Router jig design

[Kirk Amidon]

Have an upcoming project - table with round legs, which calls for routed mortises for the stretchers. In my head, I had thought about a jig that ran on rails above the work, upon which a plunge router would be held in order to route the mortises. In looking for examples, it seems that everyone has gone 90* to that idea, and placed the router horizontally. It seems that by using a fence, one can control the cut depth. Since I'm now leaning this way - wanted to check my assumptions - very important to get the router 'cradle' level. Need ability to raise and lower it easily as well. Thinking to start with a 1" metal shaft welded to a small square to attach a wooden base for the router to slide on. This assembly would fit into the banjo. I might start with a wooden prototype as I have some dense hardwoods.

If it matters, these legs will be cylindrical where the mortise is cut, and will taper below them. Also, they will be cut at 60* to each other, as it will be a triangle table. The router body is a PC 690.

Any other design criteria or gotchas I should be aware of?

 

[john lucas]

Both ways work. The advantage of having the router above is its weight of the router helps control the cut. If you have a tapered piece it becomes more difficult to build the jig. However you dont need to build a carriage for the router.
Using a platform on the banjo is much more versatile but requires you to build the platform and a carriage for the router.
Using a top mounted router you can build guides to cut odd shaped or larger mortiss. Things like dovetail or butterfly inserts are easy.
Using a platform with guides allows you to follow curved pieces such as running flutes down an ogre shaped turning.
If you have more questions feel free to ask. I've done a lot of routing over the years.

 

[Tim Hunter]

I'd pursue your original thought - I've done it before. One advantage of doing so is the ability to set a guide rail on each side to control the width of the slot using the better practice of cutting with a bit of smaller diameter than the mortise.

Another option is...(as I often say)...a patternmaker's lathe!

 

[john lucas]

here is th box I built for my lathe many years ago. If I was building another it would be a box within a box so I would have some height adjustment as well as tilting one box to accommodate tapered legs.

 

[Don Wattenhofer]

Are the legs splayed or straight up and down? Are the stretchers round? Are the tenons round or rectangular?
If the tenons are round make a jig to hold them in the proper orientation for the drill press.

 

[Kirk Amidon]

Are the legs splayed or straight up and down? Are the stretchers round? Are the tenons round or rectangular?
If the tenons are round make a jig to hold them in the proper orientation for the drill press.

Round legs, not splayed, tenons will be approx 1/2" wide by 2" long/tall.

 

[Doug Rasmussen]

In my pre-CNC days we had a jig similar to what John Lucas posted. At the ends it fit in the gap of the lathe bed. No need for metal construction, we used Baltic birch.

 

[Don Wattenhofer]

Round legs, not splayed, tenons will be approx 1/2" wide by 2" long/tall.

The simplest would probably be the box above the work piece on the lathe and the plunge base if you have it.

This is one that I dug out of a corner: it is made to fit on a PM90 and the side upright was meant to be used with an extra wide base to flatten an area of a large spindle turning. The concept is the same you would just add a board across the top with a slot as needed for the guide bushing. The plunge base or a plunge router would help tremendously. The 60 degree spacing can probably accomplished using the indexing built into many of the lathes using the Chinese castings.

 

[Gerald Lawrence]

I built a platform based on some of John's early posts on using router on lathe. The rail is a piece of angle . Note this is for straight cuts and the platform has the capability to slide in and out. It is then bolted to the lathe.

 

[Darryl Fective]

I haven't done this kind of project, but my first though was can the mortises be cut while the stock is still square?

 

[Kirk Amidon]

I haven't done this kind of project, but my first though was can the mortises be cut while the stock is still square?

If there were going to be 4 legs, and therefore 90* between legs, yes it could be cut while square. Then the thing to watch out for is tear out around the mortises, but that can be worked around with a lightly glued filler piece. For this project, the stretchers will be at 60* angles, so it will be much easier to mortise after rounding.

The plan is to leverage the indexing on the lathe to provide the angle, and make a jig to hold router, either with a plunge base if I follow Don's model, or in a holder like John's version. The patternmaker lathe idea is also quite intriguing, just for the gismosity factor, but most likely way out of scope.

 

[Don Wattenhofer]

if there were going to be 4 legs, and therefore 90* between legs, yes it could be cut while square. Then the thing to watch out for is tear out around the mortises, but that can be worked around with a lightly glued filler piece. For this project, the stretchers will be at 60* angles, so it will be much easier to mortise after rounding.

To make it work besides the tear out problem the turning blank would need to be perfectly square and perfectly centered for turning on the lathe.

 

[Don Wattenhofer]

Whatever you do get yourself a down cut spiral router bit to prevent splintering the edge of the mortise.

 

[Larry Copas]

Doesn't everybody have a Bridgeport milling machine and indexer? If not you should get one.

Kidding aside, the process is the same whether it be on the lathe, shop built jig, or a......Bridgeport. For a mortise I would use something that holds the router in a vertical position just because you have a larger size router. I do have a couple of jigs that hold the router horizontal but these are for small trim style routers.

 

[Don Wattenhofer]

View attachment 51844
Doesn't everybody have a Bridgeport milling machine and indexer? If not you should get one.

Kidding aside, the process is the same whether it be on the lathe, shop built jig, or a......Bridgeport. For a mortise I would use something that holds the router in a vertical position just because you have a larger size router. I do have a couple of jigs that hold the router horizontal but these are for small trim style routers.

That looks like the column for a pedestal table like this.
This is the one I made long before I had my Bridgeport and if I remember correctly, I used a router jig similar to the one in my post with the work piece in my 12" Delta lathe with the indexing on the edge of the 4-step pully.

 

[Larry Copas]

Yes, it is a column for the Shaker candle stand first made by the Shakers in the mid 1800's. The leg joint is called a sliding dovetail or sometimes a French dovetail.

For the curious, I put the top on the lathe to turn the bullnose as I did not have a router bit with that exact profile.