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?
I'm not sure, but it seems to me that the blades were set at different heights. One probably wasn't touching the wood.
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:
Set too high, just right, and too low, respectively.
Not sure what's "obvious" from your perspective... but different blade heights seems obvious from mine.
You'll be amazed at how much better it works when all three knives are doing the same amount of cutting.
That's only because you're a pedantic bastard! Can't you post a straight reply to anyone without swinging your dick in your hands?
That wasn't meant to be a slam, but a (weak) attempt at humor. In retrospect, though, it didn't come out looking that way. To anyone who was offended, I apologize.
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:
I'd resharpen them all as it should require little more time. You are going to want to align all of them anyway.
Somebody needs a dial indicator and magnetic base!
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.
What are you referencing from?
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.
Robert
The outfeed table. Probably best to check the infeed table also, though a problem there would show up as more wear on one side, wouldn't it?
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 indicator.
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:
Let me know if you have any questi> Well actually that's what prompted the question. I set them today the same
If all three blades measured identical distances from the outfeed table, it seems really weird that one can be untouched and yet another worn out.
Are the bearings on you cutterhead OK? Do you get a lot of vibration when the machine is running?
I'm stumped...
When I saw the wear pattern on the old set I realized
Could be as simple as having the grinds at somewhat different angles. Makes the one blade more vulnerable to chipping on a fragile edge than the one ground properly. Never had the courage to lay a stone on the outfeed and make that secondary bevel like some books recommend, but that is even less subject to wear in theory.
Also gets them nuts on with the level of the outfeed without fiddling....
On Dec 9, 8:34 pm, snipped-for-privacy@ts-aligner.com wrote: Contrary to popular
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.
John Martin Cumberland, Maine
Hi John,
That is an excellent idea! Now I'll have to go and create a whole new video!
Thanks, Ed Bennett snipped-for-privacy@ts-aligner.com
I don't know what you mean by parallel.
I did it by putting the indicator bearing over the knife and rotating the cutterhead. As each knife passed it would raise the indicator bearing. What is wrong with that? It doesn't have to be at TDC, but then you don't know if they are even with the outfeed table; just that they are even to each other.
Use a mag base to keep the relationship between cutting tip and indicator tip constant. If that distance changes, all bets are off.
Bill
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.