keensailor said..
just for my understanding, how do you end up with perfectly flat surfaces on the different timbers to allow glueing effectively. Do you use a circular saw then a planer?
Providing your circular saw doesn't have too much run out it is perfectly capable of cutting timber that is more than adequate for making tillers.
If you use a thicknesser then it may be that the timber ends up too smooth and will not be "toothy" enough to provide good glue keying, so a certain amount of surface roughness with a belt sander is a desirable thing.
As I had mentioned previously any timber that is oily in nature will need a good wash down with acetone or appropriate thinners.
The glue of choice should be Resorcinol Resin, it weathers better than epoxies and doesn't soften with heat, but these days with the proliferation of epoxy glues it is getting harder to find stockists that carry retail quantities.