SWIM smoked real good kief before. It's the as good as pure thc crystals right?
Somehow SWIM enjoys a good hash or a potent bud alot more than kief.

SWIM's plant is already quite dry.
SWIM will try to attain pure Butane gas.

I want to build one of these, but the miniature one. about how wide is the tubing/fittings?

It's best to have your pipe longer and narrow as to increase the surface exposure of the weed. Butane is the best solvent bar none but is too expensive for shake. Use it for good frosty leave clippings or bud. Unlike butane, alcohols are not selective solvents and will bring chlorophyll and other unwanted plant material alongside the THC. Another thing I like because I don't like smoking is to make dragon with it. Grind up your weed and bake it at 200 for 20 mins for full cannabinoid conversion. Then soak it in high proof alcohol for a few days or heat it at ~70c for 20 minutes and filter it. In total use 1 gallon/pound. Then drink 3 mL, put on some good music for 5 hours and make sure you have a full fridge.

SWIM has done lots of extractions of THC from plant material and lots of research as well. One of the best methods for doing extractions is to get a Dewar Flask or a vaccum flask that will allow you to place large amounts (several ounces at a time) of plant material into it, freeze the plant material and cool the liquid butane in any commercial freezer. The vacuum flask will allow the butane to remain in liquid state longer and extract more goodies from the plant material.

Here is a lab grade Dewar flask here (http://www.coleparmer.com/catalog/product_view.asp?sku=0376630&pfx=) This one costs around $100 but you can find them cheaper on Ebay.

The process is that you get near zero impurity butane or 5x filtered butane for the purest solvent possible. You can find cases (12 cans with 320ml each) online for pretty cheap of the pure stuff in most places or ask your local smoke shop. Be careful of the cheaper/less pure brands as they do have a lot of additives/impurities in addition to the butane that will end up in your product.
Place your dried plant material (make sure it is as dry as possible) into the flask until it is no more than 4/5 full, pack the material down lightly (not tightly) into the flask. The liquid butane must be able to get access to all of the plant material to extract goodies.
Place the flask and butane cans into the freezer at the lowest possible temp and let sit for at least 24-48 hours.
Do the butane extraction tek outside or in a well ventilated fume hood as butane vapors are extremely flammable and very dangerous. Use caution, be smart, wear lab gear, and no smoking or open flames or materials that could spark anywhere near your extraction. SWIM has found it is better to do this extraction at night or when the weather is cold during early morning or late evening.
Empty several cans of butane into the filled and chilled flask until you see liquid above the visible plant material. If the flask is 2/3 filled this will be about 4-5 cans of 320ml butane or if 4/5 filled will be 5-7 cans.
Once the chilled plant material is sitting in the chilled butane inside the chilled flask it can remain liquid for several hours. SWIM usually lets the plant material soak for about 60-90 minutes, but one could probably let it soak for up to 4-5 hours. If the level of liquid os no longer covering the plant material, meaning that the butane has evaped off, just add more chilled liquid butane until the level gets about the plant material again before doing the next step.
Once you are done with the chilled butane soak, put a filter bag (SWIM uses the smallest ice hash extraction bag) over the top of the flask and pours all of the liquid through the filter and into a glass baking dish or bowl.
Place the glass bowl in a double boiler (outside still as this will evap the butane rapidly and give off lots of flammable fumes) add hot water to the bottom container and allow the liquid butane to boil off and reduce. At the end you will be left with a pile of sticky and bubbling honey oil. There will still be butane stuck inside this oil, so SWIM suggests a butane purge and final cleanup using ethanol (Everclear or Bacardi 151 work as well)
Pour approx 100ml of as pure as possible ethanol into the glass bowl or baking dish and still with an ice pick while heating from the bottom double boiler at just under the point of water boiling. This will allow all the oil to dissolve into the ethanol and free the butane. Keep up the heat and stir occasionally with ice pick until the material reduces back into a thick oil.
Remove from heat and bottle up the oil in a small glass container with a wide mouth for easy access.
This tek produces really wonderful and clean honey oil that is extremely powerful. Depending on your source material, you can produce shatter glass quality final material as the photo posted earlier by the OP or extremely thick honey oil that is of equal quality. Be careful as a little goes a long way!
SWIM likes to only use glass in his THC extraction teks and would NEVER use plastic or PVC as the solvents can contaminate the final product with lots of nasties. Stainless steel could also work, but never galvanized steel. Many other metals are also not good. For smaller extractions one can get glass turkey basters online cheap. Pull off the bulb and you have a glass extraction tube you can fill with plant material, cap the large end with a filter and inject butane through the small end to collect your goodies in a glass bowl or dish.
Good luck!

Has anyone used Heptane?

EDIT:

Would the hash oil become more solid in the heptane when put in the freezer?

Here is my Idea.

Get all the herb you want to use for the extract and put it into the glass bottle or jug.

pour Heptane into the jug until the the herb is completely submerged about a quarter inch below the solvent.

swoosh around heptane gently for a minute.

Make a filter out of wire mesh and the cap to your jug.

Pour heptane into collection dish.

Put into freezer to cause oil to get solid and fall to bottom. pour heptane

back into a container to use again.

set out oil to evap off the remaining heptane.

Heptane is difficult to get out fully
And cold separation doesn't work.

Not sure how to save the batch.

This is all in theory, but you could possibly wash with distilled h20... THC has a very low solubility, but the heptane would be miscible. It may not get all of it out, but with repeated washes it may reduce the volume of heptane.