How is this done?

I need to pin some handles for which I would like to 'sink' the washers into the handle material, a bit like in the attached example.
How is this done? Simply drilling won't work because you'd get the conical shape of the drill bit.
Is there a special type of drill bit for doing this?

Look for a counter bore with the appropriate sizes.
You will pre drill the hole to the appropriate size,
the hole you drilled will work to locate the position for the counter bore.
Best done in a drill press with a depth stop set.


Attachment 160751

You need to drill the larger diameter hole first using a forstner bit, set to the proper depth using a drill press. The forstner bit will give you a flat bottom along with a cone shaped center (from the centerpoint of the bit). You can use the center cone as a guide for the smaller diameter hole and drill through the material. This system works for any size combination of countersink and through hole, and you can drill to any depth needed for your countersink hole.

I hope I explained that clearly enough...

Bradpoint drill bit will give you a flat hole.

Bradpoint
Attachment 160754

I've used loveless style fasteners that use a system like that. Personally I use piloted counter-bores like this. Attachment 160770

Not sure if the loveless style fastener is what you're thinking... Attachment 160771

This is what it looks like finished. Attachment 160772

But you could also use two bits, one to get the oversized hole started and another of the same size that is ground flat, this is what I used to do before using a counterbore.

There are also special bits for this available at knifemaker supply sites like Janz. They are made of a specific size rivet, and drill both the countersink and the hole for the shaft of the rivet at the same time. Given where you are, and the problem with shipping overseas, you are probably better off just going with forstner or brad point bits. They work just fine. Experiment with the depth of the counter bore on scrap wood first. Good luck - I'm sure the final results will match the rest of your excellent work.
PS
I see another reply posted the kind of drill I was talking about.

Thanks. Though location is usually not relevant. Shipping may be a bit more expensive but honestly usually it's only 10 $ extra which is peanuts really. And with the dollar being so low, it's usually cheaper to buy online and ship, than to buy locally.

Hi Bruno,
Yes - there is a special drill bit from the knife supply companies.They are designed for use with things like cutler's rivets, Corby Bolts, Acorn Bolts and Loveless fasteners.
The bit drills the thinner hole for the centre of the bolt, and is stepped up so the thicker part drills for the head of the bolt. You need to be sure to order the drill bit that matches the fastener you are using as they come in a couple of different sizes, such as 3/16" and 1/4", etc. The correct size gives a very snug fit. {don't ask how i know about that :o} You are best with a drill press as it needs to be dead straight/square to work properly, and you can set the depth guage to be correct. If you go too far there is no handle material held in place, and not far enough may mean you undercut the head when contouring your grips.
Regards,
Adam