When you first hear the term “lathe spider,” you might be taken aback. It certainly sounds unusual, but a lathe spider is a straightforward piece of equipment. A lathe spider is essentially a specialized lathe chuck, designed to hold a workpiece securely while it rotates in the lathe.
With that said, let’s learn about what makes a lathe spider different from a normal chuck, and how and when to use a spider for your lathe.
How it works
A lathe spider works as a custom-built spacer. It fits around and between the jaws of a chuck, most commonly a simple three-jaw chuck, leaving just a bit of the jaws exposed to grip the actual workpiece.
That’s the most common version of a lathe spider. Because the vast majority of lathe spiders are custom-built, no two are the same. Another fairly common variant is a modified chuck itself, but with the jaws set into a short length of tubing, thus extending the reach of the chuck.
What it does
If a spider sounds complicated, it’s not. Machinists use a spider when they’re working with smaller or more slender parts. Most commonly, spiders are used with small parts so that the machinist can get a secure grip and still be able to “face” the part – i.e., work on the outer face. Picture a small o-ring, which needs to be faced. The ring is small enough that getting a firm grip with just the chuck alone might be impossible without setting the ring crookedly or warping it. So the machinist uses a spider on the chuck, mounts the ring flat against the spider, and still has enough play to grip the ring.
How big does the spider need to be? That depends on the workpiece, of course, which is one of the reasons that most machinists tend to make spiders as-needed, rather than having some sort of standard set. The good news is that if the machinist is producing several rings or parts at once, using a spider ensures that each piece is mounted in the same place.
The other time when a lathe spider comes in extremely useful is when dealing with long and slender parts. The principle is the same – an unusual workpiece that requires an unusual approach to hold it securely. In this case, spiders are often built from tubing, and screws can be run through one end of the tube to serve as a three- or four-jawed chuck. By pushing the point of contact out, there’s less potential for a slender workpiece to develop a lot of warping and “play” during the turning process. And of course, the spider also helps to keep production uniform.
Special applications
Lathe spiders are found whenever there’s a need for them; you’ll rarely find them for sale, as they tend to be custom-built for the occasion. Machinists who regularly work with specialized parts are more likely to use them regularly – gunsmiths are a good example since they need to work with particularly long and slender parts.
A lathe spider is not difficult to make, and you can find good tutorials on the Internet for several basic patterns.
So if you are dealing with a tricky part and need a good way to hold it in place, make yourself a lathe spider.
