This hot end is the result of my attempt to build the Wildseyed Simple Hot End by jcabrer for my Simpler repstrap. I live in Metric land, along with the ROW (rest of the world) which started my journey down the path less taken to begin with...
I noticed that it would be possible to use the previously unused M6 thread on the MIG tip to our advantage, and make the tip itself easily exchangeable. This design also makes the fitting of the PTFE easier and more precisely aligned than I could manage on Wildseyed, with the unexpected bonus of a double seal on the PTFE rod.
Using the gas connector nipple also gives a flat face for the heater, making working with nichrome a bit easier, giving you a choice of heater technology.
Note that this hot end is very definitely a work in progress, and that the instructions will be updated as I go along.
Thread adapter nipple (Air Hose connector):
1) Push the adapter into the drill press chuck - tip first, and tighten slightly.
2) Lower the drill press and securely clamp the adapter on its base in the drill press vice.
3) Release the Chuck from the adapter, and insert 8mm drill bit.
4) Carefully increase the inner diameter of the adapter shaft, all the way through.
5) Remove the adapter from the drill press, and using the hacksaw, cut the adapter in the middle of the narrow sectoin of the shaft, as per the CAD drawing.
6) File the cut neat and flat.
MIG Welding tip:
1) Lightly clamp the welding tip into the drill press chuck, with the tip pointing downwards.
2) Similar to the adapter, clamp the MIG tip in the drill press vice, making use of the flat faces on the tip.
3) Insert the 3.2mm drill bit, and using cutting oil, carefully cut exactly 25mm into the back of the MIG tip.
4) Make sure to remove all the metal filings and cutting oil from the tip.
PTFE (Teflon) shaft:
1) Clamp a piece of scrap wood in the drill press vice.
2) Using the 3.2mm drill bit still attached to the machine, drill about 15mm into the piece of wood.
3) Remove the bit from the chuck and insert into the hole in the wood.
4) Insert the 1/2inch (12.7mm) PTFE rod into the drill press chuck, making sure to insert it deep into the chuck, and using just enough force to clamp it tightly.
5) Hold the drill bit with a long nose plier while drilling into the PTFE with the stationary drill bit. If your bit is not long enough, turn the PTFE shaft around, and drill from the other side to go all the way though.
6) The 3.2mm hole though the shaft should match nicely.
7) Using a 4.5mm drill bit drill 8mm into the 3.2mm hole. You can do this by hand - it is always nicely centered.
8) Using the drill press, and a knife or chisel, work the end with the 4.5mm hole down to 12mm (or less) to make it turn easily into the Air hose, but do not turn it in yet.
Assembling the parts:
1) Tap the MIG tip with the hammer into the enlarged tip of the adapter. It will be a tight but not necessarily press fitted match. Keep going until the base of the tip aligns with the inside of the large diameter threaded section of the adapter.
2) Insert the 3.2mm drill bit into the back of the MIG tip, with the cutting side first. This will allow us to use the shaft as a guide pin when turning the PTFE rod onto the threaded sections of the adapter and the MIG tip.
3) Turn the Rod into the adapter, allowing the adapter threads and the MIG tip to cut its own threads on the outer and inner sides of the PTFE. It should be tight, but easy enough to turn to feel when you reach the end of travel.
4) Unscrew the PTFE rod to reveal your newly cut thread, and remove the drill bit.
5) carefully screw the PTFE rod back on the thread, and check the alignment of the inner channel. It should now be easy to insert the drill bit into the back right into the copper section.
6) OPTIONAL: Use a countersunk tip to manually slightly countersunk the back end of the 3.2mm hole in the PTFE to ease filament insertion.