Ellis, they will but make sure that your setup is rigid. In other words that your work isn't going to vibrate and I would recommend only using them with a pillar drill or mill on the slowest speed you can.
A few things I found with them,
- They weren't great at hole cleaning and I to manually remove material after the hole got deeper than the diameter of the drill bit.
- The white coolant you would use with a lathe or mill worked best for keeping things cool. I also tried drilling / tapping paste but this didn't work as well. I think the coolant assisted in removing material.
- I was drilling 10mm hole and they actually seemed to prefer no pilot hole. I was initially drilling a pilot hole with a 5mm before opening it to 10mm but 10mm straight seemed to work best.
- Once the diamond head has gone then bin them, they are useless at that point.
- I had a 5mm bit snap off in the hardox (was drilling 20mm thick hardox 400). Couldn't remove it with pliers etc but the 10mm bit just went straight through the broken bit in the hole no bother.
- I quickly nackered my first 10mm bit but the second one got 80mm of hardox drilling done before it was junk.
- They are good but at the same time, not being able to sharpen them means that they have less of a life than a cobalt bit which can be sharpened on a bench grinder.
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