How to remove stripped tiny screw for hotend thermistor?
 

[Solved] How to remove stripped tiny screw for hotend thermistor?  

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hamza.b
(@hamza-b)
Estimable Member

2 months ago, after i got huge plastic chunk on my hotend (due deataching print over night), i probably damaged thermistor during removal.... Prusa sent me new thermistor. 

I tried unsucessfuly to unscrew hex tiny hex screw from thermistor, because plastic is all around there, so i used hair drier to soften the plastic, and i managed to put my allen key into screw, but things go on... i stripped hex pattern, and allen key is skipping (moving freely).

Tried using rubber band - unsucessfuly. Thought about replacing heatblock but I am not even able to replace one because i am unable to heat up hotend to unscrew it :'(

What am i supposed to do now guys?? 

Posted : 19/07/2020 11:30 am
Andrew
(@andrewld)
Estimable Member

Only way would be to drill and try reverse tap (if you have one) to remove the grub screw. If you don't have a remover tap don't bother buying one most are useless, especially soo small. Drill it to get as much out as possible and pick at the bits of thread left in the hole with a sharp pick or better yet with the correct size tapping. If you don't have a set of taps I would recommend you should buy they are useful for lots of things and if you screw up the drilling simply use a bigger tap and a bigger grub screw.

Best of luck.

Posted : 19/07/2020 5:24 pm
hamza.b and jerry.s3 liked
Andrew
(@andrewld)
Estimable Member

Oh, and try to avoid using the rounded end of the allan key in future.......they are great in a tight spot but also great at busting faces of grub screws.

 

Andrew

Posted : 19/07/2020 5:26 pm
hamza.b liked
dalee1002000
(@dalee1002000)
Eminent Member

Hi,

As an old toolmaker, I will tell you have two options short of replacement.

First, I would try heating up the hotend a bit. Aluminum and steel have very different thermal expansion coefficients. The aluminum will expand first and a lot more than the steel or brass. This is why you change nozzles when hot. Things come apart easier. find a tight fitting square ended hex wrench. This may mean using an Imperial sized wrench at this point. You may need to remove the hotend from the machine to work on it on a bench. If you do that, spot heat from a micro-torch will be needed to apply heat. Be careful - too much heat can quickly melt aluminum without warning.

If all else fails, you will need to carefully drill the grub screw out. I would use my mill and a lefthanded drill bit, but you will need a drillpress at minimum with a sharp high quality drill of tap drill size. If you carefully align the bit and the screw, you can drill the screw out. Then run a tap back down the hole to freshen up the threads. You may also need to drill things out for the next size larger screw.

Good Luck! There are no easy answers for this.

Posted : 19/07/2020 5:39 pm
hamza.b and jsw liked
59935847
(@59935847)
New Member
Posted by: @hamza-b

2 months ago, after i got huge plastic chunk on my hotend (due deataching print over night), i probably damaged thermistor during removal.... Prusa sent me new thermistor. 

I tried unsucessfuly to unscrew hex tiny hex screw from thermistor, because plastic is all around there, so i used hair drier to soften the plastic, and i managed to put my allen key into screw, but things go on... i stripped hex pattern, and allen key is skipping (moving freely).

Tried using rubber band - unsucessfuly. Thought about replacing heatblock but I am not even able to replace one because i am unable to heat up hotend to unscrew it :'(

What am i supposed to do now guys?? 

are you sure that you were using right size allen drive.  I saw your picture , I think you use wrong size allen drive

look this size you can find the which allen size need use https://www.asdscrew.com/tech/37.html  

and the screw screw has property class grade. If the property class grade too is 4.8, the hexagon socket drive will be very easy danaged and it will cause  the allen drive skipping (moving freely). I suggest you use the property class grade above 8.8 screw.

Posted : 21/07/2020 11:47 am
hamza.b
(@hamza-b)
Estimable Member

@andrewld

Thanks for helpful suggestions, but i doubt i ll have success reverse tapping that tiny screw... (if i understood correctly - you are talking about screw extractor?)

I am scared if i drill such a tiny screw that i will damage heatblock thread. On top of everyhing, its very uncomfortable access position to maneuver, and i am unable to preremove whole heatblock because i would need to heat up the hotend which is impossible without thermistor :/

This post was modified 3 months ago by hamza.b
Posted : 23/07/2020 6:53 pm
bobstro
(@bobstro)
Illustrious Member

Worst case, you can replace the heater block. It's a good opportunity to do a few upgrades while you're at it. A titanium or bi-metal heatbreak can help with heat creep and jams, and a nickel-plated copper heater block has better thermal characteristics than aluminum. I did these upgrades, along with a new thermistor and heater cartridge, when I stripped my nozzle socket.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 23/07/2020 7:02 pm
jerry.s3 liked
hamza.b
(@hamza-b)
Estimable Member
Posted by: @bobstro

Worst case, you can replace the heater block. It's a good opportunity to do a few upgrades while you're at it. A titanium or bi-metal heatbreak can help with heat creep and jams, and a nickel-plated copper heater block has better thermal characteristics than aluminum. I did these upgrades, along with a new thermistor and heater cartridge, when I stripped my nozzle socket.

Thanks for suggestion, but i assume its only possible to buy directly from E3D?

Posted : 23/07/2020 8:28 pm
hamza.b
(@hamza-b)
Estimable Member

@dalee1002000

Thanks for great suggestions, i need to try one of these !

Posted : 23/07/2020 8:30 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: @hamza-b

[...] Thanks for suggestion, but i assume its only possible to buy directly from E3D?

Oh, not at all.

  • If you want genuine E3D parts but don't want to deal with buying from the UK, there are number of resellers that sell genuine E3D parts -- including Prusa versions -- locally. In the US, Filastruder, PrintedSolid, FilamentOne and Matterhackers are good sources. I personally prefer to deal with companies that are invested in our communities, and each of these companies are excellent. MatterHackers manages to provide 2 day free shipping somehow. The others vary but are reliable and reasonably fast.
  • There are also clone/alternative manufacturers of many parts. I personally like E3D parts, but there are some quality manufacturers for various parts. P3-D makes nozzles and heatbreaks that I quite like. TriangleLab is a Chinese source of quality clone parts that are cheaper but not dirt-cheap. I like to support the originators and innovators when possible, but it's always good to have alternatives.

In my case, my heatbreak, heater block, thermistor and heater cartridge were all genuine E3D parts sourced from Filastruder in the US. I purchase P3-D nozzles directly in the US. I'll order occasional clone parts from TriangleLab as emergency backups or to experiment with.

 

This post was modified 3 months ago by bobstro
My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 23/07/2020 8:45 pm
randito liked
nathan.b20
(@nathan-b20)
Trusted Member

That's a pain. As suggested drilling out or replacing the heat block may be best options. If you're done trying to remove the grub screw using a slightly larger Allen key, penetrating spray and heat, and if you have a very steady hand, you could also try gluing an old hex key into the stripped lug and turning it out.

It's no easy feat to glue just the inside of the grub screw but a small dollop on the very end of a suitably sized (just fitting) hex key will do it (the glue spreads around the stripped area of the grub screw as the key is inserted). You'd need to use a very strong heat resistant epoxy like jb weld (up to 500 degrees Fahrenheit), let it cure fully, heat up the block to 150-175 (to be safe) and try drawing the grub screw out.

Potentially worth a shot before replacing more expensive parts.

Posted : 24/07/2020 8:52 am
hamza.b liked
charles.h13
(@charles-h13)
Famed Member

I had a similar issue and though I stipped the screw.  Try heating the block with a heat gut to 300-400 C and then try to remove the screw.  Make sure you are wearign gloved and using pliers to hold it.   Fingerprints are important.  

Posted : 24/07/2020 1:24 pm
crawlerin
(@crawlerin)
Honorable Member
Posted by: @charles-h13

Fingerprints are important.  

Your phone had to say something about it? 🙂  Heating it up o cooling it may be a good idea, depending on which metal expands more with heat.

Posted : 24/07/2020 4:04 pm
hamza.b
(@hamza-b)
Estimable Member

EDIT : SOLVED - preheated to 200C and used thicker toilet cleaning rubber glove as grip. 

This post was modified 3 months ago by hamza.b
Posted : 24/07/2020 11:51 pm
nathan.b20
(@nathan-b20)
Trusted Member

 

Posted : 25/07/2020 12:03 am
hamza.b liked
Karl Herbert
(@karl-herbert)
Famed Member

@hamza-b

👍

If you don't already have one, I would place a hot air gun in the first place in the tool cabinet for the printer. This can be very helpful for such maintenance work, e.g. this one or similar: https://www.amazon.com/-/de/N2030-Temperature-120%C2%B0F-1200%C2%B0F-Protection-Attachments/dp/B07FS5DQ2H/ref=sr_1_32?__mk_de_DE=%C3%85M%C3%85%C5%BD%C3%95%C3%91&dchild=1&keywords=hot+air+gun&qid=1595689469&sr=8-32

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 25/07/2020 4:07 pm
charles.h13
(@charles-h13)
Famed Member

@karl-herbert

The Prulde heat gun kit is not a bad deal for a heat gun.  If I needed another, I would hope on it.  

Posted : 25/07/2020 4:29 pm
charles.h13
(@charles-h13)
Famed Member

@hamza-b

Glad to be of service!

Posted : 25/07/2020 4:30 pm
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