teach me about hammer drills/rotary drills

[rfuerst911sc]

Pretty soon I will be installing my 2 post lift . I will have to drill 12 holes 3/4 " in diameter and about 6 " deep . This concrete is high strength fiberglass reinforced and was poured aprox. 6 months ago . Yesterday I drilled 4 holes with a standard 1/2 " drill with a 1/2 " standard masonary bit and it was tough going !!! So my understanding is there are hammer drills and rotary drills .

I'm not going to buy one I will rent one , but which is the better tool for what I need to do ? These will be vertically drilled holes so line the bit up , stand over the drill and go to town . Advice from those that have used these is appreciated .

[GH85Carrera]

Go big!

I have a 1/2 hammer drill that is great for small occasional jobs. I tried to punch a 1 inch hole through the stem wall of my house. After 30 minutes I was just part way done. I went and rented a big Bosch hammer drill. It punched through in a couple of minutes. It was an amazing difference. That was 20 years ago and I know things have changed. Renting is for sure the smart move.

[stomachmonkey]

[aschen]

I bought this to install my maxjax in my garage. This is the first link I found but I think it was under 200$ at one of the amazon vendors (refurb).

https://www.amazon.com/Bosch-RH328VC-RT-SDS-Plus-Rotary-Hammer/dp/B004KCQSO6/ref=sr_1_12?ie=UTF8&qid=1523453736&sr=8-12&keywords=bosch+hammer+drill


It laughed at drilling the 6" by 1" holes in my garage. It seemed to taunt me with "is that the best you got?". Anyways no problem you could prob get away with a smaller model.

On the rent vs buy: I was in for about 210$ for the drill and bit, vs 50$ + tax + bit for rental. I was going slow and careful and it was great to not have to be in a hurry to return the tool. I figure if I use it one more time if if I lend it out a couple times it was worth buying. My buddy has already used it for a bigish job

[dad911]

SDS bits/system. I've used the harbor freight one, it will get it done. Less than $100 with bits. Also works as a small jackhammer for light demo.

https://www.harborfreight.com/power-tools/hammer-drills/1-in-sds-variable-speed-pro-rotary-hammer-kit-63433.html

https://www.harborfreight.com/12-in-SDS-Masonry-Bit-Set-5-Pc-62480.html

[aschen]

Also for your real question. Its pretty straight forwards you just need the rotary hammer and the bit. No pilot hole. Dont put any downward pressure on the drill, it needs to bounce.

The most important thing is to be OCD about cleaning the holes, particularly if you are using epoxy set anchors. I managed to find an appropriate sized stiff wire brush. The cleaning and vacuuming is the worst part.

It is best to have a template to drill thorough. I just left the posts standing to do this. I heard some stories about excessive walking if you try to do it freeform. Each hole takes less than 1 min with the rotary hammer. I used a Bosch Bulldog bit

[aschen]

sds are the smaller bits and drills which are prob fine

sds plus is the medium sized setup which is what I used

and sds max are the big dawgs

[dad911]

Good points Aschen.

As I recall I did it with lift standing also. I vacuumed them out, then cleaned.

[Eric 951]

When drilling anchor bolts we use hammer drills with SDS bits. As was mentioned, when drilling, be sure to stop occasionally and vacuum out the holes( a shop vac with a narrow tube taped to end works well). A quick cheat, determine the depth required, measure bit, and install electrical tape at the correct depth on the bit so you know when you get the correct depth.

[carreradpt]

I rented a rotary hammer drill from the lcl home depot. I bought my own bit vs renting that too, a SDS plus 7/8" bit. I initially used a 5/8" bit to start a couple holes thru the lift mount holes and then enlarging the holes. I was not happy doing that so I marked the floor and drilled with the correct size all the remaining holes. Marked the bit with tape for depth. Worked perfectly. Just drill with easy pressure and back out often to remove the material. It's a quick job.

Getting the holes perfectly vertical is the hardest part.

I cleaned the holes very carefully and repeatedly as I was using epoxy set anchors as well. Vacuuming with a small tube, brushing, very important to get those things dust free.

Buy an extra tube of epoxy to have on hand. You'll use more than you think. And clean those holes one more time just for chits and grins.

[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.

[rfuerst911sc]

Great advice guys thank you

[herr_oberst]

Originally Posted by carreradpt

Buy an extra tube of epoxy to have on hand. You'll use more than you think. And clean those holes one more time just for chits and grins.

At least one. Might as well get a couple; it's spendy enough that you'll definitely take back the tubes you don't use. If you've never used this stuff, make sure to watch videos on how to use it. In my experience, it set lots faster than I thought it would, but because I kind of knew what to expect, and I had sort of done a dry run, things worked out.

[Bill Douglas]

Originally Posted by GH85Carrera

I went and rented a big Bosch hammer drill. It punched through in a couple of minutes.

Ah ha, good advice. I've tried a number of times drilling through concrete and brick without much success, so I'll try this.

[Brian 162]

Rent a Bosch or Hilti hammer drill, like a hot knife through butter

[rwest]

I found that drilling the holes first with an 1/8” bit helps to get the big holes lined up for accurate placement, otherwise they bounce around and the holes are off.

[jcommin]

You should drill through the concrete. If you ever need to remove the lift you can simply hammer the anchors thru the concrete. Otherwise you need to grind them flat. The template is a good idea as well.

[rfuerst911sc]

This is the install kit I purchased , it states they are wedge bolts . They are 3/4 " diameter so I drill a 3/4 hole correct ? No mention of epoxy but epoxy could be added right ? Or is there no value adding the epoxy ? In regards to the bit wandering I was planning on using the holes in the foot of each post as my drill guide that will work right ?

I figure I will drill the holes , insert shims as needed and install the bolts . If you guys think some epoxy would be good " insurance " then I will do so . I want to do this right the first time

https://www.carliftparts.com/product/bendpak-lift-installation-install-kit-16-wedge-anchor-bolts-30-pack-shim-kit/

[javadog]

No need for epoxy, generally you use the same size drill as the nominal size, I'm not a fan of the plastic shims. I usually use Hilti products, not generic/unbranded stuff.

You can use the base plate to drill through if there's enough room between the posts and the hole locations for the drill to fit. If the holes in the base plate are oversized, though, I'd probably make my own drill guide.

[URY914]

Don't epoxy the wedge bolts. If it ever fails your insurance company will blame you for it.