The Nature of Wood and Metal Slides

Wooden drawer slides have been the traditional choice of furniture makers throughout history, and are still the hallmark of finely crafted furniture. They do have four main drawbacks though, they require a good understanding of the nature of lumbers, they require a fair level of skill in wood joinery, they are prone to wear over time, and with extreme changes in seasonal humidity they can either bind or become sloppy. Mechanical (metal) slides were developed to address these problems.

Mechanical slides come in a wide variety of styles and mounting configurations. They can be visible or hidden, a single slide mounted in the center of the drawer, a pair mounted along each side of the drawer, or something as simple as a couple of plastic guides with rollers on them. Slides have also become quite popular for mounting doors in entertainment centres where the door can be opened and then slid out of sight into the cabinet. There are also specialty slides for computer desks and filing cabinets. In fact, it seems that there is a slide for almost every conceivable situation.

Metal slides offer several advantages over the wooden versions. They are impervious to seasonal changes in humidity, which means your drawers will run as smoothly in January as they do on a muggy August afternoon. Plus they speed up and simplify the construction process in most cases.

If you will be using metal slides in your project, be sure to purchase them before beginning construction. As with much in life, you get what you pay for, with the best slides being more expensive than utility grade slides. Choose your slides carefully based on the intended use of the drawer. For a drawer filled with heavier items, or one that is used every day, using higher-end slides will pay off in the long run with years of smooth, trouble free operation.

Center-Mount Slides

A drawer can be supported with one slide at the center of the drawer, but this is not always the best method. With center-mount (a.k.a., under-mount or bottom-mount) slides, the drawer can have a tendency to rack from side-to-side when they are overloaded or when fully extended. These slides can be made of wood or metal, but by far the best under-mount slides are made of metal and utilize the same captive ball bearing design that the side-mount versions use.

Center-mount slides do have one use that they are uniquely suited for. If you are confronted with a cabinet with one side longer than the other, requiring an irregularly shaped drawer, using two center-mount slides, a shorter one in combination with a longer one, will allow the drawer to utilize the full depth of the cabinet.

Metal Slide Mechanics

Metal slides usually consist of a pair of metal guides with some sort of roller or ball bearing system between them to provide the motion. The most basic of these are the steel utility slides found on most kitchen drawers and mass produced cabinetry. These consist of a pair of metal arms with a nylon roller, one of which attaches to the bottom of each side of the drawer and the other to the cabinet carcase. One side is lipped to keep the drawer from shifting from side-to-side in its travel and they are usually self-closing in the last few inches of travel. The one limiting feature of this type of slide is that they extend 3 ½” less than the length of the slide.

When choosing slides for your project, the mounting position is just one of the things to consider. You also want to think about load capacities and length of travel. When planning a cabinet project using slides, determine what the load on the slides will be, in pounds. If you’re not sure, build a drawer box and fill it with the items that will go into it and weigh the whole thing. It’s a good practice to add 50% to that weight when choosing the slides, though my personal preference is to choose the best slides that meet the load requirements and budget constraints.

You should select and purchase your hardware at the design stage, as the drawer size and opening size must fall within certain tolerances for the slides to work. When possible, choose slides that have a higher rating than is required. Another critical factor affecting drawer slide selection is the amount of travel required. In the shop, we have a row of cabinets with drawers in them that are 12″ deep. On top of that is a counter with a two-inch projection. Using the example of the utility slides mentioned earlier, they would allow the drawer to be pulled out 3-1/2″ inches less than the total length of the slides, only 8-1/2″.

The counter top projection uses up another 2″, so the effective access to the top drawer using that sort of slide is about 6-1/2″, or just slightly more than one half the depth of the drawer.

The Extension Slides

To address this, better quality slides come with different amounts of travel. In the case of the top drawer, the best slide for this position would be an over-extension type, which allows the back of the drawer to extend past the front of the carcase. This extra travel helps reclaim some of the space the counter overhang would block, making it easier to reach items at the back of the drawer.

For the second drawer down in the cabinet, slides with slightly less travel would be more appropriate. Full extension slides will allow the drawer back to be brought flush with the front of the carcase. Since there isn’t any countertop overhang to contend with, this will provide full access to the interior of the drawer.

Standard or single extension slides will bring only part of the drawer past the front edge of the carcase. The difference between the length of the slide and the actual length of the drawer travel is called the extension loss. For a given style of slide, this loss will be the same no matter how long the slide. In the case of the common utility slides in our shop, the extension loss is 3-1/2″. This is much more noticeable on a drawer that is 12″ deep than one that is 22″ deep.

Mechanical slides come in a myriad of configurations, from concealed ball bearing under-mount slides that would remain hidden in use, to basic utility slides. There are slides for frameless cabinets as well as slides for face frames, and some can be used with both with additional mounting hardware. Determine which style and type of slide the drawers in your project will require, and purchase them early in the design process. The slides are just one factor that will determine how smoothly your drawers operate. The drawer box and the carcase must be built with the proper clearances for everything to function properly. A properly selected and installed slide should provide a lifetime of smooth operation.

Drawer slides available at

Home Hardware – homehardware.ca

Lee Valley Tools – leevalley.com

In this article we’ve covered some of the options and considerations to keep in mind when selecting slides. In the December/January 07 issue we’ll take a closer look at slide installation. It’s easier than you think, so don’t miss it.