---
product_id: 149138050
title: "Brush Research GB31212 FLEX-HONE®, 3-1/2\" (89mm) Diameter, 120 Grit, Silicon Carbide, For Mild Steel, Stainless Steel, Cast Iron and Softer Ferrous Materials"
brand: "flex-hone"
price: "₨35387"
currency: LKR
in_stock: true
reviews_count: 8
category: "Flex Hone"
url: https://www.desertcart.lk/products/149138050-brush-research-gb31212-flex-hone-3-1-2-89mm-diameter
store_origin: LK
region: Sri Lanka
---

# Optimized for mild steel & ferrous metals 120 grit precision abrasive Self-centering & self-aligning design Brush Research GB31212 FLEX-HONE®, 3-1/2" (89mm) Diameter, 120 Grit, Silicon Carbide, For Mild Steel, Stainless Steel, Cast Iron and Softer Ferrous Materials

**Brand:** flex-hone
**Price:** ₨35387
**Availability:** ✅ In Stock

## Summary

> 🛠️ Elevate your finish game — flawless surfaces, zero hassle!

## Quick Answers

- **What is this?** Brush Research GB31212 FLEX-HONE®, 3-1/2" (89mm) Diameter, 120 Grit, Silicon Carbide, For Mild Steel, Stainless Steel, Cast Iron and Softer Ferrous Materials by flex-hone
- **How much does it cost?** ₨35387 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.lk](https://www.desertcart.lk/products/149138050-brush-research-gb31212-flex-hone-3-1-2-89mm-diameter)

## Best For

- flex-hone enthusiasts

## Why This Product

- Trusted flex-hone brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Self-Centering & Self-Aligning:** Engineered oversize design ensures perfect alignment and consistent pressure every use.
- • **Versatile Material Compatibility:** Ideal for mild steel, stainless steel, cast iron, and softer ferrous materials.
- • **Dual-Action Finishing & Deburring:** Simultaneously smooths surfaces and removes burrs in one efficient setup.
- • **Precision 120 Grit Silicon Carbide:** Delivers a flawless 35-50 microinch finish for superior surface quality.
- • **Made in the USA with Trusted Quality:** Crafted by the original inventors for unmatched reliability and durability.

## Overview

The Brush Research GB31212 FLEX-HONE® is a 3.5-inch diameter, 120 grit silicon carbide abrasive tool designed for precision honing and deburring of mild steel, stainless steel, cast iron, and softer ferrous materials. Its patented oversized, self-centering design ensures consistent pressure and alignment, producing an oil-retentive crosshatch plateau finish that enhances seal life and engine performance. Made in the USA by the original inventors, this tool is a must-have for professionals seeking efficient, high-quality surface finishing and deburring in hydraulic, pneumatic, and automotive applications.

## Description

The FLEX-HONE® tool was originally created by Brush Research Manufacturing to deglaze cylinder walls in automotive applications. Brush Research embraced the benefits of a plateau finish and pioneered the concept of plateau honing culminating in the introduction of the FLEX-HONE® tool in 1972. The FLEX-HONE® has gained many nicknames over the years and including ball hone, ball style hone, flexihone, dingleberry hone, bead brush, glaze breaker and glaze buster. Flexible honing with the FLEX-HONE® tool produces an oil holding cross hatch pattern and a true plateau finish free of cut, torn and folded metal. Any type or size of cylinder can benefit from the FLEX-HONE®. These abrasive bead style brushes are produced in standard diameters from 4mm to 36 inches. Nine abrasive types are offered including Silicon Carbide, Aluminum Oxide, Boron Carbide and Diamond allowing the tool to be tailored to finish any base material. A choice of 11 different grit selections are available for precise control of finish parameters. The elimination of peaks results in rapid ring seating, better oil control, reduced seepage in hydraulic and pneumatic applications and provides better seal performance and longer seal life. Successful applications include firearm chambers, shotgun barrels, musical instruments, combustion chambers, air compressors, pumps, valve bodies, valve guides, brake cylinders, wheel cylinders and the list goes on and on. FLEX-HONE® tools are also very effective for deburring cross drilled holes, port radiusing and edge blending. Because of its unique construction, the FLEX-HONE® is self-centering, self-aligning, and self-compensating for wear so it does not require an elaborate set-up or special training. Deburring can be effectively automated and combined in the machining process to allow a complete cylinder finish in one operation or it can be employed as a secondary operation with equal results.

Review: Five stars - The FLEX-HONE® is a game-changer for surface finishing! The 240-grit silicon carbide abrasive works flawlessly on mild steel, stainless steel, and cast iron. It delivers a smooth, uniform finish while removing burrs effortlessly. Durable and easy to use—highly recommended for professionals and DIYers. Consistent performance and great value. Five stars
Review: Engine Performance Booster - Being a motorsport engineer, the flex hone is my go-to for ensuring peak engine performance. I never skip the step of running the engine with this tool before reassembly, especially when honing isn't fully done. Its precision and efficiency elevate the process, delivering flawless results. I swear by the flex hone for a seamless and effective engine reassembly routine.

## Features

- [QUALITY]-Proudly Made in the USA. Quality and consistency you can count on made from the inventors and makers of the tool.
- [DESIGN]-The FLEX-HONE is intentionally manufactured oversized. This engineered oversize creates the optimal amount of pressure inside the cylinder wall allowing the tool to be self-centering, self-aligning and self-compensating for wear and easy use.
- [FINISHING BENEFITS]-Offered in a wide variety of grits to achieve specific finishing tolerances as well as a beautiful crosshatch finish. Ideal for rebuilding hydraulic and pneumatic cylinders, engine and brake cylinders, valve guides, pumps, compressors and more.
- [CROSSHOLE DEBURRING]-Accomplish finishing and deburring simultaneously in a single setup. Can be used in virtually any rotating spindle from a hand drill, drill press or CNC equipment.
- [120 GRIT SILICON CARBIDE ABRASIVE]-Excellent on mild steel, stainless steel, cast iron and other softer ferrous materials. Typically achieves a finish of 35 - 50 Microinch (.9 - 1.4 Micrometer).
- [WHAT'S INCLUDED]-1 Each of a GB Standard Duty FLEX-HONE: 3.500" (89mm) Bore Diameter, 3.50" Abrasive Part Length, 0.310" Shank Diameter, 13.5" Overall Length. For Use on Bore Diameters Between 3.251"-3.500". PLEASE NOTE: ORDER BY BORE SIZE.

## Technical Specifications

| Specification | Value |
|---------------|-------|
| ASIN | B002XUL1DK |
| Best Sellers Rank | #4,972 in Industrial & Scientific ( See Top 100 in Industrial & Scientific ) #2 in Flex Hones |
| Brand | Flex-Hone |
| Brand Name | Flex-Hone |
| Bristle Type | Abrasive Globule Bonded To Flexible Nylon Filament |
| Compatible Material | Other Softer Ferrous Materials, Stainless Steel, Mild Steel, Cast Iron |
| Customer Reviews | 4.8 out of 5 stars 2,420 Reviews |
| Grit Material | Silicon Carbide |
| Grit Material Type | Silicon Carbide |
| Grit Number | 120 |
| Grit Type | 120 Grit |
| Included Components | GB 3-1/2" (89MM) 120SC FLEX-HONE |
| Item Dimensions | 13.5 x 5.1 x 5.1 inches |
| Item Weight | 0.71 Pounds |
| Manufacturer | Brush Research Manufacturing |
| Material | Silicon Carbide |
| Material Type | Silicon Carbide |
| Number of Pieces | 1 |
| Recommended Uses For Product | Deburring, Finishing |
| UPC | 843469142832 |
| Unit Count | 1.0 Count |
| Warranty Description | Manufacturer Warranty |

## Product Details

- **Brand:** Flex-Hone
- **Bristle Type:** Abrasive Globule Bonded To Flexible Nylon Filament
- **Grit Material:** Silicon Carbide
- **Grit Type:** 120 Grit
- **Material:** Silicon Carbide

## Images

![Brush Research GB31212 FLEX-HONE®, 3-1/2" (89mm) Diameter, 120 Grit, Silicon Carbide, For Mild Steel, Stainless Steel, Cast Iron and Softer Ferrous Materials - Image 1](https://m.media-amazon.com/images/I/61f9Ueb7-8L.jpg)
![Brush Research GB31212 FLEX-HONE®, 3-1/2" (89mm) Diameter, 120 Grit, Silicon Carbide, For Mild Steel, Stainless Steel, Cast Iron and Softer Ferrous Materials - Image 2](https://m.media-amazon.com/images/I/8156ob+ylqL.jpg)
![Brush Research GB31212 FLEX-HONE®, 3-1/2" (89mm) Diameter, 120 Grit, Silicon Carbide, For Mild Steel, Stainless Steel, Cast Iron and Softer Ferrous Materials - Image 3](https://m.media-amazon.com/images/I/71LI+vNqxIL.jpg)
![Brush Research GB31212 FLEX-HONE®, 3-1/2" (89mm) Diameter, 120 Grit, Silicon Carbide, For Mild Steel, Stainless Steel, Cast Iron and Softer Ferrous Materials - Image 4](https://m.media-amazon.com/images/I/81aPGQTXemL.jpg)
![Brush Research GB31212 FLEX-HONE®, 3-1/2" (89mm) Diameter, 120 Grit, Silicon Carbide, For Mild Steel, Stainless Steel, Cast Iron and Softer Ferrous Materials - Image 5](https://m.media-amazon.com/images/I/81X4pgWlJtL.jpg)

## Available Options

This product comes in different **Size, Style** options.

## Questions & Answers

**Q: Wish one is best for a cylinder wall that is 75mm (2.95 inch) ?**
A: For the cylinder wall bore size of 2.95", the 3" Flex-Hone is the correct choice., Enter this ASIN # B002N3AA2A  in the Amazon search bar for the correct hone.

**Q: Hello, my cylinder bore is 3 1/8" what size tool do i need to purchase thank you.**
A: For a 3.125" bore,  your application will require the 3-1/4" (3.250") diameter Flex-hone. The 3-1/4" will work perfectly in the 3-1/8" bore as the 3-1/4" Flex-hones working range is down to 3.000". Thank you for the inquiry.

**Q: Can i use this to hone out an old cast iron pipe?  it's about 3 3/4" now and i want it at 4" id. thanks**
A: This hone is not coarse enough to remove that much material. It would take forever and the hone would wear out first. You would need a lathe to remove that amount of thickness.

**Q: I see that it says tool is oversized. For a cylinder bore of 3.66, should I be getting the 3.75 or the 3.50 model?**
A: 1I bought a 4.50 and used it on a 3.55 bore with no problem I  didn't hone as much as instruction said for large bore, hatch marks were beautiful  so go bigger and you can use it over a broad area of bores.

## Customer Reviews

### ⭐⭐⭐⭐⭐ Five stars
*by T***O on April 28, 2025*

The FLEX-HONE® is a game-changer for surface finishing! The 240-grit silicon carbide abrasive works flawlessly on mild steel, stainless steel, and cast iron. It delivers a smooth, uniform finish while removing burrs effortlessly. Durable and easy to use—highly recommended for professionals and DIYers. Consistent performance and great value. Five stars

### ⭐⭐⭐⭐⭐ Engine Performance Booster
*by A***E on October 22, 2025*

Being a motorsport engineer, the flex hone is my go-to for ensuring peak engine performance. I never skip the step of running the engine with this tool before reassembly, especially when honing isn't fully done. Its precision and efficiency elevate the process, delivering flawless results. I swear by the flex hone for a seamless and effective engine reassembly routine.

### ⭐⭐⭐⭐⭐ Perfect Tool for Smoothing Various Metal Surfaces
*by D***S on July 8, 2025*

I recently tried out the Brush Research GB41824 FLEX-HONE® in 4-1/8" diameter with 240 grit, and I am amazed by its performance. This tool is ideal for working on mild steel, stainless steel, cast iron, and other softer ferrous materials. The results were fantastic – the surfaces were smooth and polished to perfection. I love how versatile this FLEX-HONE® is, making it a valuable addition to my workshop. I highly recommend it to anyone looking to achieve professional results with ease.

## Frequently Bought Together

- Brush Research GB31212 FLEX-HONE®, 3-1/2" (89mm) Diameter, 120 Grit, Silicon Carbide, For Mild Steel, Stainless Steel, Cast Iron and Softer Ferrous Materials
- Brush Research FHQ FLEX-HONE® Oil, Specially Formulated Honing Oil, 1 Quart Bottle (32 fl oz)
- Permatex 81950 Ultra Slick Engine Assembly Lube, 4 oz. , Red

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*Product available on Desertcart Sri Lanka*
*Store origin: LK*
*Last updated: 2026-02-23*