Sawblade Wear Question (how long between sharpenings)

[David Weaver]

I have received some puzzling questions (more than one, so this is not singling out anyone) about a sawblade I have below, and am curious (though I don't know why..my days of circular sawblade use are numbered).

I'd like to poll the membership here, maybe I'm in the dark about how long a TS blade lasts, the question and variables are as follows:

* forrest WWII blade, 40t thin kerf
* 3000 rpm blade speed (goofy, i know, saw was a delta hybrid)
* 300 linear feet of cut in s4s (clean, no dirt) lumber over a period of three years, lets assume 2/3rds of it the cut is hard maple, and the rest is softer stuff like cherry, but nothing pitchy
* there has not been burning in any of the cuts, and there has never been a significant amount of pitch on the blade
* neither plate nor teeth have been subject to corrosion

If this is your blade, your assessment of how close it is to needing to be resharpened would be:
1) It has a lot of life left before it needs to be resharpened
2) It's probably halfway to resharpening
3) It needs to be resharpened asap

If I'm way off, I'll assume I need to reassess what the blade is worth.

[David Weaver]

For anyone not wanting to figure out how many minutes of cut time that is, it's probably about 10-15 minutes of material being fed through a blade, maybe less.

[Grant Wilkinson]

You are not even close to needing it sharpened. I don't believe that this is an exact science, but after less than half an hour of cutting, if I needed to sharpen a blade, I would searching for a problem with my saw or technique.

[scott spencer]

There are many variables that are hard to estimate, but you did a good job of listing several. You mentioned that it never had much pitch build up, but do you clean it regularly? If not, it could have been subjected to additional heat. Hard maple can be tough stuff, and moisture content, flatness, thickness, saw alignment, and feed rate are all variables. My best guess is that it's probably more than half way toward needing sharpening, but I'd probably send it in to be sure, and/or buy a back up blade. The fact that you're wondering is enough to suggest sharpening now based on your descriptions of usage/age...it's better to sharpen somewhat early vs way late. After 3 years, its a very small price to pay and know for sure!

[David Weaver]

Actually, it slipped in my hand when i was laying it on my bench and cut my finger. It's still sharp, both in inspection of the carbide and performance on the saw. I was just surprised to hear that 300 linear feet of cutting in a sawblade could be perceived as something near needing sharpening, as a ww buddy of mine has at least 10 times that on a woodworker I thin kerf, and he grenanded it on a nail last year before ever having a chance to it to be sharpened.

I basically cut one laminated maple top (2'x5') worth of 4/4 wood with it and two medicine cabinet sized projects. The rest of the stuff I have made has been done mooching time on someone else's tools (in a shop with tools much nicer than mine).

I set up the saw with a couple of thousandths of toe in toward the fence. All of the wood cut has been kiln dried, which I would assume is more abrasive than green, at least based on working wood by hand.

[John Coloccia]

This is really an excellent thread. I tend to neglect stuff like this and only sharpen when I'm obviously getting poor results...which is far too late!

I'm sure a lot of us newcomers will be keeping an eye on this thread. How the heck do you really know when the right time is?

[David Weaver]

This is really an excellent thread. I tend to neglect stuff like this and only sharpen when I'm obviously getting poor results...which is far too late!

I'm sure a lot of us newcomers will be keeping an eye on this thread. How the heck do you really know when the right time is?

If I had used my TS enough, I would've taken this approach, too. For thrift, I guess. That's why I'm curious whether there are people who send sawblades before performance degrades. I sharpen my hand tools religiously, but it's free to do that. I tend to use power tools until they're spent (specifically bandsaw blades) and only resharpen them if they are a lot more expensive to purchase than to resharpen.

The saw blade in question is obviously the one that is already spoken for from the classifieds below. If it's perceived as needing sharpened, I'm more than willing to be publicly called out (and will of course make it right) - I have no pride over such things. It's all part of learning.

[Jay Allen]

I generally look for a slight performance drop to show first. Slight as in feed resistance, it's just a feel thing, I don't wait to actually "see" a cut degradation.
I do go to the "bother" of changing the blade to suit the cut, something that some in the shop can't say.....and they wouldn't "waste" the time.

I have several blades, of different tooth configurations, that I switch around on my personal SCMS to match the material being cut. Most of these have a "back-up" that I can use while the other is being sharpened. I may have them done more often than most because we have a service that takes care of all of out blades and bits. It costs me nothing but the tooth loss, but they are very nice to our stuff, not removing any more than necessary. I have a few blades that have been sharpened quite a few times and they still perform very well.
Same with my table saw blades.

Going by the "feel" of the teeth or the fact that it may cut your fingers when handled is a bit misleading. A negative rake triple chip that you would use for solid surface material may never actually "feel" sharp. But an aggressively raked Hi-angled ATB will still cut your fingers when it is long over-due to be sharpened.

[Tom Walz]

We figure roughly a mile of cutting before a blade with ordinary carbide tips needs sharpening.

This is based on a study we had done by Forintek at the University of British Columbia campus.

You can see the report at the following address:

http://www.carbideprocessors.com/pages/Forintek-Research-Paper.html

As with all discussion of this sort there is a great deal of room for other opinions. This test was very well controlled and Western Red Cedar was used because its chemistry is particularly hard on carbide.

The Cermets tested led to the development of a much more user friendly Cermet 2 grade that gives 2 to 10 times the life of carbide.