DIY Drum Restoration

Part 3: Bearing-Edge Basics

You might question why a column dealing with drum restoration would set out to discuss the ins and outs of bearing edges. After all, haven't we read about this topic ad nauseam? True, an abundance of information on bearing edges is available to us today, mainly on the Internet. But what we find is often fractional and sometimes even fictional. My aim here is to dispel many of the myths, uncover the mysteries, and bring the important facts together in one place.

In the restoration of vintage drums, recutting and/or optimizing bearing edges is often the most vital step toward achieving a great-sounding finished product. Though the word restoration implies bringing back cosmetic and structural integrity, properly (or improperly) cut bearing edges are largely responsible for determining a drum's final sound, tunability, and playability. The more you understand how bearing edges and other factors-including the shell, heads, and hoops-interact with the drum as a whole, the better off you'll be when it comes time to bring an old drum back to life.

To help you fully understand what makes a drum sound its best, here are a few facts you should know about drum construction.

Bearing edges can make or break a drum sound.

Uneven bearing edges can seriously affect tunability. A peak in the edge will create higher tension at that spot on the drumhead, and, conversely, a valley will create lower tension. The net result will be a varying degree of difficulty when you're trying to establish an even pitch at all tension rods. The problem is exacerbated at lower tunings, where wrinkles in the head at the edges can become apparent, resulting in nasty overtones.

I'm often asked why bearing edges are so critical nowadays, given that many vintage drums had edges that were less than perfect. The answer: plastic drumheads. Back when drummers used calfskin heads exclusively, imprecise bearing edges weren't an issue because the pliable natural skin would conform to just about anything. High spots, low spots-calfskin heads don't care. As a result, drum makers weren't too concerned with how evenly they cut their bearing edges. Nor were they very careful about the accuracy of shell diameters. (Most were oversize.) That's why some vintage drums are difficult to outfit with modern plastic heads.

Plastic drumheads are made from a polyester film called PET (polyethylene terephthalate). Most people are familiar with the DuPont brand name Mylar, which is the trade name for a type of PET film that's also referred to as polyester nylon. Regardless of the manufacturer, all PET drumheads exhibit similar characteristics. For starters, the film is supplied in a flat state, so it doesn't readily conform to radical curvatures such as those created by the bearing edge of a drum. In order to form a collar, the circular head blank punched from the flat film is placed in a press that heats and softens the collar area and then applies pressure to create the collar. (This process is called thermoforming.) As the film cools, it retains its collar shape, and the area becomes stiffer because of molecular changes in the film.

When you mount a plastic drumhead on a drum with imperfect edges, imagine how this somewhat stiff and unforgiving synthetic material is going to conform to uneven areas. It won't. Instead, it rides over the low spots, which creates wrinkles when the head is tuned at lower tensions.

Thinner films have an easier time conforming to uneven areas. A typical medium 10 mil, 1-ply head (.010'') will tend to ride over low spots, while a thinner 7 or 7.5 mil head (.007'' or .0075'') can negotiate the bearing-edge roller coaster a bit better. But the trade-off is that thinner heads are less durable, and they have a brighter and more open tone.

Films thinner than 7 mil are relegated to snare-side heads. Even with these much thinner films (snare-side heads are typically 2, 3, or 5 mil), drummers who own vintage snare drums with deep snare beds have witnessed wrinkles at the snare bed edges, regardless of how tightly the head is tuned.

All drum shells are not created equal.

Let's examine another problem area: an oversize shell. In order to accommodate synthetic heads, drum shells really need to be undersize by about .25'' so that the collar area of the head seats on the bearing edge and doesn't enter the playing area. If the bearing edge is too far outward, the preformed collar of the head will sit inside the playing area, creating a full-diameter wrinkle. Ideally you want the collar to sit directly on the bearing edge, but some edge profiles can hamper this critical contact area. (More on this later.)

Modern drum shells often have undersize diameters. Ply shells are created inside circular molds and are built from the outside in, so that they maintain a consistent diameter. Solid shells are steam bent and lathed to the correct diameter. Vintage drum shells were created around circular molds and then clamped with full-circle ring clamps until the adhesive cured. In a perfect world, this wouldn't be an issue, but the thin wood veneers used to create shells aren't always of the exact same thickness. So sometimes shells would end up being thicker than usual, creating a larger outer diameter. With old steam-bent shells, where each end of the shell panel is beveled to create an overlap area for the scarf joint, the joinery was sometimes inaccurate and was often eye-balled into place. All of this can spell disaster when you try to use plastic drumheads on slightly larger drums.

Properly cut bearing edges can alleviate most issues.

Look at the illustrations below. These are the most common bearing-edge profiles seen on modern drums.

(with reinforcement rings only)

Most vintage drums will sport either standard (illustration 1) or vintage roundover edges (illustration 4). The standard edge has variations. It's sometimes used on shells with reinforcement rings, and it's sometimes seen with a rounded outer countercut instead of a true bevel (also referred to as a chamfer). You'll find the latter variation on vintage Rogers drums.

Likewise, the vintage roundover, as seen on 3-ply Ludwig and Slingerland drums, might employ a 45-degree inner bevel instead of the more common 30-degree edge. (I've seen both 30- and 45-degree bevels on factory Ludwig drums.) While the inner bevel is important, it's not nearly as crucial as the outer countercut or roundover, or the placement of the peak formed by the intersection of the inner and outer cuts. While standard and vintage roundover edges might work just fine on properly undersize shells, they can often cause tuning issues on vintage drums that have oversize shells.

If you own troublesome vintage drums with oversize shells, you can make them better handle plastic drumheads by having the outer edge recut to a double 45-degree edge (illustration 2) or a 45-degree edge with a roundover (illustration 3). Those deeper cuts will move the apex of the edge inward, which will move the collar of the head outside the playing area and increase the tunability.

The decision of whether or not to modify your drums is ultimately up to you. Ask yourself if you want to play the drums or just keep them as collector's items. Then determine whether you want to use synthetic or calfskin heads. To me, drums are meant to be played. But to play them, you must be able to tune them, which could require the edges to be recut first.

In our next installment we'll dig deeper into bearing-edge profiles and their advantages and disadvantages, and then we'll shed light on the often misunderstood topic of snare beds. See you then!

[Author Affiliation]

J.R. Frondelli is the owner of Frondelli USA Drums, which specializes in repairing, reworking, and restoring vintage drums, as well as building new vintage-style drums. For more info, visit frondelli.com.