2

So I attempted using a couple of shitty plastic screws to attach an air pump to the water bottle mounting holes in the frame. I was using a long-arm torque wrench and the head of one of the screws just came off, leaving the body inside.

I need those threaded holes in order to install the pump!

Thinking of burning the screw body with a soldering iron and then forcing a steel screw in, to clean the thread.

Would this be a good idea? Maybe drilling would do better? Anything to be careful about?

8
  • 1
    Pick up a screw extractor kit from a hardware store. They're inexpensive and extremely handy. I'd worry that melting the plastic would cause it to stick to the threads of the braze on.
    – WTHarper
    Oct 10, 2013 at 12:03
  • @WTHarper, great, I never knew this existed! However, this should not be comment - it is not requesting clarification of the question.
    – Vorac
    Oct 10, 2013 at 12:14
  • 2
    Drill them out. Just use a small bit, so you don't muck up the threads too much. Use successively larger bits until the screw drives on through by itself or it gets thin enough that you can pick it out. Oct 10, 2013 at 12:36
  • 1
    Since they're plastic, if you drill a small hole in the middle as @DanielRHicks suggested, and then wedge something in the hole (needle nose pliers?) you could probably get enough grip to unscrew the plastic bolt. Or if you want to melt stuff, heat up the tip of a screwdriver, to make a new head on what's left of the screw.
    – Kibbee
    Oct 10, 2013 at 13:04
  • @Vorac bicycles.stackexchange.com/help/privileges/comment I wanted to provide information that I didn't think constituted a complete answer (but I guess technically we shouldn't be discussing community behavior/site policies? I don't know.)
    – WTHarper
    Oct 10, 2013 at 22:01

6 Answers 6

11

As the comments have stated, here's your options:

  1. Screw extractor: Inexpensive and easy to use.
  2. Drill: Use successively larger drill bits until most of the screw is gone.
  3. Drill and extract: Drill a spot large enough to put something in the middle and pull it out.
  4. Screw/Nail Extract: Lightly tap a nail or smaller screw into it and then try to unscrew the stuck body.
  5. Melt it: Not really recommended but you could do it. Be prepared to retap the threads if things go awry.

Note, these are not in any order and some can be tried before others.

0
10

You could try heating up a screwdriver and pushing that into the screw, then (after everything has had a chance to cool down) using it to turn the screw out. Start gently and increase the heat until it works.

2
  • 2
    I would make the slot and then wait for it to cool down before turning.
    – Mark W
    Oct 11, 2013 at 9:03
  • @MarkW I agree - I'll update my answer, as that's what I was thinking of but didn;t write clearly.
    – Chris H
    Oct 11, 2013 at 9:41
3

The source of the problem was that the plastic body of the screw threads difficultly into the thread. The feeling is comparable to those metal bolts with rubber seal to prevent vibration.

Consequently, when I was screwing the bolt in, there was no increase in the feedback torque - it was moderately difficult to screw the bolt in, up until the head broke off.

So, firstly I tried to burn a slot in the body of the screw with a heated screwdriver. I got it several millimeters deep, but when I attempted to turn, half of the screw broke off.

Next I tried drilling with a dremmel. The bolt is in the bottom of the front triangle, so even though I used a flexible arm (like the ones at the dentist's), I was unable to attack the screw co-axially and the drill bit constantly hit against the aluminum frame.

Next I tried a soldering iron. Bought a cheap, thin-nose, 30W iron and managed to remove a lot of material. This was the most successful method so far ... almost.

Having done everything possible, I inserted a steel screw and tried to chase the thread with it. To my disappointment, it didn't work. The "nipple" at the frame began rotating, with respect to the frame. The bolt become stuck within the "nipple". Now I need to go to a LBS and ask if they could replace the thing.


Bottom line: don't use plastic screws: they are evil. If you must, use a short-arm wrench e.g. 10 centimetres.

2
  • You may have had better luck with a real thread chaser since it would have sharp edges to scrape out the plastic and grooves to let the scraped off plastic out. Since melting likely bonded the plastic with the metal, the metal screw couldn't push it out of the way.
    – Johnny
    Oct 22, 2013 at 15:06
  • 1
    @Johnny, indeed, I should have listened to WTHarper. Foolish was I, in those days long past: wast week.
    – Vorac
    Oct 22, 2013 at 15:09
2

I know this is old but for some reason it came up while I was looking for something else and I just want to add this in case it's coming up for others as well.

Everyone here missed the most important point on this entire thing, which is; Plastic, aluminum, titanium, brass, steel, etc. no matter what type of fastener you are using, ALWAYS start it by hand first and get it in a few threads before putting any kind of driver on it and as long as the threads on both the fastener and whatever you are fastening it to are in good shape, there should never be any such issue to begin with! Also if you do notice any unusual resistance while you are driving a fastener, STOP immediately, back it out and figure out what is causing it before continuing!

I know the OP was already in a situation at the time he posted and all the answers were trying to help but I feel this should be added because whether or not the issue was solved, many times if people don't get the info that could prevent another such incident, they may well just find themselves back there again. I know this may sound trivial to some but I can't count the number of times I have witnessed people doing the same thing over and over because they simply weren't told or shown how to avoid it happening again.

Hope I'm not out of line here but I just saw an opportunity to add a bit of useful info in case others find this before they are in a situation in order to avoid one or so that people who are already in one may be able to avoid another similar situation. It's one of the fundamentals of any type of mechanical work and saves probably billions of headaches when applied.

1
  • You're right - it's not an answer, but this is good advise about how to stop things going wrong like this in the first place. Well written answer - keep up the good work.
    – Criggie
    Mar 19, 2023 at 21:37
2

Ok, I am trying to remove the plugs on my used 2016 Trek 7,3Fx so that I can add a rack to the back of the bike. Gently prying the edges along all sides of the plug just folded then upward when I tried to pull. So I tried using pliers to pull the plug out by the folded edges, but the edges of the plug just rip off. I tried drilling a hole in the plug, but I couldn't get a clean start on the surface. Cutting off the exposed top of the plug with a box knife Then, I was able to drilling out a small hole. I was then able to use a pointy tool to poke down the drilled hole and pry out the plug. It worked.pointy tool and the removed plug pointy tool placed in the drilled hole to pry out the plug

0

I drilled a hole at center of plastic screw. About 1/4 inch deep, and the broken screw started turning. With some work it come out.

1
  • Welcome to Bicycles SE. We ask that you write to the best of your ability on this site. This means proper capitalization, proper punctuation, and complete sentences. As your answer stands, it is a bit unclear. Please use the "edit" button to clean your post up. If you do not, it may be downvoted, flagged, and possibly deleted.
    – jimchristie
    Aug 10, 2015 at 19:14

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.