Milling and drilling slate

I have a piece of slate which is 6mm thick and needs to have some holes drilled, and some small areas 6mm x 20mm for a smooth surface to be milled. For drilling 3mm holes I would of thought a masonry drill using coolant at high speed. Im not sure if I can mill the smooth surface with a end mill or not, any ideas please. For cutting to size will scribing a line similar to cutting a tile will do the job, Im asking as I only have one piece so one chance only.

Thanks Bob.

Edited By BOB BLACKSHAW on 18/01/2019 15:00:44

It will depend on what the slate is like, some is quite soft and laminar, other is more solid. I have drilled some slate with an ordinary HSS twist drill and it sanded quite easily. If you apply water you will need enough to ensure that it is being washed out of the hole while drilling. I would probably do small pecks, drill and withdraw, and blow the dust away, far less messy.

Old twist drill and a blunt milling cutter should work fine, not too fast then you can use dry.

As for cutting diamond wet saw or a small angle grinder is the way to go. If hand cutting you need to support on a metal edge and use a chopping action to shear off the waste. It won't scribe and snap like tile.

Cut and drilled a piece of 20mm thick polished slate off a wash stand.Hard as steel,so don't think that all slate is soft.I formed a well with putty where I was going to drill and filled this with oil ,then proceeded to drill with a sharpened masonry drill, and with my drill being variable speed I had to find the best speed for it to cut efficiantly.If it is a critical piece why not approach your local stonemason I'm sure they would help.

Frank

For drilling I would suggest a tile drill, usually a spade type drill made from carbide, 3mm may be a problem? try at a tile shop. As already suggested a diamond tile saw will be best to cut the slate, I have cut tiles using an angle grinder but a tile saw is much better - maybe a pal has one ? For the flats a carbide end mill should do the trick.

John

Having roofed a building with slate, the traditional way to put holes in slate (certainly that thickness) is to punch them. Seriously.

As to cutting them to size, one way is as Jason says, with something like a small sharp hatchet, or a bill hook (the straight part) etc, or these:

**LINK**

I have never drilled slate but I would be concerned about breakout when the drill exits the back side of the slate. How do you prevent it? I have seen some small diameter diamond core bits from China. Would one of them be a better choice than a twist drill or masonry bit?

Just rest it on a bit of MDF or ply to support the back.

The diamond drill are what I mentioned above and will do it particularly if hard, I use them a lot on tile and glass but spade type tile drill will fly through faster.

+1 for tile drills the long taper works really well for brittle materials.

N.