Make Thermal Barrier With Drill Press
Start with a 3/8 inch peek rod. The actual diameter isn't too important, but I found thinner is cheaper and this was about as thin as I felt would be strong enough. I ordered mine from . You can also use PTFE, it is however preferable to use PEEK as it has less thermal creep.
However the actual diameter you will want to find is 5/8 inch or 16mm diameter as this is the size that is used on the RepRap extruders. The difference between imperial and metric is ~0.2mm.
Cut a 32 mm length. I clamped it in a vice and used a block of wood as a guide and cut it with a hack saw.
Next, use a 10mm x 1.5 die to put a thread on the outside of one end. Aim for about 7 full threads, which required that I make 10 full turns with my die.
If you are using the thermal barrier with a RepRap extruder, the suggested die you should use is 16mm x 2.0 or 5/8". (This will need to be double checked to ensure a good cut).
In order to drill straight down the rod we need to build a jig to hold it in place. Start by clamping a block of wood to the drill press' bed. You will need to have room between the drill press chuck and the top of the block of wood to use the hand tapping tool. Do one final check to make sure everything is locked down tight. Once you drill the next hole, the block of wood must remain stationary.
Alternatively you can buy a table vice with a "V" notch in it, and use a "G" clamp to clamp it to the table of the drill press.
Whatever method you use, everything MUST stay concentric/true
Drill a hole with an 11/32 inch drill bit that is 30 mm deep. Use the hand tap with a 10 mm tapping bit to tap the hole you just drilled. I marked the bit before I started so that I knew when to stop. If you go too far, you could damage the thread.
Screw the tapped end of the PEEK into the hole as far as you can without damaging it. Don't worry if you can't get it in completely, do not use the drill press to turn the tap, as this is very unsafe.
The safe method is to use a tapered tap and tap as far down as the tap stops, DO NOT force it, the plastic may crack. Use what is known as a bottom tap (or cut down your tapered tap and use that as your bottom tap) to cut the thread all the way down the shaft, again don't over force the tap or the plastic may break.
At no point should you use a cutting compound, as it may eat into the plastic making it unuseable
Drill a 3.5 mm hole all the way through the PEEK. Drill a #20 hole 15 mm deep into the PEEK. Tap the hole with a 6 mm tap. Do not go past the 15 mm deep hole you drilled earlier as this will create a void where plastic will form a bulge and damage the thermal barrier over time. It is a good idea to mark the tap with a piece of tape so you know where to end. Finish the thread with a 6 mm bottoming tap.
You will probably need a pair of vice grips to remove the PEEK. Make sure the finished piece fits on the heater barrel and that the filament moves easily between them.