What to use with a hammer drill?

[Toller]

Is there anything special about drills for hammer drills? I have a bunch of carbide drills I got at garage sales over the years, and while I don't mind wearing them out, I would like to use the ones best suited for the task. I just want to drill some shallow holes in a conglomerate rock that I think is probably pretty hard.

[Spud]

[William Brown]

[Robert Allison]

Actually what he needs are percussive bits made for hammer drills. A simple masonry bit will be destroyed within the first 20 revolutions on a hard material. Percussive bits or hammer drill bits are the ONLY thing that will not be destroyed in a hammer drill.

[HMT]

I just had to drill qty. 20 size 1/4" and 5/16" holes in a fieldstone hearth to install a screen. You've correctly identified your need for a hammer drill, and other posters have also correctly identified the need for special bits. Lowe's and Home Depot sell them (make sure they're marked as for a hammer drill), but I wasn't pleased with their longevity.

I recommend doing what I did - ditch the big boxes and go to your local contractor's fastener supply house - look in the Yellow Pages under "Fasteners - Industrial and Construction". I bought Simpson bits and anchors and was pleased

Also, the sleeve, wedge, and epoxy anchors I looked at were priced at about

25% of what they charge at Lowes'/Home Depot, so that's a big savings depending on how many you need. You can also get advice on your specific needs. (I ended up with sleeve anchors.) At places like this, paying cash helps the process, since they're usually set up for contractors and don't like to mess around with credit cards or checks from random homeowners.

So, with the Simpson bits, it took up to 45 seconds or so to drill 2" deep in stone, but less than 10 seconds to drill the same depth in the mortar between the stones. Also, one bit was good for about four to six holes (assuming a mix of drilling into stone or mortar). The bits were priced at about $3.50 each, which was comparable to the prices at Lowe's and Home Depot, but as I said, in my experience these bits did much better for the same price.

FYI, Simpson is one big fastener company - the other is Hilti. Hilti makes really good stuff, but it's expensive and some of the tools are proprietary. Simpson is a little more user friendly.

Misc. thoughts: earplugs and glasses are a must. Shopvac out the dust in the hole before installing anchor. The bits get super hot so be careful when changing. Just for kicks, I tried a straight carbide bit

- it never penetrated the surface more than 1/8".

Anyway, as always, your mileage may vary. I have no connection to either company except having used their products. Good luck.

Regards,

HMT