and a single pitch of the thread is about 0.5mm (= 0,01969in). I don't know exactly what to search on the web, eg. I tried "m1 screw" but I found onlyM1.2 screws for metalon aliexpress, I mean with different thread (pitch=0.25mm) while I guess these screws are specific for plastic.I think my only other option is to fix them, I mean I'd use a saw and make a deeper cut on their heads so I'll screw/unscrews them by a flat head screw-driver. In this case I think my main problem is how to keep them enough firmly while I use the saw to avoid to ruin their heads.Suggestions?

author: PlainName
author_rank: Super Contributor
timestamp: April 04, 2022, 07:16:42 pm
content: QuoteTwo bits of wood clamping the screws. Usually you'd clamp the wood and drill slightly undersize holes at the join for the screws, but these are so small that just pressing the two bits of wood together would probably have them deform around the screws.Is that scale 1mm? If so, the pitch doesn't look lik 0.5mm to me but more like 0.3mm, which would match M1.3 or so. The unthreaded part is likely slightly smaller in diameter (so it doesn't snag on the thread if it goes it that far). I would be tempted to get the M1.2 and try it - worst case you're out a few pence and however long it takes to turn up.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 04, 2022, 07:55:13 pm
content: Wood will probably work as might any stiff plastic or rubber, particularly if you are just cutting a slot. I would just drill a 1 mm hole in the wood and turn the screws into the hole. They should fit snugly enough not to be a problem.For other work, like turning the heads, I use annealed copper or lead strip in a 3-jaw or 4-jaw to keep from damaging the threads. That works good for holding gears when you need to bore them.

author: Gregg
author_rank: Super Contributor
timestamp: April 04, 2022, 09:32:03 pm
content: You could possibly grind or file the worn part of the head flat and silver braze another torx or similar head cut off another suitable fastener.The trick is to get both surfaces as flat as possible and use as little as possible high silver content silver braze wire. Test this method on some scrap fasteners to develop the methods necessary.

author: RJSV
author_rank: Super Contributor
timestamp: April 04, 2022, 11:36:42 pm
content: Funny coincidence, was just thinking as I cleaned up the bench, the Plastic Toys use that size...Approx 12 mm length, and completely flat, under the head. So it seats down fully, not a 'cone' shape.The commonly seen 'TOY' screws are 'silver' colored, Philips, fully threaded length.Exactly my thoughts, concerning what a 'full' bench supply would contain.Synchronicity, that's common.

author: SeanB
author_rank: Super Contributor
timestamp: April 05, 2022, 08:19:52 am
content: Yes, clamp in wood, though you will definitely find the steel is quite hard, and you need a very narrow blade to cut the slot. Otherwise look for some other tossed out generic Chinese goods that have similar screws, at least matching head diameter, length, though you might not find them with that partly rolled thread form. Did that yesterday, replacing some painful to open security screws with some old Sony made red screws, which were exactly the right head diameter and length, and also had the right thread to tap back into the same groove.

author: ThunderZed
author_rank: Regular Contributor
timestamp: April 05, 2022, 05:03:51 pm
content: I took some more detailed photos (see attachments) and measurements (where possible). These are my results:- # of pitches = a bit less than 10;- threaded part = a bit more than 4.5mm but less than 5mm-> pitch = a bit more than 0.45mm, so let's say 0.5mm- threaded part diameter = 1.25mm (VS 1.00mm not threaded part)- head diameter = 2-2.25mm (2.25mm=0,088582677in)So the above linked M1.2x12mm screws could be a chance though the pitch is the half part (0.25mm VS 0.5mm) and I theoretically doubt they'll stay firmly inside the holes. Another theoretical chance could be M1.2 pan headed screws for wooden likethese onesand they could be ok due to their wider pitch though they're only 10mm long and the pointy end won't turn inside the holes, imho.About working on the screws.Maybe my main problem will be the blade to use, I mean I guess it's necessary a sort of high density teeth blade for these precision works else I think I'll ruin the heads though the screws will be well clamped. Consider my blade isthis one.I guess it'd be good if I found a way to make a deep "mark" on the head before sawing, I mean another and deeper mark than the mostly ruined philips cross traces. What do you think about all that?Anyway I've not yet red your suggestions about this option so maybe later I'll ask you some questions

author: PlainName
author_rank: Super Contributor
timestamp: April 05, 2022, 05:20:34 pm
content: Instead of a saw blade like that, perhaps a Dremel-sized cutting disk:https://www.amazon.co.uk/dp/B0781S621S

author: richnormand
author_rank: Unknown
timestamp: April 05, 2022, 06:29:36 pm
content: In a similar situation I used a diamond wire homemade "saw" to make a slot in the damaged head under a stereo microscope.Diamond wire is available in very small diameter and you just need to tension it in a C clamp and use it as a hacksaw and a few drops from a damp sponge for cooling and lubrification.The screws were clamped between two pieces of wood. Be careful as the cutting action is quite efficient.

author: Bud
author_rank: Super Contributor
timestamp: April 05, 2022, 06:43:18 pm
content: Try a local computer/laptop repair shop. They should have plenty of small screws.

author: rdl
author_rank: Super Contributor
timestamp: April 06, 2022, 12:40:02 pm
content: Does the box have threaded metal inserts or do the screws just go into plastic?

author: ThunderZed
author_rank: Regular Contributor
timestamp: April 07, 2022, 03:01:35 pm
content: The 2 "shells" are made only of plastic (see attachment).I'll try with a local computer repair shop but I guess it will be just luck if I'll find what I'm looking for because I've already searched "laptop m1.2 screws" on aliexpress but I got nothing. I think the main problem is the length, I mean you can find a lot of M1 and M1.2 screws but not so long as I need. I bet the device brand asked a 3rd brand to build these special screws, I mean it could be a unique patent.Now some questions about your above suggestions:Quote from: jpanhalt on April 04, 2022, 07:55:13 pmI didn't understand the advantage. If I fully screw them down to the wood so only their heads are out, how could I damage their threaded parts?Quote from: Gregg on April 04, 2022, 09:32:03 pmHonestly? Arab for me. I admit I'm a too much beginner for that. I can only guess you suggested to usesilver brazing sticks like thesebut... 1) I think I need a right tool for soldering and 2) I first try to find cheaper solutions if possible. Anyway if I misunderstood please explain that in other words.Quote from: dunkemhigh on April 05, 2022, 05:20:34 pmQuote from: richnormand on April 05, 2022, 06:29:36 pmLike this one?I've just found my saw blade is too large for this job so I wonder if the best solution for me is a diamond wire in a C clamp or a diamond disk. I know the wire diameter will be about 0.26mm but what about the disk width?

author: PlainName
author_rank: Super Contributor
timestamp: April 07, 2022, 04:52:21 pm
content: From the Dremel website it seems the disc is 1mm thick. But they explicitly say not to cut metals with it, so I guess that's out.

author: richnormand
author_rank: Unknown
timestamp: April 07, 2022, 07:53:02 pm
content: From ThunderZed:"Like this one?I've just found my saw blade is too large for this job so I wonder if the best solution for me is a diamond wire in a C clamp or a diamond disk. I know the wire diameter will be about 0.26mm but what about the disk width?"Exactly. Wire is available in several thickness and quite good. I cut sapphire and glass stuff with it too in my automated see-saw jig.Also if you are near a hobby shop you might be able to get a whole kit with several wire thickness.Only drawback of diamond saws is to keep the wire well lubricated with water or it will tend to load up with soft materials or to break.Once you have the basic kit you will find many more applications for it.This link will give you an idea of the various diameters availablehttps://www.mtixtl.com/diamondcuttingwires.aspxI got about 200 feet of the 0.25mm about 10 years ago and I am not past the halfway point on the spool.

author: ThunderZed
author_rank: Regular Contributor
timestamp: April 07, 2022, 11:35:05 pm
content: Thanks for your suggestion, I think I'll get some diamond wire. What do you think is a perfect wire diameter for my job? Remind the screws heads are 2-2.25mm and the not threaded part is 1mm. I think I'll buy it on aliexpress and there're several options:-https://www.aliexpress.com/item/1005002768044594.html- from 0.028mm to 0.1mm x 200m - about 2USD-https://www.aliexpress.com/item/1005001320421686.html- from 0.04mm to 0.1mm x 100m - about 2USD-https://www.aliexpress.com/item/4000614589146.html- 0.26mm or 0.38 x 1m - about 3USD-https://www.aliexpress.com/item/4001042615745.html- 0.4mm or 0.6mm x 1m - about 5-7USDI'd not consider more than 0.6mm, imho.By the way what's better to use for my job, a c clamp or a "pull rod" as you can see in the 2st item description picture?

author: Gregg
author_rank: Super Contributor
timestamp: April 08, 2022, 12:11:35 am
content: For such a shallow saw slot, a fine tooth hacksaw blade can be ground thinner along each side to get the width you want. This is a good way to use up the still sharp ends of otherwise worn out hacksaw blades. It will take out any set of the saw teeth which will make the blade stick to the sides of a deep cut; but for a screw head it should be OK. You can start a very shallow groove with a triangle jeweler's file to guide the hacksaw blade and cut on the pull stroke with the flattened hacksaw blade.

author: ThunderZed
author_rank: Regular Contributor
timestamp: April 08, 2022, 11:49:02 am
content: My saw blade is new. Can I use a sharpening stone (for knives) to make its teeth thinner? What do you think if I keep my saw firmly and move the screws by my hands, I mean to get a more precise though slower job?

author: Carel
author_rank: Regular Contributor
timestamp: April 08, 2022, 08:38:02 pm
content: It is called a self tapping screw.

author: BrokenYugo
author_rank: Super Contributor
timestamp: April 08, 2022, 09:14:31 pm
content: Take a small hammer and gently cold work the displaced metal back into a screw head shape, then clean up the slot (or cut one new in your case). Pretty common job if you work on stuff full of custom slotted screws that people like to booger up.