When is a blade dull?

[Tom Jones III]

Specifically, I was checking my jointer setup last night and I've been wondering if the blades are dull. According to Mastering Woodworking Machines a jointer knife is dull if you can see the edge?

Does anyone have tips for how to tell if blades/knives are dull? Not just for the jointer, but for the planer, BS, TS, etc. As the blades slowly get dull, I slowly get used to them. At some point, I will suddenly realize that I've been using dull blades for a long time and change them. Surely people here have some good ideas.

[Jim Becker]

Jointer and planer knives start to tell you that they need attention when you start to see more scaloping and it takes more effort to push the material through the jointer...especially on face jointing.

The knives will be long-dull before you notice the edge!

[Keith July]

Tom,
I agree with Jim, your jointer blades will become dull before you can see the edge of the blade. The table saw is a little easier to detect. I check the cut for tear out. The bottom side of the board will start to show signs of dulling when the blade is tearing more than cutting, even with zero clearence inserts. I test my blades by cross cutting a piece hardwood plywood.
When in question...have your blades sharpened.
Don't forget the saftey side of the question. Sharp tools are much safer to use.

Keith

[Russell Svenningsen]

To add to what Jim said about the jointer, I tend to begin to notice it when it seems that the blades are "hammering" the wood. It does become difficult to push the wood through and there is a change in how the blades are cutting the fibers, as I mentioned, it "hammers" it. The noise difference is quite noticeable as well. The jointer become downright noisy at that point.

As for the planer, same sort of thing. The machine seems to labor more, tear-out increases, and a fine finish becomes almost impossible to achieve.

As for the TS, I have sharpened my Freud blade once in 2 years. Most times, all it needs are a good cleaning. This depends on the wood you've cut, the amount of wood, etc.

Best,
Russell

[Alan Tolchinsky]

To add to what Jim said about the jointer, I tend to begin to notice it when it seems that the blades are "hammering" the wood. It does become difficult to push the wood through and there is a change in how the blades are cutting the fibers, as I mentioned, it "hammers" it. The noise difference is quite noticeable as well. The jointer become downright noisy at that point.

As for the planer, same sort of thing. The machine seems to labor more, tear-out increases, and a fine finish becomes almost impossible to achieve.

As for the TS, I have sharpened my Freud blade once in 2 years. Most times, all it needs are a good cleaning. This depends on the wood you've cut, the amount of wood, etc.

Best,
Russell

Yep, I agree. Hammering is a good description of the sound. In general it starts to get a lot noisier. When you put in new blades it gets so quiet and smoother. Ahhhhh! :)

[Todd Burch]

Tom, larger commercial shops will install an amp meter on their equipment to tell them when the blades are dull.

Todd