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Union Butterfield 4531 High-Speed Steel Expansion Chucking Reamer, Straight Flute, Round Shank, Uncoated (Bright)

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Product Specifications
Cutting Direction
Cutting Length
1.1/8  inches
Finish Types
Uncoated (Bright)
Shank Type
Material Type
High Speed Steel
Brand Name
Precision Twist

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3/8 " Inch 0.3750" 7" 5011204 B003JY6PG2 yes $56.67 Buy Options
13/32" Inch 0.4062" 7" 5011205 B003JY6P9O yes $58.24 Buy Options
7/16" Inch 0.4375" 7" 5010778 B003JY6PHQ yes $59.96 Buy Options
15/32" Inch 0.4688" 7" 5010779 B003JY6PAS yes $60.37 Buy Options
1/2 " Inch 0.5000" 8" 5010780 B003JY6P80 yes $63.43 Buy Options
17/32" Inch 0.5312" 8" 5010781 B003JY6PBC yes $66.15 Buy Options
9/16" Inch 0.5625" 8" 5010782 B003JY6PIU yes $21.46 Buy Options
19/32" Inch 0.5938" 8" 5010783 B003JY6PBW yes $69.47 Buy Options
5/8" Inch 0.6250" 9" 5010784 B003JY6PH6 yes $69.38 Buy Options
21/32" Inch 0.6562" 9" 5010785 B003JY6PD0 yes $78.17 Buy Options
11/16" Inch 0.6875" 9" 5010786 B003JY6P8K yes $81.90 Buy Options
23/32" Inch 0.7188" 9" 5010787 B003JY6PDK yes $78.06 Buy Options
3/4" Inch 0.7500" 9-1/2" 5010788 B003JY6PFI yes $81.98 Buy Options
25/32" Inch 0.7812" 9-1/2" 5010789 B003JY6PE4 yes $83.58 Buy Options
13/16" Inch 0.8125" 9-1/2" 5010790 B003JY6P94 yes $88.53 Buy Options
27/32" Inch 0.8438" 9-1/2" 5010791 B003JY6PEO yes $27.26 Buy Options
7/8" Inch 0.8750" 10" 5010792 B003JY6PIA yes $103.56 Buy Options
29/32" Inch 0.9062" 10" 5010793 B003JY6PEY yes $101.23 Buy Options
15/16" Inch 0.9375" 10" 5010794 B003JY6PA8 yes $30.11 Buy Options
31/32" Inch 0.9688" 10" 5010795 B003JY6PGM yes $31.86 Buy Options

Key Features

  • Expandable as wear decreases its cutting diameter, so it can be reground and re-sharpened to its original dimensions for increased life
  • Morse taper shank for accurate alignment and firm hold in the socket of a toolholder
  • Straight flute for general-purpose reaming of uninterrupted cuts in through holes and blind holes
  • Uncoated (bright) tools have no additional surface treatment or coating, suitable for general-purpose applications
  • 45-degree bevel at the cutting tip facilitates entry to pre-drilled holes

Product Description

The Union Butterfield 4531 high-speed steel straight flute expansion chucking reamer (also called a machine reamer) is an uncoated (bright) round shank tool with a 45-degree bevel lead, commonly used for reaming of uninterrupted cuts in high-production runs on abrasive materials. An expansion reamer can be expanded using a screw in the center of the reamer as wear decreases its cutting diameter, so it can be reground to its original dimensions and re-sharpened to prevent rapid loss of reamer size or finish. This tool can be used in a drill press, screw machine, or lathe, or other good-quality toolholders.

Straight flute reamers make small, circular, and precise enlargements to through and blind holes. They can be used on a wide variety of materials. Round shanks aid accurate centering; they are designed to be held in a chuck or collet for high-torque applications. High-speed steel (HSS) is a general-purpose steel for cutting tools that is compatible with many metalworking materials, and is often lower in price than other cutting tool substrates. This reamer has a 45-degree bevel lead at the cutting tip to facilitate entry to pre-drilled holes.

In the Union Butterfield 4531 series, reamers 0.3750” to 0.9688” in diameter have six flutes, 1.0000” to 1.3750” in diameter have eight flutes, 1.4375” to 1.8125” in diameter have ten flutes, and 1.8750” to 2.0000” in diameter have 12 flutes. Tolerances for 0.3750” to 1.0000” reamers are +0.0001” to +0.0005” and tolerances for 1.0312” to 2.0000” reamers are +0.0002” to +0.0006”.

Reamers are used to finish existing holes. When holes are created using common applications such as drilling or punching, they often have minute imperfections. Their roundness may be flawed, or their diameters may be slightly smaller than required. Reamers are made to exacting tolerances so they can correct such errors and create precisely round holes with exact dimensions. Reaming is often used before tapping screw threads.

Precision manufactures machine tools under the following brands: Precision Twist, Precision Dormer, and Union Butterfield. They have locations around the world, and provide tools adhering to ANSI, NAS, and DIN standards.

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