I use the small ¼ ounce Testors model paints.
They are great for small projects. The paint is excellent, covers well, hides brush marks...you get the picture. But, any paint in small bottles can be a real pain. That's especially true for high pigment paints like Testors. The pigment can drop to the bottom of the bottle, leaving the solvent only at the top. You have to really shake them up to get the two back in perfect consistency for the paint to do it's job. Shaking them up by hand is simply all but impossible. Besides being time consuming, it is tiring. By the time you get the paint mixed, your hand is numb from all the shaking. I looked around for a good small bottle shaker...still have not found one I can afford...in fact, as far as I know there are none you can buy at any price. So, I came up with this idea and I have used it for years. It works great. And, so far, I have not had any accidents with it such as the bottle coming out or the rig coming apart. It thoroughly mixes the paints in about twenty seconds. So, I thought, why not share my great invention so others can make one, too?
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Step 1: Things You Will Need
The main part here is the little paint bottle box. I designed this one in Autocad and printed it with my Maker Gear M2 3D printer from PLA plastic. It is designed with filleted corners for extra strength and is 1/8 inch thick on all sides and bottom with countersunk screw holes in the bottom for attaching it to the plywood laminate "Paddle" that surrounds the old saber saw blade. The blade is solidly epoxied in.
If you do not have a 3D printer, the "Box" can be made from 1/8th" plywood. Use good clear, solid wood and securly glue the pieces together. There is tremendous strain when the thing is shaking, so really reinforce the corners. The inside dimensions are 2.25" x 1.75" and .75" deep. Keep the construction as light and strong as possible. There are two holes in the bottom for two #6 x 3/8" flat head wood screws to fasten the box to the blade "paddle". These should be countersunk so the heads of the screws do not protrude inside the box.
For the blade, I recommend a very coarse blade...the larger the teeth the better. Any old dull or even new blade will do. Just be sure to remove any grease, oil or wax from the blade before using it...I wiped the blade down with lacquer thinner. Fingernail polish remover will work also (same thing).
The "old saber saw" is one that the guide foot broke off years ago. I really do not even know why I still have it. But, it is nice to be able to recycle something that still has a use rather than let it go to a land fill. Be sure your saw has a good solid working bearing and the blade mount is in good shape. This paint shaker puts some extra load on the saw machinery inside. That's another reason that it should be a variable speed saw. If you were to run this too fast it could put excess strain on all those moving parts and the box, too. So, don't use a saw that is too much out of shape. If you are using a saw that is still fully functional, remove the guide foot before using it to shake paint. You will not have enough clearance to get the paint holder box fully embedded on the blade.
For the foam rubber, I used some cut from those interlocking garage floor pads. You could also snip off a piece from a foam exercise mat. I have also used the firm but soft packing foam from an electronics shipping box. Just remember, the foam should be firm, and hold it's shape a bit while holding the bottle in the box and keeping it from rattling around during the shaking process. Do not use rigid "foam" like styrofoam. It is not resilient or tough enough for repeat use.
Use some good old common sense in building this and it will work wonders for you in shaking these stubborn little bottles of paint.
Step 2: More Stuff You Will Need
I used 3/4" Velcro. But, the box for 3D printing is really designed for 1/2". It's not a big deal so long as the Velcro strap stays in place during the shaking.
Step 3: Draw the Cutout for Your Saber Saw Blade
Set the blade on one of the pieces of 1/8" ply and outline it. You don't need to be overly accurate. Just so the blade will fit in it and you have three closed sides. Leave about 1/3rd of the blade sticking out. You might want to hold this arrangement up to your particular saber saw to make sure when the blade is all the way up in the saw, the plywood does not crash into the saw body.
Step 4: Cut It Out
Remove the material in the outline you drew so the blade, teeth and all, fits loosely inside. This is so there will be plenty of room for the Epoxy to fill all around the blade. This is important.
Step 5: Make the "sandwich"
The idea is to glue the three pieces of ply together with the blade firmly embedded in epoxy inside. Clean the blade of any oil or wax with laquer thinner or fingernail polish remover (same thing) before applying the epoxy. You do not want this to come off the blade in operation. You could really have a disaster of paint splatters if it does. Mix the two part epoxy according to instructions and use plenty of it on the wood. Completely drown the blade on both sides. Now you see why the "U" shape cutout...It keeps the epoxy from running out when you tip it up with all three pieces together in the next step. I did not use Gorilla Glue here because it foams up and can displace the parts if not clamped down well. I also believe the epoxy is stronger (I know...some would disagree...Oh, well.).
Step 6: Tip It Up
All three pieces together with the blade inside. Rest it vertically, clean off any excess epoxy and let this set up for at least double the recommended setting time. In my case, I used five minute epoxy and let this rest like this for half an hour.
Step 7: While You Are Waiting for the Glue to Set.
Cut some little rectangular shapes of the rubber foam to fit in the top and bottom of the box. They should fit snug with the sides of the box and leave a little bit sticking up..like 1/8" to 1/4" is fine. Do not glue these in yet...just trial fit them.
Step 8: Time to Fit the Bottle
Lay the cut foam pieces flat and set the bottle across them like this. Draw some lines to make a snug fit to the bottle. You'll be cutting this foam away to make a little "pocket" to fit the bottle.
Step 9: Surgery
Okay. Time to be extra careful. The foam is soft, spongy and awkward to cut. You do not have to be perfect with this cut. Just trim away about half way down into the foam and then carefully use the blade to trim out the part you need to remove. Work in small slices and be patient. It does not have to be pretty...just enough to hold the bottle steady in the pocket. Trial fit the rubber foam and the bottle in the box and trim more away if it is too tight. The bottle only needs to be snug, not crammed in there really tight. Remember after the paint is mixed, you still have to get the bottle out.
Step 10: Hot Melt Glue the Foam Into the Box
If it all fits to your satisfaction, glue it in. You could use epoxy or even super glue here. I like hot melt because it never gets brittle. It just seems to last through all the vibration and sticks well to the foam and to the plastic or wood box.
Step 11: Mark the Holes
Place the box onto the wooden "paddle" and mark the holes where the screws will go. You should place the box no higher than the edge of the wood where the blade tang sticks out or you could make it so it won't clear the body of the saw when it is mounted. Trial fit to your particular saber saw to make sure the box clears the saw when the blade is highest inside the saw. In my case, my old saw had broken the guide foot off, so I did not have to worry too much about clearance. You might want to remove the guide foot of your saw, too. If you want to get creative with the placement of the screws, just remember the blade inside the wood! That's why the screws are toward the sides and not in the middle.
Step 12: Drill It
Using the 5/64th" drill bit, drill out the pilot holes for the #6 x 3/8 flat head screws. I make these pilot holes deliberately a size too small for the #6 wood screws. You need a pretty tight fit and the plywood is strong enough it won't break. It is important to use flat heads and counter sunk holes in the box so the screw heads do not touch the bottle. With all that shaking, the screw heads will impact the bottle if they are not counter sunk. Scratches and such can cause weakness in the glass- A situation you would want to avoid. If you are making your own box from plywood, remember to countersink the holes. If you are using my STL files to print your box, the holes are already countersunk.
Step 13: Screw in the Screws
You might wonder why the box is attached with screws and not epoxy or some other glue? I used screws because I might want to shake up bottles for my air brush or for my wife's toll painting...completely different paint bottle sizes. And I would need to change the bottle box to fit them. If the box is glued on, you have to build the whole thing from scratch for different sizes. I found that these little screws twisted into slightly undersized pilot holes in this hard plywood hold just fine.
Step 14: Stick the Velcro
On the back side of the "paddle" you will need to adhere the Velcro safety strap. I glued just the hooked side of the velcro with the hooks facing out. Then I just cut a similar size "fuzzy side" and let the Velcro do it's thing.
Step 15: Inspection Time
This is pretty much what it should look like with the bottle in it. The Velcro strap kind of settles in the little side pockets in the box when it snugged up, even though they are made for 1/2" Velcro, the 3/4" Velcro sets down in there nicely. Not perfect looking, but it perfectly works. Also, as I have found out in practice, the strap is more of a safety precaution. I doubt the bottle would fall out if it is snug enough in the foam lined box. But, I don't want to take a chance it might go flipping out...Oh, the mess!
Step 16: This Is It in Action
This is it working. You can see it does a great job of mixing the paint in seconds...no more tiresome arm shaking for such a little bottle. I found that 20 seconds of medium speed shaking perfectly mixes the paint in any of my little paint bottles, even paint that's been sitting for years (paint that's still liquid, that is!).
Don't get too crazy with your super fantastic nuclear powered saber saw- if you are using one of those! If your saw is really fast or not variable speed, you could over do it. You do not need really fast speed. All that high speed shaking will do is over stress your rig and the saw and could lead to metal fatigue of the blade or even facture the bottle. Liquids are non-compressible. Paint is a liquid and if you shock it against the glass inside the bottle too much, you could concievably create a "paint splatter, broken glass" disaster. Use this device wisely and patiently...what's 20 seconds vs all that old fashioned hand shaking you had to do before? Remember, moderation works best.
Happy, easier painting!
Step 17: STL File for the Box
Made to fit the Testors 1/4 ounce paint bottle. Use PLA filament and make sure your printer is tuned up to make good strong layers.