Stair Rail - Mortice at an angle

[Ian Bond]

Hi

I'm attempting to re-introduce the attic stair rails in my house. A previous occupier has discarded the original rails, leaving an un-guarded opening.

Here's a plan view of my proposed design - 4 posts and 3 pairs of rails that will be mortice and tenon jointed to the posts.



The opening isn't square, so the posts marked A & B are out of line, and the rails must meet these posts at an angle. The shoulders of the rail tenons can be angled to meet the posts.

The problem is that the mortices will need to be cut out at an angle too. I've never tried this before and I will need to be accurate. I've only ever made (reasonably) square things with M&T joints at 90 degrees.

None of my text books show angled M&T joints like this either, so any advice on how to cut a mortice at a precise angle would be gratefully received.

Many thanks

Ian

p.s.
The stairs are more of a ladder, and anyone climbing them risks bashing their head on the tie beam (which could explain a lot about me). The awkward configuration of the stairs means I'm pretty well stuck with the posts in the positions shown.

 

[Nigel Watts]

Ian

I faced the same problem not long ago when making a piece of furniture which had mortice & tenon joints at strange angles.

I found it easiest to cut a conventional mortice (ie one with sides at 90 degrees to the the surface) and to angle the tenon. Becasue the tenon is sawn to scribed lines rather than chopped out it is easier to get it accurate. Your drawing shows the opposite - a straight tenon and an angled mortice.

Nigel

 

[skier-hughes]

Practice with some old softwood first.

I think Nigel's suggestion is perhaps the easiest route.

Graham

 

[Ian Bond]

Hi Nigel

Thanks for that -it sounds like an excellent plan.

I did consider it but got it into my head that the tenon would be weaker, but I could be wrong here. I'm trying to:

a) make the stair rail as strong as possible
b) make the job as difficult as possible for myself (as usual)

The posts are 2 3/4 ins square and the rails 1 3/4 by 2 3/4.

Many thanks for the suggestion, I will give it a go. It does sound so much easier to cut the tenons on the angle than drill and chisel the mortice.

Cheers

Ian

 

[Ian Bond]

Thanks Graham, too. Good idea, best to get the angles right on some off-cuts, instead of ruining a good bit of wood!

I'm reusing some old pine for the rails, and having to buy 3 of the posts, which will be from 75x75 PAR redwood - and I'm going to paint them.

 

[worms]

If you really do want to make things as difficult as possible, presumably the best way to cut an angled mortice would be on a router table with a jig of the correct angle? This would give you the added work of making a router table and a range of jigs!

 

[Ian Bond]

I like it Worms!

Ha - but I'm compromising enough by using a power drill to make lighter work of chopping out the mortice.

Usually I insist on hand tools only!!!!

 

[worms]

Ian, I admire the approach but unfortunately I need the mechanical assistance to cover up for my deficiencies in skill and finesse. The idea was uppermost in my mind as I'm half-way through making a router table for myself out of an old kitchen worktop and a cheap work-mate bench.

 

[Nigel Watts]

Chopping mortices by hand can be a pretty satisfying experience. The key thing is to have a chisel of the same width as the mortice, and preferably a good old-fashioned one with a very thick, heavy blade and oval section handle. These are not only more robust but they are less likely to twist as you are working.

I always used to clamp my work to the bench before chopping, but this is not necessary. If the cuts are made vertically the work will not move so no clamping is needed. The thing to watch, especially with softer woods, is that no chippings get between the workpiece and the bench otherwise they will bruise the surface when you deliver the next whallop with the mallet.

 

[biffvernon]

I'd go for a straight tenon and angled mortice. If the tenon were angled it would be weaker as you would be cutting across more of the grain.

 

[Nigel Watts]

I used angled tenons in a base for an English elm table I made recently and they proved perfectly satisfactory, but I agree that an angled mortice is stronger. If the angle is not large the loss of strength should not be too great; dovetail joints rely on the wood not shearing along the grain, and they are pretty strong.

 

[Ian Bond]

Thanks Biff.

I did wonder about that, as I would be cutting across the grain on the tenons.

As this rail is guarding an open well, I'd like it to be as strong as possible.

If I do angle the mortices, the only way I can think of to get them at the correct angle is to fix a batten to the post as a (sight) guide for my drill.

 

[Ian Bond]

And thanks Nigel, too.

I just couldn't make up my mind which way was best - your suggestion is the easiest in terms of getting an accurate angle on the rail, and Biff's suggestion would be stronger but harder to do (for an amateur like me).

The tenons will only be 1/2 inch thick and 2 3/4 wide, and perhaps not the strongest.

Hmmm - I think I'd better practice on some scrap wood first - It'll give me something to do this weekend.

Thanks again

Ian

 

[worms]

Ian, you tell us that the job is for the attic stair rails AND that the joint needs to be strong because it protects an open well! You've got to be the only one on here with a well in the attic!

 

[biffvernon]

Must be a stare well, not a treacle well.

 

[worms]

...and perhaps I should think well before posting!

 

[Ian Bond]

Ian, you tell us that the job is for the attic stair rails AND that the joint needs to be strong because it protects an open well! You've got to be the only one on here with a well in the attic!

Ha! Yes, it's probably something to do with the leaking roof!!!

 

[Penners]

Ian

Just for the hell of it, here's another idea. Do the square stocks at the top of each post have to have vertical faces? If you were to cut the "upstream" and "downstream" faces to the angle of the rail, you could then cut a simple, straight tenon on each end of the rail, and a mortice at 90 degrees to each face of the stock.

Just a thought.

David

 

[Ian Bond]

Thanks David,

I see what you mean, and it would work

The thing is I'm trying to copy the next door neighbour's stair rail.

I've got a lot of respect for the skills of the joiners back in the days when the house was built. They'd be laughing their heads off at my attempts to replicate these missing bits of the house.

When I've done it, I'll stick a picture up on the forum!

Cheers

Ian

 

[Penners]

And how about a photo of "work in progress"? Pictures of skilled artisans practising their trade are very appropriate to this forum.

Go on - I dare you! :wink: