My Store:
Change Store
  • CMT Pattern Following Bit

CMT Pattern Following Bit

Making The Template

The thing that takes the most time when setting up to make a quantity of identical components is making the original pattern. It has to be accurate, smooth and durable. If you take the time with your pattern, the work produced at the end will need less finishing and less adjustment to fit together.

When making templates, draw your designs onto plywood (I find 12mm- 15mm thickness works well). It‘s a matter of cutting out the pattern almost to the line using either a bandsaw, jigsaw or fretsaw. I then use a combination of planes, spokeshaves and sandpaper to shape any curved lines and smooth out the edges. Once I am happy with my template, I move on to the solid material that my project will be made from.

A pattern following bit (Fig.5) is fitted with a bearing that follows along the edges of the template. The cutter underneath will repeat on the workpiece, whatever the bearing comes into contact with. If there are any bumps or inconsistencies in your template, they will show on the edges of the finished component.

Using The Template

Trace your pattern from the template onto the timber you’ve chosen for your project (Fig.1). Cut it out leaving 2-5mm of timber proud of the line. This will depend on the timber being used. Leaving too much material will mean your router bit will have to work hard to remove the excess. Cutting too close to the line could mean you might not remove saw marks or leave enough room to adjust your pattern.

I have chosen to use my router hand-held with a pattern following bit that has a top mounted bearing so my template is facing up (Fig.2). I can more easily see the line that the bearing has to follow. Choose a bit that is slightly longer than the thickness of your work as it will give a smoother cut. Check that the bearing on the bit is in good working order, tightly fastened and the right size for the pattern bit you are using.

Fixing the template to your work can be done in several ways, screws, tacks or my current favourite, double sided carpet tape (Fig.4). It holds things really well and is reasonably easy to remove. Clamping is a straight forward affair but you will need to raise your work off the bench or route over an edge and move your work and clamps around.

A couple of things to keep in mind when routing are grain direction and end grain. Either of these can cause problems, particularly grain running against the direction of the cut. It can tear out and leave an ugly problem to sort out. A climbing cut (backwards cut) will help reduce tear-out when you are forced to rout against the grain. This is a potentially dangerous operation and I wouldn’t recommend doing it unless you are very experienced with router usage. NEVER do a climbing cut on a router table.