Loose Holes with Hilti SDS-Plus Rotary Hammer Drill

[Alan Lightstone]

Have a problem that I'm not sure of the answer to.

I have a workshop/garage that has almost entirely cinder block walls. When we bought the house, I knew I'd be doing a lot of drilling into the blocks, so I bought a very good rotary Hilti Hammer Drill.

The drill goes through the blocks with ease. Much better than my previous Makita (which was no slouch either).

The problem is, that many of the holes are slightly too large, and often, Tapcons are too loose in the holes. I've tried, at times, to use one size smaller drill bit, but it seems almost random when the holes are too big. I'm not drilling massive numbers of holes, just occasional use.

Is it a dull bit (It has happened with a few different sized holes, and I have replaced the bits)? Some other technique thing? Something I'm missing?

[Tom M King]

Try a lighter duty hammer drill. I have two that get the most use. One is an SDS-Max, that I use for holes starting at 1-1/8", for frostproof wall hydrants, and up in size. The other is a regular one with a standard chuck, that gets used for all smaller holes in masonry. It gets used for smaller holes, including ones into soft brick for anchors. I've never tried to use the big one to drill the small holes, but I expect it would be a little too violent to drill an accurate sized small hole.

The small one is the Bosch in the background of the tools on the chimney top. I last used it setting anchors in cinder blocks, and it worked fine.

[Mike Kreinhop]

I have a Bosch hammer drill for my heavy-duty concrete applications. However, I never use it for the German equivalent of the cinder block. I learned after a few botched attempts that the impact of the hammer drill was a bit too much for the blocks and tended to make larger holes and destroy the inner partitions of the block. Instead, I use a smaller drill hammer with a masonry drill to make the holes.

The difference between the hammer drill and the drill hammer is significant, mainly with the force of the impacts. It takes a little longer to bore a 10mm hole in the German blocks, but the plastic anchors fit snugly and don't pull out under load.

[Mark Bolton]

Best trick in the world when you get an oversized hole for a tapcon is to take a piece of 12 or 14 gauge copper wire (strip some out of romex or steal some ground wire out of romex) and cut a small piece, bend an small leg on one end (shape of an L) and stick one leg in the hole and run your tapcon. Will save you every time.

Often times in ripe cinder block the holes will oversize a little bit. Other than taking a diamond wheel on an angle grinder and grazing the edges of the carbide on the bit there isnt a great solution if your drill/block is consistently drilling oversized.

The copper wire trick works like a charm every time

[Gregory King]

Alan, I worked in the university buildings for most of my career. Brick on the outside applied over concrete blocks. No doubt, we've drilled a good many of these. We found the best solution was the soft lead anchors. 1/4 " or 5/16" x 1.5" long. Then use the appropriate screw. Never had an issue after that

[Tom M King]

I really like these Greenlee anchors, and their setting tools. The tool sets the anchor as flush with the surface as you want it, and not at all dependent on the hole depth, as long as you drill it a little deeper than you acturally need it, so they work in through holes too. The setting tools aren't cheap though. They come in a bunch of different sizes.

[Tom M King]

I use little, round rare earth magnets to locate exactly where a hole needs to be. The one on a piece of masonry ductape, in the earlier picture holds the place over the threaded insert. Roll one around the outside, and it will find the one on the inside. Need another marking method for steel boxes though-headless machine screw, and lipstick.

[Alan Lightstone]

Tom:

I can't quite get my head around how those Greenlee screw expanders work. Can you explain?

[Ryan Yeaglin]

Using an SDS type drill for tap-cons is like using a sledge hammer to pound in 4 penny finish nails, WAY over kill, they work great if you want to your drilling concrete for wedge anchors or the like. A battery drill or corded drill with hammer function is all you need. Me personally I don't care for Tap-cons and prefer many of the other style anchors mainly because tap -cons strip out and are very picky about the hole diameter. Plastic insert anchors work well for mounting elect rial boxes and the like, Drive style anchors (drive rivets) work well and only require a 1/4" hole, the lead expanding anchors work, but require a large hole. If it's going to be a heavy application, I would suggest through drilling and using a 3"x3"x1/4" flat-bar wall plate with thread rod.

[Tom M King]

You screw the threaded rod into the insert, and stick the whole assembly in place, with the insert in the hole. The knurled knob is just to operate that screw. With it in place, you tap the outer end of the knurled knob with a hammer which pushes the lead sleeve down around the harder inside part, that includes the dovetail end, expanding the lead sleeve without moving the threaded part, locking it in place. To finish, you use the knurled knob to unscrew the treaded rod, which removes the installer, and leaves a REally secured threaded insert in place. They are very strong.

I think they come in sizes from no. 10 up through 3/8". I bought all the installers off ebay over a long period of time. They don't give those to you.

The one you use a simple tool to pound the insert in the hole need a closely correct depth on the hole, and also are easily screwed up in the process, and you need a range of fastener lengths to fit in different hole depths. With these, you know what length fasteners you can use to start with, and they will work in a through hole as easily as they do in something solid.

I believe Greenlee calls them "caulk in anchors".

edited to add: Greenlee calls them "caulking anchors", so I was close. These tools use the same anchors as this simple pound in the bottom of a hole tool. but do a much more precise fit. https://www.greenlee.com/us/en/caulking-anchors They call the tool a "screw expander".

Best found used, on ebay: https://www.amazon.com/Greenlee-868-.../dp/B001SGP1I6

[John Lanciani]

Using an SDS type drill for tap-cons is like using a sledge hammer to pound in 4 penny finish nails, WAY over kill, they work great if you want to your drilling concrete for wedge anchors or the like. A battery drill or corded drill with hammer function is all you need. Me personally I don't care for Tap-cons and prefer many of the other style anchors mainly because tap -cons strip out and are very picky about the hole diameter. Plastic insert anchors work well for mounting elect rial boxes and the like, Drive style anchors (drive rivets) work well and only require a 1/4" hole, the lead expanding anchors work, but require a large hole. If it's going to be a heavy application, I would suggest through drilling and using a 3"x3"x1/4" flat-bar wall plate with thread rod.

Ive installed literally 1,000’s of tapcons into poured concrete by drilling with an SDS rotary hammer and setting the screws with a cordless impact driver and I’d peg my failure rate at less than 2%. The issue here is the block, they tend to be coarse and fairly fragile if drilled in the cores. Setting anchors into the webs solves most of the problems but is not always possible.

Tapcons are one of those things that people either love and rely on or they hate them and have bad luck. I’m not sure if it’s technique, tooling, or just plain mojo. They are always my first choice for light to medium duty anchoring in masonry.

[Frank Pratt]

A rotary hammer is sometimes overkill for cinder block. Because it's so soft, the relatively violent hammering action of the rotary hammer just makes for a bigger, sloppier hole. Try turning off the hammer action & see how it does. The drilling will be slower, but the block is so soft that it will still drill it fine.

[Charlie Knauer]

Check and make sure the masonary bit is not bent. The bit for a TapCon is not that big in diameter and will bend easily.
I have noticed guys at work setting the drill down bit first. It don't take much to bend the bit.

[John K Jordan]

I didn't get to read all the posts. Are these "cinder" blocks? I use a bit SDS hammer drill for concrete but never for cinder block unless it's filled with concrete. For cinder block I use a carbide masonry bit in a non-hammer drill.

JKJ

Have a problem that I'm not sure of the answer to.

I have a workshop/garage that has almost entirely cinder block walls. When we bought the house, I knew I'd be doing a lot of drilling into the blocks, so I bought a very good rotary Hilti Hammer Drill.

The drill goes through the blocks with ease. Much better than my previous Makita (which was no slouch either).

The problem is, that many of the holes are slightly too large, and often, Tapcons are too loose in the holes. I've tried, at times, to use one size smaller drill bit, but it seems almost random when the holes are too big. I'm not drilling massive numbers of holes, just occasional use.

Is it a dull bit (It has happened with a few different sized holes, and I have replaced the bits)? Some other technique thing? Something I'm missing?

[Bruce Wrenn]

Seldom do I use TapCons by them selves. My weapon of choice is to use Alligator brand anchor sleeves. Drill hole for correct size, then use either TapCon, or screw to do fastening. For real fun, try fastening into masonry blocks that were frozen while wet. They have absolutely no strength, just crumbling beneath fasteners, or drill bits.