Routing mortice slots

Pond · 18 Dec 2012

Hi,

I am about to explore the wonders of making loose tenons :?

Before I start wasting lots of expensive timber, I was thinking of the best way to produce accurate and repeatable mortise slots with a router.

Is there any reason why I shouldn't do them on the router table? I don't have to make a jig for plunging, I would only have to place stops on the table for the width, which is simple.
It's starting them that concerns me. Is it sensible to position the timber over the cutter, wind the cutter up to start the cut, increasing the depth in small increments whilst the router is running (I have an easily accessible fine height adjuster)?
I realise that I would have to clamp the workpiece to the table to start and then remove or loosen any clamps to run the workpiece along.
Is this too complicated and should I just bite the bullet and sort a jig out for plunging them?

any thoughts gratefully received.

ta

siggy_7 · 18 Dec 2012

You can do them on the router table, but that doesn't mean that you should. If you must do them on the table, then the technique I've seen is as follows:

1. Mark the start and end of the mortice slots on the router table, either by drawing on it or by making marks on some masking tape
2. Set the fence width to centre the mortice on the work
3. Bring the bit up to the first cutting depth
4. Turn on the router, and line up the work with your first mark. Then, pivot the work up so that the leading edge is in the air, bring it against the fence, and lower it down on the bit to start the cut. Push along until you reach your second mark, then pivot the trailing edge up and remove the work away from the bit
5. Step up the cutting height and repeat until you're at the required depth
6. Adjust the fence and mark positions for each mortice

The problem is usually that you don't cut one mortice - for a frame, you're usually making at least four if not eight joints, which will likely require the fence and mark set ups to be adjusted right several times. Then there's the repeated height adjustment of the router to stage each cut as well. My experience is you'll get better results a darn sight quicker with a jig and a hand-held plunge router. I would recommend a few scraps with slots for a guide bush if it's a one-off custom job, or making a decent jig otherwise. It won't take long or cost a great deal to make.

SurreyHills · 18 Dec 2012

I think ziggy is right you are better making up a jig - it's safer and is a lot less hassle. This type of joint is best done by taking the router to the wood rather than the other way round.

Steve Maskery · 18 Dec 2012

The technique described above is called "dropping on". It does work, but it's not without risk. It's also difficult to do with small workpieces.
I use a pair of mortice cheeks in my vice. They have locating stops and travel stops. The router cannot wander and they are quick and easy to set up, my fingers do not get close to the cutter and it is easy to do identical parts and mirror image parts. It doesn't take long to make and doesn't cost much either. A couple of Bristol levers, sliding nuts, some plastic laminate and I have a Rolls Royce of a jig that will be a joy to use.
S

mseries · 19 Dec 2012

I use a very simple slot template and guide bush for mortices with my router like siggy_7 suggests. Here are some pictures in my flickr page http://www.flickr.com/photos/mseries12/ ... 552602471/ Router table method worked, two side fences does too but neither is as easy, quick or repeatable as a simple temple in my opinion.