Hello CAM 1109 students. As I said this is a 1109 and its surface grinding
section (Lab 4). So we're going to start out talking a little bit about safety.
Surface grinding can be very dangerous, but so can every machine in the shop.
Some people feel like grinding is more dangerous than others, but we're going to
go through a little bit of the safety factor and then some of it will bring up
as as we actually start doing some grinding. But the very first thing is
right here, those safety glasses. Now we should have safety glasses for all of
our machining in here but even more so important when we're doing surface
grinding. We have had occasions where a grinding wheel student makes a
bad move or something like that and a wheel can blow up. We also have a vacuum
system in here and I want to talk a little bit about that. For example
it's very important that we keep this magnetic chuck clean because if we have
the least amount of dirt or grit from the grinding wheels this will not set
down flat like it was there and we're actually doing tolerances as compared to
other machining to one ten thousandths not 0.001 to 0.002, 0.003, so a lot more.
So a little bit of dirt or grit from the grinding wheels. But back to this right
here. You see a brush here? This is what we clean this with, okay - back and forth.
And then after that we wipe it off with a brush, okay. Part not being on there, we
take our hand and wipe it off like this this. Thing right here all right is a
no-no on surface grinding, because normally we would have our vacuum system
on here which is right here comes up this tube and the centrifugal force of
the wheel, it's running several thousand rpms, and
the suction here. You can be something like this wiping it off which is a no no.
No rags around the grinder, okay. It can suck it like this and a wheel being on here, so
instinct is that you try to pull it back and it can pull you into the wheel. And
you do not want anything like that. So tolerate the dirt, use the brush, then
your hand. The other thing is when you're doing that this is a table lock. You want
this to be clear out here like this, okay. So that you have room and are away from
the wheel. So very important. When you're not grinding, here's your table lock. Now
you can't move that, so it can't pull away here. So a combination of centrifugal
force and vacuum, towels are not allowed! Nothing like that. You see me wearing
short sleeve shirts, for example. Loose baggy clothes (not allowed). We have signs all over the
place: no hoodies, no long sleeves, no shorts, no open-toed shoes. When you take
the class your instructor will go through all that again as you enter the shop.
We're going to talk a little bit of the types of wheel. The biggest cause of
failure in your grinding, remember we talked about tolerance one
ten-thousandth we're working with. Heat is the biggest problem. The grinding
wheel generates a lot of heat and when you generate heat your part actually
swells up, okay. And when it does and then it cools down it changes again so when
you're again doing tenths. So we have to eliminate heat. Certain grinders use
flood coolant, which really makes a mess and trying to get everything cleaned up
is that way. So we're better off to make the proper wheel selection, okay. Very
important! If we come over here and take a look. See all these grinding
wheels. There's all different colors: light blue, dark blue, light blue, brown,
white ,dark brown. Which one do we use? The rule of thumb for grinding is
the softer the piece that you're going to grind the harder wheel you want that.
That helps control heat and vice versa. The harder the piece, the softer wheel you
use. Now when we say hard and soft we don't mean we can squeeze this like a
marshmallow, okay. It means that the composition of the wheel. And that all
depends. We have some numbers here on every wheel and those numbers mean
something. The most important one is the center one here, okay. Which says 46-H.
46 is the number of granules that are in a certain area, okay. And H means it's
medium hard, okay. And we're going to grind soft material today, that's why
we're probably going to use a soft wheel. Color sometimes designates
XYZ company. It may be XY company uses a
blue wheel it's a 46-H and XYZ company uses a pink wheel. So there's a there's a
lot to the technology of selecting the proper wheel. All kinds of shapes, you can
see one this is called a cup wheel because it looks like kind of like a cup.
Used for mostly side grinding. Most of
the grinding that we do is ground in this fashion with a wheel on here like
so and we're grinding with the bottom of the wheel.
So safety of the grinding wheel.
you