How to: Make your own trim
Unique profiles, crisp results and money in your pocket
Trim–it really does tie a room, woodworking project or built-in project together. And, in spite of all the varieties available commercially, I recommend you make your own. There are three reasons using a router table as a trim-milling machine makes sense, the last of which is the substantial money the process saves. Trim quality and variety are more powerful motivations for me, and they’ll probably become yours too. Give the mill-it-yourself option a try and you’ll never go back to store-bought. Crisp edges, smooth profiles, top-quality wood and unique designs all have a way of raising the bar on the projects you produce. Once you’ve reached a certain level, those qualities are not things you’ll want to give up. The key to good trim, of course, is getting the details just right–starting with wood preparation.
Making your own trim is the closest you’ll get to an industrial process in your workshop. And like all industrial processes, this one needs consistent inputs. In this case, wood strips need to be created with a specific width and thickness, with perfectly square edges. At first, your trim might look OK even with slightly inconsistent strip sizes, but eventually this error will catch up with you because profiles won’t meet properly during installation.
Most of the trim I make is relatively small (ranging from 1„4″ x 3„4″ to 1″ x 21„2″) and used as part of a layered approach that couples one moulding profile with another. Even if you choose to mill larger trim, the need for accurate stock preparation remains the same.
Although you can use a tablesaw to prepare stock for milling into trim, a jointer and thickness planer make it faster, easier and more likely that you’ll succeed because of the consistency these machines impart to your wood.
I always start by jointing one face of my trim stock flat. Then I create a 90° edge along an adjacent side with another set of passes over the jointer. Next, rip your stock to width on the tablesaw. Be sure to make extra strips to be used for machine set-up and to replace any installation blunders you may commit.
The thickness planer really is the ideal tool for the final sizing of trim blanks. It’s more accurate than sawing strips, and it creates a smoother surface. Just be careful. If you’ve jointed your trim blanks, it’s key that you complete the initial planing passes with one of the jointed faces of the wood resting against the planer bed, not one of the sawn surfaces. Look closely as you feed your wood into the planer, since planing with one of the sawn edges down against the bed could ruin the all-important square edges you have created on the jointer. Once you have all sawn edges planed smooth, however, it doesn’t matter how the trim blanks are fed into the machine. Continue planing until the strips are sized correctly for the trim profile you’ll be milling. Are your trim strips narrower than 1„2″? Check out “On the Edge” (below) for more planing tips.
At the Router Table
Although you can use just about any style of router table for milling trim, the shape of the top and the design of the fence are critical. The top must be flat or slightly convex, never dished. A dished shape causes the trim strip to rise and fall relative to the router bit as the wood is being milled, and that’s a huge problem.
As the leading end of the strip first encounters the cutters, the wood is in full contact with the “valley” at the centre of the router tabletop. But as the end of the strip slides farther along, it travels up the side of the valley, causing the middle part of the strip to move up along with it before sinking back down again as the trailing end moves down the dished side to the centre of the table. Dished tops create inconsistently routed profiles that rarely meet properly at mitred corners.
Use a carpenters square or jointed piece of wood to determine how flat your router tabletop really is, then adjust if necessary. Wooden shims placed in the middle of the top before its ends are fastened to the support base with screws can sometimes pull a dished top flat.
Featherboards are another essential part of milling trim because they support each strip firmly as it slides along, ensuring consistent routing action from one strip to the next. You’ll know a good fence and tabletop by their ability to accommodate a lot of featherboards. At a minimum, you’ll need one on both the infeed and the outfeed sides of the fence–pushing trim strips down tightly to the tabletop–and another pair on the infeed and outfeed sides of the top–pushing strips against the fence as they slide. That’s at least four featherboards in all for small and medium-size strips. Add another pair of strips on the fence if you’re working with large stock.
The adjustment of a featherboard’s position is key. But before that happens, you need to install the bit you’ll be using, then position and lock the fence in its final location. I find it helpful to mill the first few inches of one trim strip at this stage, to help me get the height of the bit and the fence location just right. Routing just the end of a strip like this allows me to keep my fingers well away from the spinning cutters.