Stud Guns

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jmellc

Senior Member
Location
Durham, NC
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Facility Maintenance Tech. Licensed Electrician
Worked on a job this week where we used stud guns to strap conduits to a ceiling slab. I had a lof of trouble with the pins blowing out the concrete. In fact, I have seldom had stud guns do well in older concrete, while I have had fair success in newer & less brittle concrete. We were using yellow loads and various fasteners with about a 1 inch pin.

What experience have others had?
 
I understand why people use powder actuated sometimes, but I really, really hate having to come in later to redo or upgrade and remove a panel or conduit straps etc. that have been shot into the concrete.
 
I dug up some other straps/pins and will try them Mon. If they still don't do well, I will drill and use plastic or lead anchors.
 
jmellc said:
Worked on a job this week where we used stud guns to strap conduits to a ceiling slab. I had a lof of trouble with the pins blowing out the concrete. In fact, I have seldom had stud guns do well in older concrete, while I have had fair success in newer & less brittle concrete. We were using yellow loads and various fasteners with about a 1 inch pin.

What experience have others had?
Click to expand...

lotta ricochet rabbits.....

the only gun i've got experience with that just sets stuff and
doesn't spall is the hilti dx-600, and that is a discontinued one,
and getting shots is iffy, as hilti doesn't support their stuff very
well.

it's a single shot, and slow as hell. sprinkies use them mostly,
for setting 3/8" threaded studs for fire pipe. they seldom blow out.

if working on old stuff, i'll use a milwualkee 12 volt hammer drill,
with the little pick up vac that goes with it. no crud falling down
on you, and it's fast... then i'll use wedge anchors and nuts or
rod couplings, as required.
 
PetrosA said:
I understand why people use powder actuated sometimes, but I really, really hate having to come in later to redo or upgrade and remove a panel or conduit straps etc. that have been shot into the concrete.
Click to expand...

Agree completely. I really dislike powder actuated fasteners. The pins often are terrible at actually securing the desired object nailed to the concrete, but getting them out is almost impossible. I find I often have to take an angle grinder with a cutoff disk to the pins to clean up a wall or ceiling when doing installs of new equipment. We've essentially banned them where I work, along with the lead anchors that you secure by driving the little steel pin with a hammer.


SceneryDriver
 
Fulthrotl said:
lotta ricochet rabbits.....

the only gun i've got experience with that just sets stuff and
doesn't spall is the hilti dx-600, and that is a discontinued one,
and getting shots is iffy, as hilti doesn't support their stuff very
well....
Click to expand...
Well you can tell how long it's been since I have shot anything into place. I had know idea they were discontinued. That stinks. They worked really good.
 
If you read the instructions for that fastener they will tell you how much penetration is optimal for that fastener. From there you can determine the length of the fastener you need. In attaching to concrete or masonry after the fact, it's all about depth of penetration.

Too much and you blow it out. Too little and it falls out.
 
mgookin said:
If you read the instructions for that fastener they will tell you how much penetration is optimal for that fastener. From there you can determine the length of the fastener you need. In attaching to concrete or masonry after the fact, it's all about depth of penetration.

Too much and you blow it out. Too little and it falls out.
Click to expand...

Even when you follow every direction and instruction to the letter there will still be concrete they will not work in.

Too brittle, to much aggregate or crappy aggregate are the common issues I run into in old buildings in my area.

There are buildings in Boston that have seashells in as aggregate. :roll:
 
For me it's always interesting to read up on any given subject matter.

After one month most concrete is cured to it's desired PSI strength.
concrete curing time chart

I'd be drilling and put in lead anchor or other metal attachments in aged structures.

I know I've blasted out concrete, I'd just shift the location and fire into
the edge of the broken area, It worked for me, but not always a good thing!
 
I agree every shot is not going to be perfect but I'v worked with a whole lot of concrete and my exerience is that it's all about the penetration. Too much penetration and it blows out; too little and it falls out.

Whether it's a power fastner, a hard cut nail, a concrete nail, a redhead too close to an edge, etc. there will be success and failure.

The manufacturer of that product wants it to work for you and they put forth great effort and expense into telling you how their fastner works best. They want you to fall in love with it and keep buying it. If you follow their instructions you'll have the best results.

As to cure time, when you hear of "2,500 psi concrete" that's a projected 2,500 psi compressive strength at 28 days. Concrete continually hardens even after decades of being in place. When we do test cylinders in the field and break them in the lab, we do 7, 14, and 28 day test cylinders plus one spare. When we break those cylinders at 7, 14 & 28 days, it's almost guaranteed that you're past your 28 day design strength at 14 days and often you're there or really close on the 7 day break. If you're working on what we call a threshold building in Florida (highrise, any building with 300 people in one room, and some other buildings) those cyliders are tested prior to removal of the supports for the formwork. Once that's done you're certainly good to go. As to connection failure due to concrete not being sufficiently cured, I haven't heard of that and if it happens I'm sure it's quite rare.
 
iwire said:
They don't hold but you can't take them out?

Pick a position, or are you a politician? :D
Click to expand...

They often don't sink in far enough to securely hold the device/box, but you can't pull them out to try again with a new fastener.


SceneryDriver
 
SceneryDriver said:
They often don't sink in far enough to securely hold the device/box, but you can't pull them out to try again with a new fastener.


SceneryDriver
Click to expand...

If the fastner went in as far as it's going to go, and it's in there such that you can't pull it out, yet it's not down against your box such that your box is wobbly, it is most likely that your fastner is too long.

It's all about the length of the fastner.

When choosing your length, take into consideration optimal embedment for that style of fastner (from the instructions) plus the distance from the face of the surface you're mounting on to the face of the surface which your fastner will be against (the thicness of the back wall of the box in this example), and add those distances together. The sum of these numbers is likely to not result in an exact match to lengths which the manufacturer has to offer, so buy them both long & short of that distance and see which works best. The shorter one is likelly to work best when you have a good, flat working surface and the longer one may work best when you have uneven surfaces (such as masonry laid against a column or beam).

And when dealing with brick, go for the mortar joints. The compressive strength of the mortar is lesser than that of the brick and will better deform to accomodate your fastner without blowout.
 
SceneryDriver said:
They often don't sink in far enough to securely hold the device/box, but you can't pull them out to try again with a new fastener.


SceneryDriver
Click to expand...

Operator error. :D

In new construction they work very well due to the green concrete.

Almost all types of commercial ceilings, including sheet rock are supported entirely from shots.

We use 1000s of shots to support fixtures, pipe and cable. We don't usually use them to support panels of large junction boxes. You can always shot in a threaded stud so the items are removable.
 
iwire said:
Operator error. :D

In new construction they work very well due to the green concrete.

Almost all types of commercial ceilings, including sheet rock are supported entirely from shots.

We use 1000s of shots to support fixtures, pipe and cable. We don't usually use them to support panels of large junction boxes. You can always shot in a threaded stud so the items are removable.
Click to expand...

This is the key to really successful installation of powder actuated device fasteners. Concrete continues to cure basically until you demo it out. For nominal 3,000psi concrete, if it was a good, clean, pour, you will find it 30 years later to be more like 10,000psi concrete.
 
We tried other pins & still had blowouts, then the gun jammed. Blessing in disguise. I used a hammer drill & lead anchors for the last few runs. I like the convenience of stud guns but too hard to keep up with different sizes of loads & pins. This particular building was decades old & lots of agg too at the surface.

Where I've usually had good luck was new buildings, shooting threaded pins or hanger wire pins through a metal rib into concrete ceiling. Fewer than 10% failed, as I recall. Whenever I have a choice in the future, I will use lead anchors, steel anchors or pipe spikes in old ceilngs. I know what to expect from them. Even plastic anchors are better than a questionable pin that could fall out any time it gets stressed. I also like wedge anchors though the 1/4 inch ones seem to fail fairly often. 3/8 or 1/2 inch wedge anchors seldom fail unless I hit an air pocket.
 
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