Does this mean my jointer needs new knives?

[tpuzio]

if my jointer produces a bumpy edge does that mean its time for new blades?

The edge has small scallops in it like a back-country road with hills every 30 feet.

It seems to be getting worse and worse, so i'm guessing it's because they're dull.

True?

[ASLNROX]

Thomas.

Check and see if one of the knife slipped, bet one is higher. This is usually the cause of scallops. Also, the speed you pass over the knives has some cause and effect. I can get a VERY clean surface if my feed rate is slow, while speeding it up gives me marks or scallops. This is one of the reasons that many WWers make a clean up pass with a hand plane.

I would check the knife height first.

Blessings,
--Mark

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[JBark]

I have to agree with Mark, it would seem to me that a blade has slipped. Scary idea since it can slip again . . . as in out.

[tpuzio]

it's a good thing i have that magnaset thing

[arcticfox46]

Maybe one of the knives slipped and maybe not.

Feedrate is really important and most overlooked when using a jointer.

I know for me it is really all to easy to feed WAY too fast over the jointer.

One second per inch rings a bell in my mind.

Try feeding really really slow, one secon per inch or slower. Also don't cut more than, 1/32 or 1/64 on the final pass. Do you get the same scallops or are they really a lot smaller?

An inherent characteristic of a jointer is a scalloped edge or face. It is a function of the machine. You cannot make it go away entirely. A hand plane will make a more uniform, and smother surface, because of the cutting action of a single fixed blade vs a rotating two or three blade jointer.

[tpuzio]

leo

my feed rate is good, and i've tried varying it to test it out. The slower i go the less is noticeable, but what everyone's missing here is that those things are constant. In other words, i was feeding the same rate with perfect results on this jointer for a couple years. I have replaced the blades once (fairly recently) but have sent a lot of lumber through it since then.

I've noticed a gradual degradation of quality over the past few uses. Before then i could feed at any rate and i'd get the same results, nice and smooth.

I do only take off 1/32 of an inch, never more (it's set here since i got it and i've never changed it).

For what it's worth i've noticed the same thing happening with my planer (ryobi 13") and i've done nothing to that but lub it in the two or three years i've owned it.

This brings me back to my original question. Couldn't it be that they are dull? What results do dull jointer knives give assuming feed rate and depth of cut are constant?

Or is this a product of a bigger problem such as the cutter head not spinning fast enough? Time for a new jointer?

I own the Craftsman 6" professional jointer (the one with the stand) in case you're wondering.

[JBark]

I would not replace the jointer. It is easier and cheaper to get a good book on machine maintenance or buy some new belts than buying a new jointer. If the RPM of the cutter head is off you can tighten the belt that drives it. If the blades are dull, sharpen them. While not a good practice I have used a jointer with dull blades and not gotten the results you are experiencing...for what that is worth.

John

[dcarter636]

Have you recently beeen processing a different kind or species of lumber? Some woods, like Jatoba or Ipe, wear out cutting edges faster than others as noted in many wood properties tables.

[Danford C Jennings]

The edge has small scallops in it like a back-country road with hills every 30 feet.

Any number of things can cause this, all of which have been mentioned. At the very least, the knives should be re-sharpened. Dunno if they need to be replaced, takes alot of re-sharpenings for that to happen. Since you'll need to re-set them, any who, that should eliminate at least two of the symptoms, providing you re-set them correctly...FWIW.

Dano

[arcticfox46]

Seems as though all the obvious stuff is ruled out. Your not new at using the machine, either.

I would have the knives resharpened.

I would then carefully and totally clean out the pockets that the knives fit into. Be extra careful when replacing the knives. Check the set-up adjustments.

Give it a new go with newly sharpened knives.

[dcarter636]

One other item, after you run a machine for an hour or so, check the tightness of any screws that you've messed with. Just like the wheels on your car things can settle and shift a little and want to be re-torqued.

[tpuzio]

thanks for the input fella's i'm going to get some new knives (they are fairly inexpensive, and are the throwaway kinds anyway)

When i set them, i'll check the link belt, perhaps it's loosened up with age. I'll also make sure to be extra careful in setting the new knives, although i've found this process to be the biggest pain the the @$$, more so than any other maintenance task.

I've got the magna-set knife setting tool, and a dial guage with magnetic base, so it will hopefully go smoothly.... no pun intended.

[ASLNROX]

Let us know how is comes out Thomas. I hear you about knife changes! That us the reason I changed the head to spiral head with indexed knives!

Good luck.

Blessings,
--Mark

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[DCarr10760]

Usually jointer knives dull fastest at the end near the fence (where they get the most use). If your jointer has a means to move the fence toward the front of the machine, you could do a test run at a sharper point on the blade, just to see if it cures your trouble, if it does than sharpen or replace the knives.

Do the valleys appear to be shiny like they are being burnished by the knives? Or is there more tear-out than there was before? Both of these things happen when the blades get dull too.

David

[tpuzio]

got sidetracked rebuilding a 56' long fence for my dad. I'll be stuck on this for a few days. I've got 10 post holes to dig and there are some terrible root problems looming.

[Steve Wilson]

It sounds like knife alignment and/or dull knives. Get the knives resharpened, install them, and realign the knives. I hated the time it took to realign jointer knives on my PM60 so I use to use hand plane to get rid of the washboard effect. Since then I changed jointers and a Tersa cutterhead is great - quick blade changes and no aligning the knives (they self algin).