Cylinders aren’t just random geometric shapes that only occur in your textbooks. In fact, cylinders are some of the more common shapes found in industrial and machining applications. Screws, bushings, basic metal rods – all are cylinders or variations of them.
For most cylindrical work, there’s no better tool than the metal lathe. Lathes hold a workpiece between two centers and rotate it rapidly, allowing a cutting tool to slide along the length of the workpiece and remove material. This process is known as “turning down” or simply “turning.”
For cylinders, lathes are ideal; but what if you don’t have a lathe? How can you turn down a metal rod or other cylinder without a metal lathe? Is there any way to recreate the rotation and cutting action of a lathe?
None of the solutions we’re suggesting here are ideal, but all of them will work – in a pinch. None will come anywhere near giving you the finish and fit of a CNC lathe, but if you need something rough-and-ready, we can suggest these two solutions.
- Drill press
To re-create the rotary action of a lathe, you’ll need a tool that spins. Drills have a rotating action and are commonly found in workshops and home tool rooms across the country, but the average handheld drill won’t have the finesse and control you need.
Fortunately, there’s a heavy-duty alternative that is fairly common. A drill press is a heavy upright drill, with the drill and bit suspended from a gantry above the workbench. When a workpiece is mounted on the bench, the drill can be lowered or “pressed” into the workpiece. Drill presses are commonly used to create holes, pre-drill for screws, or even in place of a router to hollow out sections of the workpiece.
The biggest challenge when using a drill press as a lathe is the orientation of the drill. In a lathe, a workpiece is mounted horizontally, parallel to the workbench. With a drill press, the orientation of the drill is perpendicular to the workbench. This calls for a considerable amount of creativity in order to get the cutting implement mounted correctly.
If the project is simple enough and the workpiece is small enough, then a simple metal radius could be attached to the drill by means of a chuck.This gives the workpiece the desired rotation, and some of the horizontal movement can now be replicated by the vertical movement of the drill.
The challenge comes in the mounting of the cutter. Positioning it correctly will often require additional chucks or vises, and it will be extremely difficult to mount an actual cutting tool or bit. However, if there isn’t a large amount of material that needs to be removed, then a flat surface can be positioned near the workpiece and used as a platform for a metal file.
- Grinder and handheld drill
This method relies heavily on the machinist’s handheld precision, but can work for impromptu projects. The advantage of this option is that both instruments, the cutting tool and the workpiece, are rotating at high speeds. This helps to keep the overall finish smoother, given that the machinist handles everything well.
Bench grinders or sanders are typically used to remove material quickly, literally grinding something down into a new shape. They are nowhere near as precise as an actual lathe. Using the chuck of a handheld drill to hold the workpiece gives the operator a bit more control, lessens the resistance of the grinder, and ensures that material will be removed equally across the radius of the metal rod.
The catch is that any horizontal movement to the workpiece has to be done by hand; the operator needs to feed the workpiece into the grinder slowly and steadily, applying exactly the right amount of pressure to remove material equally along the length of the workpiece. If the pressure isn’t correct, the radius at one point won’t be the same as the radius at another point.
Problems and solutions
Turning down a metal radius without a lathe is a last resort. The first step, nearly always, should be to go get a lathe! But for quick projects that only require a general shape and not a carefully calibrated dimension, both of the above methods will work. The drill press gives the operator a bit more control over the movement of the workpiece, but the grinder-and-drill method allows for more freehanding and finesse.
The results aren’t likely to be a machinist’s finest work, but they can work in a pinch.
