A center punch is a tool with a pointed end that makes a dimple in your piece of material right where you intend to drill a hole.
A center punch mark accomplishes two things:
- It gives a physical resting place for a drill bit so it stays right where you want your hole to be
- When you begin drilling, the recess of the dimple relieves pressure from the flat tip of the bit (the "chisel tip" or the "web".) This prevents bending, chipping, breaking.
- Consider center punching a REQUIREMENT for making holes in metal with drill bits
- Use a center punch for bits up to (arguably including) 1/2" in diameter.
For larger bits ( > 1/2"):
- make a center punch
- drill with a bit the size of your intended bit's chisel tip (this is called a "pilot hole")
- drill with your intended bit.
For this demonstration, I'm drilling a hole in a piece of mild ("hardware store") steel. Well, in the interest of full disclosure, I'm making a corner bracket. :)
And, naturally, I did all deez workins at Techshop Detroit! www.techshop.ws
Step 1: Tools
L to R:
- Ball peen hammer
- Solid steel center punch
You may be familiar with the "hammerless", spring-loaded centerpunches. I don't generally like to use them with metal because you can't control the force of the blow - the spring exerts the same force every time - and because if/when the spring breaks, it's useless. I don't mind them for softer materials like wood... But this is how I like to get the job done.
A Ball peen hammer (notice the ball "peen" or face to the left) is a good all-purpose hammer for a metal shop. You're going to use the flat face to make blows on your center punch, which will inevitably mark up the face. Those marks will transfer to whatever softer material you hammer next so... dedicate this hammer for general mashing/banging/tool-hitting purposes.