Wednesday 4 February 2009

Top tip

I got the tip to use welding tips for an extruder nozzle from Andy. They come in packs of five from Halfords for £4 on-line and £5 in the shops.

They are made from copper and have a 0.6mm hole down the middle. The thread is M5.

I drilled out the one on the right to 3mm, almost to the end, to reduce the pressure needed to extrude. They drill easily if the drill is lubricated with a little paraffin. It's a shame they don't work as is, but all the same it is much quicker and easier than turning, drilling and tapping the standard design.

They also simplify my evolving extruder design because the heater block no longer needs a spout. I can simply drill and tap the bottom of the melt chamber M5 and screw these in. I can also change the M8 penny washer for an M6 one. That allows me to reduce the outside diameter of the PEEK collar to 8mm so it can be made from the same stock as the thermal transition. The area of the collar will be less so it will conduct less heat.

The 0.6mm orifice can be made smaller if necessary by filling it with high temperature solder and then drilling it with a fine drill. Solder is very easy to drill so less chance of breaking a fine bit. Also Vik Olliver suggested you can make a small hole by soldering in some fine Nichrome wire and then pulling it out again to leave the hole (solder does not stick to Nichrome).

I haven't tried one yet but I can't see any reason why they wont work well.


  1. Great TIP off to halfords to get some thanks.


  2. It looks like you have solved the problem I had with too much back pressure by drilling it out-obvious when you think about it!- great when ideas are shared!(screwfix also sell them)

    I am just waiting for the PEEK to arrive so i can copy your great new design Chris


  3. Don't be too quick to cheer, check what they're really made of and what's their thermal conductivity, preferably by experiment. I've been thinking about using welding tips too, but the problem with them is that they're not pure copper. In fact, it's one strange piece of an alloy and the additives in it are actually meant to *reduce* thermal conductivity by quite a big factor - the tip is there to conduct electricity down the feed wire, not the heat up the welder (or in any other direction, really).

  4. Interesting I always thought thermal and electrical conductivity went pretty much hand in hand for metals.

    I am planned to cover with a PTFE tube to stop the filament sticking so that will help to insulate it.

    I may have been a bit rash boring it out to 3mm as that does not leave much wall thickness. 2.5 or 2mm may be better.

    Lots of experimenting required I think.

  5. I saw those on a Praktiker hardware store in Germany.

    They are quite affordable but I wonder if it's possible to drill them out precisely with just a normal drill?

  6. It might be tricky but they do have a pilot hole already!

    If I didn't have a lathe but did have a drill press I would do the following: -

    I would bolt a thick block of metal to the drill press and drill it and tap it so that a second chuck could be screwed to it. That would then line up exactly with the axis of the drill.

    I would put the drill bit in the stationary chuck and the work piece in the drill's chuck.

    You could then do all the drilling and tapping operations that a lathe can do for a small fraction of the price.

    A vertical version of the Afghan lathe.

    To realign it after disassembly and reassembly just put an accurate straight rod in both chucks. The sort of rod you get from an old printer would be ideal.

  7. I was able to make one (drilled out to 1/8th inch) by clamping it in a vise on the drill press, no afghan lathing necessary. I was able to extrude from 1/8th inch ABS by hand when I strapped it to a 10 watt resistor, although it did take quite a bit of pressure.

  8. Hi Corwin,
    That's good to know. I am currently building a jig to quantify "quite a bit of pressure" so I will be able to compare different tips soon.