Brush Research BC78400AO FLEX-HONE®, 7/8" (22.2mm) Diameter, 400 Grit, Aluminum Oxide, for Aluminum, Brass, Bronze and Softer Non-Ferrous Materials

I decided to rebuild my snowmobile motors as preventative maintenance, and was replacing pistons and rings. The piston suppliers all recommend cylinder prep with these type of ball hones. I bought two hones, one for my 500 cc sleds and one for my 800 cc sled. There are many grits and compounds available, but for Nickasil cylinders these 320 grit Aluminum Oxide versions are recommended. They worked perfectly for de-glazing and refreshing the crosshatch to help in proper cylinder oiling and piston and ring break-in. Choose the ball hone size you need based on the actual cylinder bore diameter. If you buy the hone that matches your diameter it is actually slightly oversized to create just the right amount of pressure to the cylinder wall for effective honing. Using these ball hones takes a bit of technique, but in a home shop environment I found doing the honing in a 5 gallon bucket worked to contain the lube oil from flinging all over the shop, I also made a short spacer to place under the bottom of the cylinder edge inside the bucket to lift the cylinder just enough off the bottom to allow the hone to effectively reach through the cylinder with a full stroke, but not protrude too far through and allow the balls to wrap the lip and bind. Holding the cylinder solid in the bucket also helped to keep the hone centered within the cylinder as cocking it at any angle while holding the cylinder by hand tended to end up with the hone hooking a port or the lip and stopping the process (my first attempts were a bit of a learning curve). Once I figured out how to hold the cylinder and limit the travel properly the remaining cylinders were easy to complete. If you do bind the hone and twist some of the ball fingers, they are very forgiving, and easy to re-set the fingers, straighten them out, and continue on, being more careful about your process. These hones should last forever if you're only using them periodically in a home shop. Using them per the included instructions left a beautiful surface with correctly angled cross-hatch, and made for a perfect top-end rebuild. These are far better than the old spring loaded stone-hones of old, especially for nickasil. These also have a far less likelihood of catching a port if you keep it centered. And if it does catch one due to your (My) own mistakes, it will simply bend around itself but not cause any damage, unlike the potential damage that could be caused if a stone catches a port with the old style hones. Highly recommend this product and the seller.

Great product!! Worked perfectly!! Will definitely buy again!

I never remember what these things are called when I need one, which is always an issue, because search engines are absolutely of no help when you're looking up 'flexible grinder things' or 'ceramic balls on a shaft for grinding' or whatever terms I try and use when I can't quite recall the Flex-Hone name.But I've owned several of these, and I've used them for everything from cleaning the insides of 3D printed steel designs to slowly expanding 7/8" tool holder ports to 1" to just giving some small 1/2 steel valve ports a nice cleaning. Ultra useful, and there's not really anything else quite like it on the market.

I needed a flex hone to clean up the inside of a Moen Positemp shower valve, when replacing a leaking cartridge. This worked perfectly to clean the corrosion and scale from the inside of the valve body, and left a pristine surface for the new cartridge to seal against. I’ve used these for years on engine cylinders, so I had no doubt it would do the job needed. These are a bit pricey, but it was less expensive than replacing the entire faucet assembly in my shower.

It's a fine little brush.

This hone performed great! Rebuilding a few small engines and used this to cross hatch cylinder walls.

All good

Worked great.