A common question I get when I show someone a piece that I’ve made on my lathe is:
How did you make this?
This question gets asked regardless of what type of product, part, or component I have produced. It could be as interesting as a precision spinning top or as a boring as a flange.
This curiosity makes sense. Most people don’t have the machinery or technical knowledge needed to turn a piece of solid stock into a usable item. The process used to make something useful or beautiful from a chunk of metal isn’t always obvious from looking the finished product.
This article provides a sneak peak of how to make a spinning top on a lathe using the process that I generally follow for Scovie precision spin tops.
It begins with an idea and a design
The process of making a top actually begins long before I get my lathe up and running. Behind every good spinning top there is an idea and a design that I’ve thought about, drawn, reconsidered, and modified – sometimes many times over.
Sometimes my inspiration for a new top comes from a top that I’ve previously made. I see how an existing top could be improved or how the design could be adjusted to make it different in some way. Other times, I’m inspired by the look and feel of another product or toy, a video or image that I see, or even a part that I’ve been making for some of the custom precision turning work that I do.
Once I have a design in my head and on paper, I begin creating it in a in a computer-aided design program. This allows me to label and adjust various elements of the top, like dimensions and radiuses. I can see the design in 3D and view it from all angles.
I also determine the materials I’ll use at this stage, as well as the machining process I’ll follow to make the top.
Starting at the core of the top
The machining process for a spinning top begins the center part – the core – of the top. I often use different materials for the core and the body of my tops in order to best distribute the weight for long spinning times.
The process begins with metal stock in the form of a solid, cylindrical bar. I insert the stock into the lathe, set up the tooling that will cut the stock, and then start it up. Each action taken on the stock or the partially-machined top in the lathe is known as an operation, or “op” for short.
The first operation is a rough facing turn. Facing refers to cutting the surface of the stock perpendicular to the stock’s rotational axis. I use a bar feed option to feed the stock through the machine at a constant rate as the facing tool removes material. This operation removes most of the excess metal that surrounds what will eventually become the top core.
The rough facing turn is followed by a finish facing turn, which removes even more material from around the core.
Most spinning tops that I make have a knurl on the stem that helps you grip the top as you spin it. At this stage of the process, I machine the patterns of angled, crossed, or straight lines into the core’s stem to make the knurl.
Next comes a rough turn and a finish turn before cutting off the spinning top core from the rest of the bar stock.
The other side of the core
The entire process above was to machine just one end of the core. To do the other side, I flip the part around in the machine so that the cutting tools can reach it.
The process for this side starts out similarly: there is a rough facing turn followed by a finish facing turn to bring the part approximately to the right size and shape.
A finish face and turn then brings the core to exactly the intended size.
Finally, I make a bore at the bottom of the core and then press a hardened and ground ball bearing into it, which will serve as the point of contact with the surface while the top is spinning.
Machining the top body
All the steps of making a spinning top are enjoyable, though machining the top body is usually the most exciting part. This is because the body is what gives the top its shape and overall appearance. Most people can pick up a traditional spinning top and know it’s a spinning top because of the familiar shape of the body.
It’s fun to see the metal stock start to take the form of a top as I machine the outside profile.
The process of machining the body is somewhat similar to that of machining the core. The stock is initially bar fed for a rough face and turn, which essentially gets rid of most of the excess diameter of the stock.
I then use an insert drill to begin to hollow out the part. After the initial drill comes a rough bore operation through the center axis of the body.
Finish operations come after these rough operations. A finish turn creates the smooth, visually appealing profile of the top body. At this point, I also add design elements to the outside of the body, such as grooves.
A finish bore completes the internal diameter, which will serve as the hole through which the core will be pressed in. A key here is that this hole needs to almost exactly match the outside diameter of the core so that friction will hold the two pieces tightly together via a press fit.
The other side of the body
As with the core, the body needs to be cut off, taken out of the lathe, and flipped around in order to machine the other side.
The next operations include a rough face and turn for the second side of the body, followed by a finish face and turn. As before, grooves or other design elements can be added.
You’ll notice in the steps above that I always perform a rough turn before finish turns. I like to avoid heavy cuts in favor of skimming. This is to slowly break down the metal to give consistent diameters and a good finish.
Putting it all together and finishing touches
Once the core and body components are completed, it’s time to press the core into the body. I always include what’s known as a lead in the bore of the body or on the diameter of the core. This lead is about 0.001 inches and helps to get the two parts lined up and get the press fit going.
I press the core and the body together with an arbor press. This involves making a tool with a hole in it that is big enough to sit over the top stem so that force can be placed onto the wider, stronger portion of the top rather than the thin stem. If the stem were to bend even a little, the final top may not spin straight.
For some tops, I put the top back into the lathe for two final operations. These are to turn the profiles on both sides to achieve a perfect blend between the core and the body where they meet.
The top can then be inspected and tested. “Testing” a top is really just spinning it. I observe it to make sure the spin is smooth and I time how long it spins.
…and that’s how to make a spinning top on a lathe
In a nutshell, that’s how Scovie precision spinning tops are made!
Of course, each top design requires slight variations to the machining process. Different types of metals require different cutting strategies. My vision for the top – long spin time or visual appeal, for example – can also affect the process.
You can see, feel, and spin the result of this process by purchasing a top for yourself. Check out our top shop!
