Brush Research GB33432 FLEX-HONE 3-3/4ft 320 Grit - Precision Finish

Our review of the Brush Research GB33432 FLEX-HONE finds it best suited to mechanics, machinists and hobbyists who need a straightforward way to produce a plateau crosshatch finish inside bores. The single biggest reason to buy is its consistent, self-centering design that makes achieving an oil-retaining finish quick and repeatable; users report professional-quality surface appearance on mild steel, stainless and cast iron with minimal setup. This review focuses on real-world finishing, ease of use and value for rebuilding cylinders and similar bores.

Key Features

• Made in the USA: Built by the original maker for consistent quality and materials you can rely on during repeated shop use.
• Oversized engineered design: The intentionally manufactured oversize lets the tool self-center and self-compensate for wear, reducing the need for constant adjustment.
• 320 grit silicon carbide abrasive: Delivers a fine plateau finish typically in the 18 - 30 microinch range ideal for oil retention and bearing surfaces.
• Crosshole deburring and finishing: Finishes and deburrs in a single setup and runs in common rotating spindles from a hand drill to CNC equipment.
• Versatile application: Effective on mild steel, stainless steel, cast iron and softer ferrous materials for engine, pump and hydraulic cylinder work.

Who It's For

The FLEX-HONE GB33432 is aimed at users rebuilding hydraulic and pneumatic cylinders, engine cylinders, valve guides, pumps and compressors who want a reliable abrasive brush that produces an oil-holding crosshatch and plateau finish. It is particularly useful when a uniform surface with minimal torn or folded metal is required and where time-saving single-setup deburring is a benefit.

It is less appropriate for non-ferrous metals that require different abrasives or for precision bored parts needing traditional rigid honing stones to remove large amounts of material; those tasks call for alternate cutting hones or specialized tooling.

Pros & Cons

Pros

• Consistent finish quality and ease of use thanks to the self-centering oversized design.
• Good versatility across mild steel, stainless and cast iron with the 320 grit silicon carbide abrasive.
• Works in simple shop equipment from a hand drill to drill press or CNC spindle for flexible setup.

Cons

• Not intended for heavy stock removal; best for finishing and deburring rather than aggressive material removal.

Specifications

Our Verdict

The GB33432 FLEX-HONE is a practical, well-made finishing tool for anyone rebuilding cylinders or restoring bore surfaces who needs a reliable plateau finish and crosshatch for oil retention. It represents good value when consistent surface quality and simple setup are priorities, though it is not a substitute for aggressive stock removal hones.

Frequently Asked Questions

Can this hone be used in a hand drill?
Yes, it is designed to run in virtually any rotating spindle including a hand drill, drill press or CNC equipment.

What materials is the 320 grit best for?
320 grit silicon carbide is excellent for mild steel, stainless steel, cast iron and other softer ferrous materials to achieve a fine plateau finish.

What bore sizes will this tool fit?
This model is for bore diameters between 3.501 in and 3.750 in; order by bore size to ensure proper fit.