Changing a nozzle: hot tightening and torque by maker

Short answer

There is no single correct nozzle torque. Each maker publishes its own figure for its own parts: Prusa uses 2.5 N·m at 280 °C on MK3-family V6 nozzles, E3D about 2 Nm at 285 °C for brass V6, Slice 1.5 Nm, and 3DVerkstan 0.5 Nm (never over 1 Nm) for the Olsson Ruby. Some systems, such as Revo and FlowTech, need no hot tightening at all.

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Why hot tightening exists

On a threaded nozzle, the nozzle and the heat break meet inside the heater block. Metals expand as they heat, so a nozzle snugged cold can loosen at printing temperature and leak. Hot tightening sets the final seal at temperature. Prusa says V6 nozzles must be tightened while hot to avoid leaks.^[1]

Each maker's figure, for its own nozzle

• Prusa (MK2.5/S, MK3/S/+, MK3.5/S, V6 nozzles): Prusa's nozzle-change guide heats the nozzle to 280 °C and gives 2.5 N·m as the torque its service team uses.^[2] Prusa makes an exception for the Olsson Ruby, which follows its own maker's instructions. This procedure is not for Nextruder printers.
• E3D V6: hot-tighten brass nozzles at 285 °C to about 2 Nm, and E3D's other materials (plated copper, hardened steel, Nozzle X, ObXidian) at 20 °C above your printing temperature.^[3] E3D says to wait about a minute at temperature and use a 7 mm spanner.
• Slice Engineering Copperhead: Slice recommends 1.5 Nm for nozzles and warns not to apply torque to the thin Copperhead heat break when installing it.^[4] Slice also warns that not all nozzles can take 1.5 Nm.
• Olsson Ruby: 3DVerkstan says to install and remove it only with the heater block at printing temperature, using 0.5 Nm and never more than 1 Nm.^[5]
• Dyze Design tungsten carbide: Dyze publishes maximum installation torques that fall as temperature rises. For the M6 1.75 mm version, that is 1.9 N·m at 25 °C and 1.1 N·m at 400 °C.^[6]

Nozzle	Temperature	Torque the maker gives
Prusa MK3-family V6	280 °C	2.5 N·m
E3D V6 brass	285 °C	about 2 Nm
E3D V6 other materials	print temp + 20 °C	(see E3D)
Slice Copperhead setups	(see Slice)	1.5 Nm, never on the heat break
Olsson Ruby	printing temperature only	0.5 Nm, never over 1 Nm
Dyze tungsten carbide M6 1.75 mm	25 °C / 400 °C	max 1.9 / 1.1 N·m

The spread is wide: the Ruby's ceiling is less than half of Prusa's figure. Use the figure for your own nozzle, never one borrowed from another maker's table.

Tool-free nozzle systems

• E3D Revo: each nozzle is a nozzle and heat break in one unit, changed by hand when cold without hot tightening.^[7] This applies only to a Revo nozzle in a Revo assembly, not to threaded V6 or MK8 nozzles.
• Micro Swiss FlowTech: Micro Swiss says FlowTech nozzles need no hot tightening and can be changed with one hand.^[8]

After the change: re-check Z offset

E3D notes that you may need to adjust your Z offset after changing a Revo nozzle.^[7] A nozzle of a different length or seat moves the tip, so re-check the first layer after any swap.

Cleaning without damage

• ObXidian: E3D advises against needles, steel wire brushes and blow torches, and recommends a brass brush for the outside.^[9]
• Olsson Ruby: 3DVerkstan advises against wire brushes, because a strand can lodge in the orifice and crack the ruby.^[5]

For other nozzles, check the maker's cleaning advice before using anything harder than the nozzle itself.

Next

• Which nozzle standard your printer takes
• Nozzle materials and their temperature ratings
• Bed probes, Z offset and bed mesh
• Maintenance schedules from printer makers