Cutting & grinding slate

Myself I think I would use a core drill and then use a cutting disk to cut away the sides to leave a groove Something like this will do the job

Richard

It's soft stuff, you can use ordinary tools, e.g. drills, hacksaw, rasp, scrapers... not sure about using an abrasive disk, it might clog up, never tried one on slate. I would not use anything with hammer action.

IME slate cuts very easily cleanly and smoothly with a continuos rim diamond disk. So slots with clean sides are easy. (it also cuts well with a segmented disk, but that leaves a less smooth finish)

For rounded edges, then as Tricky suggested, a core drill will work well. The carbide or grit edged versions would also work, it does not have to be diamond.

If drilling a fresh hole, then personally I would drill a starter pilot hole with a normal masonry bit (no hammer), then use that to guide the pilot bit of the hole saw for the first bit of cut. Once a ring of cut is established right around you can then carry on without the pilot bit.

This makes it quite easy to drill a hole that is not perpendicular to the outside surface. At more extreme angles you can start the pilot hole perpendicular to the surface, but then pivot to the required angle after you have a shallow starter hole. That is what I had to do when drilling the post holes in a sloping wall here:

If you want to enlarge an existing hole, then a plug of wood inserted into the existing hole, can act as a recipient of a pilot hole, and be used to guide the start of the cut. Again once established you can lose the pilot and remove the plug.

Whatever you use, core drill or whatever, cut that slate with a diamond edge

That is why I would choose a system with a pilot drill. It would be very 'tricky' otherwise, if not near impossible.

It is quite common practice to use something like a plywood piece with a hole the same diam. of the core drill as a guide which can either be secured to the wall or held by hand depending on the size of hole if you do not have a suitably long pilot drill. Once the core drill produces an initial groove it will not wander. Not having a pilot drill or removing it before the hole is completed usually makes for a neater breakout.

Richard

The slate mine I visited in Wales used an 8ft diameter diamond saw, heavily lubricated, to cut the slate blocks to size before splitting, if that helps.

With a sideways step:

I see. Anyone in particular? Were you there, or simply had knowledge of them?

Chris

I'm going to need a bigger pond! ;-)

Chris

Some of them were still teachers when I was there (1982 - 1987)

No old Ma Jessop on the photo, but she could have been teaching at the girls high school at the time.

We used to have great fun measuring Mr Moulton's flares from under the desk when he was not looking.

And yes it was me that used to put plugs with a LN short into the sockets.

Mr Stocks ISTR went onto work at the sixth form college (lived next to my Grandad in Silkstone).

Your other photos also have some good memories of the school.

When I was there one of the top corridors had pigeon holes to hand in your homework.

Thanks

I was taught by both of them.

I was there 1960 -1967. We still have reunions, and a group of us were able to make it to the open day just before closure, when I went round taking those shots.

The stockroom behind room 15 was a sanctuary nobody was allowed into, but had windows looking out in three directions. As I went in to take photos, I could see that whoever was looking after the classroom was itching to warn me off, but what could they say? I was hardly in line for detention!

Was that just outside the staffroom?

There used to be lots of lockers to store your books and textbooks, it seems nowadays everything has to be carried all the time.

Examining my photos later, I reckon that from the stage I could just see the two planks I installed above the suspended ceiling from which to hang the faux mirror ball that I had made (Gym hoops covered with cardboard strips, then squares of cardboard with aluminium foil, driven by a Proops synchronous motor and Meccano reduction gear)

Chris

Yes.

And we still has boys and girls entrances

I guess that did make sense, since, IIRC, the toilet entrances were in the lobbies adjacent to the outer doors.

On my photo visit, the group of us oldies did have the opportunity for a quick chat with the retiring headmaster. It was a strange feeling to be in that office without a feeling of tension, not that I ever experienced anything beyond a stern word.

Chris

Well, the core drill was certainly the way to go, though it was much harder work that I had anticipated.

My slitting disk cuts the material as easily as one would expect, but the core drill was a real pain.

I used

with

The pilot drill is so loose in its taper that although it followed the pre-drilled hole, as suggested, the core drill moved quite a bit relative to it.

In order to keep things on track I probably applied more pressure than was advisable, and the cutting went very slowly indeed.

I guess I probably lost a lot of the diamonds :-(

Cleaning up the sharp edges of the cuts was easy enough with a coarse flap wheel.

Chris