Hardware and Tools - Printing in Plastic: Build Your Own 3D Printer - page 24

Figure 2-17. A transfer punch is helpful for marking centerpoints of drill holes.
Once you've marked the centerpoints using the transfer punch, the brad point bits (with their sharp
tip) will make it easier to drill on the exact centerpoint. Again, the punch and brad point bits are just a
recommendation; they're not required. But we think you'll find it easier to drill accurate holes with brad
point bits than standard spade or twist drill bits.
As for counterbores, you can also use standard drill bits. But we recommend the use of Forstner bits
shown in Figure 2-18.