What kind of drill do I need to easily drill holes into the cement sub-floor of my house (for a flooring project)? I've already tried two different types of masonry bits with my cordless, 18 volt Bosch (model 3850). I'm thinking that the bit isn't the problem, it's the drill. It takes about 10 minutes and a way too much effort just to drill one hole. Any suggestions?
A Masonry bit is what you need You also need the correct drill. It is called a hammer drill. As the name implies it hammers while rotating. The hammering is necessary to break the small rocks embedded in the concrete. On small jobs and without a hammer drill I have used a metal punch to break any rock that prevented the bit from boring farther. Don't confuse the two common types of bits. One has three cutting blades on the face of the bit, use this one on brick. The one you need looks similar to a metal cutting bit and has two cutting blades on the cutting end.
I would go to a rental store and rent a SDS drill these drills are designed to drill concrete and will drill a 1/4x6 hole in about 30 sec.You will also need to get the appropriate sds drill bit . Also when you drill concrete drill a 1/2 then pull up on the bit then drill again and so on this will save your bits and drill faster the action helps the bit pull the concrete out of the hole. The rental for a sds drill in my area is 20-25 bucks a a day.
The previous answers are correct. Rent a good SDS bit hammer drill and it will drill your concrete as easy as sticking your finger in butter. You'll drill all those holes so fast you won't believe it. Those masonry bits used with a regular rotary drill are only good for drilling mortar joints or soft brick. As you already discovered, they are just not adequate for concrete. Actually, if you do a lot of your own work, a residential grade 120 volt DeWalt hammer drill is not that expensive and a handy thing to own. I have one myself -- it can be used on rotary or hammer settings.
You need to rent a Rotary Hammer and bit. Ask for an SDS rotary hammer if your holes are 1 or less in diameter. You need to rent the special bit that fits this drill. Ask for an SDS MAX Rotary Hammer if your holes are 1 or larger in diameter. You need the SDS MAX bit also. Now if you have a lot of deep holes that are about 1 go for the SDS MAX hammer as this drill is much heavier duty. Make sure you use a heavy duty extension cord 12/3 wire or larger, and try not to use a cord over 25' long. Let the bit and drill do the work, you should not have to push very much on the drill at all. Drill down a little then pull bit out to clean out hole, then drill some more. Regular hammer drills are about a thing of the past, they used metal to metal gears to provide the hammer action, you can actually hear the difference as the old type hammer drills scream when the operate. Your rental center will know what I am talking about. Note: There are some older Rotary hammers that are spline drive. They work fine, they just have a different kind of groove in the end of the bits, and an accomodating receptor in the hammer. Whatever Rotary hammer you get, rent or purchse the right bit for it. You cannot mix SDS , SDS MAX, SPLINE bits with other type rotary hammers. Ask the rental clerk to show you how to insert and remove the bits also. Good Luck
masonry bits are the correct bit. Buying a good carbide bit will work better than the cheap ones and last longer. Use a slower speed on the drill. You don't want the drill bit getting too hot, that will ruin the bit. Problem with drilling into cement is that it is full of gravel and the masonry bits don't go through gravel all that well. That's why they made hammer drills. Buy, borrow or rent a hammer drill, use a masonry bit designed for hammer drills and use a slow speed. If you are going for a large hole, it can help to start with a smaller bit and work up to the hole size you ultimately need.
