How to remove shreded screw  

Re: How to remove shreded screw

I would advise to get a torx version of those screws - perhaps in stainless steel as you are at it. Then use a torque wrench as Randolph proposed ... that should solve any problems in the future once and for all.
I ordered some but have not fitted them with my nylock bed leveling yet ... but I exchanged the M4 screws on the frame like that (after busting one original screw head) and used 5 Nm torque on them - end of side story 🙂

Re: How to remove shreded screw

Note - the 6x6x3T standoffs were hard to find. I had to go to a real hardware store that sells every kind of screw, bit, nut and bolt possible, including custom made to find something that would match. Not even ebay had any hits. Just curious if others have had similar issues getting a single replacement part for the MK3.

Not sure where you are located globally but McMaster-Carr is my goto for ordering such things.

https://www.mcmaster.com/unthreaded-spacers
Specifically: https://www.mcmaster.com/94669A009

Re: How to remove shreded screw

I would advise to get a torx version of those screws - perhaps in stainless steel as you are at it. Then use a torque wrench as Randolph proposed ... that should solve any problems in the future once and for all.
I ordered some but have not fitted them with my nylock bed leveling yet ... but I exchanged the M4 screws on the frame like that (after busting one original screw head) and used 5 Nm torque on them - end of side story 🙂

with M4 SS into aluminum at 5 NM you are risking galling which I think was the cause of the OP problems. at 5NM you are about double the proper torque for M4 see the chart I put at the top of page 2 of this thread... Galling is a hidden problem for most folks in this area as it does not feel like you really over tightening.

Re: How to remove shreded screw

I would advise to get a torx version of those screws - perhaps in stainless steel as you are at it. Then use a torque wrench as Randolph proposed ... that should solve any problems in the future once and for all.
I ordered some but have not fitted them with my nylock bed leveling yet ... but I exchanged the M4 screws on the frame like that (after busting one original screw head) and used 5 Nm torque on them - end of side story 🙂

with M4 SS into aluminum at 5 NM you are risking galling which I think was the cause of the OP problems. at 5NM you are about double the proper torque for M4 see the chart I put at the top of page 2 of this thread... Galling is a hidden problem for most folks in this area as it does not feel like you really over tightening.

My mistake ... the screws for the frame are not M4 but M5x16 ... but the torque of 5 Nm might still be a bit on the high end (Prusa assembly manual says 4.5 Nm) ... but I see what you are getting at Randolph - steel screw zinc plated might be better wrt. thread galling.
I just personally perfer the strength of the A2 head in combination with the torx.
Cheers,
Mark

Re: How to remove shreded screw

Note - the 6x6x3T standoffs were hard to find. I had to go to a real hardware store that sells every kind of screw, bit, nut and bolt possible, including custom made to find something that would match. Not even ebay had any hits. Just curious if others have had similar issues getting a single replacement part for the MK3.

Not sure where you are located globally but McMaster-Carr is my goto for ordering such things.

https://www.mcmaster.com/unthreaded-spacers
Specifically: https://www.mcmaster.com/94669A009

LMAO - that's what I meant by real hardware store. That's exactly where I got it. But nothing from brick and mortar and the usual e-shopping sites had anything close to it. But McMaster's came through. Expensive, but they could and did deliver.

Re: How to remove shreded screw

i used a torque driver at 10 inch pounds for these screws and I also lapped the spacers to be the same length as the shortest provided this brought my bed to level enough the the mesh bed system worked quite well; but to be able to get a good first layer across the whole bed right to the edges I am using the 7x7 modified firmware .

Do you have suggestions for a good manual adjustment procedure? I see -0.4mm difference between center and left most position, and +0.1mm betwen center and far right (all center). I thought the X axis carriage was the issue - not the bed, but adjusting that only makes the numbers worse all over. Far left is where the troublesome screw was located. I'm thinking of putting a small spacer/washer under the heat-bed on top of the stand-off to push up the left side enough - but given your comment I was wondering what suggestions you have to do the initial level calibration manually.

Re: How to remove shreded screw

i used a torque driver at 10 inch pounds for these screws and I also lapped the spacers to be the same length as the shortest provided this brought my bed to level enough the the mesh bed system worked quite well; but to be able to get a good first layer across the whole bed right to the edges I am using the 7x7 modified firmware .

Do you have suggestions for a good manual adjustment procedure? I see -0.4mm difference between center and left most position, and +0.1mm betwen center and far right (all center). I thought the X axis carriage was the issue - not the bed, but adjusting that only makes the numbers worse all over. Far left is where the troublesome screw was located. I'm thinking of putting a small spacer/washer under the heat-bed on top of the stand-off to push up the left side enough - but given your comment I was wondering what suggestions you have to do the initial level calibration manually.

First sorry about my not noticing when you shifted from talking about the Y carriage heatbed fixing screws at 3mm, to the M5 frame screws. You can see the right settings for these common sizes in the chart I included at the top of page 2. For setting the right torque with out a proper torque wrench or driver... that is a bit more complex. one way is to have years of practice wrenching stuff but that is not very useful in this context and I do have those years and I still don't trust my fingers on anything less than about 12mm Good Torque screwdrivers for these sizes of fasteners can be had for about $50 to $80 I use this one in this size range https://smile.amazon.com/Wheeler-Accurizing-Measurement-Gunsmithing-Maintenance/dp/B0012AXR4S/ref=sr_1_5?keywords=Torque+screwdrivers&qid=1551042921&s=gateway&sr=8-5 if you search thingverse you will find ones that you can print for a given torque. they are based on the one that the Ruby Nozzle folks provide on their web page.
the old fashioned shadetree mechanic method is easier with foot pounds than with inch pounds as a 10 foot pound torque is a ten pound force at one foot from the fastener... and 10 inch pounds works the same way... it is not a lot of force which is why I use the driver I linked to above