Oh, I have found some 306 stainless stock in what looks like a rough approximation in size to the PEEK curerntly in my my machine, so it looks like I will have no excuse not to give that a shot too. You know it's funny that one of the most rewarding experiences I've had with regards to 3D printing and the Solidoodle has yet to involve any actual 3d printing with my Solidoodle.

I'm not against removing the barrel from the peek,

Not to say this is gospel, I've taken mine apart already a couple times but I don't think I'd make it mandatory if I was designing a hot end assembly.

http://www.soliforum.com/post/11089/#p11089

there's a table.

Chrome nickel steel and stainless are the best metal insulators. (though there is question as to whether they are insulation enough)

given how cheap it is, (and how easy to work with) I might try making a mould of a block, and cast one from cement. (read I want to, but can't imagine having the time for a little while!)

look at the thermal conductivity of Granite, how good would a polished granite block look! (that would be very difficult to do though!)

for measurements on the grove mount style blocks that the solidoodle uses look here:

http://www.reprap.org/wiki/RB_Thermal_Barriers

I've created a new thread today with the new heater I did at the weekend:
http://www.soliforum.com/topic/1847/hot … placement/
It's a bit like the heater you're making except I'm using a heater stick instead of resistor, and mounting the thermistor in the block as well instead of taping it to the hot end so it should hopefully be more secure. (also mine is square as I don't have a lathe!)

feel free to incorporate or ignore any ideas that you might get from there.

is there a benefit to this shape? (I think that there is probably a downside with increased surface area?)

other than that, as said above, making the nozzle and barrel the same piece will make it harder to clear clogs. if would seem like there is less to take apart, but there is more.

I'm not against removing the barrel from the peek, (in fact I'm working on a design myself very similar to this, the difference is that I'll be using 6mm aluminium rod and making the nozzle right in the barrel.)
a heater that screws on, (just like the one you've made, or the traditional heat-core that came with the machine.)
(there seems to be no point in having any hex type component to the nozzle if it's not detachable, (probably better to have a hex part further up the barrel as this can then start to act as a heat-sink hopefully dispersing the heat before it gets to the plastic carriage part.

Peek is used as an insulator because of it's high melting point and good thermal insulation. stainless steel is the only metal that has reasonable thermal characteristics (doesn't conduct well).

but peek does limit the temperature that you can print at...

with a longer barrel and heat sinking, you can attach a metal barrel to the machine and not worry about pre-mature melting, but the downside of this is that you need to sink away the heat very well, so that they top of the barrel stays cool. but the bottom of the barrel you need to heat like crazy to keep it hot enough!!!

Do you have a link for the kick starter one?

I've found that there is some limited space around the brass barrel before you'll be fouling the x carriage.

Where do you plan to mount your thermistor?  If I were making my own design I think I would put a little pocket in there where the thermistor could sit so I was assured it sat the same way each time. 

Last thing, I bought some .35mm bits from ebay with 1/8" shank and a small twist drill chuck that looks like a jewelers screwdriver.  I made the mistake of buying carbide though which together with a handheld twist drill makes for some pretty frustrating moments.  It came in a set of 10 with my plan being to drill out a clog I had rather than melting it with acetone, but since carbide is so brittle I snapped 5 straight before getting it to work.  I had intended to use them by hand without disassembling but I'd need plain steel ones not carbide to try that.  Took me forever to find the broken pieces on the kitchen floor. 

Good work so far, looking forward to watch the evolution.

You should take a poll of users here and say "If you could make your own nozzle and had access to a machine shop how would you make it and start there.  There are some brilliant people hanging around this place.