Okay, I've been away for a while, but it's time to return
...as I just got to make the concave!
I thought I will put together a little DIY write-up for those who might want to do their own concave as well.
Let's get started then...
As material I have used a piece of a broken cutting board. It's nice solid wood. (It was nearly unused when it broke so it has absolutely no contamination nor smell or anything.)
You can of course use almost any type of wood, but avoid the plywood kind of materials (they can be dangerous for the featherless chicks because of the prickles).
At the next step we mark our material with the desired size. (I was lucky, only had to make one cut.)
This is the saw I used. It's a hacksaw, but it was a good choice for this solid wood; and it also gives a nicer cut then a regular handsaw.
So let's cut them wood!
(It may be necessary to take away the burr from the wood after the cut.)
Now we've got to decide where we want to place our concave. As I have the entry hole on my nest box on the left I will place the concave to the opposite side. (it only makes any difference if your nest box doesn't have the same width on both ends - mine box is also hand made and it's a little wider on one side - also the cutting board broke that way)
Although it's not necessary yet it's a good idea to mark where the hollow should be "milled" and what diameter it should be.
It's time for the interesting part.
I have used this go' old angle grinder; with the shown disk.
If you have the opportunity, do this part outside - it makes a lot of dust. Use safety glasses!
You should have a good grip on your material before you start to work on it with the angle grinder.
(If you are not familiar with the angle grinder I also strongly recommend you to read after the way of its safe handling - it's a dangerous tool! You don't want to hurt yourself or anyone around you.)
I got a good vise to use, but you can use simple clamps too.
Now, you should take away the material little by little, otherwise the wood may catch fire. Take your time.
This is how it looks like when it's done.
As you can see I didn't do a precise job here; while it's not like me, my birds won't mind anyway
so to make it nicer would've been pretty much just waste of effort.
Alternately, you can use carbide burrs in a drill or in an air die grinder instead of the angle grinder. But then you will need to refine the surface with sandpaper.
I hope this helps.
All comments are welcome! I don't mind to alter the wrire-up according to your comments.
This was the first time I made concave. In fact I'm not 100% positive that the depth of the hollow is ideal.
Anyway the hen who got to use this concave has all three of her eggs right in the middle of the hollow.