Are the torque specifications for the hotend assembly, extruder, etc. documented anywhere?
I’m not a big friend of phrases like “tighten them accordingly” or “careful not to overtighten” but would rather have exact Nm numbers.
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I do not think you will find them anywhere. However, as a machinist, I can say there are standard torque settings for socket head cap screws of a given diameter that you can look up. In machine assembly very few fasteners have a specific torque specification. Those that do are special for some reason. The rest are all just standard torque for that fastener size.
Just for fun 
, wrenches are sized differently in order to provide the leverage for a typical man to apply the correct torque that that size fastener. (A 24mm wrench is much longer than a 6mm wrench.)
I have a set of these by my printer. They are hard to over-torque with.
The picture does not convey the size well. The one that I use for the hot end assembly has a handle about the size of my pinkie finger.
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Thanks @julie777, much appreciated.
I’ll probably just order some Wera Allen keys. I don’t feel comfortable with the keys that come with the printer. Or I’ll just look up the torques as you suggested and use my Proxxon.
I just thought that BL does have the torque specs for factory assembly and was hoping they would be available 
I would think its pretty easy to over torque those screws, even with a driver with only a ball handle. The worry isn’t the normal stripping of the screws, but breaking the tool head. IMO, when in doubt ALWAYS go with too little torque and tighten it up as needed if it backs itself out. If you are edgy about it, go snug + 1 hour (e.g. 12 o’clock to 1 o’clock) and see if it loosens up. If I’m not mistaken they are M3’s, and M3’s generally go to 1.0 Nm on the lower side, but I still wouldn’t say that is perfect for this application.
According to the shop the hotend screws are “M3-14 Step Screws”. But it doesn’t mention the property class.
If they’re 6.8 then 1 Nm would be spot on I think.
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The only problem is at that light of a torque spec you need very specific tools. I have a 10-50in/lb driver, which is very specific itself, and 1 Nm is the absolute bottom of the range (1.1 Nm). I wouldn’t trust that driver and would prefer to go by feel. I can honestly say, I’ve stripped more screws using a torque wrench and trusting it to be accurate, than just going by feel. Granted, I love torque wrenches/drivers and they make some tasks brain dead easy. Its just applications like this and others like a known damaged threads where I’ll go by feel.
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Absolutely. I wouldn’t use a tool that barely hits the range either and go by feel instead.
But I do have a 0.4 - 2.0 Nm screw driver and I would prefer to use it if possible.
I’m pretty confident I’ll manage to just tighten by hand, but if you have the tools it would be nice to be able to use them, even if it’s just for peace of mind.
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What the heck, I will provide the full information.
The screws the hold the hot end assembly are M3x14 low head socket head cap screws (SHCS) partially threaded.
Metric SHCSs are available in three grades: Property Class 8.8, 10.9 and 12.9. The 12.9 are the strongest.
The ones that came with my spare assembly are not marked which means that they are 8.8, or possibly just cheap ungraded screws that do not meet any ISO, ASME or ASTM standard.
For M3 class 8.8 the nominal torque is .8NM, but the low head modifies nominal torque by some amount.
I did not find the number for low head 8.8, but a normal M3 10.9 SHCS nominal torque is 1.83 and the low head reduces it to 1.15.
I’ve asked support to provide torque specs and they sent me some pictures. Unfortunately no torque specs included as far as I can tell.
But maybe someone more knowledgable than me can deduce the specs?
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Being they are being torqued in to a molded brass insert, I looked for the spec a insert maker suggests. Here is the doc I used, https://www.pemnet.com/wp-content/uploads/sites/2/2022/06/sidata.pdf
Looks to be something in the range of .5Nm to 1.6Nm, but it will be difficult to confirm which type molded in insert it is. The torque specs start on page 10 but you’ll have to match the type of insert you think it is.
As for the drawings, all I see is the dimensional specs for the screw.
Sorry for grave digging this old post, but has anyone found a solid replacement for these? The factory provided ones suck for a gentleman with no concept of “a quarter turn”.
Thanks!
I haven’t found a replacement screw. But with the information provided to @weak in his post. The torque spec for those screws are 1.15NM or 10 inch pounds for us Americans. Or anyone else who uses the imperial system.
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