or 'How to drill a straight hole without a proper lathe'
The best description is on the official reprap blog page
WARNING: DO NOT TRY THIS AT HOME
This is what I've done: I know that it's potentially dangerous, and I'm an irresponsible adult. If you copy me that's your own lookout. Remember, Darwin's theory of evolution is still working, so please don't remove yourself from the gene pool.
- Standard electric drill (slight rust optional)
- Black and Decker workmate (battered)
- 'swivel' small vice (£4.50 from the local market hardware stall)
- HSS metal drill bits
- Junior hacksaw
- Rasp/File/Needle file
- scrap wood
- safety glasses (scratched)
- 8mm PTFE rod
- 8mm PEEK rod
Technique (or lack of it)
I set up the workmate in the one corner of the garage that isn't full of junk. I used a scrap of 2x4 and a section of skirting board, held in the workmate, and bolted the vice to the end. This made a flat platform with a small corner.
I cut off about 40mm of PTFE and PEEK rod, about the same length as my 3.5mm drill.
Placing the rod in the drill, you can spin the drill and use a file to smooth off the end nice and flat, and chamfer the corner to make it easier to get the die started. Make sure you hold the drill down securely (use some cable ties or another clamp or two), and it helps if you have a button on the drill to lock it on.
I used an M8 die to cut a thread into the PEEK rod. Note that PTFE is so soft, a standard nut will cut it's own thread - you don't need to use a die. PEEK does need a die.
Now for the interesting bit. I placed a drill the wrong way round in the chuck.
I screwed up the drill into the vice. It takes a lot of adjustment to get it held right and all done up, but you want it lined up very straight, before tightening everything up. Note that my drill wouldn't hold properly in the cheap vice (damaged drill), so I fudged it by holding a pair of pliers holding the drill and doing it up *real* secure. I'd rather use a proper drill chuck, I might get a hand drill (I think there's one for £3.50 on the market stall) and harvest the head.
Then I could put the PTFE back in the drill chuck and check the alignment. I used PTFE first as it's softer and easier to work with.
Using the drill to spin the work, held into the corner of the scrap wood, I could slide the drill up and down in line with the bit. Very carefully, you can guide the bit into the centre of the work and *gently* drill out the hole, backing off frequently to allow the swarf to clear. It worked OK for me for PTFE and also PEEK.
It seems to work: I got a nice straight hole through the PTFE and PEEK.