Abrasive Resource can have sanding belts made up for you in
any width or length you may need for grinding or polishing metal. We show the
more popular sizes in an aluminum oxide material on our Sanding Belts page,
but we can custom fabricate any size, grit or abrasive material you require in
just a day or two!
Offhand grinding
on metal is the most traditional way to use sanding belts and covers all the
methods of abrading metal where the operator holds the workpiece in their hand
and presents it to the abrasive belt (as opposed to the piece being held in a fixture.)
This type of grinding is done on a Backstand Sander—also called a polishing jack or belt grinder.
These machines vary considerably in horsepower, ranging from one to 75 HP.
Typically, units with 7-1/2 to 15 HP provide a good working power for most
applications at speeds between 3500 and 7000 sfpm. All grinding should be below
the center line of the contact wheel and the workpiece should be brought up to
the belt.
Optimum belt speed
depends mostly upon the material you are grinding. Testing indicates that as
the belt speed increases, so does the amount of metal being removed. However—as
belt speed increases, the amount of heat generated also increases which may
result in premature dulling of the abrasive grains (glazing) and/or heat damage
to your workpiece. The optimal speed
range in sfpm for grinding belts is shown in this table:
Next you need to factor in grinding pressure. Pressure is an important part of the grinding
process as it causes the abrasive grain on the belt to fracture and create a
continuing supply of fresh, sharp cutting edges. An operator will generate this
pressure against the contact wheel in a range of 20-50 psi. On an average
offhand operation of moderate stock removal, a 70-75 durometer rubber contact
wheel is the most useful. For more information on contact wheels, refer to our
2005 Sandpaper Blog post “Contact Wheels for Abrasive Belts”.
Finally, remember to
check that the abrasive belt, idler assembly and contact wheel are enclosed
within a sheet metal hood when using
a backstand grinder. The hood must confine flying sparks and fumes as well as
protect the operator from a belt breakage.
