How To Know When Your Blade Is Dull

Article - February 12, 2008

This week’s question comes from Stu. He writes:

“Alright Marc, got a new one for you. What is a reliable way to tell if your table saw blade is dull? I know if its cutting slower it might be dirty or dull. I know with a chisel the blade should catch your nail or shave the hair off your arm or be able to split a hair form across the room, etc. Also I have a 40 tooth freud Diablo – so its not REAL fancy, I’m just poor, so I’d rather be able to clean it than have it resharpened or buy a new one.”

And here was my reply:

“Hey Stu. Its really something that takes a little time to get a feel for. At some point, you will realize you have to push much harder than you used to for something as simple as a ripping operation. You will also notice more burning on woods that didn’t burn before. In addition, you should notice more tearout on your cuts. If you don’t notice any of these changes, or they just arent that severe yet, then I would say the blade is still sharp. The first time I notice these things, I clean the blade. After 2-3 cleanings its time for a resharpening. Hope that helps.”

Discussion

Tom Micheline February 13, 2008 9:32 am

Just as a matter of common sense (I’m so new to woodworking that I’ve never had to either clean or sharpen my tablesaw blade) I’d think that if a good cleaning doesn’t help, it is probably dull. Just my $0.02.

Reply
Pops February 13, 2008 9:47 am

Great blog Mark. Good info and I really enjoy your humor. What about the 40 tooth freud Diablo, is that a good blade for the beginning woodworker that can’t afford a Forest blade. That blade is available at the local big box store and at a good price. Pops

Reply
Che February 13, 2008 11:49 am

I just read an article on running shoes that could apply. The question was the same… when are my shoes worn out. The author suggested getting two identical shoes (blade in our case) Make one pair the “primary” and the other the “secondary”. Run with the primary most of the time but use the secondary pair once every week or two. When you can notice a difference between the two (after cleaning) the primary shoes are done (blade needs to be sharpened / replaced). Shift your secondary shoes to your every day shoes and get a new set of secondary shoes (or have the blade re-sharpened

Reply
Germain February 13, 2008 5:34 pm

I just went through this trying to determine if my Forrest WWII was dull. I kept cleaning it and that helped at first. Then it just wouldn’t cut well even right after cleaning. I found a very good local sharpener. After he got through with my blade, it cut better than new. I highly recommend asking around in your area to locate a good sharpener. The services provided by woodworking stores, who just send blades out, can give you mixed results.

Reply
Jim February 15, 2008 1:54 pm

Pops; I use the Diablo blades all the time, yet to have to get one sharpened. There was a good blog a while back at http://www.lumberjocks.com on the very question on which bades to use. Most of the hobbiest said the Diablo blades were fine and I agree, I get great cuts and they stay sharp a long time. Cleaning is key. Expecially if you cut gummy woods…pine is nasty, and there are a few hardwoods that gum things up as well (Sapale is one). Like the Marc says…clean if first if that doesn’t work find a guy to sharpen them, or you can send them back to the factory…I think. Best of luck.

Reply
George February 18, 2008 12:30 pm

Don’t wait too long to sharpen! I have a Forrest WWII that I love. After 2-3 cleanings it was obvious that it needed to be sharpened (lots of force to get it though the blade and considerable burning on soft maple) but I wanted to finish the current project I was working on. Bad idea. I sent the blade to Forrest to be sharpened and added a note in my order to check the blade for flatness because I had been noticing a lot more vibration in my saw and thought that would also contribute to the burning. Well after they recieved the blade they called me and said it was definitely out of flat. When asked how that could happen they said when the blade gets too dull it gets hotter and hotter in the cut, hence the burning, and this heat causes the blade to loose “tension”, thus warping. Makes sense when you think about it. Anyway a $20 sharpening turned into $45.

Reply
Usta B. Slim in Phoenix September 11, 2015 9:30 pm

Here’s a sneaky little secret that the commercIal sellers of those pricey “blade cleaners”won’t welcome.

Formula 401 spray cleaner and a brass bristled brush do the job great and cheaply.

Just rinse it carefully, dry it with a paper towel, put it on the saw and run it for a minute to complete the drying.

Reply
Kirk July 21, 2016 6:21 pm

In cabinet making school we learned that you can tell a blade needs to be sharpened by a visual inspection.

Look down on the blade and reflect light on the top flats of the carbide tips. if the very tip of the carbide catches light light differently than the rest of the tooth the tip of the tooth has fractured off and should be reground.

Reply
Paul Brown July 25, 2017 1:36 pm

The Rockler cleaner is mostly an ammonia derivative (though the exact blend is proprietary) and has a pH as shipped (the concentrate) of 11, which is rather caustic or “very strongly alkaline”. Most “citrus cleaners” have a pH of around 9.5 (which is a logarithmic difference- or more than 50x more caustic in this case). Citrus’ as most people know are acidic, the opposite side of the pH scale. So “citrus cleaner” tends to refer to the chemical smell added and not that it is derived from or similar to citrus, or like using a natural citrus-based product like lemon juice (pH 2.3). Caustic cleaners will degrade brass, copper, and aluminum fairly rapidly, though not as much in other metals. So make sure you rinse with plenty of fresh water. It is also important to point out that with a pH of 11, gloves should be a requirement.

Reply
Jerry Gilles August 1, 2020 2:59 pm

I have a 40 tooth diablo 10 in. blade .I know its never been sharpened . I cut a 2×4 and it cut a clean cut but smoked the wood while cutting. I put it on the blade sharpener went around 3 times went to cut the same piece of 2×4 and same thing .I sharpened it again went around twice more but haven’t tried it yet . The teeth look very nice and I did clean it before I sharpen it . SO whats with the smoke? The cut is clean both sides .

Reply

Cookie	Duration	Description
cookielawinfo-checbox-analytics	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Analytics".
cookielawinfo-checbox-functional	11 months	The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional".
cookielawinfo-checbox-others	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Other.
cookielawinfo-checkbox-necessary	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookies is used to store the user consent for the cookies in the category "Necessary".
cookielawinfo-checkbox-performance	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Performance".
viewed_cookie_policy	11 months	The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. It does not store any personal data.

How To Know When Your Blade Is Dull

Advertisers