Dan Cameron
06-29-2009, 5:41 PM
I was inspired by Matthias Wendel’s (www.woodgears.ca) shop built slot mortiser to try my hand at building a similar device, but with some differences. For one, I wanted to use wooden dovetails lined with uhmw tape as the sliding mechanism. Secondly, I wanted it easy to remove the router for other tasks, and I needed to be able to store the unit in a garage cupboard. The router comes off with four screws, the actuator arms come off with two wing nuts, and the whole vertical “tower” comes off with two more wing nuts to lay flat.
A dovetail slide exhibits a lot of friction if you try to actuate it with an arm which is some distance off the centerline in any direction so I couldn’t copy Matthias’ slick one arm actuator. The two levers work ok for woodworkers with the same number of arms. Actually, there is enough friction one can use one arm in an alternating fashion.
Matthias’ turns counting mechanism is clever, but I bought a 50 cent wooden ruler and put a cursor line on the edge of the router mounting plate. The handle on my crank moves in and out, out to allow cranking and in at an exact position to lock the shaft at an index position. Since I also used a 3/8-16 threaded rod, my cursor lines-up on the rulers 1/16 marks each revolution. It is easier for me to think inches rather than revs.
To tie the shaft to the router slide I used a chunk of HDPE, drilled and tapped as a “zero back lash” nut plate. This gives a nice amount of friction to hold the shaft at any angle if desired. It seems when you tap HDPE it does cut but it also stretches so you end up with an undersized thread which is perfect for this application.
It was the intent in using my mortiser to clamp it to a bench, so I built a little “outrigger” support to hold the other end of a long board.
The downside to building a machine with wood rather than cast iron is the fact that the wood is to some extent springy. So to keep the slot dimensions reasonably accurate one is advised to cut slots using small increases in depth and many passes. The good news is that a slot mortiser is really good at just that.
To make the angle (dovetail) cuts I used a precision ground steel bar that I have as a straightedge, clamped it to a piece of plywood (taking out the bow) and ran a router with a chamfer bit down each side. The downside is that the length of cut on my 45 degree bit is less than ¾ inches, so I used a 22-1/2 degree bit I had. 45 degrees would make it easier to minimize vertical “slop”.
The many fender washers you see are for making the dovetail gibbs adjustable. The gibb on one side of each slider is fixed and the other gibb is attached with screws, t-nuts, and washers, with a clearance hole. I chose not to add screws for adjusting the tension.
I am sorry to report that I have no plans available.
A dovetail slide exhibits a lot of friction if you try to actuate it with an arm which is some distance off the centerline in any direction so I couldn’t copy Matthias’ slick one arm actuator. The two levers work ok for woodworkers with the same number of arms. Actually, there is enough friction one can use one arm in an alternating fashion.
Matthias’ turns counting mechanism is clever, but I bought a 50 cent wooden ruler and put a cursor line on the edge of the router mounting plate. The handle on my crank moves in and out, out to allow cranking and in at an exact position to lock the shaft at an index position. Since I also used a 3/8-16 threaded rod, my cursor lines-up on the rulers 1/16 marks each revolution. It is easier for me to think inches rather than revs.
To tie the shaft to the router slide I used a chunk of HDPE, drilled and tapped as a “zero back lash” nut plate. This gives a nice amount of friction to hold the shaft at any angle if desired. It seems when you tap HDPE it does cut but it also stretches so you end up with an undersized thread which is perfect for this application.
It was the intent in using my mortiser to clamp it to a bench, so I built a little “outrigger” support to hold the other end of a long board.
The downside to building a machine with wood rather than cast iron is the fact that the wood is to some extent springy. So to keep the slot dimensions reasonably accurate one is advised to cut slots using small increases in depth and many passes. The good news is that a slot mortiser is really good at just that.
To make the angle (dovetail) cuts I used a precision ground steel bar that I have as a straightedge, clamped it to a piece of plywood (taking out the bow) and ran a router with a chamfer bit down each side. The downside is that the length of cut on my 45 degree bit is less than ¾ inches, so I used a 22-1/2 degree bit I had. 45 degrees would make it easier to minimize vertical “slop”.
The many fender washers you see are for making the dovetail gibbs adjustable. The gibb on one side of each slider is fixed and the other gibb is attached with screws, t-nuts, and washers, with a clearance hole. I chose not to add screws for adjusting the tension.
I am sorry to report that I have no plans available.