Using granite blocks for a supporting base for a cnc router ?

[the great waldo]

Hello All

I've got the builders in at the moment and it looks like there are going to be a few large blocks of granite 100x25x8.5cm leftover. Two of these blocks side by side would be just the right size for my sorotec compact line cnc base (https://www.sorotec.de/shop/Portal-milling-maschine-CL-Line-0805-DIY-4863.html). I would assume that i'm going to either epoxy or cement the two blocks together and drill some holes for tie rods to help hold the blocks together. I would either mount this on a steel frame (to be welded together) or just lay it on the wooden bench that I have my current machine on. I would like to attach the c-line machine with bolts and washers to the granite as there are two fairly hefty aluminium extrusions running end to end. Is all of this a good idea or a waste of time as i'm mainly going to be cutting wood. I've bought finally some of the jmc 180watt servos and aparently they are quite fast, so I figured a bit of extra weight might help to keep things stable. If anyone has any comments or recomendations i'm all ears.
cheers
Andrew

[Chaz]

A feasible idea. I looked at similar before going for Thor (search for my build on here) all Concrete machine. Slightly ;p larger than yours (2 ton) but similar ideas.

[the great waldo]

Hi Chaz
2 ton would probably have me going through the floor into my cellar. The granite blocks are pretty heavy I just hope the builders don't need them for my pathway.

Cheers
Andrew

[Chaz]

My point was that its very feasible as an idea. No need to do 2 tons ;p

[the great waldo]

Hi Chaz
Yes I got that. No worries I won't be shifting granite gravestones about the place. Just out of interest does anyone on the forum any experience of drilling granite? I want to drill a few 12 mm holes through the slabs which are 25 cm wide. I've got a pneumatic hammer drill.
Cheers
Andrew

[phill05]

No you don't want Pneumatic hammer drill you need a diamond tipped core drill (PCD) and lots of water.

Phill

[Chaz]

Yep, that. Impact will cause a problem. You dont 'drill' granite, you cut it.

[JAZZCNC]

Just out of interest does anyone on the forum any experience of drilling granite? I want to drill a few 12 mm holes through the slabs which are 25 cm wide. I've got a pneumatic hammer drill.

Whatever you do, don't turn hammer on it will crack it like Eggshell. While it seems rock hard Granite actually fractures very easily if handled wrong.
Ideally, you need a Slow speed Drill with high torque and like been suggested PCD Core bit and lots n lots of clean water. Do not try cutting without Water with PCD otherwise, they just fail quickly.

[the great waldo]

Hi All
I think i'll give up the idea of tie rods and just epoxy or cement the two blocks into a steel welded frame. Does anyone have any ideas as to fixing the base onto the granite. I figured just drilling some holes through the granite and connecting them with bolts and t-nuts into the ali extrusion. I've attached a couple of photos of the base plate. It's machined flat the base is 20mm thick and the ali extrusion is 60mm square. All comments gratefully accepted2668626687

cheers
Andrew

[Boyan Silyavski]

I believe there must be a mechanical connection between frame and granite. Not just glue or epoxy as for me it will defeat the purpose. Best would be to be clamped somehow to bottom of the frame. But if clamped comes the danger for breaking so a thin layer of polymeric glue will help. Which again makes me doubt the whole purpose.of the operation.

Anyway, for that exact machine polymeric glue will suffice. The kind of glue that fixes metal to metal or metal to stone. It must be sticky like sh_t, not the ones that look like silicone at the hardware store that say xxkg of force, blah blah. I dont know in Uk but in Spain you find that at a place where constructors buy their stuff. Cheaper and much better than epoxy for the purpose.

[Chaz]

I used DWH Diamant stuff to glue Thor's 2 concrete bits together. Its expensive but it works.

[the great waldo]

Hi Chaz
Thanks that looks just the ticket. I don't mind spending a few bob more on some glue, the machine has cost enough as it is. I just hope the builders leave me a couple of blocks !!

cheers

Andrew

[Chaz]

Hi Chaz
Thanks that looks just the ticket. I don't mind spending a few bob more on some glue, the machine has cost enough as it is. I just hope the builders leave me a couple of blocks !!

cheers

Andrew

Its more than a few bob but in my view worth it.

It currently holds two 1 ton blocks together on my mill without any other form of connection. Its used extensively in the industry for this and similar purposes.

How much would you need? I still have some but not sure if its still OK but worth a try if you can use it.

[the great waldo]

Its more than a few bob but in my view worth it.

It currently holds two 1 ton blocks together on my mill without any other form of connection. Its used extensively in the industry for this and similar purposes.

How much would you need? I still have some but not sure if its still OK but worth a try if you can use it.

Hi Chaz

Thats very kind of you. the blocks are 100 x 80 cm so I would be gluing those faces together and would like to fix the 2 ali extrusions 8.5 cm x 100cm. I,m in Austria but would be quite happy to pay for any costs to you. I'll check out how much it is over here and let you know.

cheers
Andrew

[Chaz]

Hi Chaz

Thats very kind of you. the blocks are 100 x 80 cm so I would be gluing those faces together and would like to fix the 2 ali extrusions 8.5 cm x 100cm. I,m in Austria but would be quite happy to pay for any costs to you. I'll check out how much it is over here and let you know.

cheers
Andrew

Ok pity not closer but do find out what the costs would be locally.

[the great waldo]

Hi Chaz.
I see what you mean about more than a few bob. What's the stuff like to work with. Ie, araldite consistency or runny and is there anyway to figure out how much one needs? I'm at work at the moment but will checkout if I can get some locally. Just out of interest how much do you have left and has it gone far over it's shelf life (the shelf life ratings on epoxys is usually conservative while polyester goes rotten real quick)
Cheers.
Andrew

[Chaz]

Hi Chaz.
I see what you mean about more than a few bob. What's the stuff like to work with. Ie, araldite consistency or runny and is there anyway to figure out how much one needs? I'm at work at the moment but will checkout if I can get some locally. Just out of interest how much do you have left and has it gone far over it's shelf life (the shelf life ratings on epoxys is usually conservative while polyester goes rotten real quick)
Cheers.
Andrew

You can get it in a putty form and also then a liquid. I used both.

Mine is fairly old, its gone hard but we found before that boiling it in its container softens it up and allows it to be used. That said, its been here for over 2 years. If we can get some of it to you for cheap, its worth trying.

[the great waldo]

Hi Chaz

let me know how much you want for it including postage (that might be ridiculous with parcel force) I'll pm you my address.
cheers
Andrew

[Oldtech]

I would not sweat epoxying it. After all it's not a bridge. Read about the Lin Cove Viaduct. https://www.nps.gov/blri/learn/historyculture/linn-cove-viaduct.htm Epoxied together.