how to test TS blade sharpness & touch up

[Lynn Kasdorf]

Ok- this may seem like a dumb question. But, I have a lot of TS blades. Most of these are fairly old, carbide blades of good quality. Have any of you worked out a way to determine just how sharp the carbide is on a blade, without mounting it in the saw and trying it?

I'm thinking of something analogous to testing a chisel by shaving your arm hair.

I'm on the verge of finally getting my SCMI sliding table saw on the air. Over the years that I've had this thing, I have picked up about a dozen or more blades, up to 16" that will fit this beast.

Fortunately, it will also run the same 12"x1" arbor blades that I run on my Powermatic #70 TS. And I have about a dozen of those as well.

The blade on my powermatic at the moment is a little less than perfectly sharp. But it still scrapes my fingernail when I drag it across a tooth.

I think I may get out a jeweler's loupe and look closely at the edges.

Along these same lines, anybody had any success with touching up carbide teeth? I once saw a diamond grinding wheel with holes in it so you could see exactly what you were grinding. The demo guy was hand sharpening a TS blade.

[Dewey Torres]

The loupe may work way better than trying to do touch ups on your own. I have multiple blades and the sharp ones serve as a touch reference for the in use blades getting dull. If you touch a sharp blade and then touch a dull one you will be able to tell right away but it is very difficault if not impossable without that reference unless your blade is totally shot (sharp-wise).

Another note:
Sometimes depending on what you have been cutting, the pitch buildup on the carbide will make it seem like the blade is dull when it really just needs to be cleaned.

[scott spencer]

The fingernail scrape test (or even just a feel test) has tons of potential for flaws and variability due to the huge variety of different grinds used on blades.....the grind with the sharpest point tends to feel sharpest, but if the grind of the blade is a flat top or triple chip with nearly no points, even a sharp version of that grind is likely to feel duller than a dull version of a Hi-ATB with 40° bevels.

A good look with huge magnification may help if you know what to look for, but for most of us it's easiest to determine dullness as we notice increased burning and bogging even when the blade is clean. I suspect that a lot of blades brought in for sharpening are really just dirty.