DIY Sieving Frames
BUILDING YOUR OWN DRY SIEVE FRAMES AND HARVEST BOXES INEXPENSIVELY
For those of ya’ll who like to sieve by hand, or to further refine dry sieve by re-sieving it through different size meshes, here is a simple frame that will accommodate either a stainless mesh, or permit a silk screen fabric to be rolled in and properly tensioned with a spline.
The retaining strips, that hold the silk screen spline or stainless mesh in place, are cut at an angle, which matches the angle cut in the top of the frames, so that after assembly, they conveniently nest for storage.
Cost per frame for the wood depends heavily on what you pay for your wood. In the examples shown, I picked up 8′ finger grooved mahogany trim from a lumber re-cut liquidator, for $0.99 a stick, so lumber cost was about $0.50 per frame.
I prefer a hardwood, as they are less prone to splitting and hold dimensions like groove width over time. It doesn’t matter what kind, and I’ve cut up free for the hauling hardwood pallets to make hardwood parts.
The whole frame can be cut out using just a table saw. I build mine on a cheap $200 fold up portable that I picked up at Home Depot, when I got tired of hauling my big cast iron 240V Craftsman around for rental repairs. It came a 1/8″ wide carbide blade, which is what I used to make all of the pieces.
I wouldn’t want to build a house with it, but for trim and such, it is excellent.
Before we move on, lets discuss safety. If you are unfamiliar with the safe operation of a table saw, please seek hands on instructions. Besides being a dear friend and cherished tool, they instantly remove digits, so must be used concisely and with respect. Wear safety goggles and use a pusher stick, in addition to the fence and slide.
Cutting frame and retaining strip:
The first cut is the 22 degree angle in the top for the nesting feature. For this cut, I use the fence and a pusher stick to feed the stick through the saw.
The piece that is cut off in this cut, is the same piece that the retaining strips will be cut from and screwed on to the bottom.
Next the groove for the spline is cut into the bottom, and here is why a 1/8″ blade is important, as that is how wide the slot is. The groove is centered in the bottom of the board using the fence and blade height is set at approximately 3/16″ deep
The frame board profile is now complete, except for radiusing the sides of the spline groove, so that the spline rolls in smoothly.
I use a router in a stand to radius the sides of the spline grove. A chamfer may be used instead, or the corners scrapped away with a sharp blade, instead of routed. The purpose is to facilitate rolling the spline into place, and can’t be seen with the retaining strips installed.
Once the profiles are all cut, it is time to cut the parts to length. The ones in the pictures are 1 1/2″ deep X 10″ X 10″ screens, but I prefer a 12″ X 12″ X 3″, which is what the attached print was designed for.
There is nothing magic about any dimension, only the nesting feature and the spline slot to proportionally locate.
Next step is to cut all the parts to length. That is easy, because they are all cut to the same length and at a 45 degree angle. A miter saw is faster and easier for this step, but it is also easily accomplished using the miter feature on the table saw slide.
Last, cut on the frame members, is to cut an 1/8″ X 3/4″ deep slot in the center of each end, for the wooden keys that we will lock the corners with, during gluing.
The retaining strips are then cut to exactly the same length as the frame parts, and three holes drilled and counter sunk for #4 screws in them. There is one hole 1 1/2″ from each end, and one exactly in the middle.
After any light sanding required, we are now ready for assembly! For this purpose, I use corner clamps and after smearing the ends with Elmer’s glue, I clamp them together and drive in the corner keys.
I clean any glue out of the spline channel, before it hardens.
When the glue dries, I trim away the excess corner key with a razor knife.
Next I use a countersink bit to pre-drill the holes for the retainer stips, so the screws install easily.
Lastly, I chamfer the inside corner of the spline channel with a sharp wood chisel.
Choosing a screen material:
Frame is now ready for assembly and how we do that, depends on how it is to be used. If it is to be used for primary sieving, or as a harvest screen to handle your material on, then you may wish to use a stainless mesh, that is durable and easy to clean.
If on the other hand, you wish to further refine the previously extracted kif, a silk screen is a better choice, because it can be stretched taughter, giving it a better spring action.
Some silk screen material is woven with single monofilament threads, and some are made of threads comprising multiple twisted smaller fibers. For sieving purposes, we want a monofilament, as the opening sizes between the threads are more consistent, and they don’t fray fibers into the kif.
Choosing a micron size:
The correct micron size depends heavily on the task, so more than one sieve size is called for.
For an initial dry sieve, 130 to 150 micron has worked out well for us and we prefer stainless steel for this task.
We use 100 mesh stainless steel bolting cloth from Howard wire. Our last bulk purchase was about $6.50 ft/sq, but metal prices are volatile, so check for current pricing.
We like stainless because of the durability, and the harsher treatment that it sees, than the latter sieves refining and classifying the kif afterwards.
150 microns is adequate for most mature trichome heads, and not so large as to permit entry of larger plant particle sizes.
Refining and classifying:
Once the kif has been separated from the plant material, you may wish to separate it further, to eliminate immature kif heads and plant debris. This is done by passing it through successive smaller mesh sizes, so that you have several different grades.
If I re-sieve, it is typically at about
130, 110, and 75 microns, and I pitch anything above 130 and make oil out of anything below 75 microns. That gives us two prime grades left on the 110 screen and left on the 75 micron screen.
Each strain has its optimum sieving sizes, so experimentation is the best way to zero in. A quick way to shorten the experimentation time, is to measure the trichome heads first using an optical comparator. Here is an inexpensive portable microscope that I picked up off of E-Bay, which has an optical scale on the eyepiece.
Picking average mesh sizes, here are the thoughts of Robert Clarke, in his book, HASHISH. Using a precision sieve stack:
150 microns – large plant debris
130 microns – very large resin glands
110 microns – large resin glands
90 microns – medium resin glands
70 microns – small resin glands and debris
50 microns – very small debris and little resin
below that – very small dust and debris
Understanding the mesh chart terms:
Discussing the hole size between the wires or threads can be confusing because often only the mesh or thread count is given.
In fact, with only that information, it not possible to determine pore size, because that number depends heavily on the diameter of the threads or wires used.
Attached is a chart of average pore sizes by Mesh, which is the same as Thread Count. If you want actual pore size, you may calculate it yourself as follows:
(1) minus (Thread or Mesh X thread diameter) will give you the total amount of open space per unit.
There are one less openings than threads or meshes, so dividing the total amount of open space by (thread or mesh count minus 1) will give you the size of the individual openings.
A micron is one millionth (10-6) of a meter. To convert your answer from threads per inch, divide the answer in inches by .00003937 to get microns
IE: 200 mesh or 200 thread count by the chart below, depends on the thread or wire size to be .0021″.
1 – (200 X .0021″ thread diameter) = .5771″ Open space
Open space divided by (200 -1) = 74 micron Pore size
Pore size in inches divided by .00003937″ equals microns.DIY Sieving Frames BUILDING YOUR OWN DRY SIEVE FRAMES AND HARVEST BOXES INEXPENSIVELY For those of ya’ll who like to sieve by hand, or to further refine dry sieve by re-sieving it through ]]>