--- 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: "€ 101.91" currency: EUR in_stock: true url: https://www.desertcart.pt/products/149138050-brush-research-gb31212-flex-hone-3-1-2-89mm-diameter store_origin: PT region: Portugal --- # 120 grit silicon carbide for superior finish 3.5" diameter precision fit 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:** € 101.91 **Availability:** ✅ In Stock ## Summary > ⚙️ Elevate your cylinder finish game—precision honing that means business! ## 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?** € 101.91 with free shipping - **Is it available?** Yes, in stock and ready to ship - **Where can I buy it?** [www.desertcart.pt](https://www.desertcart.pt/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 - • **Proudly Made in the USA:** Trusted quality from the original FLEX-HONE® inventors ensures consistent, professional results. - • **Versatile Compatibility:** Ideal for hydraulic, pneumatic, engine, brake cylinders, and more—one tool, endless applications. - • **120 Grit Silicon Carbide Abrasive:** Delivers a smooth 35-50 microinch plateau finish on mild steel, stainless steel, and cast iron. - • **Dual-Action Finishing & Deburring:** Achieve crosshatch finish and deburr in a single setup using any rotating spindle—boost efficiency. - • **Engineered Oversize for Perfect Pressure:** Self-centering and self-compensating for flawless cylinder wall contact every time. ## Overview The Brush Research GB31212 FLEX-HONE® is a 3.5-inch diameter, 120 grit silicon carbide honing tool designed for mild steel, stainless steel, cast iron, and softer ferrous materials. Its engineered oversize design ensures self-centering, self-aligning, and self-compensating action for optimal pressure and finish quality. Perfect for rebuilding hydraulic, pneumatic, engine, and brake cylinders, it simultaneously deburrs and finishes with a distinctive oil-retentive crosshatch pattern. Made in the USA by the original FLEX-HONE® inventors, this tool delivers consistent, professional-grade results with minimal setup. ## 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. ## 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 | #8,722 in Industrial & Scientific (See Top 100 in Industrial & Scientific) #2 in Flex Hones | | 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 | 4.7 4.7 out of 5 stars (160) 4.7 out of 5 stars | | Grit Material Type | Silicon Carbide | | Grit Number | 120 | | Grit Type | 120 Grit | | Included Components | GB 3-1/2" (89MM) 120SC FLEX-HONE | | Item Diameter | 3.5 inches | | Item Dimensions | 13.5 x 5.1 x 5.1 inches | | Item Weight | 11.36 ounces | | Manufacturer | Brush Research Manufacturing | | Material Type | Silicon Carbide | | Model | GB31212 | | Number Of Items | 1 | | Number Of Pieces | 1 | | Part Number | GB31212 | | Recommended Uses For Product | Deburring, Finishing | | Unit Count | 1 Count | | Upc | 843469142832 | | 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. ## 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 --- ## Why Shop on Desertcart? - 🛒 **Trusted by 1.3+ Million Shoppers** — Serving international shoppers since 2016 - 🌍 **Shop Globally** — Access 737+ million products across 21 categories - 💰 **No Hidden Fees** — All customs, duties, and taxes included in the price - 🔄 **15-Day Free Returns** — Hassle-free returns (30 days for PRO members) - 🔒 **Secure Payments** — Trusted payment options with buyer protection - ⭐ **TrustPilot Rated 4.5/5** — Based on 8,000+ happy customer reviews **Shop now:** [https://www.desertcart.pt/products/149138050-brush-research-gb31212-flex-hone-3-1-2-89mm-diameter](https://www.desertcart.pt/products/149138050-brush-research-gb31212-flex-hone-3-1-2-89mm-diameter) --- *Product available on Desertcart Portugal* *Store origin: PT* *Last updated: 2026-11-09*