Project Information
I put this together today. In the past when I've used the router to cut a pattern, I've either attached the pattern to the workpiece with double-stick tape, or I've built an oversize pattern with a toggle clamp so that the pattern becomes a jig. Double-stick isn't cheap, and can leave gummy stuff, and building a custom jig for every part results in a lot of jigs hanging around never to be used again. I needed to do some pattern routing today, and thought it was time to do it differently!
This jig allows me to clamp the pattern and workpiece together, and the jig can be used for any number of different patterns. The pattern can go above or below the workpiece, depending on which kind of bit I'm using. I put two handles on it for good control, and left the ends open so pattern and workpiece length wouldn't be restricted. I think it should also work for holding small pieces during routing operations.
The handles, cams, and fence are oak. The baseplate is 1/4" ply and can be replaced when damaged. The jig is 12" long.
[EDIT] Forgot to mention … a series of holes is drilled in the fence to raise and lower the cams so the jig will accept different thicknesses of stock/templates.
-----PLAN ADDED 11/14/2007-----
There seemed to be a lot of interest in this jig, so I'm putting up a few drawings and instructions to help along anyone who decides to build one. You may want to adjust the size of the jig based on the templates you usually use. I tried to duplicate my table saw throat plate and found that my jig was a little too long.
First things first -
Hardware! I've had no end of frustration discovering that the hardware I had planned to use for a project was not in my shop and the hardware store was fresh out. For any project - find your hardware first! I used machine screws with wing nuts for the cam pivots and wood screws for assembly.
Construction -
Handles (2): The handles just need to be a place to hold on and they need to set the fence at 90 degrees to the base. A couple of triangles would work, but I like to make my jigs comfortable to hold and use. I've found this shape comfortable for my smallish hand:

If your hands are largish, you could increase the 3¾" and 4¼" horizontal measurements and the 2.125" radius by ¼" or so. I made my handles out of 3/4" oak, but have used ply and melamine in the past. MDF might work, but I don't know how well it will hold the screws. If you use wood, the grain should be oriented horizontally. Roundover both sides of the finger hole and the grip area.
Cam levers (1 LH, 1 RH): Cams can be made with an increasing radius, but I just make mine round and drill the pivot hole off-center.

The cams on my jig are 3/4" oak, but ply will work fine. Melamine and MDF are not up to this task! Wood grain should be oriented along the length of the cam lever. Drill the pivot hole so the bolt fits snug - too much slop and the cams won't stay tight against the workpiece. Countersink the hole for the bolt head. When countersinking, the hole should be right of center for one cam and left of center for the other cam - this will give you one RH and one LH cam. NOTE The cams in this drawing are 1", but I recommend that you increase this dimension to 1½" or even 2". This will help prevent the cams from loosening with vibration.
Fence: I used 1/2" oak, but ply or melamine should be fine.

Again, drill the holes so the bolts will fit snug. By staggering the holes, you get a pretty fine adjustment for just about any thickness of material.
Base: 8" x 12" x 1/4" ply. This base plate is sacraficial - it will get cut up and chewed up as you use the jig. When it isn't providing the necessary support any more, just cut another one.
Assembly -
Handles to Fence: Clamp the handles against the fence one inch from each end of the fence. Drill and countersink two holes through the fence into each handle and insert the woodscrews (see diagram below).
Fence to Base: Turn the base plate upside down and set the handle/fence assembly on the inverted base. Trace the outline of the handle/fence assembly onto the bottom of the base. Turn the base over and clamp the handle/fence assembly to the base. Using the lines you just traced, locate and countersink one hole into each handle and two holes into the fence taking care to avoid the screws that are holding the handles to the fence.

Cams to Fence: Pass the machine screws through the cams and through the fence, and secure them with the wing nuts. By switching the cams from side to side, you can make them tighten either by lifting by pressing down the handles.
I hope this is clear, but if you have any questions, please feel free to ask.
This jig allows me to clamp the pattern and workpiece together, and the jig can be used for any number of different patterns. The pattern can go above or below the workpiece, depending on which kind of bit I'm using. I put two handles on it for good control, and left the ends open so pattern and workpiece length wouldn't be restricted. I think it should also work for holding small pieces during routing operations.
The handles, cams, and fence are oak. The baseplate is 1/4" ply and can be replaced when damaged. The jig is 12" long.
[EDIT] Forgot to mention … a series of holes is drilled in the fence to raise and lower the cams so the jig will accept different thicknesses of stock/templates.
-----PLAN ADDED 11/14/2007-----
There seemed to be a lot of interest in this jig, so I'm putting up a few drawings and instructions to help along anyone who decides to build one. You may want to adjust the size of the jig based on the templates you usually use. I tried to duplicate my table saw throat plate and found that my jig was a little too long.
First things first -
Hardware! I've had no end of frustration discovering that the hardware I had planned to use for a project was not in my shop and the hardware store was fresh out. For any project - find your hardware first! I used machine screws with wing nuts for the cam pivots and wood screws for assembly.
Construction -
Handles (2): The handles just need to be a place to hold on and they need to set the fence at 90 degrees to the base. A couple of triangles would work, but I like to make my jigs comfortable to hold and use. I've found this shape comfortable for my smallish hand:

If your hands are largish, you could increase the 3¾" and 4¼" horizontal measurements and the 2.125" radius by ¼" or so. I made my handles out of 3/4" oak, but have used ply and melamine in the past. MDF might work, but I don't know how well it will hold the screws. If you use wood, the grain should be oriented horizontally. Roundover both sides of the finger hole and the grip area.
Cam levers (1 LH, 1 RH): Cams can be made with an increasing radius, but I just make mine round and drill the pivot hole off-center.

The cams on my jig are 3/4" oak, but ply will work fine. Melamine and MDF are not up to this task! Wood grain should be oriented along the length of the cam lever. Drill the pivot hole so the bolt fits snug - too much slop and the cams won't stay tight against the workpiece. Countersink the hole for the bolt head. When countersinking, the hole should be right of center for one cam and left of center for the other cam - this will give you one RH and one LH cam. NOTE The cams in this drawing are 1", but I recommend that you increase this dimension to 1½" or even 2". This will help prevent the cams from loosening with vibration.
Fence: I used 1/2" oak, but ply or melamine should be fine.

Again, drill the holes so the bolts will fit snug. By staggering the holes, you get a pretty fine adjustment for just about any thickness of material.
Base: 8" x 12" x 1/4" ply. This base plate is sacraficial - it will get cut up and chewed up as you use the jig. When it isn't providing the necessary support any more, just cut another one.
Assembly -
Handles to Fence: Clamp the handles against the fence one inch from each end of the fence. Drill and countersink two holes through the fence into each handle and insert the woodscrews (see diagram below).
Fence to Base: Turn the base plate upside down and set the handle/fence assembly on the inverted base. Trace the outline of the handle/fence assembly onto the bottom of the base. Turn the base over and clamp the handle/fence assembly to the base. Using the lines you just traced, locate and countersink one hole into each handle and two holes into the fence taking care to avoid the screws that are holding the handles to the fence.

Cams to Fence: Pass the machine screws through the cams and through the fence, and secure them with the wing nuts. By switching the cams from side to side, you can make them tighten either by lifting by pressing down the handles.
I hope this is clear, but if you have any questions, please feel free to ask.