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Hotend Grub Screws - Potential Problem?  

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Rick
 Rick
(@rick)
Trusted Member
RE: Hotend Grub Screws - Potential Problem?

I couldn’t loosen the grub screws with a hex wrench. I’m pretty sure the heads were stripped out during assembly at Prusa. What finally worked for me is a T6 torx/star bit. With moderate pressure it will get a bite in the screw head. I had to use a wrench on the bit while maintaining pressure on it to break the screw loose. Just a tiny turn with the wrench is all that is needed. Then I could finish backing the screws out with my fingers and the T6 bit. I ended up using the same screws and the T6 wrench but just snugged them up by hand and no wrench. They seem to be holding fine. Luckily I have a set of these bits on hand.

This post was modified 3 years ago by Rick
Posted : 22/03/2020 1:06 am
Simon liked
Area51
(@area51)
RE: Hotend Grub Screws - Potential Problem?

I use torx drive too when I have a difficult hex unbacho grub screw - sometimes it works as in your case. I think the torx system has a cone shape and that gives a good grip if it can fit in with the tip.

Have a look at my models on Printables.com 😉

Posted : 22/03/2020 1:21 am
PortalFPV
(@portalfpv)
New Member
RE: Hotend Grub Screws - Potential Problem?

@olef

I build racing drones and have a TON of these screws in a variety of lengths...I don't know why I didn't do this when the first one rounded out on me ¯\_(ツ)_/¯

Posted : 15/04/2020 6:04 pm
Olef liked
jamisonsword
(@jamisonsword)
New Member
RE: Hotend Grub Screws - Potential Problem?

Obviously this advice is too late for most of the people who have posted here, but in case anyone else finds themselves in this thread while googling for a solution to the tight set screw problem: I had two screws that were so tight that they had partially rounded out, and I managed to get them loose by lubricating them with a PTFE based penetrating lubricant spray. You'll want to remove your magnetic sheet, of course, and throw a towel down to keep the lubricant out of places that shouldn't be lubricated. One spritz on each screw, and they loosened right up.

Posted : 20/04/2020 4:27 am
wpisteve
(@wpisteve)
New Member
RE: Hotend Grub Screws - Potential Problem?

I wanted to check here to see if anyone had more suggestions of what to do if the screws are not catching at all.  I am new to 3d printing...have had the mini for about 3 weeks and am really enjoying getting into it.  Unfortunately, I had a print last week that got messed up...and then after that, it wouldn't print anymore.  I was able to get it to unload and load filament, cleaned out the extruder, did a few cold pulls, but it would always end up underextruding or not putting anything out at all while clicking from the extruder.  

I figured it was time to open the hotend and try to address the issue similar to threads I see here on the forums.  I got 2 of the 3 screws out but have been unable to get the 3rd out...and am pretty sure the screw is completely stripped now.  I'm pretty bummed as I only recently got the printer and selfishly with being in quarantine, was enjoying getting into things here.

I have NOT tried drilling into the screw...it is so small that I am worried it won't work and I will just damage the hotend.  Should I try that?  I have tried lubricant on the screw (maybe not well enough?)...maybe if I find a good enough pliers or such to grip the screw from the outside (seems unlikely to work...and hasn't with the one pair I tried it with...although that wasn't a very good set).  I have bought new M3 screws with a larger head to replace them with if I can get the last one out.

Any other suggestions?  Will I most likely need to get a new hotend from Prusa?

This post was modified 2 years ago by wpisteve
Posted : 03/05/2020 7:11 am
Stu
 Stu
(@stu)
Active Member
RE: Hotend Grub Screws - Potential Problem?
Posted by: @wpisteve

Any other suggestions?  Will I most likely need to get a new hotend from Prusa?

Have you tried a torx driver? This worked for me and others on this thread. The torx driver gets some bite, even to a stripped screw, if you keep firm pressure.

One other idea. In the spares which came with your printer there's a spare PTFE tube. This goes inside the hot end. I found the spare tube was longer than the factory fitted one, and worked well while I ordered new screws. The tube needs to be under slight compression to avoid the melted filament getting under the lower end of the tube. The whole issue seems to be about avoiding a small doughnut of filament forming under the lower end of the tube.

Posted : 03/05/2020 1:01 pm
wpisteve liked
wpisteve
(@wpisteve)
New Member
RE: Hotend Grub Screws - Potential Problem?

@stu

I wasn't able to get it out with a torx driver.  However, I did switch to the spare tube...originally, I didn't because they looked to be about the same size...but when looking today, I guess it is very slightly longer.  I put it in, put the different screws I bought in for the 2 grub screws I had managed to get out...fired it up and it appears to be printing...or at least is making it way farther than anything I tried earlier in the week.  I already had ordered some PTFE tube to have here for future fixes...although I am left in a spot where I can't undo one final screw...but I am optimistic it will print other things now which is light years better than I've been over the past week.  I feel dumb for not just trying out the spare tube earlier.

Thank you for the advice and quick response!  

Posted : 03/05/2020 6:08 pm
Uncle Jessy
(@uncle-jessy)
New Member
RE: Hotend Grub Screws - Potential Problem?

Stripped my grub screws but thankfully had a tool from a Nintendo Switch Repair kit that fit perfectly and allowed me to unscrew them after heating it up a little.

Posted : 16/08/2020 11:00 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Hotend Grub Screws - Potential Problem?

I use a stainless steel M3x4 Tork screw to clamp the cartridge heater. I have never had a problem removing it. Of course the cartridge is heated up to 250 degrees so that the screw can be loosened better.

M3x4 Torx

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 : 21/08/2020 4:24 pm
Texy
 Texy
(@texy)
Reputable Member
RE: Hotend Grub Screws - Potential Problem?

Had my first encounter with this grub screw problem - the allen key hex ball end broke inside the grub screw. Now the only resolve is to drill it out....darn it.

Texy

Posted : 29/08/2020 9:17 am
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Hotend Grub Screws - Potential Problem?

@texy

That's bad luck 🙁 
Then I hope that the allen key was not hardened, otherwise it will be difficult to drill out.

goodl luck!

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 : 29/08/2020 10:53 am
pydron
(@pydron)
New Member
RE: Hotend Grub Screws - Potential Problem?

I have five Prusa Minis and all of them have this grub screw issue.  I tried the T6 torx bit trick on a few with no luck.  Does anyone have any information on screw extractions?

Posted : 09/03/2021 2:59 pm
mark
 mark
(@mark-3)
Reputable Member
RE: Hotend Grub Screws - Potential Problem?

I have used the tapered T6 tool that comes with this kit with success.

https://www.amazon.com/gp/product/B001KBEO1O

The tapered tip really bites into the grub screws well and actually digs in and remakes the hex rather than rounding it off.

Regards,

Mark

Posted : 06/04/2021 2:18 pm
Clarmrrsn
(@clarmrrsn)
Honorable Member
RE: Hotend Grub Screws - Potential Problem?

Grub screws are always tricky little beasts,  so easy to round the heads with a worn allen key, or even a slightly smaller key will get you into trouble.  Some cheap grub screws/hex keys are not really that great a fit, even with the correct allen key.

+1 for the The TORX trick, this is one I have used many times to remove grubs that have rounded heads at work, when another engineer has got a bit enthusiastic with a worn allen key.

Sometimes a little love tap on the torx to make sure the torx but is really tight before attempting removal is wise, so the torx doesn't lose grip.  I use torx bits for this, easy access to give a gentle tap with a toffee hammer.

This post was modified 1 year ago 2 times by Clarmrrsn

Tank you very much!

Posted : 06/04/2021 2:57 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Hotend Grub Screws - Potential Problem?

A good tool to loosen grub screws reliably for example is this one: https://www-de.wera.de/en/great-tools/hex-plus/

So far, I have not had any problems with worn-out inner hexagonal edges.

If the screw can't be removed with torx and allen tools, maybe it will work with such a tool: https://www.amazon.de/ALDEN-Grabit-Broken-Bolzenausdreher-St%C3%BCck/dp/B000Q60UOO

The last option is to drill out the grub screw, which should go well, however, as the China screws are rather soft.

Good luck to all who have to deal with such problems 👍 

 

 

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 : 06/04/2021 6:56 pm
NeoxReeq
(@neoxreeq)
New Member
RE: Hotend Grub Screws - Potential Problem?

The first time when I used the Torx drive was a couple of weeks ago, and to be honest, I didn't expect that it would give me so many issues.

Posted : 02/07/2022 11:52 am
NeoxReeq
(@neoxreeq)
New Member
RE:

Honestly, after that, I decided to abandon those freaking grub screws, as they gave me a lot of headaches. The most absurd thing is that when I tried to use some simple screws that I got to use on these hangers https://www.scrooz.com.au/hardware/joist-hangers/ , they worked perfectly here as well! I didn't even have to lose the screws and so forth. In the end, the easiest choice was the best solution.

This post was modified 3 months ago by NeoxReeq
Posted : 02/07/2022 9:04 pm
Sugarlumpz
(@sugarlumpz)
New Member
RE: Hotend Grub Screws - Potential Problem?

I just wanted to thank all the contributors to this thread. I had a similar problem, and by the time I was able to remove that particular screw, it was so tightly bound to the allen wrench that I think it's a permanent addition.

For the short term, I substituted M3x8. They did not bump the x-axis motor. Then I ordered these: https://www.amazon.com/dp/B07B6TTHN3. They are the perfect length for securing the heatbreak (they don't sink in all the way to the screw cap, so you can be sure they have made contact). They also blend in nicely, especially compared to the M3x8 that looked like Frankenstein's neck bolts. 

Posted : 29/07/2022 3:44 pm
Damiano_PL
(@damiano_pl)
Eminent Member
RE: Hotend Grub Screws - Potential Problem?

Folks, I have maybe stupid but not so stupid question.
For what it's neccesairy to unscrew grub screws always whe we change shrinked PTFE tube ??
It's really neccesairy ??
When I have proper lenght of PFTE tube 43,4mm and proper one turn loose of PTFE tube fitting for what I must unscrew grub screws ??
In my opinion is not neccesairy at all.

How are Your opinions ?? I'm right or I'm wrong ??

Posted : 02/08/2022 11:31 am
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