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johnjack11 03-10-2012 10:23 PM

Best drill bit for old concrete
Hi there,

I have found a lot of answers on this forum, and appreciate the great wealth of information here.

I am working on making a finished space in my basement, it is a 1925 home in Indiana. I put down xps foam on floor and on walls today, and then cut all the 5/8 osb to go on the floor.

I bought 400 ultracon screws, and started to drill the holes for them. The bits that came with the ultracon screws seem woefully inadequate. It could be that I have a really solid basement floor, but I am guessing the drill bits were just not good enough. The bits are lasting no more than two holes.

After I drill the holes I have been using a shopvac to clean them out, but it still does not matter. It seems like the bits wear out very quickly, and cannot get deep enough.

Can anyone recommend a good bit that will stand up to what I guess is very old/solid concrete. I don't mind paying extra for decent bits, there has to be something out there that will drill more than two holes without being used up.

I am using a corded hammer drill by the way, it just seems that certain areas of the concrete are really tough.

Thanks for the help,

princelake 03-11-2012 07:06 AM

A rotary hammer drill is key to drilling that old concrete and if the hole just isn't drilling start a new one because your hitting something that will just burn out your bit. If you don't have a rotary hammer drill cause the rotary hammer drill bits in your regular hammer drill. Also buy a good brand drill bit like hilti or dewalt.

Just Bill 03-11-2012 07:08 AM

Old concrete with lots of agregate can be hard on bits, and a good hammer drill is a must. Carbide tipped bits specifically labeled for hammer/percussion drills. Avoid anything made in china.

johnjack11 03-11-2012 07:37 AM


Originally Posted by Just Bill (Post 875196)
Old concrete with lots of agregate can be hard on bits, and a good hammer drill is a must. Carbide tipped bits specifically labeled for hammer/percussion drills. Avoid anything made in china.

I have a hammer drill, I think I must be just hitting something really hard in certain spots. I will just stop drilling those wholes and try again close by I guess.

Is there a brand that is much better than others? I will make sure to get carbide tipped ones. Anyway to resharpen those after they get dull, or do you just throw them out?

Thanks for the replies,

robs660 03-11-2012 08:35 AM

Hammer drill is drill is different then rotary hammer. A rotery hammer spins slower and hits harder with each impact. They will drill through very hard material quite quickly.
Here is a link to a good quality Bosch at a good price.

Hammer drills are known for burning up bits. They spin too fast and create too much heat

princelake 03-11-2012 10:53 AM

I've found the hilti ones to be the best. And there's no the carbide tip either wears or falls off. Regular bits you can sharpen them with a grinder and put it up to 2 nuts together giving you the correct angle or buy a bit doctor

jomama45 03-11-2012 11:46 AM

As stated above, a normal hammer drill relies on speed to get the job done, sometimes as fast as 3000 rpm. They have very little hammering/impact though.

A rotary hammer is quite the opposite, with far lower speed and far greater impact. As well, the SDS+ bits tend to last far longer than any generic smooth shank pecussion drill bit. Even though the SDS+ have a unique shank drive, they can still be placed into a standard chuck (as long as it's 1/2" cappacity) with a little trial & error, and will perform much better on both the speed of drilling & the lifespan of the bit. Wouldn't be surprised to drill all 400 holes with one bit.

oh'mike 03-11-2012 01:03 PM

I seem to get the longest life from Bosch bits---Hilti are top of the line also,but not available easily--Mike--

johnjack11 03-11-2012 03:10 PM

Great, thanks for all the replies.


johnjack11 03-11-2012 07:17 PM

Anyone ever use the Chicago rotary hammer drill at harbor Freight?

It would be about $60 for me after a coupon, I am not sure that I will use a rotary drill that much after completing this project.

I have had some chicago tools in the past, their multitool has been pretty good for me.

Thanks for the help,

robs660 03-11-2012 08:19 PM

I have the Bosch and I have used it more then expected. I would assume the Chicago would work well. Make sure it takes the sds max bits

joecaption 03-11-2012 08:59 PM

Chicago Tools are trash. I use a Bosch Bull Dog with SDS bits and can do a whole room with one bit. You can rent a Bull dog or a Hilti at Home Depot.

Use Tap Con brand screws and an Impact driver to insert the screws.
I use a Ryobi driver and Dewault impact ready bits.

PaliBob 03-12-2012 02:42 AM

1 Attachment(s)

Originally Posted by robs660 (Post 875671)
…. Make sure it takes the sds max bits

The OP is using Ultracon Concrete Screws (very similar to Tapcons) which come in a maximum diameter of 5/16”. For his application the SDS-Max is overkill. The cheapest Bosch SDS-Max hammer drill that I see is the Bosch 11240.

Most of the Bosch SDS Hammer Drills use just regular SDS bits which are also called SDS-Plus.
E.g. all five of the Bosch ‘Bulldog’ Rotary Hammer Drills are SDS-Plus

johnjack11 03-12-2012 08:38 AM

I found some good Bosch bits, and drilling the holes is no longer an issue with my hammer drill.

The ultra cons can be a pain though, and I wondered if the cheaper rotary drill would help with those. Quite a few screws have gone in just about all the way but will then not go far enough to sit just under/flush with the osb.

When I take them out, drill some more and then vacuum the hole again I can usually get them in. I have had to use 3 screws in some areas though. Not sure if it is a technique problem on my part or the hammer drill.

As much as I love good tools, I would prefer not to spend a lot on a rotary hammer, I just won't need it that much. I have a large list of materials to frame out the basement. Heck the xps foam and osb was $800.

I would buy the cheaper Chicago tool if people thought it might help with the screws, any advice on technique driving the screws would also be welcome.

Once again thanks for all the replies, this is a great sounding bouts for me.


PaliBob 03-12-2012 11:50 AM


Originally Posted by johnjack11 (Post 875939)
.... Not sure if it is a technique problem on my part......

Ultracon screws are almost the same as the more commonly known Tapcons but they have an impressive history.

It sounds to me that you are not drilling the holes deep enough, or the holes are not being cleaned enough.
From the TapCon Site:

The hole drilled with the bit should be 1/4" deeper than the Tapcon® depth at which the screw will be installed into the base material.

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