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Brush Research BC4M400 FLEX-HONE®, 0.157" (4mm) Diameter, 400 Grit, Silicon Carbide, for Mild Steel, Stainless Steel, Cast Iron and Softer Ferrous Materials

4.7 4.7 out of 5 stars 1,901 ratings
#1 Best Seller in Flex Hones
$39.52
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400 Grit
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Purchase options and add-ons

Material Silicon Carbide
Brand Flex-Hone
Grit Material Silicon Carbide
Bristle Type Abrasive Globule Bonded To Flexible Nylon Filament
Compatible Material Other Softer Ferrous Materials, Stainless Steel, Mild Steel, Cast Iron

About this item

  • [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.
  • [400 GRIT SILICON CARBIDE ABRASIVE]-Excellent on mild steel, stainless steel, cast iron and other softer ferrous materials. Typically achieves a finish of 10 - 20 Microinch (.3 - .6 Micrometer).
  • [WHAT'S INCLUDED]-1 Each of a BC Standard Duty FLEX-HONE: 0.157"(4mm) Bore Diameter, 0.75" Abrasive Part Length, 0.055" Shank Diameter, 6" Overall Length. For Use on Bore Diameters Between 0.147"-0.157". PLEASE NOTE: ORDER BY BORE SIZE.

Frequently bought together

Brush Research BC4M400 FLEX-HONE®, 0.157" (4mm) Diameter, 400 Grit, Silicon Carbide, for Mild Steel, Stainless Steel, Cast Ir
$39.52
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Brush Research FHP FLEX-HONE Oil, Specially Formulated Honing Oil, 1/2 Pint Bottle (8 fl oz)
$17.59
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Brush Research GB31212 FLEX-HONE®, 3-1/2" (89mm) Diameter, 120 Grit, Silicon Carbide, For Mild Steel, Stainless Steel, Cast I
$34.69
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Product details

  • Package Dimensions ‏ : ‎ 13.03 x 11.38 x 0.47 inches; 1 ounces
  • Item model number ‏ : ‎ BC4M400
  • Date First Available ‏ : ‎ April 23, 2023
  • Manufacturer ‏ : ‎ Brush Research Manufacturing
  • ASIN ‏ : ‎ B0C39MHNSW
  • Country of Origin ‏ : ‎ USA
  • Customer Reviews:
    4.7 4.7 out of 5 stars 1,901 ratings

Product 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, Z-Grain, Leviagted Alumina, CBN 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.

From the manufacturer

Flex-Hone

Flex-Hone Benefits for Hobbyists, Machinists and High Volume Production Environments

Flex-Hone Finishing

Flex-Hone Crosshole Deburring

Flex-Hone Polishing

Flex-Hone Engine Block

SURFACE FINISHING APPLICATIONS

Working with machined parts often means ensuring a proper finish. The Flex-Hone creates repeatable finishing results with minimal setup or effort. The tool can be chucked in virtually any rotating spindle.

CROSSHOLE DEBURRING APPLICATIONS

Deburring is a costly operation for machinists. Even a small notch can cause moving parts to catch, creating the potential for accident. Deburr and finish cylinders in a single set with Flex-Hone Tools.

POLISHING & SINGLE RA FINISHING

achieve some of the most difficult finishing challenges with our large selection of grit and abrasive options. Finer grits are capable of achieving single RA finishes with minimal effort.

CONSISTENT PLATEAUED CROSSHATCH FINISHES

Deglaze cylinder walls with ease. A 45 degree crosshatch helps to seat piston rings and retains oil for lubrication. Also great for valve guides, piston pin bores, cam bearing bores and more!

Flex-Hone in Machine

Flex-Hone offers machinists the ideal combination of performance and value for professional finishing applications.

Flex-Hone Sizes
Brush Research Manufacturing's Flex-Hone Tool

For over 60 years, BRM has been a leader in the art and science of surface finishing. BRM invented the Flex-Hone to tackle a variety of surface finishing challenges, whether your need is providing a proper crosshatch on engine cylinders, finishing hydraulic and pneumatic cylinders, deburring cross drilled holes and more.

  • Invented and Made By American Craftsmen
  • Long Lasting to Help Save You Time and Money
  • Remove Repetitive Motion Operations- Works On Virtually Any Rotating Spindle

BRM's Flex-Hone Tool

Finishing and Deburring For Any Type or Size of Cylinder

The Flex-Hone Tool is a resilient, flexible honing tool used to improve the internal surface finish while also being able to deburr a bore or cylinder. It is comprised of abrasive globules laminated onto the ends of flexible nylon filaments. Its unique construction allows the tool to be self-aligning, self-centering and self-compensating for wear.

  • Proudly Made in the USA
  • Offering 10 Different Abrasive Types and 11 Grit Selections
  • Provides a Crosshatch and Plateaued Finish on Engine Cylinders, Valve Guides, Piston Pin Bores and More!
  • Ideal for Crosshole and Slot Deburring
  • Achieve Single Digit RA finishes
BC Standard FLEX-HONE BC Standard FLEX-HONE BC Standard FLEX-HONE BC Standard FLEX-HONE BC Standard FLEX-HONE BC Standard FLEX-HONE
SILICON CARBIDE - BC FLEX-HONE-Standard Duty for Small Diameters ALUMINUM OXIDE - BC FLEX-HONE-Standard Duty for Small Diameters DIAMOND - BC FLEX-HONE-Standard Duty for Small Diameters BORON CARBIDE - BC FLEX-HONE-Standard Duty for Small Diameters LEVIGATED ALUMINA FLEX-HONE ZIRCONIA ALUMINA - BC FLEX-HONE-Standard Duty for Small Diameters
See Details
Customer Reviews
4.7 out of 5 stars
1,901
4.7 out of 5 stars
239
—
5.0 out of 5 stars
2
4.5 out of 5 stars
2
—
Price $20.00 $33.20 — $29.19 $43.08 $28.45
Size Range .157"(4mm) - 3"(76mm) .157"(4mm) - 3"(76mm) .157"(4mm) - 1-1/4"(31.8mm) .157"(4mm) - 3"(76mm) .157"(4mm) - 3"(76mm) .157"(4mm) - 3"(76mm)
Abrasive Type Silicon Carbide Aluminum Oxide Diamond Boron Carbide Levigated Alumina Zirconia Alumina-Z-Grain (1525)
Recommended For Mild Steel, Stainless Steel and Cast Iron Aluminum, Brass, Bronze and Softer Metals. 240AO Ideal for Deglazing Nikasil Cylinders Carbide, Ceramic, Hardened Tool Steel and Heat-Treated Steel Medium to High Carbon Steels, Titanium and Heat-Treated Steels to 50 Rc. Final Polish On Many Materials Low Carbon to Medium Carbon Steels, Stainless Steel and Cast Iron (For Longer Tool Life Thank Silicon Carbide)
Requires Lubricant ✓ ✓ ✓ ✓ ✓ ✓
BC Standard FLEX-HONE GB Standard FLEX-HONE GBD Heavy Duty FLEX-HONE Rotor hone firearms hone, chamber hone, barrel hone flex-hone kits
BC Standard Duty-Silicon Carbide FLEX-HONE Tools GB Standard Duty-Silicon Carbide FLEX-HONE Tools GBD Heavy Duty-Silicon Carbide FLEX-HONE Tools FLEX-HONE for Rotors FLEX-HONE for Firearms FLEX-HONE Kits
Customer Reviews
4.7 out of 5 stars
1,901
4.8 out of 5 stars
1,736
4.8 out of 5 stars
796
4.3 out of 5 stars
181
4.7 out of 5 stars
320
—
Price $20.00 $58.93 $75.09 $50.66 $37.49 $200.37
Size Range .157"(4mm) - 3"(76mm) 3-1/4"(83mm) - 4-5/8"(118mm) 3"(76mm) - 8"(203mm) Design For Specific Firearms Models
Grit Options 20, 40, 60, 80, 120, 180, 240, 320, 400, 600, 800, 100/1200 20, 40, 60, 80, 120, 180, 240, 320, 400, 600, 800, 100/1200 20, 40, 60, 80, 120, 180, 240, 320, 400, 600, 800, 100/1200 60 (Coarse), 120 (Medium), 240 (Fine) 180, 400, 800

What's in the box

  • FLEX-HONE® Tool

    • Looking for specific info?

    Customer reviews

    4.7 out of 5 stars
    4.7 out of 5
    1,901 global ratings

    Customers say

    Customers like the value, pattern, ease of use, and cylinder cleaning of the abrasive. For example, they mention it's great for the price, saves time, and money. That said, they're happy with the quality. Opinions are mixed on fit.

    AI-generated from the text of customer reviews

    181 customers mention174 positive7 negative

    Customers are satisfied with the quality of the abrasive. They mention that it works well, is a nice performing tool, and is highly recommended. They also appreciate the amazing product engineering and find it very useful to have.

    "This works exactly how it should. This is now my third hone for a different size engine...." Read more

    "Worked great on my 2003 gsxr block" Read more

    "...It performed as I expected and I was very pleased with the results. Good product!" Read more

    "Nice performing tool . Have many of various sizes. All good" Read more

    36 customers mention36 positive0 negative

    Customers find the auto accessory easy to use. They say it's well-made, and makes quick work of each cylinder. Customers also appreciate the good instructions on use and the smooth, fast cuts. They mention it'll leave a perfect cross-hatched pattern fast. Overall, customers are happy with the product's ease of use and recommend it to others.

    "This is a great tool to recondition a cylinder bore. Easy to use, and if you follow the directions you will produce a nice cross hatch pattern..." Read more

    "It was fairly easy to use although doing a top end on a snowmobile wasn't very easy...." Read more

    "...This hone is very easy to use and works very well, make sure you use a good lubricant while you hone, 10w30 oil is what I used...." Read more

    "There was nothing to dislike safe and easy to use takes guesswork out of cylinder honing" Read more

    25 customers mention25 positive0 negative

    Customers appreciate the value of the auto accessory. They say it's worth the money and an easy to use tool that saves time and money.

    "...This tool helped save my engine, so it was well worth the money even if that was the only time I'll ever use it." Read more

    "...Perfect cross hatched pattern on both.Great tool and good value considering the $200 of parts and many hours of labor to complete this..." Read more

    "THIS TOOL IS PRICED AT A REASONABLE PRICE AND OUR TECHNICIAN WAS ABLE TO COMPLETE THE JOB." Read more

    "Worth every penny! It won’t let me add the pics or else you’d be as impressed as I am!" Read more

    16 customers mention16 positive0 negative

    Customers are satisfied with the pattern of the auto accessory. They mention that it produces a really nice cross-hatch pattern, and that it does a beautiful job of crosshatching the glaze.

    "...Perfect cross hatched pattern on both...." Read more

    "...While the cylinder didn’t look bad to begin with, this hone made it look great...." Read more

    "Did 2 passes with the 240grit on a RM250 cylinder and it came out beautiful , real smooth" Read more

    "...The cylinders came out looking new with a perfect cross hatch pattern...." Read more

    15 customers mention15 positive0 negative

    Customers are satisfied with the cylinder cleaning capabilities of the abrasive. They mention that it cleans the combustion cylinders and any remaining carbon buildup like a dream. It also removes bore glaze quickly, dark spots, and corrosion inside the tilt tube. It's easy for first timers and makes short work of removing light scuffs and scratches on cylinder walls.

    "...This makes quick work of any corrosion inside the tilt tube. You don't have to go wild and make a mirror finish inside, just enough to clean it up...." Read more

    "Works well in my cylinders and cleans them up well. Make sure to get the correct size" Read more

    "...Worked good and cleaned it right up. Wish I thought of using one of these sooner!..." Read more

    "This is extremely easy to use. It did a perfect job of cleaning up a cylinder on a lawnmower...." Read more

    4 customers mention4 positive0 negative

    Customers are satisfied with the bore of the abrasive. They mention that it leaves a clean cylinder bore with a nice cross-section. Some say that it works like a charm and provides the best finish for valve guides possible.

    "...brake fluid and my drill dis the rest, 4 cycles and wheel cylinder bore was spotless, very impressed." Read more

    "It did what it was intended for,honed out the cylinders,worked like a charm!" Read more

    "This is a great flex hone; it left a clean cylinder bore, with a really nice cross-hatch pattern. Worked like a champ." Read more

    "Best finish for valve guides possible...." Read more

    15 customers mention8 positive7 negative

    Customers are mixed about the fit of the flex hone. Some mention that the sizing was spot on, and it did the job it intended to do. However, others say that it's oversized to begin with, too big for a 54mm bore, and coarse for shift Chevy lifters.

    "...This go-round was for a dirtbike cylinder, and the hone fit nicely, and cleaned up the bore to put a cross-hatch pattern into it...." Read more

    "...They are oversized to begin with (my 1 1/8" hone being a few thousandths shy of 1 1/4")...." Read more

    "...This fit, and worked, perfectly!..." Read more

    "...Boy were they wrong. It was so big it wouldn't even fit in the cylinder...." Read more

    8 customers mention5 positive3 negative

    Customers are mixed about the smoothness of the auto accessory. Some mention it came out beautiful, smooth, and does a really nice job smoothing the bore out. Others say it's too coarse for a finish hone, and rough.

    "...with the 240grit on a RM250 cylinder and it came out beautiful , real smooth" Read more

    "...What I found in the chamber was nothing short of horrific - a nice thick black coating of whatever the brake fluid turned into after all these years..." Read more

    "...Unfortunately while the cylinder that this was used for is perfect, smooth, and flawless-- the hone cannot be used again...." Read more

    "...Provides a smooth consistent finish with a simple hand drill." Read more

    Worked extremely well, even for a novice!
    5 Stars
    Worked extremely well, even for a novice!
    Used this for my Predator 212cc go kart build, where I was swapping to a flat top piston for additional compression. While the cylinder didn’t look bad to begin with, this hone made it look great. I coated the hone in oil and utilized it for around 30 seconds per the instructions. Can’t wait to use its again on the next build!
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    Top reviews from the United States

    James S.
    5.0 out of 5 stars Great Tool!
    Reviewed in the United States on April 25, 2024
    Size: 2-3/4"Style: 240 GritVerified Purchase
    This is a great tool to recondition a cylinder bore. Easy to use, and if you follow the directions you will produce a nice cross hatch pattern necessary when new rings are fitted.
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    CuchelloDogStore
    5.0 out of 5 stars Works great
    Reviewed in the United States on April 15, 2024
    Size: 2-1/2"Style: 240 GritVerified Purchase
    This works exactly how it should. This is now my third hone for a different size engine. I have some hone that are 8+ years old and they still work as if they were brand new.
    Helpful
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    Bloud
    5.0 out of 5 stars 2003 gsxr 600
    Reviewed in the United States on May 3, 2024
    Size: 2-3/4"Style: 320 GritVerified Purchase
    Worked great on my 2003 gsxr block
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    Martie Stokes
    5.0 out of 5 stars Product performs as advertised
    Reviewed in the United States on April 10, 2024
    Size: 1-3/4"Style: 240 GritVerified Purchase
    I did a lot of research on this honing tool and read several reviews. It performed as I expected and I was very pleased with the results. Good product!
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    Seth C. Howard
    4.0 out of 5 stars Love Brush research stuff
    Reviewed in the United States on February 26, 2024
    Size: 9.5 mmStyle: 180 GritVerified Purchase
    Nice performing tool . Have many of various sizes. All good
    Helpful
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    BriGuyNY
    5.0 out of 5 stars Great ball hone for the DIYer
    Reviewed in the United States on January 23, 2024
    Size: 3"Style: 240 GritVerified Purchase
    Purchased this as I needed to hone the cylinder walls of an engine rebuild I was working on. First time using one of these, so I looked up a couple YouTube videos for guidance. The honing process went well, and I got a solid cross-hatch pattern from it too.

    This tool helped save my engine, so it was well worth the money even if that was the only time I'll ever use it.
    Helpful
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    Chad R.
    5.0 out of 5 stars 5/8" is the perfect size to clean out and polish outboard tilt tubes for steering cables
    Reviewed in the United States on March 4, 2024
    Size: 5/8"Style: 120 GritVerified Purchase
    After years of fighting with metal brushes and files to clean out tilt tubes for the steering cable on outboard engines I discovered this tool. Pull the steering cable out of the transom bracket. With a little bit of WD40/oil and a drill on low speed oscillate back and forth from both sides. This makes quick work of any corrosion inside the tilt tube. You don't have to go wild and make a mirror finish inside, just enough to clean it up. Go for a few seconds and pull the tool out to inspect.

    Once cleaned up I'd recommend putting a Seachoice 28251 on instead of the included plastic cap mercury gives you. it allows you to retain the grease and actually seal out water from ever getting into the tilt tube in the first place.

    Any corrosion inside there will make steering very difficult and can kill your steering cable.

    5/8" is the right size on all of my mercury outboards, your mileage may vary.

    The only complaint I have is longevity. I know these are an abrasive so they wear by design, but one lasts me one very corroded tilt tube or two moderately corroded ones. Even so, this is much cheaper and easier than replacing the tube outright.
    One person found this helpful
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    Amazon Customer
    5.0 out of 5 stars Great
    Reviewed in the United States on May 10, 2024
    Size: 1-1/8"Style: 120 GritVerified Purchase
    Great, does the thing
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    Top reviews from other countries

    Amazon Customer
    5.0 out of 5 stars Fast shipping. Works great
    Reviewed in Canada on May 4, 2024
    Size: 2-3/4"Style: 240 GritVerified Purchase
    Better than stone hone
    Report
    old photo guy
    5.0 out of 5 stars Good quality
    Reviewed in Canada on April 14, 2024
    Size: 12 mmStyle: 120 GritVerified Purchase
    totally happy with the product, gave me a nice cross hatch in the bore as needed!!
    Report
    Ian J
    5.0 out of 5 stars Great product
    Reviewed in Canada on April 2, 2024
    Size: 2-1/8"Style: 240 GritVerified Purchase
    Worked perfectly for my Rm 125
    Report
    Cody
    5.0 out of 5 stars Worked good
    Reviewed in Canada on March 24, 2024
    Size: 1-5/8"Style: 320 GritVerified Purchase
    Quick delivery
    Report
    verified buyer
    5.0 out of 5 stars Good for brake caliper slider cleaning.
    Reviewed in Canada on April 11, 2024
    Size: 9 mmStyle: 120 GritVerified Purchase
    Bought this hone to clean rusted frame holes. works perfect.
    Report