Inabra - Abrasivos e Ferramentas Ltda.

Very Coarse	Coarse	Medium	Fine	Fine	Powder
8	14	30	70	150	280
10	16	36	80	180	320
12	18	10	90	200	400
-	20	46	100	220	500
-	-	54	120	240	600
-	24	30	120	240	800
-	-	-	-	-	1000

The HARDNESS of a grinding wheel is determined by its grade. The grade is indicated in alphabetical form (the higher the letter, the harder the wheel) and each grade has a different application.

Note that the grade does not refer to the hardness of the abrasive grains, which is uniform, but to the strength of the bond that unites these grains. The lower the letter, the less the force required prying the abrasive grains loose.

The grade of a wheel will change with the job. The right wheel for a determined application will release abrasive grains from the bond as they lose their sharpness, exposing new grains and resulting in a consistent cut.

The different grade classifications are:

Very Soft	Soft	Medium	Hard	Very Hard	Extremely Hard
E	H	L	P	T	X
F	I	M	Q	U	Y
G	J	N	R	V	Z
-	K	O	S	W	-
Grades in bold are most common.

The STRUCTURE of a wheel is the relationship between the abrasive grains, the bond, and the porosity (spaces or pores) that separates the bonded grains. Porosity acts as a vent and helps the wheel achieve a cooler cut.

As before, different structures are used for different applications. The scale runs from 1 to 15; the lower the number, the denser the material.

INABRA manufactures special grinding wheels with porosity up to 50% of the wheel volume.

The LABELING featured on INABRA wheels contains the following information (in the order shown):

Grain Type	Grit Size	Hardness	Porosity	Bond	Manufacturing Code
A AA AR DA C GC	8-1000	E to Z	1 to 15	V B R E	Optional