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Milling the PCB outline. What's the endmill diameter?

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pcb routing bit sizes

Folks,

What end-mill diameters fabs typically used for routing (milling) the outline of the PCB?

I have a PCB with an inside angle. I don't want to make an inside chamfer, as in the bottom-right drawing below. That would weaken the board mechanically. Instead, I want to make an outside chamfer on a mechanical part that mates with that inside angle. It doesn't need to be a close fit. I just want to have a sufficient chamfer radius on the mechanical part.

- Nick

**broken link removed**
 

end mill bit sizes

As with all things associated with board fabrication, the size of router bits used by the fab depends on their equipment and the thickness of the board.

In general, the preferred cutter size for routing is 3.175mm (0.125 inch) or 2.36mm (0.093 inch) diameter. Smaller bit sizes can and are used, but may cost more because the fab will have to slow the route speed to avoid bit breakage. The larger the bit you can get away with, the less the fab is likely to charge you.
 

end mill copper pcb board

In cases like this I prefer to insert a non plated drill into the layout in the corners of the cut-outs - this reduces the risk of the fab house getting it wrong.
 

end mill back chamfer

IRECAD said:
In cases like this I prefer to insert a non plated drill into the layout in the corners of the cut-outs - this reduces the risk of the fab house getting it wrong.
Click to expand...
That's the inside chamfer approach, as in the upper-left drawing. That's something that I don't want to do, because it will create a weak narrow "neck" in the PCB.
 

making a pcb milling bit

I understand where you are coming from & if the chamfer is too tight to be milled with a standard mill bit size the best case scenario is the bottom left image. When you design the mechanical part to fit into this cut-out you will need to factor in a maximum mill bit allowable for milling the PCB for the chamfer. You can of course put this max mill bit dia. into the fab notes but in my experience I found it better to add the Drill to the design that way at least if in future or of you change fab houses & they use a bigger mill bit (leaving more material in the corners) you don't end up with a PCB that has an interference fit to the mechanical part- that is where I'm coming from on this.[/quote]
 

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