Hi,
I've recently been grinding a lot of toolbits after a long hiatus from machining. One thing that crops up in my mind - why do some wheels heat the part so much more than others? The obvious answer is the sharpness of the cutting media. When I sand brass on a fresh belt, there is much less heat than with an old belt because presumably the heat goes away with the chips, and there is more cutting and less rubbing. I have various wheels for shaping and sharpening, from stone to various hardness of abrasive impregnated rubber. It seems the harder the wheel, the more heat. Finer grits heat more, but that seems a smaller issue. Is the answer simply that the surface of the softer wheels wear away faster and continually expose fresh abrasive?

On Mon, 30 Jun 2014 03:21:39 -0700 (PDT), robobass
wrote:

Hi,
I've recently been grinding a lot of toolbits after a long hiatus from machining. One thing that crops up in my mind - why do some wheels heat the part so much more than others? The obvious answer is the sharpness of the cutting media. When I sand brass on a fresh belt, there is much less heat than with an old belt because presumably the heat goes away with the chips, and there is more cutting and less rubbing. I have various wheels for shaping and sharpening, from stone to various hardness of abrasive impregnated rubber. It seems the harder the wheel, the more heat. Finer grits heat more, but that seems a smaller issue. Is the answer simply that the surface of the softer wheels wear away faster and continually expose fresh abrasive?

A grinding wheel stays sharp by the surface wearing to expose new
abrasive grains and as a secondary effect it tends to keep the surface
free of any imbedded metal particles. So a softer wheel of the same
size abrasive will generate less heat than a harder one.

It also tends to cut faster :-)

And wear faster :-)
--
Cheers,

John B.

On Mon, 30 Jun 2014 03:21:39 -0700 (PDT), robobass
wrote:

Hi,
I've recently been grinding a lot of toolbits after a long hiatus from machining. One thing that crops up in my mind - why do some wheels heat the part so much more than others? The obvious answer is the sharpness of the cutting media. When I sand brass on a fresh belt, there is much less heat than with an old belt because presumably the heat goes away with the chips, and there is more cutting and less rubbing. I have various wheels for shaping and sharpening, from stone to various hardness of abrasive impregnated rubber. It seems the harder the wheel, the more heat. Finer grits heat more, but that seems a smaller issue. Is the answer simply that the surface of the softer wheels wear away faster and continually expose fresh abrasive?

There are lots of reasons.

1) Area of contact (angle, diameter of tool)
2) Grit size (the finer, the hotter, see 1)
3) Pressure used
4) Type of wheel/band (The harder wheels are usually finer grits.)
5) Metal of the bit or insert
6) Time taken to sharpen
7) Sharpness of the media

The answer is "All of the above", and then some.

--
You can ignore reality, but you cannot ignore
the consequences of ignoring reality.
--Ayn Rand

On 6/30/2014 9:47 PM, Larry Jaques wrote:
On Mon, 30 Jun 2014 03:21:39 -0700 (PDT), robobass
wrote:

Hi,
I've recently been grinding a lot of toolbits after a long hiatus from machining. One thing that crops up in my mind - why do some wheels heat the part so much more than others? The obvious answer is the sharpness of the cutting media. When I sand brass on a fresh belt, there is much less heat than with an old belt because presumably the heat goes away with the chips, and there is more cutting and less rubbing. I have various wheels for shaping and sharpening, from stone to various hardness of abrasive impregnated rubber. It seems the harder the wheel, the more heat. Finer grits heat more, but that seems a smaller issue. Is the answer simply that the surface of the softer wheels wear away faster and continually expose fresh abrasive?

There are lots of reasons.

1) Area of contact (angle, diameter of tool)
2) Grit size (the finer, the hotter, see 1)
3) Pressure used
4) Type of wheel/band (The harder wheels are usually finer grits.)
5) Metal of the bit or insert
6) Time taken to sharpen
7) Sharpness of the media

The answer is "All of the above", and then some.

--
You can ignore reality, but you cannot ignore
the consequences of ignoring reality.
--Ayn Rand



Since heat is energy and energy can neither be created no destroyed only
transformed, all that heat is being transformed into creatures that will
someday demand their place in the evolutionary scale and displace man as
the dominant organism on the planet.

And, we have Robobass to thank for the fall of humanity!