"Having purchased two 8mm diamond drill bits from a major DIY store, which I succeeded in blunting after four and a half holes( not happy). It was time to invest in some serious hardware, so off I toddled to Screwfix and purchased two of their drill bits( eight holes to drill, hope these will be of a better quality), anyhoo done the eight holes with the one drill bit, happy days. As long as you keep the tool cool and lubricated ( I used a garden hand spray, filled with water) I can't see any reason why this bit shouldn't do 10+ holes. Drilling 10mm Porcelain tiles by the way."
"Deliberated on whether to buy this drill bit, or one from a name brand for 3x the price.
It was immediately obvious that this drill bit won't last very long but it was good enough to drill the 6 holes I needed to mount various fittings in a new bathroom with porcelain tiles. Took well over an hour, but the drill bit still has diamonds on the end so I could probably get another couple of holes out of it.
This was a 2 man operation, with me very carefully maintaining a constant (medium) speed on my DeWalt 14.4V drill. Assistant used a pump-action hairspray bottle to liberally douse the hole with water. Every 10s I backed off the drill bit to let the dust wash out of the hole. Takes between 5-10 mins per hole at this shoulder-achingly slow pace.
I could probably have gone faster and more pressure on the drill, because the bit was barely getting warm.
I had to make a jig to get the holes started, else the drill bit skids off position and scratches up the tiles. Block of 1" wood with a big notch cut in it, and a hole to take the drill bit."
"I am very disappointed that screwfix continue to buy in this item from the current supplier. It seems that early reviewers seemed not to have a problem but maybe there was a change in supplier as the latter reviews reflect the actual poor quality of the bit. I used the wet drilling method on porcelain with a low speed drill and firm pressure taking it easy not to abuse the bit and managed 1 and a half holes before the glued on diamonds rub off the tip and there is just bare metal. I rang Screwfix customer services and they were happy to refund but I asked for them to credit against another bit, this time the Dewalt 8mm diamond coated tip and requested they send it to me next day delivery at no cost. They did this but I shouldn't have had to ask. After all it is b frustrating being stuck in the middle of a project isn't it! Anyway, I have managed 4 holes with the Dewalt bit so far and the coating remains in tact and looks good for another couple of holes at least. It cost £21.99 but that seems to be the minimum price to pay to drill holes in porcelain. Hope this helps you guys."
"Used the bit once. Half of the coating came away within seconds chipping some sanitaryware. Very dissapointed. Returning bit for a refund. Would not recommend and will probably get one at 5 times the cost just to finish drilling the 6 holes I need."