Woodworking joints and machines

[Tim Watts]

I was bored the other day (= putting off awkward job!) and was musing on my shed I might build next year from scratch.

I was considering some of the joints, in particular, the birdsmouth joint at the base of the roof rafters[1] to wall timber.

Now, my sliding compound mitre saw would manage one of the two cuts (the steep angle short cut).

But I've never seen such a saw that can cut much more than a 45 degree cut by tilting the cutting head - in fact if it could the piece would probably foul the head and the depth of cut would be too great.

OK - so how do people do cuts like that, especially when you need lots all the same fairly accurately?

All I can think is good jigsaw or handsaw (latter obviously the way it used to be done).

It might be something one could make a guide plate for the jigsaw shoe thus getting quick and repeatable cuts.

Or is there a clever way?

[1] and just to complicate things, I'm rather taken by having a gambrel roof - it would look different to the average workshop...

[Chris J Dixon]

Well that is something new I have learned. I hadn't realised that a true mansard is hipped.

Chris

[Tim Watts]

That's what I thought until I googled for mansard (because I couldn't remember if it was Mansard, Mansell or something else).

I *could* make the shed from Amytiville ;->

It does have the advantage of looking less boxy, having a lower roofline (shed, so this is important for PP reasons) whilst still having good headroom.

I notice in some construction plans I found that it does use seem to use nearly twice the structural timber of a normal pitch roof due to all the extra braces though.

[Chris J Dixon]

I think Mansell has a rather different approach to corners.

Chris

[Andy Dingley]

Handsaw usually, particularly softwood. Handheld circular in 12" oak.

If you want accuracy, Japanese ryoba saw

[dent]

I've just done 10 of these for my extension. I used the mitre facility of an SCMS to cut as far through as I could from each side, bringing the blade as close as I could to the inner corner of the birds-mouth without overcutting. In the corner the cut depth will obviously not be full thickness, but it's an easy job to just finish off with a panel saw which will be guided by the rest of the cut.

dan.

[Tim Watts]

see- that does look a most interesting device.

Thanks Andy - font of all knowledge as usual - I've learnt something :)

So knowing a handsaw is a common approach, the best thing (for me) might be to make up a cutting jig from two bits of ply screwed to a 2" spacing batten with slots to guide the saw. That would ensure quick setup and repeatability.

[Tim Watts]

Yes, I see. Presumably, your SCMS goes to > 45 degrees on the mitre? Sadly, mine doesn't.

Or do you make a wedge for the fence?

[John Rumm]

The traditional way it to start with a pattern rafter - then use that to mark all subsequent ones.

Decent jigsaw was the way I went. With an aggressive blade and some pendulum action you can chop lumps out of 4x2 (or whatever) at a pretty high rate.

[Tim Watts]

Ah - that seems like a good approach.

I might use this as an excuse to buy a decent jigsaw with a stable foot plate.

Ta

Tim

[Tim Lamb]

In message , Tim Watts writes

Umm... not tried it but how about clamping a set of rafters together, tacking on a softwood guide and using a hand held circular saw?

regards

[Tim Watts]

Ah, the quick way - mass production :)

[dent]

Ah yes. 57 deg so just about okay for a 38 deg roof!

I do that sometimes. I've got a selection of wedges of different angles.

A recip saw might be another option. Same idea as a jigsaw but better able to tackle the thicker timber (although a better jigsaw than mine may be able to cope with 50mmm timber).

dan.

[dennis]

Band saw and a jig?

[John Rumm]

;-) you won't regret it. The difference between a jigsaw and what most people think of as a jigsaw is astounding.

Something like:

a 3 stage pendulum, it cuts fast, and the solid cast base plug decent mechanics mean its a smooth and precise as a sewing machine.

[Tim Watts]

>> With a 3 stage pendulum, it cuts fast, and the solid cast base plug

That looks the business - Think I shall get one :) Thanks for the tip.

[John Rumm]

Can be a bit cumbersome when you need to offer up one end of a 5m long rafter to the saw though! Taking the saw to the rafter is often easier.

[John Rumm]

>>>>>>> With a 3 stage pendulum, it cuts fast, and the solid cast base plug

Or for £3 more, you can have the special edition white one with the better ali carry case:

[John Rumm]

When I did my first workshop, I planned for a 30 degree roof. But when building it, it looked "wrong" (probably because you could see it next to the neighbours one), so ended up reducing it to 20.

The plan:

adaptation:

[The Medway Handyman]

> With a 3 stage pendulum, it cuts fast, and the solid cast base plug

Alleulah. Praise the Lord. Its a jigsaw Jim - but not as we know it.