Tips for Choosing the Right Flywheel Grinding Stone

Some of the more common questions we get in Tech Services relate to flywheel grinding and choosing the correct flywheel grinding stone in particular.

We hear a lot of shops complaining that they don’t have time to stop and change the grinding stone every time they start on a new flywheel. First, let me congratulate you that your shop is busy. Second, let me tell you that you’re wasting more time by not changing the stone than you are by changing it. If you try to grind a flywheel with a stone that’s too hard or too soft for the material the flywheel is made of, you’re going to spend more time dressing the stone and grinding the flywheel that you would if you used the correct stone to begin with.

Let me explain it this way. Let’s say you have to dig a hole 4 feet deep and 1 foot across. You have a regular teaspoon in your pocket and a powered post-hole auger a mile away in your shop. Both of them will do the job so wouldn’t it make the most sense to use the teaspoon since you have it right there in your pocket? After all, you’d have to leave the job site to pick-up the auger before you could start digging. I know this is an extreme example, but it’s the same concept. You’d be able to dig the hole in less time (even with a trip to the shop and back) with the auger than you could with the teaspoon.

In the same way, by changing to the correct grinding stone for your application, you’ll be able to grind the flywheel much faster and get a better finish. Just by taking a few seconds to change out the grinding stone, you’ve saved yourself several minutes of work. Call me old fashioned, but that make sense (and dollars) to me.

Choosing the right flywheel grinding stone

There are many factors that affect your flywheel grinding stone selection, most important of which is what material the flywheel is made of. Here’s a trick we pulled from our Technical Library archives:

Most American automotive flywheels are cast iron. Most truck, bus and agricultural flywheels are cast steel. High-performance and a few import flywheels are billet steel. To determine what material your flywheel is made of (hardness), “spark test” a flywheel before grinding it. Using whatever grinding stone is on the machine, briefly touch it to the flywheel and watch the sparks.

  • Cast Iron (soft) flywheels make deep orange sparks that travel only a short distance before burning up.
  • Cast Steel (medium) flywheels make light orange to golden sparks that travel farther before burning up.
  • Billet Steel (very hard) flywheels make bright yellow-white sparks that travel very far before burning up.

We’ll have more tips and tricks about flywheel grinding in the near future, including some that deal specifically with CBN Flywheel Grinding Stones. In the meantime, check out this post  to read the rest of our original flywheel grinding tip article.

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