J-Head Mk IV-B 0.4mm

J-Head Mk IV-B 0.4mm

The famous J-Head hotend can now also be ordered from us, to complete your Prusa printer!

The nozzle size is 0.4mm and it comes with a thermistor and power resistor, all you need to do is put the items inside the hotend and connect to your electronics.

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€ 51,50 tax incl.


Warning: Last items in stock!

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The J-Head Mk IV-B has been proven to print reliably with both ABS and PLA.  (PLA will require a small fan to provide air-flow through the cooling vents milled in the sides of the nozzle holder.)

This hot-end easily interfaces with the most popular RepRap extruders, including Wade's Extuder, Greg Frost's Hinged Accessible Extruder, etc.

Please note:  The maximum operating temperature is 247 degrees Celsius as PEEK will soften at 248 degrees Celsius.  Due to many variables, affecting the accuracy of the temperature readings and settings, caution is recommended when extruding at temperatures approaching this limit. We recommend you implement a safeguard in your firmware whenever possible.

  • Internally, the filament path is identical to that of an already proven design.
  • The design is simple as the number of custom machined parts is kept to a minimum.
  • If necessary, the PTFE liner can be replaced by using an off-the-shelf piece of PTFE tubing.
  • The PTFE is not stressed nor used to provide support. This reduces a point of failure that is part of other designs.
  • A resistor is used as a heater. There is no need to wrap nichrome wire or to bake a heater core.
  • Heat transmission is improved as there is no thermal junction where a separate heater screws onto the nozzle.


  • Assembled J Head MKIV-B Hot-End
  • Power Resistor, 5.6 ohm or 6.8 ohm (depending upon availability)
  • Thermistor, 100k, Beta value 4066


  1. Insert power resistor into resistor hole, as pictured. Silicon heat compound is recommended for optimal heat transfer.
  2. Insert thermistor into thermistor hole. Secure resistor with Kapton Tape.
  3. Solder resistor and thermistor leads to appropriate wires/connectors as required by your electronics.
  4. See RepRap J Nozzle Wiki for attachment of assembled Mk IV-B to extruder.

Suggested Items (Not Included)

  • High-temperature wire for resistor, McMaster Part No. 8209K11 (or equivalent)
  • Teflon (PTFE) sleeving for thermistor lead insulation, McMaster Part No. 5335k11 (or equivalent)
  • Kapton tape for thermistor mounting.

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