When to Change Blades and Cutters

Tips on how to tell when a blade is getting dull. October 26, 2005

A machine usually cuts well with a new blade, and there comes a point when it is time to change the blade or cutter. How do you tell when that point has been reached? Sometimes it's obvious - the motor slows down, messed up edges, extra dust production, scorching etc. But should you keep using a less than sharp blade until there is such physical evidence of poor performance, or should you change it sooner?

Forum Responses
(Cabinetmaking Forum)
From contributor A:
Changing sooner is better as it is better for sharpening. There will be less grinding required. On production machines we often installed an amp meter so when the amp draw went up we knew the blades were dull. This is not practical on small machines as taking a big pass will increase amp draw so it will not be a true reading of condition.

From contributor B:
A salesman for a sharpening service once showed me a quick way to tell if a carbide- tipped saw blade was done. Hold the blade steady, and drag the fingernail of one of your remaining digits across the sharp tip of a tooth. It should dig in a little and drag, or even leave a scratch. If it just slides right across, send it out.

From contributor C:
In some situations, cutters load up with resin from the wood and act dull. Cleaning will return to sharp performance. I just experienced this after shaping a run of Jatoba. Cutters were scorching and slowing down, but had been recently sharpened. Cleaning with lacquer thinner right on the spindle got them back in shape.

From contributor D:
I've found 40 tooth ripping blades can be used successfully quite a long time. If the sawyer is in tune with his saw the feed rate really determines everything. 60 tooth plywood and 80 tooth melamine blades take a lot more diligent appraisal. Aspects like tear-out feed rate and material wandering really need to be checked almost daily in my case.

From contributor E:
I change blades or cutters when they don't meet my quality standards.