Reprap Home Made Hot End Design

By | January 1, 2014

This is still a rough draft and changes will be made. HotEnd


  • 1/2 inch teflon rod
  • ID 1.8mm, OD 2.3mm teflon, teflon tube
  • 1/2 square aluminum block
  • 5/16 inch, 18 threads per inch, brass rod
  • 5/16 inch, 18 threads per inch, brass acorn/cap nut


  • Size #79 drill bit
  • 3/32 drill  bit
  • 5/16 bottoming tap bit
  • 17/64 drill bit (or F size)
  • 11/64 drill bit
  • 5/ 32 drill bit

Teflon Rod

The rod acts as a heat buffer between the hot aluminum block and the extruder body.   Use the 3/32 drill bit core out a hole down the center.   Drill half way through one end.  Flip the rod and drill the other half from the other end of the rod.    You do this because getting a hole straight through can be tricky without a lathe.    This hole needs to be just big enough to thread the bendy Teflon tube through it.

Aluminum Block

Start with a stock 1/2 x 1/2 bar of aluminum.   Drill a 3/32 hole all the way through.   Then follow that hole with a 7/64 drill bit just half way through.    Tap the hole with 5/16-18 threads.    Then drill holes for the resistor, screws, and thermistor.   Drill two 11/64 holes for mounting screws.   Drill 5/32 hole for the power resistor.

The bottoming tap bit, vs a taper, will give you more threads in the hole and get them closer to the bottom.

To cut a length from the bar, use a circular saw with carbide tipped blade.   Put some oil on the blade and aluminum to help the chips come free.    Or you can also use a hack saw by hand if you are doing just one.

Brass Rod

Drill 3/32 hole through the rod, halfway from each side to minimize stray from the drill bit wandering.    This piece should screw into the aluminum block and should allow Teflon tube to go all the way from the Teflon rod to the tip.   Since the tapped threads in the block will be tapered a bit, you can also taper the brass rod a little to let you screw it in more.   Any gap in between the brass rod and the 3/32 hole in the block will let the teflon tube expand when under pressure and could pop a leak.   So it’s best to taper enough so the end of the brass actually touches the block.

Brass Nut

Drill #79 hole from the inside out.   The drill bit will self center.