Grinding Stone Tips

By | October 16, 2017

Getting the Best Performance From Your Flywheel Grinding Stones

Here are some useful tips for getting optimal performance and life from all your flywheel grinding stones.

Flywheel Grinding Stones

Always Keep Your Coolant Concentrate to Water Ratio Accurate.

The Coolant you use is there to not only keep your work from distortion caused by heat. It also removes the grit and waste materials from the working surface as well as provides a slight amount of lubrication. Having a proper mix is critical. If your mix is too rich with coolant additive it will cause your grinding stone to load up and thus cut less.  If your mix is too lean it will cause your workpiece to get hot and can start rust forming.

Always start with the coolant additive manufacturers recommended mixing ratio. You can use a refractometer to ensure the proper ratio is present whenever you are in doubt. Be aware that over time water evaporates and if you are in a busy shop it’s easy for employees to top off the coolant tank with just water thus diluting the mixture. I would recommend having a nearby bucket with already mixed coolant for topping off your tank to avoid such issues.

A good practice is to also use a magnet in the coolant tank on the far side from the pump pickup to help attract metal debris keeping it from going back through the pump. Clean out the accumulated sludge on a regular basis.

Use the Correct Stone

Most flywheels are cast iron. Most heavy-duty vehicles are cast steel. And the imports and high-performance vehicles use billet steel. If you aren’t sure what you have you can attempt to determine the material by doing what is called a spark test. Using whatever stone is on your machine, briefly touch it to the flywheel and take note of the sparks it creates.
If the sparks are an orange color and travel only a short distance before burning up, it would indicate a Cast Iron material.
If they are a light orange to gold color and travel further this would indicate Cast Steel.
If they are a bright yellow almost white and travel very far before burning up you have Billet Steel.
Always remember the harder the material you are grinding the softer the stone you want to use. So in the above order, you would use a harder stone for the soft cast iron and graduate to a soft stone or “Stellite” on the Billet Steel.

Typically (but not always) the Dark or black stones are harder and the lighter stones are softer. Stellite stones are usually white. For most automotive flywheels you will use a general purpose black or dark grey stone.


Dress the Stone

Before you begin dressing the stone you have selected to use, be sure to wear eye protection and correctly mount the stone on your grinder motor.

Regardless whether you have a star type dresser or a diamond-tipped dresser the process is the same. The diamond tipped dresser can be a little bit more finicky. Always be sure to avoid running the dresser too aggressively into the stone. Draw it up close to the stone before you begin. Then gradually sneak up on it. You want to sweep across the stone using a swift but consistent speed. If you sweep too slow you will actually close the pores of the stone which will cause the stone to load up quickly and not cut. You then wind up polishing the material rather than cutting it. An aggressive sweep opens up the pores allowing the stone to cut the material and break away while giving way to the more fresh cutting surface.


Change How Your Stone Behaves

If for some reason you can’t change to the best kind of stone for the type of material you are going to grind, it is possible to change the way a stone grinds. By changing the amount of pressure you exert during the grinding process you will alter the behavior of the stone on the material.
If your stone is too soft you can reduce the grinding pressure. If your stone is too hard you can increase the grinding pressure. This can save you from having a lot of different stones laying around your shop. The downside is you will likely have to dress the stone more often and so you will go through your stones faster.  So it’s really all around better to use the correct stone for the material you are grinding.


Be Aggressive

Grinding a flywheel is normally a very quick process. If you aggressively attack the flywheel with steady down-feed, a typical cast iron flywheel can be ground in about 15 minutes. If your grinder has the optional Auto-Grind feature you should never leave it to grind all by itself. The Auto-Grind machines have a sensor on the grinding motor that automatically kicks off the down feed motor if it senses the motor is working too hard. You’ll hear the machine grinding hard and then softer and then back to hard. This indicates that you need to back off the auto down-feed a little. Typically you would feed about .001 per revolution of the flywheel. Being aggressive keeps your stone cutting rather than loading up. The aggressive downward force allows the stone to work as it was designed. Unloading the material from the stone and breaking down the stone itself causing it to stay open. Proper aggressiveness should allow you to do a complete grind on a flywheel without having to re-dress your stone. Should you not be aggressive enough you will have to re-dress to clean your stone and get it to cut properly again.


Final Thoughts…

Remember, keep your coolant mixed right, match the stone to the material, dress your stone correctly and grind aggressively for the best results when using a stone on your flywheel grinder.

Having a flywheel grinder in your shop can be extremely profitable. Not only do you avoid the wait time and hassle of farming your flywheel out to the guy down the street, but you can put more of the cash from the job in your pocket.  Most shops have enough flywheel business to pay for the machine in one to two years.  And with proper simple maintenance, the machine will last a lifetime. A flywheel grinder does not take up very much floor space to operate and with accessories, you can offer more than just flywheel service. Many newer commercial trucks like fire trucks, ambulances, etc now have disc brakes. The rotors on these vehicles are very expensive to replace and can’t be resurfaced on typical automotive brake lathes. But you could do these rotors on your flywheel grinding machine. This opens up an entirely additional profit stream for you. Not only the brake service but the added parts sales for the pads and fluid, etc.. Certainly something to think about.


For any questions about Flywheel Grinders feel free to call in and talk to one of our friendly sales representatives at +1-319-377-9421.

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