Easy no-lathe one-piece extruder barrel!

For months I've been dreading trying to make the extruder barrel. I shopped around a bit, and the local machine shops all charge a minimum of $75/hour 1 hour minimum for that kind of work. So I ordered my micro drill bits, found a friend who had a lathe and a drill press, and started to make plans.

It turned out to be MUCH easier than I thought, and I didn't need a lathe, a drill press, or anything beyond a variable speed drill, a few simple tools, and some patience.

First, I bought a 1' section of 5/16ths brass rod. I was going to use aluminum, but my greatest fear was that I'd break all my micro-bits without getting even ONE useable barrel, and everybody I talked to said that aluminum grabs bits. So brass it is.

I remember somebody on the forum saying about drilling brass dome nuts that it works best to put the nut in the drill, and hold the bit by hand. So I cut a chunk off the end of my brass rod, mounted it in the drill and got started.

It's REALLY important to get the bit in the exact center - if it's shaking even a little bit, it's not in the center. Oddly enough, the important part is to hold onto the SIDES of the drill bit to stop it from turning. I tried using my fingernail to push it into the brass, but since the drill bit isn't long enough to do that AND get a good grip on the sides, the bit just spun and nothing happened.

It's also important to stop and check your fingers - if that drill bit spins in your grip (which it's going to do) it'll embed itself in your caluses, and if you don't check and pull it out, it'll go beyond that. I've got a red spot on my left index finger from that.

I used a lump of beeswax to lubricate and to clear the swarf out of the bit's fultes. I'm a beekeeper, so I had some on hand and it worked fine. I imagine that there's any number of other things that would work just as well. It's hard with a bit that small to tell that there's still brass embeded in the flutes, I eventually decided that if I could still see 'bumps' along the edge, it was good enough.

After drilling the hole in the end down deep enough (I stopped at about 1.5mm or so) I took a file to the end. I held the drill to the bench, and held a file to the end to turn it into a cone. No fancy mounts, no clamps, no table-vise mounted drillchuck to make a simple bench lathe. Just held the drill down and while I filed the end to a cone.

Then I reversed the bit of brass rod in the drill chuck, and started a hole (again, very important it be in the precise non-vibrating center) with a 1/8" drill bit. With that started in the center, then comes the fun part...

I took the brass bit out, and clamped the drill bit to the bench top such that the with the brass pressed up against the benchtop, the drill would penetrate just enough. Then I put the brass bit back in the drill, watched the bubble level on the drill for up/down angle and eyeballed the left/right angle, and pressed the brass onto the drill bit. Again I removed it often to clear the swarf. Particularly important since the flutes on my 1/8" drill bit didn't go as far up the shaft as the hole I needed to drill would.

Look ma! No drill press! I KNOW that I wasn't all that accurate on the angle, but since it's the brass rotating instead of the drill bit, that mostly evens out. I mis-measured one and punched the drill bit all the way through, it was noticably off center on the far end, but it was still very close.

It worked beautifully! I didn't break a single bit. I did wear out one 1/8" drill bit, but I'd had the foresight to buy a 10-pack of 1/8" drill bits earlier that day, so that didn't even slow me down. I made three, one 0.0020" (~0.5mm) and one 0.0012" (~.25mm). The third was my first attempt at the ~.25mm job, and I didn't clamp the 1/8" drill bit correctly and drilled all the way through.

I also drilled out the top a bit with a larger drill bit so my teflon tubing would fit into the top. Looks like that will work beautifully too.

Now the only thing I'm lacking is the die to cut threads into the top. And I still need to wrap it in ni-chrome, but I've got the electronics all done, and now the extruder barrel! So I should extrude something this week! I'm so excited!

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I'm building it with Baling Wire

Very nice!

How long of a segment off your rod did you use for this?

I didn't measure. One's about two inches, the other two and a half. Shorter than the drill bit, long enough to wrap some heater wire around.

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I'm building it with Baling Wire