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Brunswick Mining and Manufacturing of Pool Table Slate

Brunswick billiards is proud to present

slate mining and manufacturing why

Brunswick slate rocks

Brunswick uses only the finest slate in

the world for use in all of its pool

tables Brunswick assures its laid to be

completely flat to within ten one

thousandth of an inch three times more

strict and required in order to pass the

billiard congress of america standards

in this video we will review how slate

forms in the earth how it is mined

manufactured and tested to be sure

Brunswick tables remain as some of the

most consistent and accurate climb

tables available today slate is a

natural sediment rock that is created

over millions of years it comes in many

colors and hardnesses depending on the

sediments that form the slate millions

of years ago slate is often buried under

20 to 30 metres of shale clay sandstone

and dirt and is formed by millions of

years of pressure and heat when a slate

mine is discovered tests are conducted

to determine the natural edges of the

slate mine when the miners reach

homogeneous slate as shown here in the

lower layers they then know the slate is

of good quality and they can begin

mining

it has taken three years to get the mine

to this point this mine is approximately

one acre in size

however slate mines can be up to 100

acres large in Brazil the open pit

method of mining is used this method

utilizes a large saw set at the exact

depth that the layer of slate can be

extracted a slate square much like a

carpenter's square is used to set the

lines for cutting

after the lines are set near net chunks

are cut with a 12-inch diamond blade saw

water is used to help keep the saw blade

cool for better longevity of the blade

every layer of the slate is natural and

each layer that is removed can be

anywhere from four to sixteen inches

thick in the open pit method slate may

be removed with a front-end loader

affixed with forks each piece is

approximately 250 to 270 kilograms or

500 to 600 pounds at five inches thick

to cut one layer from this mine takes

about two weeks the slate naturally and

easily pulls away in approximately five

inch thick chunks each piece of slate is

visually inspected before it is loaded

onto the truck sometimes mineral

deposits such as iron quartz or calcium

will penetrate the slate making it

discolored and more difficult to work

with

Brunswick will reject slate with mineral

streaks or mineral deposits natural

cracks in the slate can also reduce the

yield approximately 10% of the slate

removed from a slate mine is unusable

due to natural cracks when the loader

reaches a full truckload of Brunswick

quality slate the truck is sent to a

nearby factory for further processing

after unloading the slate is inspected

again at the manufacturing facility to

check for any visible defects at this

point since each piece from the mine can

be anywhere from four inches to 16

inches thick the slate needs to be

sliced or cleaved into thinner pieces

after the slate is separated it is then

sent to the first of many stages of

surfacing processes

each set of slade goes through at least

six rounds of surfacing during the

manufacturing process the first stage of

servicing removes the rough portions of

the top of the slate

after surfacing each piece is then cut

to the appropriate length each cut piece

is cleaned using a squeegee and then

moved using a vacuum lift and placed on

a pallet for the next cutting process at

this point the slate is beginning to

resemble slate that is used for pool

tables

in the next step the slate is matched to

become one set workers load three pieces

on a conveyor to be trimmed and have the

holes board this is the point where the

worker marks an arc on the slate with a

special marker to match the set from

this point forward the slate will move

through the process as a matched set

the slate is forced through another

cutting process and this machine trims

the width of the match set the match set

is then placed on a machine that cuts

the pocket holes rail bolt holes and

slate attachment holes

next workers verify the holes have been

cut to the right widths and that the

pockets also have the correct dimensions

all dimensions must be within one

millimeter or 1/32 of an inch to pass

the Brunswick quality standards

the slate now goes through an additional

surfacing process to give the slate its

flatness the BCA specifications allow

the slate to be within thirty one

thousandths of an inch but Brunswick

slate is checked to be within ten one

thousandths of an inch from edge to edge

the last surfacing machine is one of the

most important steps in slate

manufacturing this machine has been

custom fabricated to meet Brunswick's

flatness requirements first the workers

will surface the top and then the bottom

in this process the speed that the slate

is forced through the machine and the

depth that it is surfaced is critically

important in addition the surfacing

disks must be in perfect balance in

order for the slate to maintain flatness

a surfacing disc contains 96 diamond

surfacing bits each bit costs $10 next

each set of slate is moved to a

temperature and humidity-controlled

curing room for 30 days where the slate

is allowed to stabilize each group of

slate is marked and monitored over the

30 days Brunswick's 30-day curing

process to help stabilize the slate is

believed to be unique in the industry

this process helps prevent crowning and

fluctuations in the natural material

after curing the slate is moved to the

framing area where pre-cut MDF is glued

to the back of 1-inch slate Brunswick

uses 45-pound grade MDF that allows

staples to enter the wood without

cracking or chipping an industrial grade

glue is used to assure a tight bond

between the wood and the slate

after allowing one day for the glue to

dry the slate pockets are then trimmed

in addition the slate counter bores are

reamed with a power drill to within one

millimeter of an inch a small plastic

gauge assures the slate screws do not

exit the bottom of the base frame cleats

a hand grinder is then used to grind off

any rough edges and to put the slight

chamfer on the edge of the slate to make

it easier to handle during installation

the pockets are then sanded all of the

sanding in the pockets helps prevent the

cloth from ripping during installation

or when a ball enters the pocket at a

high velocity

in final inspection each piece is

checked again for flatness on a bench

that is verified to be 100% flat the

workers use a level piece of steel and

two very thin pieces of metal to see if

there are any gaps from edge to edge and

corner to corner if the small metal

pieces can make it past the level the

slate is rejected the bottom of the

slate is checked for crowns Brunswick

has zero tolerance for crowning

the slate is then cleaned with a cloth

air blown and a final visual inspection

is conducted

if the slate passes final inspection it

is given the Brunswick certified slate

seal of approval date coated and as EJ

attests it's ready for shipment to

Brunswick