15 Pcs Diamond Drill Bits for Ceramic, Diamond Hole Saw Drill Bit Set Kit, Premium Glass Drill Bit for Bottles,Pots, Marble, Granite Stone, Tile Cutting 0.23 Inch - 2 Inch（6mm - 50mm） YLYL

First of all, you're not getting professional quality Diamond hole saws for $8. That said, these work amazingly well! I cut out a small section of tile for my claw foot tub in about 30 seconds. Here's what you need to do to get nice round holes: 1. Have a small vessel of water to dip the saw into before you start and at intervals as you are drilling. Lay out (mark) your exact hole location with a full circle so you know exactly where to start. Start by tilting your drill at about a 5 degree angle and spin it FAST. Diamonds cut best at higher RPMs. Slow will work poorly and slowly... fast works much better because you aren't having to try to steady the drill as much. As you start cutting on your circle mark, slowly decrease the angle (square to the surface) so your drill begins making contact with the full circle as it cuts through. Once you've made full contact all the way around the circle, you can apply more pressure. Don't forget to cool the drill about every 15 seconds of drilling time by dipping it fully into the water. The water will fill the groove as you cut. It also acts as a lubricant to clear the dust and speeds cutting. Wetter is better! If you can dribble a steady flow as you drill, even better. I cut a 2in and also a 1in hole perfectly round with this set of hole saws. They work great. They arent prefect but they definitely do the job nicely. For the price, you can't beat these! I only needed a couple uses but these will cut many holes if used properly.

Good variety and great value. Don't expect them to last as long as other more expensive bits, these are good for small jobs and they do it well enough. I had to drill a single hole in about 20 small ceramic pots and went through 6 bits in the process.

They worked for my purpose, as i only need them once. If your going to need more than 4 holes, I would buy something else.

Now I can buy non-flower pots at Goodwill and Sparrow's Nest and other resale stores and drill holes in them to use them for flowers! It's a little tricky to get them started. Pour some water in the divot to keep it from getting hot enough to crack the ceramic where you are drilling. Then go in at an angle to get through the shiny part of the ceramic and down to where the bit can grip, then tip up to be perpendicular to the pot. I usually do this standing in the grass, holding the pot between my feet to keep it from skittering away. The grass helps keep it in place and won't chip the ceramic the way my driveway would. I don't usually get a clean edge, but it's on the bottom, so I don't care. I've been using the same bit every time, and I've noticed no loss of quality. There are plenty of videos on youtube to help you if my description isn't clear (it probably isn't--sorry!).

Understand that these are all in metric sizes and this purchase was for the smaller sized bits. There are many sizes to choose from in this kit, from I think 3mm or 1/8 inch equivalent up to I think 24mm or like 7/8 inch. The sizes are laser etched on the shafts and are a little difficult to see, but the holes that they make are relatively smooth rather than just a sharp edge. The reason is that the bits are simply metal tubes that have one end dipped with metal covered crushed industrial diamond, much like sprinkles on an ice cream cone. With this said they are not lab quality sized bits, and have some cutting surface disparity due to the various sizes of chunks around the end, and this disparity will create a more rounded or smoother edge on the hole that you cut through the glass. Start out slow and at an angle with just the weight of the bit against the glass, and spin the bit against the glass until a little edge develops (I used a rechargeable drill), then add a few drops of water and start to reduce the angle and the edge starts forming a circle on the glass. Slow and steady wins the race!! This is glass, and super tiny pieces of glass are now being broken off of what ever you are drilling through so wear a mask, and have a removable work space that you can just wipe and clump up into a ball and throw away, like some damp newspaper that the wet paper will keep the super tiny glass fragments/shards from blowing away and you can just crumple up and throw away the mess with minimum wiping. With this set I managed to drill a 1/2 inch hole in the side of an aquarium for a water overflow, on one of those 2 1/2 gallon rectangle super thin glass aquariums with the black plastic frame, that still had some fish in it (do not recommend this). The hole was a success, the fitting has been installed and still the aquarium has fish in it (that suspect nothing.) Slow and Steady, listen to the screeching of the bit against the glass, if too much screeching you are either too fast or pushing too much. Slow down, add a few drops of water, and then continue on until you start to see the point where the water starts running down the glass on the other side, then slowly continue on until you have a hole drilled through whatever it was you were drilling. Note: I do not know what it would do to tempered glass, from what I know this would probably shatter any tempered glass the instant the bit scratched the surface. My use with these bits has been just plate glass and bottles. Good luck.