Louvered doors allow air cir­culation and provide privacy while the overlapping lou­vers prevent light from getting in. The purpose of this article is to show you how to make a jig that will help you accurately and quickly make the angled mortises needed for this project with a plunge router.

At this point, presumably after hav­ing taken a quick look at the photos and sketches, you may wonder why you would go to so much trouble when reno­vation centers sell CNC made doors for an affordable price. If you only need one set of doors that will be painted, you may as well buy the ready-made doors.

However, if you need several doors, want to make them with a hard­wood species with unusual sizes or you take pride in making everything in your house yourself, then you should pay attention. Making that jig may be time consuming but it is worth doing it well considering that a single 15″x 80″ closet door has approximately 65 louvers and 130 mortises. For the execution to be quick, easy to operate and accurate, you need a well designed jig.

Making the Jig

When making a jig, you want to design it to serve multiple purposes without over-designing it. Louver doors come in various thickness of stiles and width of louvers, so you have the choice of making the jig for the specific size you need or, as suggested below, make the jig to allow you to make any sizes in the future without having to make major alterations. A solution is to make the jig for the largest size and use shims to fabricate doors down to the smallest size. The usual thickness of the stiles ranges from ¾” for furniture pieces to 1 ⅛” for clothes closets and 1 ⅜” for a standard room door. Another consideration is the width of the stiles, which could range from 1″ to 2 ½”. Again, you can use fillers or shims to raise narrower stiles closer to the bit. You could make the jig only 24″ long, but you would have to move the stiles often to make a longer series of mortises and risk errors every time. I prefer 60″ so that I can make all the mortises of either the bottom or top portion of the door without having to move the stiles.

Base and Guiding Rails

The base is made of ¾” Baltic ply­wood and ¾” hardwood for the guiding rails. I prefer wider hardwood because it provides more rigidity and you can make better quality and more durable holes. The guiding rails are attached only at the ends with ¼” 20 TPI bolts and Propell nuts (Lee Valley 00N23.01). I don’t recommend attach­ing the middle of the guiding rails with additional bolts. It works better to have some looseness in the middle so that you can insert the shims more eas­ily. Besides, when the sled travels over the rails, it will tighten everything along that portion of the rails.

The distance between the ½” diameter holes in the guiding rails varies depend­ing on the thickness of the doors. The distance varies because the width of the louvers also varies. Too great a distance between the registering holes will mean that the louvers will not overlap each other. This is a basic requirement for providing privacy and for blocking the light.

Using a pin system on the drill press and a sharp brad point works best for this step. It is very important that the holes be equally spaced accurately.rounded the top of the holes with a 1/8″ round-over router bit with a ½” bearing to obtain a clean cut. The rounded edges facilitate the entry of the pin guiding the sled. While you are making the register­ing holes on your drill press, you may as well make holes in the four edges pro­vided by the two guiding rails.

The incline of the mortises remains the same for all sizes of doors; the indus­try standard is 19° but I rounded it out to 20°. It does not matter which one you pick as long as both sleds have the precise same inclination; any varia­tion between the right and left stile will result in a warped door. The space between the guiding rails and their loca­tion on the base will depend on whether you go for the multi-size jig and on the specific thickness of your stiles.

Modified Base Plate

Round base plates on routers are known to be not always perfectly round and centered. I prefer making a square base plate, ¼” bigger all around than the body of the router at the base. It can be made of plastic or plywood and kept to ¼” thick. Drill a ½” hole in the exact center of the square plate, then add a ½” inside diameter insert (Lee Valley 46J92.14) into your original base plate. Place the two plates on top of the other using a centering pin or a ½” bit to align them. Then, using a trans­fer punch (Lee Valley 24K05.40) of the exact size of the holes from your original plate, punch and drill holes in the new square plate. Enlarge the ½” to fit the insert mentioned above so that you can install the square plate on the router. The centering insert will ensure that the four sides of the base plate are equidistant from the center of the collet. Also, hav­ing a perfectly square base plate means that you will be able to use the router in the most comfortable position in relation to the handles on your brand of router.

The Sleds

The sleds are what carry the router over the guiding rails to produce the mortises. Accuracy and precision in the making of the sleds is critical. After find­ing the center of the top of the sled, drill a ½” hole at that location. Install a ½” centering pin in the collet and put the router on top of the sled with the cen­tering pin inserted in the hole of the sled. Then incline the new router base 20° to the right or the left and install guiding strips with screws. Those side strips will not need to be moved at any time. If the guiding strips on each sled are not inclined exactly the same num­ber of degrees (right and left), you will end up with a warped door. The distance the router travels will give you the length of the mortises. Therefore, the distance between the top and bottom stopper strips is the length of the plate, plus the width of the required louvers. Divide this figure in two, and install the stop­pers equally on each side of the center line. On my jig, I went for the multi-use model, therefore I used 1 ½” louver width and then used temporary double taped fillers to fabricate thinner doors (1 ⅛”).

You need to make two sleds because you will be dealing with a right and left situation when making the stiles in most cases, unless the stiles have simi­lar top and bottom rails and no offset middle rail. If you elect to make the jig for multi-sized doors, then the distance between the sled guides will be 1 ⅜”, plus twice the thickness of your guiding rails. If you decide not to use the shim method then it will be the thickness of your stiles, plus twice the thickness of the guiding rails.

The registering pin on top of the sled is made of ½” steel because it does not swell like wood. The round plastic knob on top makes it easier to pull the pin out of the holes. The piece holding the pin is made of UHMV (Ultra High Molecular Weight) because it is slippery and the hole will not expand or shrink. That piece has to be at least ¾” thick; oth­erwise the pin will not keep the sled completely stationary when you push laterally on the router to make the mor­tises. You want to avoid having the sled rocking even slightly.

The Bits to Use

When mortising, spiral bits work more rapidly and more efficiently with­out overheating as compared to straight bits. Up-cut spiral bits remove chips to the top, while down-cut spiral bits push chips down to be continually chewed up. The latter is hard on the bit and the motor. However, although up-cut bits are preferable, they have the disadvan­tage of leaving a rough edge at the top of the mortise. Unlike a mortise and tenon joint, that area on a door stile is very visible. The solution is to use an up-cut spiral bit but make the stiles at least 1/16″ oversize and then clean them up on a thickness planer after completing the mortise.

Making the Louvers

In order to make all the parts, shims etc., I used a digital Vernier calliper extensively. Working in thousandths of an inch is much more accurate than relying on rulers. If you are working in soft wood, make the louvers so that they can be inserted in the mortises by hand, but it should be snug. I bev­elled the ends on a belt sander. At this time, you should check that the depths of the mortises are all equal and clear of obstructions; ¼” to ½” is sufficient and there is no need for glue on the louvers. Not only it is not necessary, it would be messy to use glue on so many parts within the short period of time you have to assemble the doors.

Bonus of the Jig

If you are using mortise and tenons in the rails of your doors, you can use one of the sleds to make the straight mortises in the stiles to receive the ten­ons by reversing the roles. Immobilize the router in the center of the stile with blocks and move the sled up and down for the desired travel length.

Using the Jig

Ensure that the stiles will not move forward (this would, of course, ruin the spacing of the louvers), and also that they do not spring up (this would change the depth of the mortises and make some of the louvers too long when assembling the doors. A clamp, pinching the guiding rails at each end of the stile, should be sufficient. The base board will need to be clamped to the work bench.

The practice run will determine how far the first mortise will be from the registering pin hole. The bottom of that first mortise is where the top of your bottom rail will be. Please note that this distance will vary depending on the distance of the register­ing holes for different thicknesses of doors.

At first I kept the holes in the center of the base plate and the top of the sled at ½” in order to keep the dust from coming out. It worked fine but blocked the reg­istering holes too much; I had to lift the sled every few mortises to clean them up. It works much better if you make those holes 2″ in diameter and use a router that vacuums the dust through the guide posts.

Door Assembly

The biggest problem after you have inserted the bottom, middle and top rails with glue in one of the stiles, and done the same with one end of the louvers (without glue), is to rush the same pro­cedure for the other stile. Trying to have all the louvers and tenons line up is like herding cats. The solution is to make a piece similar to the stiles to use as an alignment jig, preferably in hardwood and with at least ¾” deep mortises. Using the same measurements and set-up for making the stiles, make another piece long enough to fit all of the louvers and cut this piece in half. Fit all of the louvers into one of the stiles and then place the alignment jig approximately 1 ½” from the end of the louvers to line them up for insertion into the second stile.