I broke my NK8 heat break upon tightening locknut, how should I do that?

Hi,

I tightened the locknut of my heat break against the housing of my MK8 extruder, and the heat break was torn in two. I used a small spanner and I don't think I used excessive force (and I am no Hulk, I am a nerd). Any tips and tricks on how to avoid this, other than: "Be careful!"? I already tried the 'turn until it breaks and then back off half a turn. No luck.

Cheers,

Hugo

Edited 1 time(s). Last edit at 09/08/2017 04:44PM by HugoW.

A long time ago someone told me that after you snug a nut or a bolt of any size, if you tighten it any more than a 1/4 turn then it is too tight.

(mind you sung on a head bolt is a good pull while sung on a 1mm nut and bolt is a tiny twist.)
Now their a circumstance where you have special material (case hardened nuts and bolts ect...) where you can exceed this limit.
I have lived with this rule for most of my life and have still broken, stripped and rounded nuts, bolts and screws, metal and plastic.

You can buy a torque wrench they come in many measuring tensile strengths(hahahaha) Don't buy a Torque wrench unless you have a real need for one.
We all learn the hard way we over tighten, once you have done this you will automatically be watching carefully every time, and still you will break, strip or round some off.

Edited 3 time(s). Last edit at 09/08/2017 08:42PM by Roberts_Clif.

I don't know if this applies to an NK8 hot-end, but this is the general "right way" to assemble a hot-end:

1. Heat the heater up to normal filament temperature
2. Tighten the nozzle finger-tight into the heater block
3. Back it out 1/4 turn or so
4. Tighten the heat break into the heater, finger-tight
5. Tighten the nozzle against the heater block with a wrench

This will tighten the nozzle against the end of the heat break, inside the heater block, without putting stress on the heat break itself.

I don't have any lock nuts on my heat break.

[Edit: Added the "Heat the heater..." line as pointed out by @Ludvig. This is really important.

Edited 2 time(s). Last edit at 09/11/2017 04:27PM by frankvdh.

A google search for NK-8 hotend shows me exactly the same Chinese knock off I had (not saying you have one ) and the middle of the heat break was thin like an aluminium soda cans walls thickness, so I also broke it.

I ordered a bunch of (cheap) steel breakers (I don't think you can break them with normal handling), but I just got a lot of jams so I bought a E3D hotend, and I did something around what frankvdh said except I heated the heatblock up before.

A little cumbersome to attach as it's really hot but it worked for me. Afterwards, I didn't screw on the cooling part very hard at all just by hand, it came off when heated so I forced a little bit more (but really not much) and now it's well stuck.

HTH