I have drilled many holes in unglazed clay pots using a hammer drill with no problem. I think a regular drill with a carbide drill will also do a good job, just take longer. Al

Glaze presents no problem when drilling a hole in the bottom of a clay pot. A couple of layers of duct tape or masking tape over the area to be drilled is a good idea- it makes for a cleaner hole and helps prevent any small crazing around the hole. If there is a bit of crazing, so what? It won't be seen anyway. The drill needs to be held firmly until it penetrates the glaze because the bit tends to want to slip around. After your first attempt or two you'll get the hang of it.

I have some considerable experience in drilling hard materials, with 30 yrs in the glazing contracting business (glass company). We regularly drill all sizes of holes in glass/mirrors, granite (shower door installations) and other vitrified materials (the objects people bring to us to drill holes in).

Ease of drilling varies with the hardness of the material, of course, but terra-cotta containers are not hard at all. Most containers you'll encounter can best be drilled with a "spear-point" drill. I'll link you to a picture from one of our suppliers. The drill is also called a 3-point drill. Highly vitreous containers (glass, or glass-like - ceramic - clay fired at high temperatures) may even require a diamond impregnated "core drill", but it's uncommon to find containers like this.

These drills can be found at big box home improvement stores. They should be cooled with water or a 50/50 mix of water/antifreeze as you drill. An excellent strategy is to immerse the container upside down in a tub and add enough water to just cover the drilling surface as you drill. Rotating the drill clockwise at a slight angle while drilling will greatly increase ease of operation. Alternately (I use this method), fill a squeeze container (contact lens solution bottle is stellar) with water or 50/50 water/antifreeze & squirt it at the drill/material interface as you drill. If you can't find the drill you need, you can contact me off forum & I'll be glad to help you.

Al

Here is a link that might be useful: See a Spear-point drill here.

Well not having a hamnmer drill (had to Wikipedia that one)
I guess I'll head to Orchard Supply for tape and a drill bit.
Thanks all

Cal

There are well-meaning people on these lists who tell you how they build a new kind of clock when you ask the time. Just make sure you get a masonry bit. The clerk should know what you mean. And drill slowly. If the heat builds up, you may let the drill cool a bit before proceeding.

Lolol - Ur a funny guy Elbo, but I think most people recognize ad hominem attack when they see it. I'll ignore it.

I will point out though, that your idea of a masonry bit will probably work reasonably well on unglazed terra cotta, but it is far from the best tool for the job on an unglazed pot and a poor choice for a glazed pot. It's like starting a fire with a flint and steel wool when you have a Bic in your pocket. Your idea that tape will somehow stop crazing is well off the mark as well. It will have no effect on reduction of crazing (or spale, for that matter). The spear-point (3-point) drill is assuredly a superior tool for this job (and inexpensive). I'm speaking from many years of experience and not through ..... well, through my hat.

If I cared, I'd direct you to my business website that does indeed show that I have 30 years of experience drilling all manner of hard materials. BTW - I've drilled hundreds of containers that were purchased w/o holes for myself, friends, and customers.

I will give you some unsought advice though. If you feel confrontational toward someone on a forum or wish to refute the information they provide - do it directly or pick someone more meek than I. Your current methods, as seen throughout these forums, will surely continue to diminish your personage.

Al

Thank you for your opinion that I am funny, Al, or Tapla, or whatever name you are going by today. However, it is wasted, because your opinion of me ranks #12,345 on my list of concerns.
My only surprise is that your compadre who goes by the name rhizo, or as I once typed it, rhino, which might have been more on target, has not jumped in to your defense yet. Your alliance is apparent to anyone who scans this list for more than a couple of days. (Your term elbo could be a result of poor keyboarding skills or an attempt at humor. THAT you are miserable at.)
As a matter of fact, you do talk about yourself endlessly and all the solutions to gardening questions that you have independently come up with. You do not refer to research being done in the horticulture departments of research universities. (BTW, I have a Ph.D. in English, so I "get" your term ad hominum attack. I also am well schooled enough in philosophy to be well familiar with the term. But then you threw it out to impress others, didn't you.
It appears that you see yourself, somewhat grandiously, as a Renaissance man. You like to leave the impression that you reinvent the wheel every day.
I am a keen observer of human nature and relationships, and the symbiosis between you and this rhizo is interesting. If one feels the other has been disrespected, the other jumps in to defend. It is quite boring in its predictability.
I don't doubt for a minute that you two consider yourselves the authorities on gardenweb, and from other posts, you have made converts.
A further observation, and it is risky to make judgements based on e-mail messages only, is that rhino/zo is a bitter and pathologically vindictive person who trolls messages looking for "errors" to refute or perceived slights to which to respond with a wicked tongue. You are more subtle in your aggressiveness and sense of entitlement to be the ultimate authority on any subject that comes up, but it's there.
I reject your "unsought advice" and will continue to post what I want to say as I see fit. You are now assuming the role of censor?
What makes me most curious is that you and your buddy take this list so seriously. To be honest, over the months I have scanned messages for enjoyment, I can't think of one useful thing I have "learned." I see this as pure entertainment, although when people without an agenda such as you have ask a question that I feel qualified to answer, I give a reply based on solid science.
Come to think of it, have you ever asked a question? You are strictly an answer man, aren't you.
Since you implied that I am too cowardly to openly express my opinion of you, do you still feel that way? Or would you like me to continue?

Speaking of drilling for drainage, I am usually drilling through the side of my pots at the lowest point possible, just clearing the bottom. Roots do not want to extend out into the air or go into the soil if the pot is on the ground as they do with added holes through the bottom. Thanks for the information about spear point drills, I was not aware they existed. Al

Al - If you'd like to try one, let me know. I'll send one - you'll like ... ;o)

Al

Al - Thanks for the great suggestion with the spear point drill. Going to get one soon. I have been sweating like a hell last weekend trying to drill holes on one huge pot, obviously I was using the wrong tools.

YT - Let me know if, for some reason, you're unable to find one. I've sent a few around this country - might as well include Canada in the supply chain if need be - eh? ;o)

Al

Al, thanks for the kind offer. I was told that Canadian Tire has tons of it. They don't just sell tires obviously, they even sell Banana seeds.

Thanks again, your knowledge always amazed me. I have never been growing my container plants so successful.

Winzr, on most hand held drills, they have a button which, when pushed...or a switch when pushed, or a wheel when turned down, reduces the r.p.m.'s of the bit. Makes it turn more slowly.

If you have an old piece of clay, why not practice on it....see how long it takes to make an impression where the drill bit stays in the spot. Then increased speed can be allowed without it slip sliding away.

When the bit does go through it, and goes down into the void....don't yank it out....pull up slowly or, reverse the drill bit and screw it out.

Many pots can be drilled successfully -- glass, ceramic, plastic...although plastic can split.