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A bonded abrasive tool, having a structure permeable to fluid flow, comprises sintered agglomerates of a plurality of abrasive grains and a binding material, the binding material being characterized by a melting temperature between 500 and 1400�� C., and the sintered agglomerates having a loose pack

A bonded abrasive tool, having a structure permeable to fluid flow, comprises sintered agglomerates of a plurality of abrasive grains and a binding material, the binding material being characterized by a melting temperature between 500 and 1400�� C., and the sintered agglomerates having a loose packing density of ≦1.6 g/cc and three-dimensional shape; a bond material; and about 35-80 volume % total porosity, including at least 30 volume % interconnected porosity. Methods for making the sintered agglomerates and abrasive tools containing the sintered agglomerates are described.

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We claim: 1. A bonded abrasive tool, having a structure permeable to fluid flow, the tool comprising: a) about 34-56 volume % non-elongated abrasive grain; b) about 3-25 volume % bond; and c) about 35-80 volume % total porosity, including at least 30 volume % interconnected porosity, wherein pores

We claim: 1. A bonded abrasive tool, having a structure permeable to fluid flow, the tool comprising: a) about 34-56 volume % non-elongated abrasive grain; b) about 3-25 volume % bond; and c) about 35-80 volume % total porosity, including at least 30 volume % interconnected porosity, wherein pores included in the total porosity are irregularly and randomly shaped and sized; the bonded abrasive tool being substantially free of porosity inducing media and elongated shaped materials having a length to cross-sectional width aspect ratio of at least 5:1; wherein 5-100 volume % of the abrasive grain comprises abrasive grain held within sintered agglomerates, and the sintered agglomerates comprise a plurality of abrasive grains with a binding material, and the sintered agglomerates have an average diameter that is no greater than an average dimension of the interconnected porosity when the interconnected porosity is measured at a point of a maximum opening. 2. The bonded abrasive tool of claim 1 wherein the bond is a vitrified bond. 3. The bonded abrasive tool of claim 1 wherein the tool has a maximum density of 2.2 g/cc. 4. The bonded abrasive tool of claim 1 wherein the binding material comprises at least one of ceramic materials, vitrified materials, and vitrified bond compositions. 5. The bonded abrasive tool of claim 1 wherein the sintered agglomerates are 200 to 3,000 micrometers in average diameter. 6. The bonded abrasive tool of claim 1 wherein the abrasive grains are microabrasive grains and the sintered agglomerates are 5 to 180 micrometers in average diameter. 7. The bonded abrasive tool of claim 1 wherein the bonded abrasive tool has a bimodal porosity distribution of intra-agglomerate pores and interconnected porosity. 8. The bonded abrasive tool of claim 1 wherein the tool further comprises at least one of a secondary abrasive grain, filler materials, and grinding aids. 9. The bonded abrasive tool of claim 1 wherein the tool comprises 36 to 52 volume % abrasive grain, 3 to 13 volume % bond and 35 to 70 volume % porosity. 10. The bonded abrasive tool of claim 1 wherein the bond is selected from the group consisting of organic bonds and metal bonds. 11. The bonded abrasive tool of claim 1 wherein the binding material has a melting temperature between about 500 and 1400�� C. 12. The bonded abrasive tool of claim 1 wherein the binding material is a ceramic material selected from silica, alkali, alkaline-earth, mixed alkali and alkaline-earth silicates, aluminum silicates, zirconium silicates, hydrated silicates, aluminates, oxides, nitrides, oxynitrides, carbides, oxycarbides and combinations and derivatives thereof. 13. The bonded abrasive tool of claim 1 wherein the sintered agglomerates have an average size dimension two to twenty times larger than the average size of the abrasive grain. 14. The bonded abrasive tool of claim 1 wherein at least 50%, by weight, of the sintered agglomerates are 200 to 3,000 micrometers in average diameter. 15. The bonded abrasive tool of claim 1 wherein the abrasive grains are microabrasive grains and at least 50%, by weight, of the sintered agglomerates are 5 to 180 micrometers in average diameter. 16. The bonded abrasive tool of claim 1 wherein the tool further comprises at least one of secondary abrasive grain, filler materials, and grinding aids. 17. A method of grinding comprising the stops of: a) providing a bonded abrasive tool, having a structure permeable to fluid flow, the tool comprising: 1) about 34-56 volume % non-elongated abrasive grain; 2) about 3-25 volume % bond; and 3) about 35-80 volume % total porosity, including at least 30 volume % interconnected porosity, wherein pores included in the total porosity are irregularly and randomly shaped and sized; the bonded abrasive tool being substantially free of porosity inducing filler material and elongated shaped materials having an aspect ratio of at least 5:1, wherein 5-100 volume % of the abrasive grain comprises abrasive grain held within sintered agglomerates, and the sintered agglomerates comprise a plurality of abrasive grains with a binding material, and the sintered agglomerates have an average diameter that is no greater than an average dimension of the interconnected porosity when the interconnected porosity is measured at a point of a maximum opening; b) bringing the bonded abrasive tool into contact with a workpiece; and c) abrading the surface of the workpiece with the bonded abrasive tool. 18. A bonded abrasive tool comprising: a) about 34-56 volume % non-elongated abrasive grain; b) about 3-25 volume % bond; and c) about 35-80 volume % total porosity, including at least 30 volume % interconnected porosity, wherein pores included in the total porosity are irregularly and randomly shaped and sized; the bonded abrasive tool being substantially free of elongated shaped materials having a length to cross-sectional width aspect ratio of at least 5:1; wherein 5-100 volume % of the abrasive grain is held within sintered agglomerates, and the sintered agglomerates have an average diameter that is no greater than an average dimension of the interconnected porosity when the interconnected porosity is measured at a point of a maximum opening. 19. The bonded abrasive tool of claim 18 wherein the sintered agglomerates are 200 to 3,000 micrometers in average diameter. 20. The bonded abrasive tool of claim 18 wherein the abrasive grains are microabrasive grains and the sintered agglomerates are 5 to 180 micrometers in average diameter. 21. The bonded abrasive tool of claim 18 wherein the bonded abrasive tool has a bimodal porosity distribution of intra-agglomerate pores and interconnected porosity. 22. A bonded abrasive tool comprising: a) about 34-56 volume % non-elongated abrasive grain; wherein 5-100 volume % of the abrasive grain is held within sintered agglomerates; b) about 3-25 volume % bond; and c) about 35-80 volume % total porosity, including at least 30 volume % interconnected porosity, wherein pores included in the total porosity are irregularly and randomly shaped and sized; the bonded abrasive tool being substantially free of elongated shaped materials having a length to cross-sectional width aspect ratio of at least 5:1; wherein the sintered agglomerates have an average diameter that is no greater than an average dimension of the interconnected porosity when the interconnected porosity is measured at a point of a maximum opening. 23. The bonded abrasive tool of claim 22 wherein the bond is a vitrified bond and the tool has a maximum density of 2.2 g/cc. 24. The bonded abrasive tool of claim 22 wherein the sintered agglomerates are 200 to 3,000 micrometers in average diameter. 25. The bonded abrasive tool of claim 22 wherein the abrasive grains are microabrasive grains and the sintered agglomerates are 5 to 180 micrometers in average diameter. 26. The bonded abrasive tool of claim 22 wherein the bonded abrasive tool has a bimodal porosity distribution of intra-agglomerate pores and interconnected porosity. 27. The bonded abrasive tool of claim 18 wherein the bond is a vitrified bond and the tool has a maximum density of 2.2 g/cc. 28. The bonded abrasive toot of claim 18 wherein the tool further comprises at least one of secondary abrasive grain, filler materials, grinding aids, and pore inducing media. 29. The bonded abrasive tool of claim 18 wherein the sintered agglomerates comprise a plurality of abrasive grains with a binding material, and the binding material has a melting temperature between about 500 and 1400�� C. 30. The bonded abrasive tool of claim 18 wherein the sintered agglomerates comprise a plurality of abrasive grains with a binding material and the binding material has a melting temperature between about 500 and 1400�� C., and the bond is a vitrified bond that has a firing temperature that is lower than the melting temperature of the binding material.