Rob continues with his coffee table project
The joints in the side rails need some holes cut and there are a multitude of different ways to chop them out. Over the years I’ve tried nearly all them from early attempts with a big ‘pig sticker’ chisel and lignum maul through to a dedicated morticing machine.

They all work and they all produce nice, reasonably rectangular, oblong holes in fairly smart time. The catchword here though is ‘reasonable’ because no matter how hard I tried, the edges were always a bit ragged, like a series of drunken saw teeth that have had a night on the tiles, which is fine in most cases as the edge is going to be covered by the tenon shoulder.

The ragged edge, where it’s going to be seen, as in this particular application, causes a bit of an issue as it’s got to be as smooth as the first time you ever saw Sean Connery in Dr. No!

The only way to get round this ticklish little problem is to cut the mortices with a router, which is easy enough and then square out the holes with chisels, which takes a lot longer.  There have been loads of methods developed to cut mortices with a router, using all sorts of fancy jigs and double fences but they’re all a waste of time because all you really need are a few packing pieces and a couple of decent cramps.

Morticing set-up
Morticing set-up

The set-up needed is shown in the pic above.

The real problem is the dreaded ‘router wobble’, where the base hasn’t got enough area to rest on. The piece being mortised is placed along the edge of the bench and an identical piece (usually another leg or rail, as in this case) is placed parallel to it. Note that as the mortise is going straight through, there’s a packing piece underneath, otherwise the bench top is going to look like a Swiss cheese. Then get hold of two biggish lumps of ply which act not only as cramping blocks, but also as ‘stops’ for the router travel. Set the router up, plunge in and traverse a few times. Always taking shallow cuts and the first mortise is shown, with the second one arrowed.

First mortice
First mortice

Reset for another cut and it doesn’t take too long to cut them all out.

Four mortices
Four mortices

The tenons finish just shy of the line and they’re then made square with chisels, which is a bit of a time-consuming palaver. The outside rectangles are also made longer by around 2mm to allow the wedges to expand into the joint, meaning that the end grain slopes inwards.

Sounds complicated? Worry not, it is, but all will be explained.

  • Simon P

    I cut my first ever mortises this past weekend so I’m happy to see how someone else has approached this task. I used a Lie Nielsen mortise chisel in Southern Yellow Pine (SYP) but found that the distinct difference in hardness between the early and late wood in SYP caused me some trouble. The softer wood being easily damaged and the harder wood occassionally encouraging me to use a level of force, and therefore lack of control, that was not appropriate in the adjacent softer wood. While recognising that this was only my first attempt at mortising with a chisel and that I could do with more practice I feel that a high speed tool such as a router would have been a better approach on my SYP. What put me off using the router in the first place, apart from noise and dust, was the perceived necessity of constructing or buying a jig for mortising so it’s good to see that Rob has been able to make do with a much less formal approach to using the router for mortising. I’ve read that a spiral up-cut bit is best for cutting mortises using a router, am I on the right track and what has Axminster got in terms of suitable router bits?

  • Rob Stoakley

    Good to hear from you Simon and I have heard tales of woe and wailing about SYP, although it’s not a timber I’ve ever used. Any material with alternating bands of dense, hardwood and soft mushy stuff is always going to be difficult to work with…there’s a perception that softwood ‘per se’ is easier to work with but it’s simply not the case. However, by stack laminating it and re-sawing you can (in theory) turn it into something far more manageable, which might, if the readership is interested, be the topic for a further AxBlog?
    I’ve found that over the years using a router suits me better than a dedicated mortiser or indeed chopping the things out be hand, as the router provides the accuracy and precision that I require for the sort of work I do. Yes, they are noisy but a decent pair of ear muffs soon sorts that out. Apart from that, the router is such a versatile bit of kit in the ‘shop it’s the one power tool that I simply couldn’t do without. Robert Ingham, one of my woodworking heroes also uses a router to sort out mortises and the quality of his work is beyond compare.
    Spiral cutters? In theory, yes, but if the mortise is cleaned out every couple of passes I’ve never found a problem, so I just use a standard plunge cutting bit of which there’s a good selection on the site.

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