• Bore Size
• Abrasive
• Grit

Selecting Tool Diameter
Tool diameter is determined by the nominal bore size in which the tool is to operate. The Flex-Hone® tool is always produced and used in an oversized condition. The degree of oversize creates a soft cutting action. For example, a 1" Flex-Hone size is ordered if a 1" bore is to be finished and the tool is provided oversized. If the bore size is between standard Flex-Hone sizes, the next larger standard Flex-Hone should be selected. For instance, if the nominal bore is 1.093", then the 1-1/8" Flex-Hone is ordered.

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Selecting Abrasive Type
Our standard stock abrasive is Silicon Carbide. Many other abrasives are commonly on hand and available to ship.

If the base material is:	Brush Research Suggests:
mild steel, stainless steel and cast iron	Silicon Carbide (SC)
Aluminum, brass, bronze and softer metals. For Deglazing Nikasil cylinders, we suggest 240 AO	Aluminum Oxide
Low carbon to medium carbon steels, stainless steel and cast iron.	Zirconia Alumina(Z-Grain). Z-Grain is also beneficial when you are looking for longer tool life than Silicon Carbide (SC)
Medium to high carbon steels and heat-treated steels to 50 Rc. It is also useful in Titanium, Inconel and Monel.	Boron Carbide (BC)
High carbon steel alloys and more exotic space age alloys	Tungsten Carbide (WC)
For a final polish on many materials	Levigated Alumina (LA)
For carbide, ceramic, hardened tool steel and heat treated steels.	Diamond (D)

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Selecting Grit
Standard stocked grits include 120,180, 240 and 320 Silicon Carbide. Many other grit and abrasive combinations are available.

The amount of work to be performed and the degree of surface finish improvement required govern grit selection. Coarse finishes may require progressively finer Flex-Hones to meet final surface finish requirements. In very general terms, final finish will be in the following ranges.

Grit Finish Range
800-LA Ra 3-10 (.05 - .2 Micrometer)
600 Ra 8-12 (.2 - .3 Micrometer)
400 Ra 10-20 (.3 - .6 Micrometer)
320 Ra 18-30 (.5 - .7 Micrometer)
240 Ra 24-32 (.6 - .8 Micrometer)
180 Ra 30-40 (.7 - 1.0 Micrometer)
120 Ra 35-50 (.9 -1.4 Micrometer)
80 Ra 45-64 (1.2 - 1.6 Micrometer)
60 Ra 60-80 (1.5 - 2 Micrometer)
40 Ra 70-125 (1.7 to 3.2 Micrometers)
20 Ra 125-250 (3.2 to 6.3 Micrometers)

PLEASE NOTE: These guidelines are intended to offer a starting point in selecting a grit but the final selection must be verified by actual trial. For more information on suggested RPMs, stroke rates and lubrications, please read our Flex-Hone® Resource Guide.

• Bore Size
• Abrasive
• Grit

Selecting Tool Diameter
Tool diameter is determined by the nominal bore size in which the tool is to operate. The Flex-Hone® tool is always produced and used in an oversized condition. The degree of oversize creates a soft cutting action. For example, a 1" Flex-Hone size is ordered if a 1" bore is to be finished and the tool is provided oversized. If the bore size is between standard Flex-Hone sizes, the next larger standard Flex-Hone should be selected. For instance, if the nominal bore is 1.093", then the 1-1/8" Flex-Hone is ordered.

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Selecting Abrasive Type
Our standard stock abrasive is Silicon Carbide. Many other abrasives are commonly on hand and available to ship.

If the base material is:	Brush Research Suggests:
mild steel, stainless steel and cast iron	Silicon Carbide (SC)
Aluminum, brass, bronze and softer metals. For Deglazing Nikasil cylinders, we suggest 240 AO	Aluminum Oxide
Low carbon to medium carbon steels, stainless steel and cast iron.	Zirconia Alumina(Z-Grain). Z-Grain is also beneficial when you are looking for longer tool life than Silicon Carbide (SC)
Medium to high carbon steels and heat-treated steels to 50 Rc. It is also useful in Titanium, Inconel and Monel.	Boron Carbide (BC)
High carbon steel alloys and more exotic space age alloys	Tungsten Carbide (WC)
For a final polish on many materials	Levigated Alumina (LA)
For carbide, ceramic, hardened tool steel and heat treated steels.	Diamond (D)

---

Selecting Grit
Standard stocked grits include 120,180, 240 and 320 Silicon Carbide. Many other grit and abrasive combinations are available.

The amount of work to be performed and the degree of surface finish improvement required govern grit selection. Coarse finishes may require progressively finer Flex-Hones to meet final surface finish requirements. In very general terms, final finish will be in the following ranges.

Grit Finish Range
800-LA Ra 3-10 (.05 - .2 Micrometer)
600 Ra 8-12 (.2 - .3 Micrometer)
400 Ra 10-20 (.3 - .6 Micrometer)
320 Ra 18-30 (.5 - .7 Micrometer)
240 Ra 24-32 (.6 - .8 Micrometer)
180 Ra 30-40 (.7 - 1.0 Micrometer)
120 Ra 35-50 (.9 -1.4 Micrometer)
80 Ra 45-64 (1.2 - 1.6 Micrometer)
60 Ra 60-80 (1.5 - 2 Micrometer)
40 Ra 70-125 (1.7 to 3.2 Micrometers)
20 Ra 125-250 (3.2 to 6.3 Micrometers)

PLEASE NOTE: These guidelines are intended to offer a starting point in selecting a grit but the final selection must be verified by actual trial. For more information on suggested RPMs, stroke rates and lubrications, please read our Flex-Hone® Resource Guide.