Proper drilling

Question

I was working on getting through the ceiling of my garage to install some eye-bolt lag screws to hang a boxing heavy bag.

I had issues finding the joists which was handled in: Finding ceiling joists overhead

In the process I realized that my drill bits may be insufficient.

I had a 5/16" eye bolt screw to install. First thing I needed to do was expose 5/16" through the ceiling so I can hit the joist. I started with a 5/16" dewalt masonry bit on a dewalt hammer drill. It did nothing. I then switched to a 3/16" bit (not sure what type, probably one of those multi-purpose ones) which worked fine. However, I still needed more space to push my eye screw through so I then switched back to the 5/16" bit to bust through the remaining width. It worked. However, I had to push hard and if i hit the wood, the drill bit turned red at which point I stopped.

I am looking for a good drill bit set to make the pilot holes (as small as possible) and find the joists. After that I need something to expose the wood. Not sure why masonry didn't work initially. Any recommendations on what to use? I assume hammer drill is correct to get through the ceiling. Picture below. Thanks!

Answer 1

Not all masonry bits work in hammer-drill mode; some are strictly for rotary drill use. I have a feeling you burned up the 5/16" bit by drilling at high speed. Heat kills drill bits, and for masonry, speed=heat; so, speed kills.

You should be able to drill numerous 5/16" holes with a single bit. Keep your speed (and pressure) down, stop to let the bit cool off occasionally, use water (if possible) to lubricate and cool the bit (this may be difficult when drilling overhead). And use the correct technique for the bit that you have (i.e. don't use your drill motor in hammer mode unless you have a hammer-drill bit).

Answer 2

I guess the ceiling in your garage is plasterboard. An ordinary drill bit for metal or wood would go through that in seconds. If you used a masonary bit of any kind to penetrate the wooden joist, it's no wonder it got hot. It's not designed for cutting through wood. and you certainly didn't need a hammer action for that.

Answer 3

Masonry bits are for hard materials brittle materials like concrete and well, masonry. Hey have an extra little piece attache to the end and the shank is thicker. They would best in hammering mode to chip at the material like a rock drill. They won't work drilling softer materials.

Wood bits are used for softer materials like, well, wood, and other materials like plastic AND drywall. These bits are used without the hammer mode and are quickly destroyed if used for harder materials.

As Jimmy Fix-it noted, HEAT dulls bits very quickly and is the reason for 'ruined' bits. They also will dull with use but this is happens over much longer time frames.

For dry wall (or plaster) and wood (your case) use a wood bit without the hammer mode