Are my jointer knives dull?

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Forum topic by newwoodbutcher posted 04-03-2018 12:58 AM 1105 views 0 times favorited 5 replies Add to Favorites Watch
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798 posts in 3457 days

04-03-2018 12:58 AM

I’ve had this Delta 8” jointer, 52678 for about five years, bought it for a song from a guy who just didn’t want to move it. Been performing flawlessly with moderate use. Recently it started heavely spitting chips back onto the in feed table. Thought I had a blocked Dust line, nope. Now I’m looking closely at the “chips” and they are more like fluffy shavings than chips. Here’s what they look like.

Do I have dull blades?

-- Ken

5 replies so far

View Loren's profile


10477 posts in 4254 days

#1 posted 04-03-2018 01:08 AM

The areas under the castings can get full
of chips. Also resin and chips can build up
on the castings, especially if you use a lot
of pine.

There’s no doubt they are duller than when
you got it.

Jointer knives can be stoned under power
using an oil stone with paper wrapped
around it to protect the outfeed table.
I’ve never tried it as I used to think it seemed
outrageously scary but I don’t think that
anymore and old machine manuals even
recommend it. There are also these
semi-lame jointer knife hones, at least the
one I have is. It sorta works though.

I have a machine with an insert cutterhead
now so dealing with sharpening knives is
not something I do anymore. I used to use
a Makita wet wheel and it did a better job than
many sharpening services. They have a
tendency to not clamp the knives flat when
they grind them so if you have a curved knife
it will have a curved edge when put back in
your cutter head.

View Richard Lee's profile

Richard Lee

260 posts in 1382 days

#2 posted 04-03-2018 01:29 AM

I agree with Loren,mine has done the same. Check right under the cutterhead it will probably be plugged with chips.

View msinc's profile


567 posts in 1110 days

#3 posted 04-03-2018 12:00 PM

Mine used to get plugged up pretty bad before I put a dust collector on it. One thing I found that would happen and make it seem like the blades went dull is using it with a different type of wood. Certain woods are harder and/or can have a greater tendency to tear or chip out when joined. If it is the same old stuff you usually run on it and the chips change and there are other signs then yeah, the blades are probably getting dull. But, if you are joining a different type wood and are getting tear out and funny looking chips that might just be the wood.
All that said, I cannot imagine having the same untouched blades in mine for 5 months let alone 5 years…..I do use mine a lot though. It is probably the most used machine in my shop.

View Aj2's profile


2650 posts in 2405 days

#4 posted 04-03-2018 01:53 PM

That’s great Ken, I can get very long life from my jointer knifes if I don’t run dirty wood and whett the knifes when they start showing lines in the wood. I last set knifes in my Oliver before Christmas M2 Hss. I prefer the surface knifes leave and have no illusions that a insert head is better.
Good day sir.

-- Aj

View AAL's profile


82 posts in 2033 days

#5 posted 04-03-2018 02:16 PM

Occasionally I have to sharpen my planer or jointer blades. To do this I cut a series of slot across a thick board, all to the same depth and angle (25° & 30°) on the table saw. Then I place the blade in the 25° slots, sharpen the blades with an oil stone across the tops & then repeat in the 30° slots. Works well.

-- "Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery." Winston Churchill

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