Precision CNC turning is just one of the many ways that spinning tops and other spinning toys can be manufactured. When it comes to producing the longest spinning top, this method wins – hands down.
Aside from precision CNC turning, other methods for making metal spinning tops include manual cutting, casting, forging, and forming. Non-metal materials, such as wood, can be made into tops on a wood lathe. This uses the same principles of CNC turning but without the precision.
Each method has its own advantages and disadvantages. For example, a top turned on a wood lathe has a high likelihood of being quite beautiful. A casted metal top might have an interesting, complex shape with hollow sections and decorative cavities. But no process stands up to the benefits of a CNC lathe when it comes to spin time.
Here are 5 reasons why precision CNC turning produces the longest spin times for toy tops:
- CNC turning creates perfect balance
- Press fitting optimizes weight balance and use of multiple metals
- Computer programming minimizes error
- CNC lathes are forgiving
- You can “top” it off with a flawless knurl
The remainder of this article goes into detail about each of these benefits of precision CNC turning when it comes to top spin time.
CNC turning creates a perfectly balanced product
The primary benefit CNC turning for essentially every machined component that uses this technique is its precision. CNC lathes are accurate to the 10,000th of an inch!
For a spinning top, this accuracy means that the top will be perfectly round. Its weight will be distributed around its axis to the maximum extent. This is what prevents the top from falling over. You can read more about the physics of spinning tops, but the short version is that perfect weight balance equates to a long spin time.
No other manufacturing process can replicate this precision for any component requiring symmetry about an axis.
Press fitting optimizes weight balance and use of multiple materials
Press fitting is a technique in which one part is inserted into another part with a mating hole that is just slightly larger. The resulting assembly stays together by friction – no adhesives or screws required!
This is also known as friction fit or interference fit.
Because a CNC lathe is so precise in the diameters it machines, it can create the two parts of a press fit assembly such that they glide together easily but require a huge amount of force to overcome the friction to pull them apart.
Press fitting is useful for spinning tops for a couple of reasons. First, it allows for more than one type of metal to be used in the top. Different metals have different properties that tops can take advantage of. Having a lighter metal in the core and a heavier metal on the outside results in a weight distribution that lends itself to a long spin time.
Second, the ability to assemble two pieces of a top without any adhesives or screws means that there aren’t any fasteners throwing off the top’s balance.
Finally, press fitting can be used to insert a hardened ball bearing for the top to spin on.
Computer programming minimizes error
CNC stands for computer numerical control. Rather than manually turning dials, the operator of a CNC lathe relies on a computer program to move the metal stock and machine tooling on the lathe. Having a well-written program removes some of the risk that human error and variation will be introduced.
Computer programs can also be tested and revised as many times as necessary. In many cases, errors can be fixed before they ever end up on a piece of stock or a finished spinning top.
When there is an imperfection, a CNC lathe can fix it
As described above, CNC turning leaves little room for error. But when there are imperfections, a CNC lathe can fix them. A spinning top component with a slight imbalance, for instance, can be put back on the lathe to skim off a bit and balance it out.
Contrast this to a spinning top made by casting or 3D printer. You can’t re-cast the same top or put the top back in the printer to even out imperfections.
Top it off with a perfect knurl
A top can be perfectly machined and balanced, but it won’t spin on its own. A top needs to have a force applied to begin spinning. In most cases, this force is applied by a human hand. For this reason, it’s important to be able to have a good grip on the top so that it doesn’t slip while you try to spin it.
A series of crossed lines rolled into the metal – known as a knurl – is often applied to spinning tops to assist the user in getting a solid grip.
A great example of a knurl can be seen on this giant brass spinning top that weighs nearly a pound. This top is so heavy that it would be tough to obtain an adequate spin without grip offered by a knurl (unless you have particularly large, muscular hands).
Knurls can be quickly, easily, and consistently applied on a CNC lathe.
Experience our longest spinning tops made by CNC turning
At Scovie Precision Turning, I take advantage of these benefits for nearly every top that I manufacture. This means that our longest spinning tops – such as the Cahaba series of tops – routinely spin for over 10 minutes straight on a smooth, hard surface. This is despite them being small enough to fit in the palm of your hand and light enough to carry in your pocket.
Check out our top shop to see all of our metal tops I make by precision CNC turning. Try one out yourself!