Try making your own from the off cuts. They used to call them Trennals, or tree-nails.
You need a piece of steel plate about 5 mm thick. Drill a hole in it with a SHARP drill the same size as the dowel needs to be, or better still a TINY fraction larger. You need to preserve a sharp edge on the entrance to the hole. If you can taper it very slightly, 1 or 2 degress all the better, but it's not essential.
Select some straight grained offcuts about 6 inches long, cut or split them square a little larger than the hole, round the end and shave the edges. Then tap them through the hole to make your own dowels that match your work exactly.
I've found the dowel plate is really only good for short lengths; dunno what length you need, Adam? Also, depending on the grain of your blank the finish can be pretty rough. Fine for use as dowels, but not so good for dowelling. FWIW.
In that case I heartily recommend a dowel plate. It uses up all those off-cuts, and you don't have to depend on suppliers bothering to have the wood types you want any more. Plus it's fun pounding the wood through the holes...
>You need a piece of steel plate about 5 mm thick. Drill a hole in it with a SHARP drill the same size as the dowel needs to be, or better still a TINY fraction larger. You need to preserve a sharp edge on the entrance to the hole. If you can taper it very slightly, 1 or 2 degress all the better
It'll be ready on Friday to that exact design! 6 and 8mm. It's very handy having an on-site Engineering department, and an on-site WW shop with resident chippie.
In case you decide not to make your own, PlugIt sell hardwood dowel in lengths up to 915mm, in Oak, Cherry, Maple, Walnut & Mahogany, diameters from 6.6mm to 25mm. I haven't used them so I don't have any idea on prices etc.
As an after thought, assuming that the dowels are a snug fit in the hole, they will expand slightly when in contact with the glue.
This means that if the hole is blind, the air pressure in the hole will force the dowel out (through holes don't matter).
You will need to score a relief track along the side of the dowel longitudinally to allow air and excess glue to escape.
You can make a scratch stock to do this with holes drilled through a short piece of scrap and a screw with a sharpened point just protruding into it from the side of the wood so that when you force the finished dowel through it creates a groove. One or two grooves should suffice.
This is one of the reasons why commercial dowels are grooved.
I hope that this explanation makes sense.
All you need to do is drill out the tread so that it is a plain hole. Take a 3 square file or a flat hand file and using the corners file a 'V' shaped slot across all six corners of the nut.
This done cut your stock to size ( just over the hole diameter) and sharpen one end as if it was a pencil, the other end needs to be shaped to fit into your power drill.
Put the stock into the power drill and tighten. Place the Nut into a vise and tighten. Place the sharpened end of the stock into the nut from the slotted side, switch on and push. Dowelling as long as you want when you want.
I cut all my dowels using this method and have cutters in 6 sizes.