My workshop is full of equipment, tools, and machines that I use for various jobs. Some are essential for Scovie Precision Turning to function as a precision machine shop. Others I could do without if I had to, but they make my work a lot easier or more efficient. I utilize a number of different types of equipment even when making a relatively simple spinning top.
Here are 5 tools that I rely on to make spinning tops that are precise, resilient, and attractive.
I have both manual lathes and a computer numerical control (CNC) lathe in my shop. Spin tops can be made on either type, but I generally use the CNC lathe for speed and efficiency when making batches of the same top at once.
A metal lathe uses a piece of metal (either stock or a partially completed spin top) on its axis while it advances a cutting tool along the metal to cut the desired shape. With a CNC lathe, the movement of the cutting tool is programmed into the machine before it starts cutting.
The lathe is used to turn all the round diameters of a top. It holds very tight tolerances and ensures that all the diameters are concentric to one another.
Engineers, technicians, researchers and many others use calipers on a regular basis to accurately measure the dimensions of an object. Machinists use calipers as well; however, for much of a machinist’s work, calipers are not precise enough.
As their name implies, micrometers are necessary for measuring dimensions on the order of a micrometer (aka micron). Micrometers tend to be much more expensive than calipers because they take such small, exact measurements. As such, a nice set of micrometers is somewhat of a prized possession for a machinist.
I check each part with a micrometer as it comes off the lathe after being turned. I confirm that the outside diameters are as expected and maintaining consistency from part to part. Many of the spinning tops I make use a press fit (more on this below). Micrometers are crucial to confirm that the diameters of two parts can be press fit together.
Gage pins are used to accurately and quickly measure a hole that has been drilled or bored into a part. In many precision machining jobs, bores have tight tolerances that they need to adhere to. Gage pins help to ensure that the bore is not too big and not too small.
To accomplish this, most sets of gage pins are comprised of a “go” and “no go” pin. The “go” pin is sized so that it should fit into the bore being measured. The “no go” pin should not fit into the bore. In many cases, the difference in size between the two gage pins may be only a few 0.0001 of an inch.
They are fairly simple to manufacture on a lathe. When making spinning tops, I use two sets of gage pins: one to check the bore that the metal ball bearing tip presses into, and another to check the bore on the body into which the core will be pressed.
Gage pins can be purchased pre-fabricated from a supplier, though often I machine my own custom gage pins for a specific job.
An arbor press makes it convenient and easy to apply a lot of force to an object. Though they have a lot of applications, in machining, they are often used to apply force to two machined parts to press them tightly together, creating a press fit or interference fit. This isn’t possible to do by hand because of the large amount of force required.
The arbor press delivers an extraordinary amount of force with just the turn of a handle. The handle acts as a lever and multiplies the force that is exerted on it. The lever rotates a gear, which moves a rack or ram.
Check out my arbor press in action on this YouTube video.
As mentioned above, most of the spinning tops I make use a press fit between the top core and body. An arbor press works great for this. The main risk of using an arbor press for this task is that the large force could potentially damage the spin top. To prevent this, I hold the parts of the top in custom tooling to distribute the force across a larger area. This leads right in to the final tool I’ll discuss…
Custom tooling is essentially any tool that cannot be readily purchased in a catalog to perform a required task. It is made for a specific job or project. Therefore, the tools have sizes and shapes that make them unsuitable for use with other projects or tasks.
When manufacturing spinning tops, my custom tooling includes a bottom base and a top cap to fit over the body and the core of the top, respectively. These are what hold the top in place when pressing the two parts together and, as mentioned above, protect them from the force of the arbor press.
I usually make custom tooling out of acetyl (more commonly known as Delrin). It is softer than metal, so it doesn’t cause damage to the spinning top. But it is strong enough that it doesn’t break under the force of the arbor press.
Custom tooling can be used for much more than as a fixture to hold parts during the machining process. For example, a custom plug can be made to insert into a hollow part to prevent it from crushing in the lathe. Custom tooling can also be used for inspections. The simplest example of this is gage pins, as described above, though tools can be more complex depending on the shape of the part and location of a diameter or groove that needs to be inspected.