I just changed my 6" jointer blades.
One was badly worn, one a little worn, one looked like new.
Is there any possible explanation for this other than the obvious?
(geez, it seemed to work okay...)
Do I need to get them all sharpened to maintain balance, or can I just get
the bad one done?
You most likely do not have all of them set at the same height relative to
the out feed table.
Why not sharpen them yourself? You will be surprised how easy it is.
Check out my knife sharpening jig:
As the others have already said, the knives on your jointer weren't
properly aligned. When one stands higher than the others it will end
up doing most of the cutting and show the most wear. Doug is right,
you will be amazed at how much better your jointer works when the
knives are properly aligned. Follow this link to see how it's done
with a dial indicator jig:
Let me know if you have any questions.
Well actually that's what prompted the question. I set them today the same
way I did last time. When I saw the wear pattern on the old set I realized
I must have screwed up last time and checked my work with a dial indicator.
Everything was within a thousanth! And if I did it right this time, I
should also have done it right last time. So... I am wondering if there
could be another cause for the uneven wear.
Or maybe I am just getting better at it.
If all three blades measured identical distances from the outfeed
table, it seems really weird that one can be untouched and yet another
Are the bearings on you cutterhead OK? Do you get a lot of vibration
when the machine is running?
Check your technique when you are setting the blades. Make sure after
all installation adjustments that you check one more time to make sure
they are all uniform.
Also, since the screws on my Jet are made from lead or something even
softer, I was reluctant to really snug up the holding screws. I had
similar problems with yours as the blades would eventually loosen and
move. They worked fine when sharp, but the more dulled the blades, the
more they moved. But the witness marks on the blades to set the
initial alignment told me what happened.
Replace the screws and snug well. No more problems.
It is possible that your jointer knives experienced some sloppy heat
treating at the beginning of their lives and the hardness varies
considerably. I have noticed this with the "Regrind" angle sets that I
sell. Some are so hard that they barely take my mark (not tempered).
Some are so soft that the marking raises quite a ridge around each dot
(probably quenched below the critical temperature). You can check the
relative hardness of your knives with one of those automatic center
punches (with the internal spring action). Make a punch in an
inconspicuous area on each knife and compare the size of the divots.
Big divot means soft steel. You can use a small stone to grind down
any ridges you might raise.
It is also possible that the knives weren't aligned properly the first
time. Maybe you've gotten better at it, maybe you were just lucky this
time. The traditional methods rely on a degree of subjective judgment
(which I have always had a hard time mastering). I know that my
results with these methods are rather inconsistent. Sometimes good but
more often not so good. Nothing beats the objectivity of the dial
It is possible to use a dial indicator in such a way to convince
yourself that the knives are properly aligned when they really aren't.
Unfortunately, following the directions contained in many magazines and
books will make you vulnerable to such an error. Contrary to popular
belief, you should not use a flat indicator stylus tip moving along the
knife edge to align jointer knives. You should use a round stylus tip
and move it across the edge of the knife at various points. I have a
write-up with a video on my web site about this:
Scroll down to the section entitled: "Using a flat indicator tip to set
Let me know if you have any questions or if there is anything I can do
On Dec 9, 8:34 pm, email@example.com wrote:
Contrary to popular
I like even better using a parallel on the outfeed table extending over
the knife, with a dial indicator bearing on the top of the parallel.
Rotating the cutterhead will lift the knife, and that's what you
measure with the indicator. Doesn't matter what shape the contact
point is, and it doesn't require you to lock the cutterhead at TDC.
I'm not sure what you mean by this. Are you referring to the height
(vertical position) of the indicator stylus tip? Or are you referring
to the horizontal offset between the indicator tip and the knife edge?
I can see how the vertical position is absolutely vital! As you move
horizontally, away from the knife edge, the reading will become
smaller. I was thinking that it was best to be directly over the knife
edge but it doesn't seem so critical. All you are looking to do is
minimize the change in reading as the knife graces the parallel. One
could say that this is the "carry method" without the subjective
element. I like it.
Bill in Detroit wrote:
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