Jointer problem - wavy boards

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Forum topic by Fireball posted 07-25-2007 06:30 AM 4440 views 0 times favorited 27 replies Add to Favorites Watch
View Fireball's profile


71 posts in 4305 days

07-25-2007 06:30 AM


Just bought and setup a Delta 8” jointer. It is a refurbished model, so has been sitting for 2 or so years.

When running boards across it the result is a wavy surface. It is fairly pronounced and not near as nice an edge as i was hoping for. The waves run across the width of the board, all the way up and down the length of it.

Can anyone tell me what my problem might be?? Setup? Old blades? Poor technique?

Thanks in advance for any help.

27 replies so far

View Karson's profile


35153 posts in 4639 days

#1 posted 07-25-2007 06:53 AM

To have wavy surface it sounds as if the board is bouncing up and down.

Has the blade been alligned with the outfeed table. I use an aluminum square or ruler and lightly turn the blades by hand. The blade should lightly touch the aluminum but not lift it off the surface of the jointer. If the blade is high you might be getting the blades cutting the wood and then allowing the cut surface to drop to the outfeed table there-by causing a wave cut.

So I’d suggest checking the blade allignment.

does it happen if you take very light cuts?

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Appomattox Virginia †

View Dorje's profile


1763 posts in 4235 days

#2 posted 07-25-2007 08:06 AM

This is simply a result of the blades being set differently from one another – they must all be set exactly the same, as Karson suggests, to the height of the outfeed table.

-- Dorje (pronounced "door-jay"), Seattle, WA

View MsDebbieP's profile


18618 posts in 4399 days

#3 posted 07-25-2007 11:08 AM

does the direction of the grain have anything to do with it?

-- ~ Debbie, Canada (, Young Living Wellness )

View coloradoclimber's profile


548 posts in 4306 days

#4 posted 07-25-2007 04:23 PM

have you tried different feed rates. When I’m really chopping off the wood, lots of fast passes, the surface is pretty wavy. On the last pass or two I slow down quite a bit to get a smooth cut.

I also take pretty small cuts, around 1/32 or so per pass.

If I have a really bad board I typically edge it first on the table saw or bandsaw and finish it on the jointer.

View Fireball's profile


71 posts in 4305 days

#5 posted 07-25-2007 07:47 PM

Thanks for the thoughts so far. I’ve just been in the garage playing around and here is what I’ve found.

Played around with the outfeed table as Karson suggested. I don’t have a reference straight edge so was using a fairly high quality 2’ level.

Also played around with the infeed table and set the stop to a very shallow cut. (Colorado climber, how do you measure cut depth to the 32nd?)

When I make normal speed passes the board is still wavy. It is pretty pronounced ridges.

If I slow it WAY down, I get a very nice smooth cut.

Test piece was a 2’ long piece of poplar if that makes any difference.

ANy ideas as to what might be wrong? On a long board going as slow as necesary to achieve a smooth cut would be very annoying and also might be difficult to do so and not burn the wood.

View mot's profile


4922 posts in 4274 days

#6 posted 07-25-2007 08:06 PM

Dorje nailed it. When you slow down your feed, the high blade is hitting every part of the wood and making an even cut. When you speed it up, the high blade is hitting and missing. Check your gibs where the blades are attached.

-- You can discover more about a person in an hour of play than in a year of conversation. (Plato)

View Dorje's profile


1763 posts in 4235 days

#7 posted 07-25-2007 10:16 PM


-- Dorje (pronounced "door-jay"), Seattle, WA

View coloradoclimber's profile


548 posts in 4306 days

#8 posted 07-25-2007 11:49 PM

I set my knives to the same height, level with my outfeed table. I set them within a couple thousandths. I then run my infeed table up to level with my knives / outfeed table. That is my new zero. I then use the scale on my infeed table to go down about 1/32. I usually just leave it locked there for everything. Is it exactly 1/32, probably not, but close enough, less than a 1/16th, more than a 1/64th.

The problem Dorje is alluding to, a single knife high causing ripples it true for any number of knives, 1, 2, 3, 4, any or all at the same level or not. The problem just happens to be exacerbated with fewer knives, or with a high knife.

As the head turns the knives rotate up, each knife taking a small semi circular bite out of the wood. With one knife high you get one deep semicircular cut for every rotation of the head. For three knives of the same height you three semicircular cuts per head rotation.

If you move a board across the head “fast” the small cuts do not overlap and you get the ripples, no matter how many knives you have and even if they are all at the same height. If you move slower you get more cuts per forward motion of the board and the cuts eventually overlap and you get a smooth cut. This problem always exists, it’s just worse if you have one knife doing all the cutting instead of three.

Part of the time you are moving the board over the head and NO knife is up and cutting, part of the time the board is moving over the head and a knife is taking a little round cut out of the wood. Do it too fast and you get ripples no matter how many knives and the consistency of height settings.

But in this case since the problem seems to be so severe you probably do have one knife high, just making the problem worse.

BTW, the same thing can happen with spiral head cutters. It also happens on metal cutting if you feed too fast past a multi flutted cutter, even when the cutter knives are at identical radiuses. You just get little tiny ripples if you move too fast over the cutter head.

View Lip's profile


158 posts in 4288 days

#9 posted 07-26-2007 02:59 AM

The fact that it’s refurbished brings up some key questions to mind … like … What exactly was wrong with it in the first place … what exactly did they do to it … and was it refurbished by a shop or some amateur? I’ve had some experience flipping old tools I picked up at auction … and know more than a few locals who make a living purchasing and selling old tools … and while I wouldn’t rule out buying equipment from them … I would purchase it with the understanding that their idea of refurbished isn’t the same as mine. In a lot of cases, an amateur refurbishment consists of removing the rust and making sure the parts all move … which leaves a lot to be desired.

More often than not, amateurs and shops alike will ignore the blades all together when refurbishing a jointer/planer for resale … unless of course those blades are badly rusted or chipped … and even then, tehy may take steps to remove the rust which aren’t exactly in the best interest of the blade. For most that are in it to make a buck, purchasing a new set of blades or having the old ones sharpened takes time and money … and most of the time there isn’t a significant return on their investment. Regardless of who refurbished my machine … I would start off by either purchasing a new set of blades or having the blades it came with sharpened.

Note: I’m not sure if your jointer came with the original owner’s manual … if it didn’t, I would go over to the Old Woodworking Tools web site to see if you could find it. Shouldn’t be that difficult for a Delta. I know it’s almost cliche … but make sure you read and understand what they say in that thing. Who knows, there could be a clue in there.

Now, once I’ve replaced the blades … checking/adjusting the blade height would be the next logical step in the process … as would doiuble checking … rechecking … and checking again just for the sake of being sure … but, from reading your second post … it sounds like you’ve already done that with little or no improvement.

Before I move on … let me just re-emphasize checking the height of those blades one more time!!! A jointer isn’t exactly the most complicated piece of machinery in the world … but if a good set of properly aligned blades don’t do the trick … it may be a case of that head simply not turning as fast as it should be … I’m just shooting off the hip here based on my own experience … but it may be time to look a little deeper.

The next logical step in my trouble shooting process would be the pulleys/motor. If and when you get that owners manual, check the proper pulley sizes. This may be a long shot … but there is an off chance that somewhere along the lines … someone who didn’t know any better may have accidentally pulled your pulleys off and put them back on in reverse order … or worse yet, replaced them with ones that were the wrong size. Just off the top of my head … if you have a 2” pulley on the motor shaft and a 3” pulley on the head shaft … and you swap those around … you’re most likely not going to see a noticeable difference visually, especially if you’ve never seen it run at the correct RPM before … but there is going to get a significant difference in RPM’s. I would also check the motor to make sure it’s the original motor … or at least rated the same. If you swap out a 1/2 HP 3500 RPM motor with another 1/2 HP 1250 RPM motor … again, you’re going to see a significant difference … and again something, the amateur may totally overlook.

Note: I’ve lost track of it, but somewhere over on Old Woodworking Tools, they have a calculator to help you figure out what motor/pulley configuration will give you the correct RPM’s.

It’s another long shot … but I would check the set screws on your pulleys as well. If someone removed those during the refurbishing process, there is a chance that they didn’t tighten them down properly … and since it probably hasn’t been used on a regular basis since … their just lose enough to slip when under resistance … but not lose enough to really feel sloppy to your touch.

My last concern would be the bearings … although I don’t suspect this to be your problem … but depending on where that jointer was stored for the last couple of years … those bearings may be in need of replacement … unfortunately, I don’t know of a more scientific way to test them than simply removing the belts and giving the head a good spin … to see and hear if those things are spinning smoothly. But, if your head sputters out and comes to a bumpy grinding stop fairly quickly … you may have your culprit.

Hope this helps … if not …

I would go ask the guys over at the Old Wookworking Forums to see if they had any more advice.

-- Lip's Dysfuncational Firewood Farm, South Bend, IN

View Sawdust2's profile


1466 posts in 4326 days

#10 posted 07-26-2007 04:57 AM

Well, it was refurbished by Redmond so it was a good job. Doesn’t matter what was wrong before.
All of the ideas above hit most of his problems.
He was over the shop this evening and we straightened him out. If he’d been here two weeks ago he could have helped align my jointer and gotten first hand experience at that time.
We tried to convince him that it would be in his best interest to bring his big A 8” jointer up here but he was too weak.
We’ll probably have to trek down to the fireball’s house to really tweek it.

-- No piece is cut too short. It was meant for a smaller project.

View Nicky's profile


695 posts in 4330 days

#11 posted 07-26-2007 05:14 AM

Dorje and colorodoclimber got it right.

I would just add that when you check/adjust the knives, first find top dead center (highest point) and measure both sides of each knife from this point of reference, then zero your outfeed table.

Last, Delta has a website that you can download/view manuals. You’ll need to register at , the site is a bit goofy, but you should be able to find you manual.

-- Nicky

View coloradoclimber's profile


548 posts in 4306 days

#12 posted 07-26-2007 04:55 PM

FWIW all multi tooth cutters yield the same results, cutter marks. Take a look at the results of cutting with a bandsaw, tablesaw, end mill, face mill, jointer, planer, even sand paper. Any time there are individual cutters with gullets in between and you move the stock past the cutters (or cutters over the stock) you get places where the teeth are engaging the material and places where the stock is moving past a gullet (no cutting action). If you have enough cutters (sand paper) or you move slow enough then multiple cutters hit the same areas and you get a “smooth” surface. If you move the stock through fast you get cutter marks.

You can test this with pretty much any tool you have. On the bandsaw use a low tooth count blade, 3 or 4 tpi, get some pine, so you can push it through pretty fast without bogging down, turn the pine on it’s side so you get more cut surface to look at, and cut away. You should get some pretty pronounced cutter marks where the teeth are engaging or you’re pushing past the gullets.

Do the same thing with a table saw. You should see circular cutter marks.

Take a look at the milled cast iron surface of your table saw or jointer, unless the iron has been surface ground and polished you should see a circular pattern on the surface. Circular swirls, probably 3 to 4 inches in diameter. This is from the face mill cutter moving over the surface of the iron. Same exact phenomenon just a different material and cutter geometry.

The only ways to get away from it are; slow down the feed rate, polish it out later, use a different cutting technology. For wood you can use a hand plane and get a sliced / shaved surface that has NO cutter marks, not even sanding marks. Now that’s a nice surface.

View coloradoclimber's profile


548 posts in 4306 days

#13 posted 07-26-2007 05:00 PM

Lip, good point. I hadn’t considered that with this machine being refurbed perhaps the motor was replaced and a lower RPM one installed. Maybe the motor, pulleys, cutter head are not spinning at the factory rated rpms. If the cutter head is spinning slower then you get fewer cuts per forward travel of your stock. That would also exacerbate the problem, requiring an even slower feed rate to get a good cut.

It sounds like sawdust2 has some insight that this is probably not the problem, but it would be something to consider on an older or refurbed tool.

View Fireball's profile


71 posts in 4305 days

#14 posted 07-27-2007 02:47 AM

Thanks for the replies thus far. As Sawdust2 mentioned above, this is a refurbished unit that was done by Delta, and purchased through Redmond Machinery so a 6 month warranty applies, and if something is seriously out of kilter I am sure they will make it right.

That being said, after further investigation the blades are definitely not aligned properly. Using only my 2’ level I could see that with the outfeed table set at the current height only one of the blades would touch the level. Thus, I went out today and bought one of these:

Looks like it has lots of fun uses and will allow me to go back and tune up my other equipment as well. That being said, anyone have any preferred methods for setting their jointer knives? Hopefully I’ll have some time this weekend to get everything setup and running smoothly.

View WayneC's profile (online now)


13800 posts in 4335 days

#15 posted 07-27-2007 03:11 AM

From wood centeral

-- We must guard our enthusiasm as we would our life - James Krenov

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