# Concrete Anchor Tips for Machines and Other Applications



## CalgaryPT (Apr 25, 2019)

After posting my Railing Project this week and completing installation, my neighbour came over and vented his spleen about concrete anchors and how much he hates them. Wow. Did I get an earful. I think he had decades of bottled up frustration against the "wedge anchor lobby," or "wedge anchor crooks," or some other Alex Jones type of conspiracy he thought was out there.

Anyways, after letting him vent, I gave him my tips on using these, which I thought I would add here as an addendum to the project. I don't have any pics as I use these tricks every time now and haven't had any issues in years because of them. I've secured lots of metal working machines and other stuff using them, and had to remember my mistakes from years ago, but think I got it all down....

GOLDEN RULE: NEVER HIT THE NUT. IT DOES NOT PROTECT THE THREADS. This is especially true on cheaper anchors. Only occasionally will this work, despite the manufacturer's instructions. The situation you get yourself in is the threads get damaged and you either end up not being able to get the nut back on or you can't get it off. Both are bad because the wedge is not fully engaged yet (you haven't tightened it down), so you can't force the nut on or off even with an impact wrench...the anchor just spins in the hole and enlarges it.

Here are a couple of better options/tricks I have learned, and two backup plans if you've already messed up and your threads are damaged:

1) TIP 1: If your application allows, utilize a longer anchor than needed (by about an inch, still allowing for the manufacture's minimum penetration depth—usually found on the package, but often about 1 5/8"). Next, pre-attach the structure to the wedge anchor, including washer. Use TWO nuts. Keep them close to each other at the top of the anchor, BUT NOT TOUCHING. The bottom nut will be used to secure the structure, and the top one is the sacrificial one you bang on. This way when you ruin the threads (which you will) from hitting it with your hammer, you have the second (lower) nut as a backup. This nut tightens down on the structure if the top one you banged on wreaked the threads. You just cut off the extra 1 inch as well as the nut with an angle grinder/cut off wheel, or hacksaw.

2) TIP 2: This works in all cases, including applications where you can't pre-attach the structure to the wedge anchor. Do not put ANY nut on the wedge anchor. Instead, place the anchor in the concrete hole and use a piece of softwood or plywood on top of the wedge anchor you are hitting. Plywood, such as 3/4" works well, as does a 2x4 if you have room to maneuver it in your application. Bang on the plywood. The wood protects the threads. After 6 or 7 hits your sacrificial wood will break apart—but then just move on to another part of the wood. The anchor will make a hole in the wood and you will have to wiggle it off but it will not damage the threads. DO NOT LET THE WOOD BREAK APART OR COMPRESS SO MUCH THAT THE HAMMER CONTACTS THE ANCHOR OR THE THREADS. This compresses the anchor and damages the threads from the top. Do not use a hardwood as even this can damage the threads (these anchors are not hardened to the degree you may think, maybe a Rockwell C25 or so).

3) TIP 3: Threads you have already damaged. You can't get the nut off (because you pounded on it with a nut on) or you can't get the nut to thread on for the same reason. Worse yet, you can't force it off or on because there is not enough friction between the anchor and the concrete yet, due to the fact that it hasn't been tightened down and the wedge part of the anchor remains unengaged.

This is a problem. You can't use ViseGrips to hold the anchor as this will further damage the threads. A thread file, or even a mini thread chaser like a NES rarely fits in close quarters—and dies just spin the anchor. But instead of cutting it off all together and starting over with the whole project, get out your Dremel Tool. Use a metal cut off wheel. The Dremel wheels are slightly thinner (0.04") compared to full size cut off wheels so you can get it in between the threads and cut off the anchor cleanly. A regular cut off wheel in a grinder that is about 1/16" can't usually get in between the thread and will melt/damage other threads. Check first to see where the thread damage has occurred and cut below this slightly, leaving enough thread to hold the structure you wanted to secure originally. You should be able to cut the anchor and still thread a nut back on. Don't use a nut you banged on already—you likely damaged it when you hammered on it. Use a new nut and it should thread back on. If not, cut one more thread and try again. This is another reason why using an longer anchor than necessary can save you if things go bad.

4) TIP 4: This is the nuclear option; it's not always practical, and has to be planned ahead of time. When hammer/rotary hammer drilling, if not super inconvenient, try to drill through all the way, even if you don't need to. This is only practical/economical when the recommended depth of penetration (about 1 5/8" for a 3/8" wedge anchor) is close to the thickness of your slab...say, double the depth of penetration. Beyond a 3 or 4 inch slab it's just a waste of carbide bits, unless the placement of the structure you are attaching is mission critical. You can feel the progress of the bit and sometimes you just "get in the zone" and the drilling is easier, so you might as well continue. The reason for doing this is if everything goes bad and you can't recover, your last resort (assuming you haven't already tightened the anchor in place) is that you can hammer it out the other side with a long punch and re-try with a new anchor.

Although higher end rotary hammers (not hammer drills) can use special 4 fluted bits designed to cut through rebar, you'll be there a long time trying to drill out an actual anchor and will wreak the hole diameter anyways.

My two cents. Good luck.


----------



## YYCHM (Apr 25, 2019)

Can you post a pic of the anchor you're talking about.  You lost me.


----------



## CalgaryPT (Apr 25, 2019)

Sorry...was trying to do a brain dump before I forgot all this stuff. Here are the anchors, and a pic of them attached in concrete. They are super useful devices for attaching machines to concrete shop floors. In illustration #3 on the instructions you see them telling you to hit the nut—which is the source of many problems I was brain dumping on....


----------



## Tom O (Apr 25, 2019)

I heard one the other day on a Brit forum they said to use a plate to hold the anchor and use a impact to pull the anchor closed then remove nut and plate.


----------



## Tom Kitta (Apr 25, 2019)

I found using concrete screws very convenient & faster. They are not as strong as large size anchors but plenty strong for small projects. 
https://www.confast.com/technical-specifications-for-tapcon-concrete-screws

As you can see sheer and pull out per screw is all > 500 lbs. So 4 screws for a small balustrade is plenty - well over 2000 lbs of strength. Pro-tip is use screws with hex top - you need plenty of torque to drive them in. Also some rotary hammers are way too powerful for small diameter drills - take it easy or get it bent.

I remember anchors from rock climbing - actual anchors with a special clip on ending are used for bolts.


----------

