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The same symptom, two different fixes

Both a glazed wheel and a worn-out wheel stop cutting. The edge goes dull, the operator pushes harder, the amp draw rises and the finish gets worse. One of these is fixed with a dressing stick in ten minutes; the other needs a new wheel. Guessing wrong in the expensive direction is common, because a wheel that only needs dressing still looks intact.

Check 1 — look at the cutting face, not the edge

Glazed: the diamond layer is still thick, but the surface is shiny and packed with grey paste. The metal has flowed over the diamond and is rubbing the glass. Worn: the layer is visibly thin at the rim, the corner of the diamond section is rounded, and the body steel is close to the cutting face. Look with a light at an angle — the difference is obvious in five seconds once you know which one you are seeing.

Check 2 — measure the work layer

Measure from the body face to the top of the diamond section with a steel rule, at four points around the rim. Uneven readings mean the wheel is out of true as well as worn — that is a mounting or spindle problem, not a wheel problem.

Check 3 — read the amp meter

A glazed wheel draws more current than a sharp one at the same feed, because it is rubbing rather than cutting. A worn wheel draws less as the diamond thins, then spikes when the body starts touching the glass. If you have a baseline from the wheel's first week, this is the fastest test on the list.

Check 4 — look at the chips, not the edge

• Glazed: fine, even chipping along the whole edge, worse on the exit side.
• Worn: chipping starts in one area and spreads, usually where the glass runs most.
• Out of true: a repeating pattern, one chip every revolution.

Check 5 — count hours against metres

Track hours and linear metres between changes for three wheels in a row. A wheel that dies at half the metres it used to is telling you something changed upstream — coolant, feed rate or grit sequence — rather than that the wheel was bad.

What dressing fixes, and what it does not

Dressing re-exposes diamond by removing the smeared bond layer. It works when there is layer left. It does not restore a wheel whose diamond has worn down to the body, and repeated dressing on a thin wheel brings the end closer. If you dress twice in a week and the wheel dulls again within a shift, stop dressing and measure the layer.

The order that costs least

Look, measure, read the meter, look at the chips, then count the hours. The first two are free. Replacing a wheel that only needed dressing is the most common avoidable cost in an edging shop, and the reverse — dressing a wheel that is finished — wastes a shift and a set of glass.