Paul Sellers talks a lot about precision and perfection; making the assembly jigs for the bird houses is an exercise in just that. The angles and measurements have to be exact; any errors in the jig will be replicated in the bird houses – and not just in the roof.
The jigs are my own creation and are the result of many attempts to figure out a way to clamp odd angles to the straight sides and ends of the bird houses. I’d searched the Internet looking for ideas on how to clamp weird angles and I tried several suggestions but they were all flawed or were too difficult to use or too slow. I guess my subconscious was working away for several days on the problem when it struck me that I was looking at things upside down – or I should say, I was looking at things the right way up.
The way I was assembling the houses was the way they would look, but trying to do a complex glue-up like that was far too hard and far too time consuming. I’m not sure where the idea to flip the houses upside down came from although, more than likely, it was on the loo – I seem to have my greatest epiphanies there – I’ll spare you any more detail on that though.
The first jig I built I did without any plan, just made a rough job and tried it out. There were a few bugs but the principle was sound so I started working on a ‘proper’ one. I decided to use 18mm MDF for a couple of reasons; it is perfectly flat and doesn’t suffer from movement and distortion with variance in humidity. Having said that I should also say I hate using it; it is easy enough to work but creates so much dust no matter how much extraction you have round the machines – and it doesn’t respond well to hand tools so I end up having to wear a dust mask all the time.
That first trial also showed me how important accuracy is in building jigs; the first one was a bit off but I honestly didn’t think it would make that much difference. It’s only when you start assembling all the pieces (that you have so carefully cut) that you realise how one inaccuracy leads to another – like some sort of freak domino effect – the problems compound until you end up spending more time correcting errors than you do actual building.
So when I started building my ‘fleet’ of jigs I made sure everything would be spot on from the get go. It is time consuming and frustrating; only because I consider this non-productive work – I’m not actually creating anything as these devices are just another tool; it seems like time wasted. To a point this is true but the time spent in this up front ‘spade work’ pays off later down the track – big time.
How accurate is accurate enough, as much as we would all like to be perfect with everything we do – it just isn’t going to happen. Having said that, the angles need to be within a fraction of a degree; now, you may think that is just crazy but keep in mind that a fraction of a degree over, say, a 100mm becomes significant when you are looking at a roof that may be 400 to 600mm (in the case of a dovecote roof) long. What you end up with is a gap of one or two or three millimetres between the end or sides and the roof – it looks bad and is really hard to hide. You try to correct that error by re-cutting the sides or the ends which means the base is out – and on it goes.
The photos will, hopefully, give you a guide on how to build your own; it is not as easy as it seems though. If you have an accurate table saw it is not so bad, a drop or compound saw is not really going to be precise enough without some hand planing and the same goes for hand cutting – it is possible but be prepared to employ some decent hand planing skills. The first couple I made were hand cut and planed and they were OK but the subsequent ones were all machine cut and they are certainly better.
Another piece of advice; don’t trust the scales or calibrated marks on your table saw. This is something I worked out after a while, I trusted the scales on the table saw but found the cuts were just not quite right. I think the reason is the number of variables in the position of the fence relative to the saw blade; this is why I now set the position of the fence by using an accurate square or digital angle rule and set the fence directly off the face of the saw blade.
I can’t stress enough the need for quality measuring tools like squares, Vernier calipers and digital angle rules. The square I use most is made by Colen Clenton; they are an Australian company that make the finest measuring instruments for woodworking in the known universe – but they are expensive (worth every cent in my opinion).
Hope this short blog helps when you are faced with having to glue-up weird angles; it seems so simple when I look at the jigs but assembling odd angles can be a real challenge. Many woodworkers poo-poo the idea of using jigs and I used to be one of them – but now – I’m converted; jigs are the go.
If you need any advice on making your own jigs please feel free to contact me.