Installing Drawer Slides
Skill Builder: Before you get to the stage where you are fitting the drawer slides to the project, you will have had to build the drawer and the cavity that will house it. Always purchase your functional hardware before beginning the construction of your project, as different slide designs and different manufacturers do not always require the same operational clearances, even though they may look very similar. To be sure, consult the instructions that come with your hardware.
In a previous article (August/September ’06, issue #43) we took a look at the various styles of drawer slides, and what to consider when selecting slides for your project. In this issue we look at the installation of drawer slides.
Mechanical drawer slides offer some major advantages over shop-made wooden slides. The movements can be very smooth, they can support considerable weight, and they are not affected by seasonal changes in humidity.
Mechanical slides are best used on cabinetry and utilitarian pieces, as they have a look that only a mechanical engineer would perceive as elegant. For fine furniture, stick with wooden or concealed mechanical slides.
For mechanical slides to function properly the drawer box and cavity must be built to certain tolerances, and if your drawer and cavity are not square, your slides simply won’t work.
Each drawer slide is actually composed of two pieces. The piece that attaches to the cabinet is called the cabinet profile, and the piece that attaches to the drawer is called the drawer profile. There is usually some sort of mechanism to keep both parts locked together when in use, while still allowing them to be easily separated.
Side mounted drawer slides come in pairs, and can either be handed or unhanded. Handed slides come as a pair, with one for the left side, and one for the right side. Unhanded slides are reversible and can be used on either side. Some manufacturers mark the pieces of their handed models, which helps avoid confusion and speeds up installation.
Left: undercut screws, right: flat head wood screws
Handed epoxy slides
Full extension slide showing adjustment slots
Kreg drawer slide mounting jig
When mounting drawer slides, you will be dealing with one of two different types of construction; frameless, or face frame (for more on frame and frameless construction, see Canadian Woodworking Magazine October/November ’06, issue #44). Frameless construction is what you will see with modern European style cabinetry. Frameless cabinets and the now common 32mm mounting system were developed in Germany after the Second World War in order to streamline and speed up the production of cabinets. Most kitchens built today use this method, as it lends itself to the quick and easy installation of mechanical slides. Most slides have mounting holes located in the proper location on the cabinet profile to take advantage of 32mm system holes.
Mounting slides in frameless cabinets is a simple procedure. To determine which size slide to use, first measure the depth of the cabinet. Be sure to take into account any obstructions that may interfere with the operation of the drawer. Mechanical slides come in standard lengths (12, 14, 16, 18, 20, 22 and 24″) so choose one that is the next standard size smaller than the depth of your cabinet.
For the slides to work properly they must be parallel to each other on the sides of the cabinet, as well as on the same horizontal plane.
Mounting mechanical slides in a face frame style cabinet is a little bit more involved. With the frameless cabinet, the slide is fully in contact with the cabinet side so it is a simple matter of properly locating and fastening the cabinet profile to the cabinet. With a face frame, the front of the slide will be attached to the edge of the face frame, but the majority of the slide will be suspended in air with nothing else to fasten it to. All slide manufacturers have addressed this situation by making a set of brackets and stand-offs (or spacers) that you can use with their slides. These spacers are either fastened to the side of the cabinet and, in turn, support the slide, or they can be fastened to the back to support the slide at the end. Another option is to use shop scraps to make your own stand-offs.
If your project calls for concealed or under mount slides, the construction of the drawer must take into account the requirements of the slide. For the slide to function, the drawer bottom must be recessed from the bottom edge of the drawer sides. This is typically about ¼”, but purchase your hardware before you begin construction and check the specific requirements of your hardware. Most slides of this type are mounted in a face frame type of cabinet and the rear of the slide must be supported using a bracket fastened to the back of the cabinet.
In this age of specialization, it should come as no surprise that the collection of screws you’ve been saving in a pickle jar for years may not be the best choice for drawer slides. Most side mount slides require 1⁄2″ of space per slide, with the result that the clearances within the slides mechanical movement can be pretty tight. The better quality slides will have slightly countersunk holes for the screws, but as you can imagine, the metal is not that thick, so the screws holes are only slightly countersunk. Using regular #6 screws (or screws that are too large) will interfere with the movement of the slide. Special screws with an undercut head solve this problem. They look very much like a standard flat head wood screw, but instead of the shoulder tapering until it hits the shaft, the taper is only as long as the thickness of the slides. The rest of the taper is removed, allowing the screw to sit much lower in the slide.
Doing the Jig
Like most things, mounting drawer slides is a little easier if you have some help. If you are only installing a few drawers, a simple home made jig would suffice, but if you are doing a whole set of cabinets for your kitchen, a commercially available jig will save much time and frustration. Most slide manufacturers also make jigs that increase the speed and accuracy with which their slides can be installed. However, you may need to make your own jig as, on some projects, space and construction constraints may make a commercial jig unsuitable. By using a jig, you are handing off the alignment and holding of the hardware to the jig, allowing you to concentrate on driving the screws.
Mechanical drawer slides require that they be used within certain tolerances, but they also contain a number of adjustments to make fine tuning the set up easier. Every manufacturer is slightly different, but the most common adjustment mechanism is the ‘elongated hole’. Almost every quality slide will have a number of these oriented both along the length of the slide, as well as across the width. Depending on the slide you choose there may be other clever adjustments available.
Epoxy coated slides (commonly called euro slides) have little adjustment available on the drawer profile. Constructing the drawer to the correct size therefore is critical for a smooth action. The drawer profile part is essentially a piece of angle iron with mounting holes and a wheel, and is simply screwed to the bottom edge of each side.
With the Accuride full-extension slides there is an additional, rather ingenious adjustment feature. In addition to the slotted holes, there is an ‘adjustable hole’ at the leading edge of the drawer profile. After positioning the slide on the drawer box, the back can be accurately positioned using the slotted hole at the back of the slide. To fine tune the front fit of the drawer, drive a screw through the adjustable hole and use a screwdriver to level the drawer front relative to the rest of the cabinet for an even gap all around.
When mounting both the drawer and cabinet profiles, use one screw at each end of the piece in the slotted holes. If you are using a jig, like the Kreg, it will handle the alignment of the drawer to the cabinet as well as establish the proper setback from the front edge of the cabinet automatically.
With the four parts of the slides mounted, insert the drawer to check its fit. Adjust the fit of the drawer by loosening the appropriate screws and adjusting the position of the slide. When you have achieved a perfect fit, drive the rest of the screws home in the round holes to lock the slides in place.