Conical Drilled Holes


Hello everybody,

My plan is to design a multilayer PCB with some conical holes on it.
Is it possible to design conical drilled holes instead of the classical cylindrical ones?

Thank you very much in advance,


You will need to talk to your manufacturer about that. I don’t think that something like this is part of any standard process. Be prepared that it will cost a bit more than a normal board. If you even find a manufacturer that is prepared to do it at all for you. (They might only do something like this if you buy a lot of similar boards.)

If your manufacturer offers such an option, you will need to talk to them how they want it communicated which holes should be conical. (and how exactly the holes should look like.)

A cheaper option might be to let the manufacturer drill a small pilot hole and make the finished hole yourself.


Are you talking about using a conical routing bit or a multilayer with different sized drilled holes on each layer of the stack?


Thank you for your replies.

@Rene_Poschl yes, I already tried to contact my manufaturer. They asked me for a simple design as an example for them to evaluate the feasibility of the process. Thus, I would need to design conical holes with Kicad.

@davidsrsb I would like them to use a conical routing bit to drill the whole stack of layers. Moreover, I would like to be able to specify the angle of the cone as well.

Thank you again!


Does this hole need to be plated? Routing is usually done as the final process and in that case you are just defining a position and keep out circles of appropriate size on each layer. The hard part is to control the plunge depth of the tool, not something the average PCB fab is used to doing.


@Gabriele_Borelli I have to ask, why do you want conical holes?


I assume LEGO mechanical interfacing.
It’s the only time this comes up ever, really.


KiCAD is a 2d tool. The only way to specify a conical hole generated with a conical bit is in the tool designation for drilled holes. There are no drawing features that would help to show the hole design more clearly.

The manufacturer might be asking for a 3D design or a much clearer description of exactly what is being requested. If you need 3D design, perhaps FreeCAD software could help.

Or maybe they are just asking for the 2d/layer design around it. It which case, just draw a simple representative design, and add a mechanical hole of the right surface radius. Leave as much clearance as you can since the manufacturer will be dealing with depth (Z) variation, in addition to X and Y variation. Make sure the size you use is unique, and specify that the hole of that size in the design is the conical hole.

If they are making the hole with a conical bit and vertical CNC, then your choice of angle will be limited to the bits available to the manufacturer. Hopefully you want all holes to be the same angle. If not, you’ll need to specify each as a different tool (which I think from KiCAD can be done as different sizes).

Good luck!


While Kicad only offers one diameter setting per hole, I don’t think you need a 3D CAD system for the task. Other EDA tools I’ve used allow to specify different diameters for the top and bottom layer (e.g. ADS).

Much in the same way you could define the conical holes using the Eco1/Eco2 layer for the different top/bottom diameters, but you will have to talk to the board house so they know what to do with that data.


A conical hole is likely to be made with a conical drill and the “conicity” is an inherent property of the drill used, such as in:

So my idea would be to specify a certain unused special drill diameter in KiCad and then tell your manufacturer which tool to use (and to what depth) for that particular hole diameter.