Broken plastic screw mounting

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Grossel

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Hi forum. This is not a question directly related to electronic, but it is very relevant to many repair jobs.

I bought an old (like really cheap and only pure luck if it works) Acer Aspire 5737 model, and of course it had a problem so that I needed to disassemble it to try to repair.

Then the issue I'm asking about. It turned out that the computer most probably had being exposed to violation, because due to disassembling I faced two problems. Problem one is that some of the plastic mount holes was broken (like when somebody have used a way too powerfull drill to attach the sreews) - they was simply cracked lengthwise. Into the mounting holes, there is a metal "bucket-like" with screew-threads (that one is from google translate suggestion, hope that is correct) and because the plastic mounting is broken, I had to remove those as well.

After removing the "nut", all there is left is a whole too big to attach any screew, and the structure is also too weak because it's cracked.
So I was thinking - only way to "fix" this must be filling the remaining whole with liquid plastic, where I can drill a new whole (for more coarse srews).

And so I did, using a hot air soldering gun. I tried on several pieces of plastic, most did not turn liquid enough to be able to fill into the whole. After testing several pieces of plastif (from garbage) I tried using a suck straw. This one consisted of plastic that went liquid enough to actually fill the hole - but when I assembled the laptop and was tightening the new screw - I felt that the new plastic obviously had get loose from the moutning whole, probably because the plastic from the straw went porous and weak.

Therefore I ask: Do you have any idea how to make a cracked screw mount strong again?


The other question is sort of same type, also because of the last owner have abused the laptop - I found one philips screw where it was nothing left of the original pattern - just a round whole (as if somebody have tried to drill the screw very hard into place, maybe even used a drill bit instead of proper bit).
In this particular case it was located at corner, so after loose all other screws, I was able to twist the hole bottom plate to make it out. Before that, I used my mini drill trying to make a small pattern si that I could screw it out - but no success as the screw was too solid.

So I have this Bosch multi cutter tool (oscillating movements, not rotating) so I thaught if I just had the right equipment, hard enough and small enough - it should be possible to scratch/dig out a track making it possible to unscreew.
Any bright ideas about what can be used?


Thanks in advance
 
Grossel said:
I found one philips screw where it was nothing left of the original pattern - just a round whole
Click to expand...
For this I usually use a small hacksaw and cut a slot for a normal flat blade screwdriver.
If your Bosch multi cutter can cut a suitable slot, that is also a good solution.

To fix these things, I usually clean the plastic and remove any small broken pieces, and the stick it all back together with the "metal nut" using either an epoxy glue, or a cyanoacrylate type glue.
Where there is missing plastic, you can build up the hole with epoxy glue, or if you are using a cyanoacrylate (Super Glue) you can build up material using baking soda.
Look here:
An English lesson:
a metal "bucket-like" with screew-threads - could be described as a "Threaded Bush" or an "Insert"
Look here: https://uk.rs-online.com/web/c/fasteners-fixings/sheet-metal-panel-fasteners/inserts/
and here: https://uk.rs-online.com/web/c/fasteners-fixings/sheet-metal-panel-fasteners/rivet-bushes/

You are confusing hole and whole, they sound exactly the same but the meaning is different.
"I can drill a new whole" should be "I can drill a new hole"
" twist the hole bottom plate" should be " twist the whole bottom plate"

Your English is far better than my Norwegian, I can read a little bit, but I don't attempt to speak it.

MVH

JimB
 
I've found that PVC or ABS pipe cement, or even just the primer if you work quickly (the type plumbers use) works wonders for melting plastic chemically. If you can strengthen it with some plastic taken from a non-critical part of the case, then you'll probably end up with a joint that's at least as strong as the original.
Super glue doesn't work at all!
 
Can you post a picture. If the screws are nylon or epoxy plastic, they are quite difficult to weld (melt together) compared to plastics like PVC and ABS. There may be other solutions.
 
Jim B
Thank you for very helpful answers (and some language assist), I try not to make a lot hole of typos
A small hacksaw won't do because the screw is still located down in its hole beyond reach, so it must be somethinh slim that also fits into the same hole.
I'll get some cyanoacrylate type glue for this use.
Now when I know the name Threaded Bush, I did search for it and I found some images showing variations with a fastening plate too, but hose may not work unless the fastener is perpendicular to the underlaying plate.
Baking soda trick was new for me, next time I open the computer I'll surely give this a try.

hyedenny
I searched for ABS pipe cement on web, but cannot find any description saying it actually melting plastic. Also, due to a wast number of products in the serie, I'm not sure what to choose. Think I stick with the "soda trick" and if it somehow turns out to be not strong enough, I give other cemical solution a go.

jpanhalt
The screw itself is made of hard steel (or at least too hard to let me make a track on its head). The mounts is made of the same plastic material as the casing for laptops - which I don't know what is.
I have taken some pictures, I'see if the quality of those is good enough and then upload.
 
Four obvious options for "hard" steel:
1) If cheese head or fillister head, you can try a small vise-grip or needle holder (a type of surgical forceps) to grab the sides and unscrew it. Access and quality of needle holder can be a problem. Those heads are high enough that you can get a decent grip.
2) Grind a slot with a Dremel-like tool. I use a non-fiber reinforced carborundum disk. It gives a narrow, but sufficient slot. Access can be a problem.
3) Use a cyanoacrylic glue ("super glue") to attach something you can turn it with. Probably the weakest of the methods, but access in not such an issue.
4) Of course, the classic method of drilling it out (carbide will drill hard steel) will work, but can make a real mess too.

Looking forward to the picture(s).

John
 
For hardened steel I use a 20 mm dia diamond coated cutting disc in a Dremmel tool. They work great & are very cheep on Ebay from China. They will cut a slot for a screwdriver in the hardest of screws.**broken link removed** $2.79 for 10 discs
 
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Hi. The screw itself is sitting down into a hole, so it's not accessible for regular tools - I did an illustration (explains better than photos):
 
Both the threaded bushing and screw are probably right-hand threads. I once faced a few phillips head screws (IMHO, the hardest to get out) that were rusted in and the slots were completely cammed out by someone else.. Drilled a small cavity in the top, then used a left-hand threaed tap "cut" to the right length to get them out. The other screw heads may not even require drilling.

Ordinary screw extractors have too coarse a thread and require too deep a hole to work. Cheap carbon steel or HSS taps can't be sawed. I ground a slot and broke it off as if I were cutting glass tubing. You could grind it completely off, but be sure to keep it wet. It needs to be hardened.
 
If you can get a set, left hand drill bits might be an option.
Sometimes, the heat from drilling can make the screw expand slightly and some pressure can get the drill bit to 'grab' and break the screw free.

O.T. I had a job to remove a seized sleeve a couple of weeks ago and my go-to multi-spline extractor failed, as it grips only in the anti-clockwise direction and I came against a stop - trying to back it up in the clockwise direction only loosened the grip of the extractor. I had some square bar stock and ground a taper on all 4 sides, hammered it in and got the sleeve moving again. Improvised tools are sometimes much better than off-the-shelf tools in certain situations.
 
First of all - I have managed to get the screw out, so it is a solved problem - at least until next time I encounter same type of problem.

And - because I have a little language barrier, not all name of tools gives sense - and not all names is possible to do a "internet search" to figure out what the true meaning is. Mickster had a problem with a "seized sleeve", but Google tells me that a "seized sleeve" is an arm full of tattos - I got no clue - why the heck would you tell about an upper arm that is stuck - feel bad figure out somebody is crazy enough to try using power tools when an arm is stuck
Also "cammed out" is something I had to google to get the true meaning behind - and Google tell me that is a race car - beleive me Google is not very helpful at here. But at least I can guess that it means somebody have tried to drill onto the screw head, and miserably failed - I'm I right?

jpanhalt
Since this question is asked more than once, I got to check the wikipedia site for screws and it figures out to be frearson type of head. I do have a drill press, yes (Bosch) - but I don't see how I'm going to secure the whole bottom plate of a laptop onto it.

Mickster
When I get over my temporarly language barrier I might got an idea what to respond.

Sorry for this OT post
 
As for Frearson (Reed & Prince) head, that is quite uncommon in the US. I happen to have a screwdriver for the most common size of it though. The included angle on the tip is different from the much more common Phillips head, and the fit in the screw head feels different when you have the wrong driver:



I am a stickler about using the right driver (both size and style) and not messing up the head of a screw. "Cammed out" was just a term I learned years ago to describe messing up the slot or slots in a screw head by letting the screwdriver twist out and shave off part of the edge you need to turn against to remove or install it.* Once that happens, the torque you can apply to the screw is greatly reduced. You usually see it on the edges needed to remove the screw. Thus making it effectively into a "one-way" screw (https://en.wikipedia.org/wiki/List_of_screw_drives#One-way). A slang term for that type (i.e, one-way) of intentional head is a "prison" screw. In the US, you see them used often in restrooms to keep vandals from removing the privacy dividers -- don't have any firsthand knowledge about whether they are also used in prisons.

Glad you got the screw out. BTW "sleeve" and "bushing" are sometimes used for the same thing.

John

*My guess is the term comes from the shape of a cam surface to convert rotary motion to linear or visa versa.
 
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Just a little update for the sake of not lying about - screw the lie about the screws? Because when I look close on a screw, it has a flat head indeed:

 
My comments. Tough project. Try to obtain a case.

Attempt to drill out.

Milling might be possible.

This http://www.amazon.com/PC-Products-P...DJ6/ref=cm_cr_arp_d_paging_btm_2?pageNumber=2 stuff I've had pretty good luck with, It's initially soft with a separation layer of plastic. You remove that and mould it. A drinking straw might work. Not sure how easy it would be to flare out the bottom.

Get an insert similar to:

http://www.banggood.com/100pcs-M3x5...s=search-left-hotproducts__1&cur_warehouse=CN

Just make sure the hole is filled with grease.

ABS/PVC is usually solvent weldable or a solvent cement. See http://www.plumbing-geek.com/solvent-cement.html

This http://www.michaels.com/10161780.html was always useful for models.

The 281216, here http://www.testors.com/product-catalog/testors-brands/testors/adhesive/cement/ is probably one of the better cements for plastics.
 

That's actually a very poor picture of Reed & Prince screws. The sides of the driver are tapered to a point (i.e., the walls of the cross are not parallel). A properly made Reed and Prince driver will fit the smallest Reed and Prince screw.

 

Adding to this old thread for new people coming by to figure this out. I've fixed at least a hundred laptops with this exact problem. I quickly gave up gluing, cementing, epoxy, etc as the original hinge being good was the problem the post broke in the first place. That means, your gooey gluey cement repair will be very temporary. In addition, opening the laptop again without a mess or more damage is a problem.

So, easiest way is to just use Sex Bolts. Drill from the top of the notebook to the bottom in a clear path and fasten them with a light bit of thread lock. Ugly? Sometimes. But there usually is a reason we're not ordering new parts for the broken ones, right? They come in all kinds of sizes, shapes, screw heads, diameters, materials, etc. Available in large hardware stores.
 
Nice thread to "keep alive".

Let me add this resource for threaded inserts: http://www.ezlok.com/ Mcmaster-carr is a source for the inserts.

Another cross-point screw style is the JIS screw. A discussion is here: http://conurus.com/forum/viewtopic.php?t=10

I have the Moody set. 4 sizes, 2 lengths, ALWAYS make sure the cross-point screwdriver fits. Phillips, JIS, reed & prince, Pozi-drive or some I missed. Posi-drive does have a distinctive marking, 4 radial lines and have been used on HP equipment,

A Phillips screwdriver will strip a JIS screw and less likely the other way around.

A note about plumbing. You have a cleaner, a primer and a "cement", It softens the material. Some are muli-material: PVC and ABS.

All it takes is once. I've yet to use anti-sieze for small screws.
 
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