Turning a Hybrid Sphere using Woodpecker Ultrashear turning tools

I first became interested in wood turning after watching Woodturning with Tim Yoder on TV. I watched how organic and creative the process was and it just looked fun. I saved up some money and bought a midi lathe and its the same one I still use today. I didn't really want to make anything that was structured like pens or bottle stoppers, even though I eventually enjoyed them. I wanted to take the biggest weirdest piece of wood and make it into whatever it was meant to be. I turned lots of bowls and platters until the market (me and my wifes home) was saturated. Now instead of making something utilitarian like a bowl, I prefer to make more artistic pieces. I’ve used dyes and played with shapes and even made segmented turnings. Now I have discovered resin. Resin combined with wood opened up a ton of creative opportunities. I could dye the resin, wood or both. I can also add pigments for added visual effect. All of these new ideas have brought to my latest creations, hybrid resin and burl spheres. I enjoy the challenge of learning the casting process and the creativity of adding color and texture to the spheres.

The first thing you'll need is a dry block of wood. Preferably something with some character like a burl. Then choose a mold shape. I find that a disposable plastic cup makes a good mold as long as you use a resin that wont overheat it. The inexpensive 1 quart measuring cups found at your hardware store work great too and a lot of times the cast will pop out and leave the cup perfectly clean. I like round molds since they waste less resin and are easy to get to round when starting to turn on the lathe.

I went with a small plastic cup for my mold. It gets wider at the top which worked for this project because it would be wider right at the outermost part of the sphere. I used the cup to draw a rough circle onto the burl cap. I then cut it out on the bandsaw staying outside of the line. I take the cup to my disc sander and set the table to the same angle as the side of the cup. This makes it to where I can sneak up on the shape and get the wood blank to sit perfectly in the cup.

Once I get the wood to fit nice and snug I set it on a silicone mat and remove as much dust as I can from the cap. Dust and moisture are the enemies of a good resin cast. Moisture in the wood can react with the resin and cause bubbles. You can cook the piece in an oven and try to dry it out. You can stabilize the wood in a vaccum chamber with heat activated resin too. Both of those processes can add a lot of time to an already lengthy process. I have had great success with painting the wood with a 2:1 penetrating epoxy. It penetrates deep into the wood and blocks any moisture from interacting with the casting resin. An added bonus is that when the penetrating epoxy becomes tacky and is almost set, I pick it up(with gloves of course) and set the piece in the cup. Thats gets it off the bench so you can clean your space and sticks it to the cup so that your wood won’t float when you pour the resin. You can also use hot glue or UV resin for this but I like to save a step if I can. I will let the wood with the penetrating epoxy sit overnight before I attempt to pour casting resin onto it.

Now that the wood and the mold are ready I am ready to cast the resin. The resin I use is Alumilite clear casting resin slow. It has a 12 minute open time and a demold time of 2-4 hours. To achieve a bubble free casting I use a pressure chamber. It is a converted pressure paint sprayer from a hardware store. The pressure reduces the bubbles to a microscopic size and will make the casting crystal clear. With an accurate scale, measure both parts A and B to equal amounts 1:1 per the instructions for this product. Other products will vary. Mix thoroughly for about a minute scraping the sides of the container and keeping the stir stick in contact with the bottom of the cup to keep from creating bubbles. I then pour that mix into a clean cup and add my color. This ensures that your mix doesnt have any unmixed resin on the sides. I mix the dye until the color is nice and even throughout the resin. Now that I have my resin mixed and the blank ready in the mold, it’s time to pour. Pour the resin from a few inches above the wood and pour it nice and slow so that it doesnt fold over itself and cause any bubbles. Don’t worry too much because the pressure chamber will take care of the rest. Carefully take the mold with the freshly poured resin and set it gently into the pressure pot. Tighten the 4 handles and attach the air nozzle from the compressor to the inlet valve with the valve shut. Slowly open up the valve to let air into the chamber. Opening the valve slowly reduces the wind blowing the resin around in case you filled it to the top of your mold. I fill the chamber to 55 pounds of pressure and leave it overnight.

Pressure pot makes the bubbles microscopic

The next morning I pull the casting out of the chamber and breathe a sigh of relief. The casting is perfectly clear due to following all the steps up to this point. I cut the side of the cup with a utility knife and most of the cup comes off of the casting. The rest can be turned off while turning on the lathe. With the disc sander table still at the angle that matched the cup I can sand the bottom flat and clean. I find center of the blank and my waste block and use my dividers to draw a matching circle on the waste block. This will help center the piece when gluing them together and will make turning the blank round easier in the beginning. I use super glue and an activator to attach them together. The activator is pretty instant but I still give it 30 minutes or so to cure. My waste blocks have a dovetail tenon turned on the opposite side of the blank. The dovetail angle matches the jaws in my 4 jaw chuck. This makes it easy when I have a few projects at different stages of the process and I can easily remove and mount the next project onto the lathe.

-With my lathe speed set to 700-1500 rpm’s, I start to rough the blank to a round shape. Even though the blank was mounted centered to the waste block, it isn't perfect. Normally I use the Ultrashear Mid size Round tool since it is less aggressive. Since this is resin, you can use carbide tools with a little modification to the tool position. For normal use you hold the tool level to the floor and the cutting edge of the tool centered with the drive center of the lathe. With resin I find that a less agressive cut makes for a smoother surface and its less stress on the resin. I hold the tool at a higher angle so that the rear of the tool handle is close to my chest and the cutting edge is still centered with the drive center. I try to keep my tool at 90 degrees to my workpiece too. Once I figured this out I didnt get one chip or anything from the resin.

Angle tool down for a less aggressive cut in the resin

Now we finally get to turn. The great thing about turning is that anything goes as far as shape. I really like spheres right now so that’s what I am going to make. You could also leave a flat bottom on the sphere to make a gear shift knob or even the top of a walking cane.

Spheres can be intimidating and even a little difficult. I learned how to make one a while back and it involves turning 2 cup centers to hold the rough sphere between centers on the lathe and then turning the object close to sphere and mark the center with a pencil and then turn the object 90 degrees and turn the “shadow line” off until you get to solid material and keep doing that until its perfect. It takes a while. There are also sphere jigs on the market to buy if you want to make a perfect sphere. They’re expensive but make the task very easy. I would recommend getting it close to whatever shape you like.

Once I get to my desired shape I start sanding. I begin at 220. Sometimes I start at 120 for all wood projects but I’ve found that 120 puts very deep scratches into the resin and is difficult to sand out. So I go from 120 to 220 and then to 320. I sand with the lathe at a low speed and once I finish with a grit I turn off the lathe and sand by hand at 90 degrees to the turning direction and then at 45 degrees. I then wipe it down with denatured alcohol. I do this with every grit. I then switch to mesh sand paper at 400 and 600 grit going across the piece with the lathe off and wiping with alcohol in between grits still. After sanding to 600 and wiping with alcohol I examine the piece to see if there are any noticeable scratches. This would be the time to address them and sand them out. I then use Yorkshire Grit which is a micro abrasive. I wipe it on the piece with a good even coat. Keep in mind that once you turn on the lathe that it could splatter a little so dont go crazy with it and wear a mask. I turn on the lathe and with a blue paper towel I rub it into the piece and work it back and forth. I use the blue paper towels since they are lint free and if it catches on anything then it will rip instead of grabbing it out of your grip. If you're creating heat and its drying then turn down the lathe. You want it to slowly “sand” the surface. I usually go through this process a couple times and examine the piece to make sure there are no deep scratches. This is when all that sanding and smooth turning finally reveals itself. Once I turn off the lathe I am looking at a nearly crystal clear sphere.

Now it’s time to remove the piece from the waste block. I use the Ultra Shear Paring Tool Ci to part the piece off of the waste block. I will push the parting tool into the waste block and not the burl. I usually part almost all the way and finish with pull saw. This guarantees that the piece won't end up on the floor. I now have a sphere with a flat base that needs rounded off so I mount it between shop made cup centers and get it as perfectly centered between them as I can. I then turn the lathe on and I can see the shadow line. That's where you see blur of the flat base (see pictures). Using my Ultra Shear Full Size round tool I slowly turn away the base until I just barely start turning solid material. You can get this close and sand down to your solid sphere too. Then you re-sand with the same process as before.

Finally I installed a 3 part buffing wheel system onto the lathe. It has three wheels and each has a different buffing compound. First is tripoli then white diamond and last is carnauba wax. I set the lathe at a medium speed, around 1000 rpm, and work my way up the system. I start with tripoli and slowly buff every side of the sphere and in different directions. I then go to the white diamond wheel and do the same. I don't use the carnauba wax but it wouldn’t hurt to add a little extra protection if you'd like. Wipe the sphere down with an old T-shirt or clean cotton cloth and enjoy the view.

The entire process to make a hybrid resin turned piece is lengthy and tedious but once you look at the crystal clear resin and perfect form then it is all worth it. I certainly enjoy making these and I even enjoyed the process of learning how to make them even with a few learning experiences along the way. I hope I inspired you to try something new and to turn amazing things on the lathe.