Cranking up feed rates: General Industry Coverage

Dear Doc: I use resin- and metal-bond diamond wheels and used to manually stick them. Now our machine does it automatically and I don’t have the “feel” to determine if the wheel is being stuck hard enough. Is there a way to know how fast I should stick?

The Doc Replies: For some reason, companies that were sticking aggressively suddenly stick timidly when they switch to auto-sticking. Here’s a ballpark equation to calculate how fast to stick:

Sticking aggressiveness = 76,000 × sticking velocity (ipm) ÷ wheel speed (sfm)

Aim for a sticking-aggressiveness value around 250.

Finding an effective grit-penetration depth is critical to successful plunge grinding. If it’s too large, you’ll rip the wheel apart; if it’s too small, you’ll burn the workpiece. Illustration courtesy J. Badger.

Let’s say you’re sticking at 1.0 ipm on a wheel running at 3,000 sfm. That gives a sticking aggressiveness of 25.3 (76,000 × 1.0 ÷ 3,000). That’s a timid stick. To get in the ballpark of 250, increase sticking velocity to 9.0 ipm. This gives a sticking aggressiveness of 228—an aggressive stick.

Finally, an effective way to see if you’re sticking correctly is to monitor grinding power. If the power doubles because of wheel loading, a good stick should drop the power close to its original value. On the other hand, a timid stick will only drop it 10 percent.