Legacy Milling Jig
When I built the newel posts featured in another article on this website, I was faced with making over 20 cuts on each piece. The pieces were too big to switch in and out of the machine, and the cuts needed to be as close to exact as possible on each one. In other words, while the actual dimension was not all that important, the same dimension at the same place on all nine posts was.
This article describes a jig I designed and built for my Legacy milling machine. As with just about anything at this point of human development, it was not designed in a vacuum, and I cannot take full credit for it. I combined ideas from two other Legacy owners who are acquaintances of mine and produced a jig that is fast, easy to use, and accurate.
The problem was, I needed to be able to make all of the 20 plus cuts on each post, and then repeat them on each following post. Doing some simple math, this worked out to over 180 cuts. Setting the depth for a rope twist or some such element is straightforward to a certain extent. Setting a bunch of depths over and over again in a reasonable amount of time wasn't, until I came up with this idea.
The idea is simple, and easy to implement. It requires a few careful measurements, but once they have been completed, the depth of any router bit may be set consistently and accurately any number of times. The first step was to make a thick wood board that attached to the bed of the Legacy. I made this by gluing a piece of ¼" plywood to a piece of 2" thick ash. Any wood will do, as long as it is reasonably hard and straight grained. Once the glue is dry, the assembly is attached to the bed of the machine with cap screws and locking plates.
This is a shot of the jig base attached to the machine. Once the blank is attached to the machine a bottom cleaning bit is installed in the router, and is VERY carefully set so that the bottom of the bit is EXACTLY in line with the center of the bed. In other words, the bit is set at exactly zero diameter - no higher, no lower. Once I was satisfied that I had the bit as close to zero as I could get it, I milled a shelf on the jig. The size of this shelf is not critical, but I made it big enough that it would be easy to use with any bit I planned on using.
Here is a closeup of the jig base after milling.
The second step was to select a board of straight grained hardwood which was think enough to meet all of the diameters I was using. In actuality, it only needs to be thick enough to meet the raduis of any diameters being used. If you can't find anyting thick enough, lamination is always an option. I used solid wood since it was going to be machined to various thicknesses which needed to be dead on.
I ripped various thicknesses on my table saw, concentrating on the thicknesses I would need for this specific job. Others could always be added as needed. Each piece was labelled and cut to fit within the milled portion of the jig mounted to the machine. Please note: Each thickness represents the RADIUS of any profile, not the diameter. For example, a 1" block will yield a diameter of 2" on the workpiece.
Stacked set up blocks in the cabinet.
This shot shows one block in the jig for setting the depth of the router. This block will yield a diameter of 3". It is very simple to use. Put the block in the jig, install the desired bit in the router, plunge the router until the bit comes in contact with the block, and set the stop rod. It's done. By doing a little bit of math, depths may be set very accurately, even for curved profiles such as roundover bits, etc. All one needs to know is the diameter of the workpiece and the various dimensions of the bit to be used. It is important to remember though, that the depth is gauged by the bottom of any bit installed.
As with anything else on this website, if you want to use this idea please feel free to do so, but please use common sense as well. If you have any questions, feel free to write me.
