teach me about hammer drills/rotary drills

[Eric Coffey]

The only thing I would add is: Make sure you know your slab construction.
For instance, if it's a post-tension slab you don't want to be doing ANY cutting/drilling unless you 100% know the cable layout.
If it's PT and you don't have the cable run layout, you can have it x-ray'd to locate them.

[mopydick]

Update on inserts progress:

I bought a new hammer drill, mainly because the one I was borrowing wasn't that great (Habor Freight), and the new one (a Ryobi) is pretty good, at least relative to the Harbor Freight one. Hammering action is better and I didn't have to lean on it as much to get it to drill at a reasonable rate.

I also took the advice to drive straight through the cement pad. Now I know that the pad is 6-7" thick.

With these two changes, the remaining inserts installed as I would expect. I hammered the inserts in with less force and they engaged with the cement at about 1 to 1.5" of the thread head was exposed. They look right and the vertical lift supports are rock solid (haven't put the horizontal cross member on yet which should stiffen things up even more).

The initial 4 inserts (two per side) are a bit of a quandary. Two of them, I would consider good based on them tighten up with about 1.5" of exposed thread. The other two have about 2.5" of exposed thread before they finally tightened up. Luckily, its one on each side of the lift.

I stopped by a friend's professional shop which has a old Bendpak that's been there for 10+ years. The insert thread height varied. Most where around 1.5" but a couple had 2" exposure. The lift has seen lots of cars and obviously held up fine.

So, I believe I'm all set. Thanks everybody for your comments!

Peter

[Zeke]

Originally Posted by mopydick

Thanks for all the feedback. I'll take some pixs of what I have going this weekend when I get back to the garage.

To answer some of the questions:

- concrete slab was poured in the 1970's

- I drilled a test hole in the corner of the garage before ordering the lift, and found I could go 5" deep and still not pop out the other side. Maybe the the thickness varies from one area to another but I would have thought I would have felt the bit punch through the other side while drilling the holes that I have done.

- The threaded bolt head height of the ones that 'took' are about 1 to 1 1/2" above the nut.

- The loose ones are 2" or more and I feel that I could pull them out with some light force (haven't done it yet but I'm curious to see what the expanding end looks like now - maybe it got beat up to much when being driven in). I did have to hit them pretty hard to insert them (everything is relative but I do have some meat on the bones).

I did have the thought of using an impact wrench (with ultra low pressure) to give them a quick spin to see if I could get the wedge part to catch some concrete. I'm pretty sure once the wedging action starts, then one is home free, and torque slowly and methodically.

I won't be able to play with them again until this weekend and I'll take some pixs, and report back on any success or failures. I like the idea of drilling all the way through the slab and wish I had done it with the four that I've started. I'm also glad that I only drilled four and checked the fastening before drilling all 12.

Thanks everybody,

Peter

i wonder if you uber cleaned the holes before inserting the anchor? They will easily slip with a bit of dust in there. Also I wonder it pouring some epoxy in the holes and then ragging it back out with a rag wrapped around a small stick would provide more integrity to the side wall of the hole. Some concrete is not that good down past the surface.

Lastly, for slabs not prepared for a lift with thicker sections under the posts, I would love to see a 3/4" toggle bolt that would turn itself in the dirt or base below the slab and clamp the post flange to the concrete.

[Alan A]

Originally Posted by VincentVega

I bought an sds hammer and its useful but I dont use it much. Rent one from HD. I used their medium sized sds for some some foundation penetrations and it was pretty amazing how fast it went.

I don't use mine much either, but when I do I don't want to be driving to HD and hoping they have one to rent. I paid $125 for mine. It's $160 on amazon right now. Without wishing to sound like an advertisement it's not worth the time to not have it.