David DeCristoforo
07-06-2009, 1:07 PM
I made this mortising jig many years ago and it has served me well. A number of people have commented on it so I thought I would share it here. It is very easy to make and very easy to use. The file is too big to upload so I have linked to it.
http://www.daviddecristoforo.com/Misc/mortice_jig.pdf
Mine is made from a piece of 5/8" thick clear lexan. The base of the jig replaces the router's sub-base. I have an "original" Elu plunger that I use for mortising but any plunge base router should work fine.
The dimensions are not critical, nor is the size of the bearings. What is critical is that the distance from the center of the collet to the center of each of the bearings be the same. I attached the piece of lexan to the router first by drilling and countersinking for the mounting screws. Then I mounted a 1/2" straight bit in the router and plunged it through the base. Next. I removed the sub-base and used the bit hole to lay out the location of the bearings. I drilled and tapped the base for two "allen" bolts and attached the bearings with thin washers between the bearings and the base. That's it... it's done!
To use this jig, you only need to set it on the edge of the stock and rotate it until the bearings contact the sides of the stock. (The jig will make the mortice in the center of whatever stock thickness you use it on.) Then plunge and rout away.
There are a few "limitations" to keep in mind:
First, the distance between the bearings will determine the maximum stock thickness that can be morticed.
Second, since there are no stops, you must control the length of the mortice "by eye". But since the base is clear, it's easy to see a pencil mark. Of course you could clamp some end stops to the stock but this would be somewhat "fussy" and defeat the simplicity of the whole thing.
Third, you cannot cut a mortice too close to the end of the stock because if the bearing "falls off" the end, you have a problem. If I need a mortice very close to the end of the stock, I "work around" this by not cutting stock to final length until after the mortice is milled.
Fourth, Because the jig "automatically" centers the mortice in the center the stock, you need to attach a shim to one side of the stock if you need to offset the mortice.
This is a very simple jig to make and use. I recently used it to mortice the stiles and rails for twenty six interior doors. It works just as well on ends as it does on the edges. In use this jig is surprisingly stable.
http://www.daviddecristoforo.com/Misc/mortice_jig.pdf
Mine is made from a piece of 5/8" thick clear lexan. The base of the jig replaces the router's sub-base. I have an "original" Elu plunger that I use for mortising but any plunge base router should work fine.
The dimensions are not critical, nor is the size of the bearings. What is critical is that the distance from the center of the collet to the center of each of the bearings be the same. I attached the piece of lexan to the router first by drilling and countersinking for the mounting screws. Then I mounted a 1/2" straight bit in the router and plunged it through the base. Next. I removed the sub-base and used the bit hole to lay out the location of the bearings. I drilled and tapped the base for two "allen" bolts and attached the bearings with thin washers between the bearings and the base. That's it... it's done!
To use this jig, you only need to set it on the edge of the stock and rotate it until the bearings contact the sides of the stock. (The jig will make the mortice in the center of whatever stock thickness you use it on.) Then plunge and rout away.
There are a few "limitations" to keep in mind:
First, the distance between the bearings will determine the maximum stock thickness that can be morticed.
Second, since there are no stops, you must control the length of the mortice "by eye". But since the base is clear, it's easy to see a pencil mark. Of course you could clamp some end stops to the stock but this would be somewhat "fussy" and defeat the simplicity of the whole thing.
Third, you cannot cut a mortice too close to the end of the stock because if the bearing "falls off" the end, you have a problem. If I need a mortice very close to the end of the stock, I "work around" this by not cutting stock to final length until after the mortice is milled.
Fourth, Because the jig "automatically" centers the mortice in the center the stock, you need to attach a shim to one side of the stock if you need to offset the mortice.
This is a very simple jig to make and use. I recently used it to mortice the stiles and rails for twenty six interior doors. It works just as well on ends as it does on the edges. In use this jig is surprisingly stable.