Hand-drill geared extruder

I managed to break my original BfB extruder :-(. The acrylic had flexed too many times, and the top retaining bracket broke in half. The screw thread now carefully unscrews itself rather than driving the filament down :-(

So, time to update to a modern wade-style or similar extruder, using a hobbled bolt. Of course, I could have bought the gear drives from the many RepRap shops or ebay, but that's too easy :-).
Instead, I found an old cheap hand drill, with similar sized gearing. It turned out to be on an 8mm shaft.

I added a 5mm to 8mm sleeve to a stepper motor (made from a sex bolt)  and drilled and tapped a 4mm hole for a grub screw - I could then attach the smaller gear to the stepper shaft. The larger gear I cut a small square indent to match a carriage bolt, and cut some teeth into the threads using a dremmel cutting disc. A plastic cutting board and an Ikea bracket made a mount, and three skate bearings (8mm 908) made up a channel for the filament.

It's not pretty, and it's heavier than ABS gearing, but it grips the filament like anything - I can't stop it using my full strength grip, and really forces the filament through. 

I'm currently building a heater block and nozzle to add on the bottom. Hopefully this 'RepStrapStruder' will last long enough for me to print a proper wade's extruder. 

Learning more and more

I've been building more nozzles and drilling some holes in metal. I tried drilling out a stainless steel bolt to make the extruder barrel, but it was hard work and didn't feel right. Usually when that happens, I'm doing something wrong...
So, I googled and read up on drilling into stainless steel.

Apparently, when the drill rubs over the metal in the hole, it starts to heat and work harden a thin layer of steel - making it harder and stronger - and more difficult to drill.

The advice is to drill at a slow to medium speed, apply lots of pressure, and drill few mm then pull right back to clear the swarf. This is pretty much the opposite of my original technique.

This works *really* well - you get lovely long spirals of swarf (razor sharp splinters) and the hole is much easier to drill. I found it much easier to drill out welding tips and have drilled a couple of stainless bolts using the afghan lathe technique.

Top Tip: Read instructions before using.