I will get new photo’s to go on this page soon, but I want the right piece of timber to take pictures of! For now please see the YouTube video.
Timber needed (think in 2 logs but obviously can be one cut up) The BOX section is cut in Spindle mode i.e. grain along the lathe bed, and needs to be between 180 and 220mm diameter with a length of 220 to 250mm. The Top section is cut in BOWL mode i.e. grain across the lathe bed and needs to be as wide or wider than the diameter of the BOX section and slightly longer to give an overhang on the front.
BOX: On bandsaw cut a slice from the back, this will give a flat surface that can be used to mount to a tree directly or a plank which can in turn be fitted to the tree, this also gives a flat to sit on the drill press, which is very handy.
My Installers want a clean spot on the front as well as they are going to put numbers on the boxes they install in acrylic paint (presumably to help the postman!) That is also helpful in drilling the entrance hole, so I am taking a slice off the front too. BUT as a rule leaving as much bark on as possible is good as bark is pretty good habitat for all sorts of creatures, and in the case of Ash dieback not a problem as the danger is in the leaves not the bark or timber.
LID: Canny turners will aim for a bigger diameter log, cut it into 3 planks using the 2 outside ones as lids for 2 boxes and squirrelling the middle bowl blank away to dry for future projects, as long as it is > 20mm thick to provide the insulation needed and covers edge to edge with a small overhang at the front to protect the entrance from rain. It will make a good lid. The bark can be a pain as you will be needing to drive it on the lathe from the bark side, but it is only a very light bit of turning and it works.
Use Forstner bits to make a stepped entrance hole, The bottom of the entrance hole must be at least 125mm from the floor of the nestbox. If it is less, young birds might fall out.
Start with the 45mm make a step 3 to 5mm deep (after clearing the bark if you leave it on), then the 35, 28, and finally 25 drill on in to where the hollow will be.
BOX: Mount the box between centres, find your largest chuck jaws and cut a tenon on the base (opposite end to the entrance hole) to fit, alternatively put a Face plate on the end, but you are going into the grain not through it, and this is green wood, so if using a faceplate use lots of big screws and appropriate caution!
On top of the box you want a tenon to position the lid, as water doesn’t run up hill a tenon on the box and a mortice on the lid will keep the inside dry. Mark it out as big as possible, then transfer the measurements to the bottom of the lid.
LID: may as well do this now as you are still turning between centres, position the lid and mark the back of it, the centre for the mortice will be measured from the back edge, I would say about 5mm less than the centre of the tenon to the back edge on the box (gives wiggle room for the installers to fit a plank to the back or attach to a tree.) mark your centre and using the toolrest as a sight guide find where the corresponding drive point is that will allow the lid to sit square on the lathe.
It is not strictly required, but doesn’t hurt to make your mortice with a tenon to fit into the chuck later if you decide you want to shape the top. Remember because of the overhang on the finished piece you are cutting off centre and watch your lathe speed.
BOX: Hollowing, my method:- The inside hollow needs to be between 100mm and 150mm obviously it depends on the log. You will want between 20 and 30mm minimum wall thickness to keep the inside temperature right. So the usual rules of even thickness doesn’t split doesn’t really apply to this sort of thickness. Also the only reason to have a neck narrower than the inside is to allow for the top tenon, or for fun! I usually go for 90mm opening and aim at 120mm average inside guided by the timber of course.
How I start. I use a 50mm Forstner bit, this is bigger than my Jacobs chuck and allows me to drill the 180 – 200mm depth (leaving 20mm or more in the base) in one hit. Because of my workshop layout it is a pain to have to drill it in stages, but that would probably be the more sensible route! I then set to it with the Brother System 2 hollowing tool and hollow out the space I want. Nothing fancy, and it is important that the walls are not too smooth, fledgling birds will need to climb the wall to the entrance at some point, they like rough sawn timber not polished!
Final part: Drill some drainage holes in the bottom, I do 3 holes at 7mm which is more than enough but it makes me happy to put 3 in, If you have a pith line in the base, drill it out! Fit the top over the tenon (not a tight fit! Allow a bit for warping) and fix with a single screw.
So you have a draft free, dry space, the other thing that birds want is NO CHEMICALS! If you must put any preservative on your piece only put water based pet friendly stuff on the outside only, same as marking it with numbers make sure it is water based. Slowly decaying timber is a far better bird home than a highly polished and painted piece of sculpture, they don’t weigh much and it will take a lot of years for 20mm of Ash timber to rot out to the point a bird can’t stand on it!
If you get a problem with cracks then moss, mud, or if required PVA and sawdust will sort them out.
Being green timber, I then pack the nest boxes with shavings from the floor, fit the lid on and if I feel it needs it wrap the lid in cling film. The Installers can get rid of the shavings for me, and take the plastic off when fitting it to the tree, after that it is down to luck, but they shouldn’t be fitted on the sunny side of the tree, and this will be autumn so there is a good chance the boxes will survive the drying process.
Please Email me, or post on the facebook group any ingenious hollowing methods. Or any improvements to the process generally, I usually find many short cuts I could have used towards the end of a cutting run, often the day after I have cut the last piece!