Can’t get a clean cut on my new Jointer
I bought one of the white, closed stand, Jet 6″ jointers. I’ve never been able to get a cut that was as clean as even my Dewalt planer that has only two blades. I get a very rippled cut. Everything I read and everyone I speak with says it can only be caused by blade adjustment. I’ve tried many times to set the blades. I’ve used a dial indicator, the method that measures how far a block of wood moves and a magna-set, all to no good ends. Could something else be causing this type of problem? I have the jointer on a mobile base so the unit isn’t as stable as it would be on the floor; could vibration cause this problem? Could it be some other sort of alignment problem? Bad blades? I called Jet and they told me it had to be the blade height. So am I just really bad at setting the blades or could it be something else?
Thanks,
Dave
Replies
I get cleaner cuts from my planer as well and have always put it down to the fact that the feed rollers in the planer apply enough pressure to hold the stock down to the bed firmly and the knives also force the stock down to the rigid bed. A jointer kicks the stock up with every blade contact causing it bounce very slightly, resisted only by the pressure you apply. Precision blade setting, sharp blades and slower feed rates all reduce the visible scalloping but it's tough to eliminate.
It may not be mis-adjusted blades. Jointers and planers cut by rotary motion "scalloping" out material. This rotary cutting leaves the ripples you are experiencing.
You can reduce them by slowing down the material movement thereby getting more cuts per inch and the ripples will be closer together. However, any board run over a jointer or a planer needs to be smoothed before finishing. For edge gluing, the ripples do not affect the glue joint strength.
But, if you have one blade higher than another, then that blade is the only one that will cut and you will get exaggerated ripples. So, re-check your blade heights to be sure they are all to the same height.
Dave,
As already mentioned, jointers caused a scalloping cut. But if you run the work slowly through the machine, the surface can seem to be perfectly smooth. It can't be as good as that from one sweep of a hand plane, but it can be almost that good. And the feed rate does not have to be agonizingly slow to get this.
Setting jointer knives to the same height requires care, but it's not all that difficult. It sounds like you are doing something simple that's throwing you off. This happens - we get into a little habit that we don't notice and trouble happens. Any one of the methods that you use should get you very good results.
Is there anyone else in your area who could watch you as you adjust the knives, to see if you're doing it right? You have a good machine and I don't believe that the mobile base can be causing your problem.
Rich
It's been my gut feel also that it is still me not getting the blades set correctly. After a while I want to find something else to blame. I understand the mechanics of the cut and that there should be some rippling, but I think I have too much. I read about people cutting on the table saw and then going to the jointer to leave a clean edge and that wouldn't work for me. I can use my jointer to flatten and square, but it definitely doesn't leave a clean edge. I expected that given the 3 blades on the jointer and the 2 on my planer, that the jointer would have a cleaner cut. I get a much better cut with my Forest blade on the table saw or with my little Dewalt portable planer.
I would love to get someone with some experience into my shop. I have really picked up most of my knowledge (or lack of) from books and high school shop class (20 years ago). My shop is at my weekend place in western Mass. Because I'm only there on weekends I don't know a lot of people in the area and would have a hard time joining a local woodworking club. I've read on these forums about people who will come out and tune machines. How would I find these people?
Dave
Dave, whether you have 2 blades or 3 blades is not the issue. It's the number of cuts per inch of material movement. Many 2 blade planers rotate at a higher rate than 2 blade induction motor jointers. Of course, with jointers, the cuts per inch are controlled by the operator and how fast and smoothly the board is fed over the cutter.
Also, if you are getting a smooth cut from your saw blade, there is no reason to run the board through a jointer. Most good combo/general purpose blades or good rip blades will give "glue line" cuts directly off the saw.
Here's an idea, old and not mine, and a bit of a risk, so be careful. Set your knives as close to the same height as possible, using a straight edge off of the outfeed table. I use the base of a machinist's square as the straight edge. Put your ear to the table to hear the touching of the knive to the edge.
Then, when done, lower the outfeed table as little as possible. About .002" would be great. Clamp a stop block on the infeed table parallel to the cutterhead about 2" away. Take a sharpening stone, and with the jointer running, joint the knives by moving the stone across the outfeed table. You will need to continually flatten the stone, as the knives will cut it away quite quickly. I use an old oilstone for this, and that is the only thing that I use the old stone for. I flatten it on a diamond stone. The stop is so that if there is a grab, the stone does not get away from you. Only joint the edge as little as possible, as if you do so too much, the bottom of the secondary bevel will hit the wood before the edge does, and it will cut poorly, with much bounce.
Does anyone else do this? Am I crazy?
Are you crazy? Dunno. What's your shrink say? But I do know you are lucky that you haven't been injured. And that you aren't doing the blades any good. You are really risking very serious injury.
I have used a stone to hone a micro bevel on blades while they were locked in position. But while the machine is running!!!!
[shudder]
Rich
Edited 9/24/2002 11:08:11 AM ET by Rich Rose
Amen!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Tage Fried, in Volume 1 of his woodworking series for Taunton, describes a very simple jig for evening the height of jointer knives. It involves a router with a cone grinding stone mounted in the chuck, and a piece of plywood 16" or so long with the router mounted on one end. The jointer is unplugged and the cutterhead locked with a knife in top dead center. The router-mounted stone is lowered to touch the outfeed table and locked in that position. The outfeed table is lowered just a hair below the least-high knife. Then the jig is slid back and forth on the outfeed table to grind each knife to table height. A metal strip screwed to the infeed table can be used to slide under a knife and jam the cutter head. Then each knife can be locked in the same position as its siblings.
Quick, effective, cheap, and no hazard to the operator.
Don,
I remember trying Tage's method after reading his article in FWW many more years ago than I care to admit (it must have been late 70s, early 80s?). It scared the hell out of me and I couldn't get it to work. I was using a Craftsman router then (I still have it) which ran at 25,000 RPM. Now that I have a speed control on my Bosch router I might try it again at low speed.
Does that article describe using a bench stone to hone the knives on the machine? If it does, I believe there is a sentence which warns against using the stone on the running knives as the stone could explode.
Rich
Edited 9/24/2002 1:08:55 PM ET by Rich Rose
Rich-
I've used the router-mounted grinding stone at high speed with complete success. I think the secret is to grind just a little bit at a time, and if the knives are badly out of alignment, do it in serveral steps until you've ground the last one. That is, grind all three knife positions with successively lower outfeed table positions. Lower router speed should make the technique even better.
I don't remember if the article mentioned using a bench stone, but I'd certainly back away from using one on a rotating cutterhead. The direction of the action in that case is to put tension on the stone, and I don't think those things have much tensile strength.
Don,
Thanks. I seem to remember the router process to establish the main bevel (bezel) and the bench stone for the microbevel. But I may be combining 2 articles in my brain.
Gotta go dig it up.
Rich
Regarding the issue of honing knives under power. My old Powermatic jointer manual DOES suggest this method, (including illustration of procedure) using an Arkansas stone and a block of wood clamp to the infeed table to prevent kickback of the stone. I tried it once, that was enough for me.
On the problem of ripple cuts, it sounds like a knife is set too high, Mark Duginski's video on mastering power tools has a very detailed explanation of jointer problems and how to properly set the knives.
Greg
Setting safety issues aside for the moment, is sharpening jointer knives under power against a stone really effective? I wonder if this isn't one of those old-timer techniques that's just plain baloney.
This entire discussion has centered on the ripple cuts a jointer makes. That is, the blade first enters the wood at an angle, is parallel to the stock in the middle of the cut, then exits at the reciprocal of the entry angle. It would follow the same path if a stone is substituted for the wood. Is this the way we are taught to hand sharpen any tool: start out at a steeper angle than the original grind and then rotate the tool during the sharpening stroke?
So we'd produce a rounded cutting edge. Is this desirable?
I agree with your and others' diagnosis that one blade is too high. In effect, planing with a one-blade cutterhead.
Edited 9/24/2002 6:15:17 PM ET by Donald C. Brown
My sawyer uses this technique on his beasts. I suppose when hundreds of board feet run through your jointer and planer everyday experience dictates shortcuts to minimize down time.
As a hobbyist I'll stick to my magnaset with a cold beer and a little patience-
A series of ridges indicates feeding too fast, even if only one knife, set higher than all the others, which is the norm, is effectively cutting. Dropping an oil stone on the revolving cutters, even in 'controlled' circumstances, is not something I'd recommend in a million years, but I've heard of it many times before. Never done it, and never will-- I may be daft, and like a beer or six, and other stuff, but I'm never going to try that one, ha, ha, and in addition you can always make a wee thin plywood sled to carry the stone and do each knife individually with each iron locked top dead centre with the outfeed table dropped by the thickness of the plywood sled. And you might simply be feeding the wrong way, i.e., against the grain. Slainte. Website
Sgian,
I'm having following... How does a fast stock feed produce ripples? I've never experienced waves, ripples, or heavy scallopping unless one of the knives is set improperly, regardless of feed rate. Are you referring to tearout?, which, either feeding fast or in the wrong direction will produce.
Greg
Greg, a slow stock feed also produces ripples, but they're just less noticeable because the high spots and low spots of the washboard effect are closer together. They're caused by the circular cutting action of the knife in the block. Compare this with planing with a handplane where the iron sticks out at a consistent depth. The ripples from machine planing and shaping are generally fairly easy to see in wooden parts fitted in houses, such as door facings, skirting boards, window trim, cornices or crown mouldings, etc.. Paint and varnish tend to emphasise all blemishes on the timber surface. Feeding fast, and in the wrong direction, i.e., against the grain, can result in both ripples and tear out, with the latter usually most obvious. Slainte. Website
Sgian,
I agree that ripples, or scalloping, exists on any wood surface that's been rotary planed, certainly noticable if you wet the board with something like mineral spirits, however, this fellow seems to be describing something quite a bit more severe, referring to "a very rippled surface" if I recall. In my experience, any ripple or waveform going beyond visual examination to where you can feel it with your finger tips is always a problem with knife set-up. Further, I'll go out on a ledge and say I really don't think stock feed rate plays a significant role, considering a cutterhead turning at so many thousand rpm, you should still receive a satisfactory surface, provided sharp knifes. Too slow a feed, on the other hand, brings into play the other side of the coin, burnishing.
Greg
FWIW, the manual for my Grizzly jointer also suggests the stone-&-rotating-cutterhead method, with stone on the outfeed table.
The router method in Tag's book is with cutterhead stationary and fixed in position. Repeat for each knife.
When using the new 2 speed Delta planer, there is a significant and noticable difference between the fast speed and the slow speed. The slow speed gives a smoother surface. It's only the feed rate that is changed. The cutterhead RPM stays the same. However, there are still ripples and these must be removed before finishing.
Rather than get involved in the on-jointer stoning, I would just suggest that the appropriate section of "Understand Wood" by Hoadley be looked at. Hoadley spends some time analysing the cutting action relating to blade cutting angle.
Greg, I did suggest in my first post that one cutter was probably doing all the work, and if he pushes fast enough then regularly spaced ripples would be obvious, and to me, unacceptable, but I'd have to agree that what's acceptable to me in most cases might be nitpickingly pernickety to others.
On the other hand, it sounds like Dave might be new to overhand surface planers or jointers, therefore not familiar with all the terminology. It's crossed my mind that he might actually be trying to describe a series of steps (rather than a constant ripple) caused by the piece being flattened rocking backwards and forwards on either or both tables. If he's sure that the machine is set up correctly, and the symptoms are as I've described, then technique is likely the cause of the problem. (Sorry in advance if I'm mis-reading your level of experience Dave.) Slainte.Website
Thanks for the input. I always appreciate reading your posts. I'm convinced now that my problem is just in my knife setting, with one blade doing all the work. I've tried setting them quite a few times, some attempts better than others, but never got the cut quality I believe I should get. My purpose in posting originally was just to make sure that it was only me and not something wrong with the machine. Given all the responses I've gotten, I'm going to try a new set of knives this weekend and just keep trying until I get it right.
Thanks for all the feedback.
Dave
I have a 12" General jointer and my instruction manual also says to use a stone on the rotating cutterhead to level the blades to the outfeed table. But it says to use it on the outfeed side. I tried it a few times but what happens is the secondary bevel causes a compression of sorts because of the way the blades hits the wood. Since my jointer has 4 blades if you try to joint a 12" wide board with blades like this the board vibrates something fierce and the sound seemed to double. Especially if it's hard Maple or something along those lines. Plus on a machine this size it's a scary as hell. Sure does leave a nice surface though.
I am positively amazed at these descriptions of the use of a stone on the rotating blades!
Live and learn. (Not that I am tempted to use the method)
Rich
I don't make the news...I just report it........
The fact is this technique's been around quite a while. As I said, I only tried it once, a long time ago, so I wouldn't consider myself an expert. I believe it's basically for honing the blades, not really grinding them. If you get past the point of honing, as someone pointed out, you end up rounding the knifes over too much. The knives have to be removed and re-ground at this point.
When I reached the level of skill when I could reset jointer blades precisely and consistently I've never had a problem with jointer performance since, ( poor surface, snipe, etc)
Joint well.........
Greg
Regarding using a stone while the jointer is running:
Uh your're not crazy. I've done it myself. It works fantastic when your knives are really dull and no longer respond to just honing while stopped.Keep in mind youre just taking off a thou or so under controlled conditions.Patrick Speilman covers this in his book Sharpening.
It's safe if done correctly and it works but I don't think Dave should go there NOW.
Dave, back in 1970 I lived in Greenfield, Mass. and hitched once a week to N Adams,Mass. to a Community College to study woodworking. Even if you're only around on weekends, an instructor at your local community college should be able to give you a few names.
Full circle...now I'm an instructor at a college....
cheers,silver
Edited 9/25/2002 2:22:05 AM ET by silver
Am I crazy?
Maybe so, but you're not alone. When I first had to remove and replace the knives on my jointer, I turned to some of the ww "professionals" on the project I'm working on. They really *are* professionals in the truest sense of the word. One of them suggested jointing the knives as you suggest. Needless to say, I found a way to get them set pretty durned accurately with the power chord unplugged!! Of all the tools in my shop, the jointer is the one I respect most for the damage it could do to me.
No, I don't own and don't intend to own a shaper (grin)
Dennis in Bellevue WA
[email protected]
Dave
a shot in the dark: I don't think it's your blade height.Sounds like you've got that one covered.
How is the height of your back table in relation to your knives..One of the.most common jointer problems and could possibly cause your problem. On a fairly straight piece take a 2" bite. Shut off- and slide the snipe you just made onto the back table. Should be bang on...raise or lower the back table if necessary and then at a moderate feed rate you should get a flat even jointed edge...only thing I can think of; maybe you already tried it.
silver
Just to clarify. Your saying that the height of the outfeed table could be too high or low causing my problem? I think at one point I had to drop it a couple thousanths to get a straight cut.
My shop is in my weekend place. I'll give this a shot this weekend.
Thanks,
Dave
Well, I have that same jointer, and I don't have that problem. My knife setting ain't the best, either. Try a real thin cut (~1/32") and go slow. What does that do?
Are your knives sharp??
PlaneWood by Mike_in_Katy
PlaneWood
It gets better when I do this, but I still think it is not the cut I should have. I also wondered about the blades. They are the blades that came with it and I haven't put many hours on the machine at all. They seem OK, but I've thought about getting them sharpened just to make sure.
It looks more and more that it is just me not setting the blades well. I was hoping someone was going to point me to some possible defect or something, but no such luck(?). I'll just try setting the knives a few more times.
Dave
Dave, I've been wondering about the blades a bit myself. You never know. Since you'll probably be wanting an extra set at some point anyway, how 'bout buying a new set and trying them?
If new/sharpened blades, meticulous blade setting and slow feed with steady pressure don't solve the problem, I'd get on the horn to Jet again. This machine has an excellent reputation, and so does Jet customer service, so there's no reason for it not to work properly. forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Here's a simple experiment you can try. Run a piece of soft wood, like 1x pine, at relatively high feed and shallow cut, while someone with a stopwatch times you. You'll need to time this relatively accurately. Practice a few times until you can keep a constant speed start to finish. Calculate seconds per inch of feed by dividing elapsed time by the length of the test board [example 4 s/12 in = 0.333 s/in]. The cutterhead on that machine turns at 4800 rpm (published figure, which I assume is under full load; it's probably more like 4900 rpm under light- to no-load). 4900 rpm is about 82 rev/s, so a high knife will make 82 passes per second. Multiply seconds per inch of feed by 82 rev/s to get number of scallops per inch of board [example 0.333 s/in * 82 rev/s = 27 rev/in or 27 scallops per inch]. Or, in one step, use (82 * elapsed time / length of test board) = scallops per inch. If you measure, from the example, +/-27 scallops per inch, look for the high (or low) knife.
If the scallops per inch are about 3/4 of what you calculate, or 20 per inch from the example, look for a bent or eccentric motor shaft, or out of round drive pulley. This can be hard to determine, since the casting can look wacky but still run true at the pitch diameter. Die cast (aluminum) drive pulleys are more likely to be flawed than a cast iron or machined steel unit. Also remove the belt and run the motor to check for vibration with the pulley on the shaft. If vibration is noticeable, remove the pulley and check again. If it goes away, replace the pulley; if not, talk to Jet about replacing the motor. Another way to check for pulley eccentricity is to put a mark on the pulley (unplugged, please), and check belt tension as you slowly rotate it. If it tightens and loosens, even a little, in the same places on either pulley consistently, the pitch circle of the pulley is not concentric to the shaft, and the pulley should be replaced.
If the scallops are much farther apart than either of the above cases, I'd guess the drive belt is causing the problem. a 52 in belt on a 3 in OD (2.85 in pitch diameter) cutterhead pulley will make one revolution for every 6 of the cutterhead. Therefore, if you measure about 4.5 scallops per inch (although harmonics can make multiples of this), by the above example, I'd look for a non-uniform belt, or one with lots of set. Even if the table just seems to vibrate too much, whatever that means. There's lots of reasons for this, and a little non-uniformity goes a long way, but you can try loosening the belt until it runs smoother (people tend to overtension them anyway), or better yet replacing it with a link-type belt. I haven't tried them, but plenty of others swear by them for vibration reduction.
As a side note, I just ran a test on my ancient 4" Delta precision jointer at 4200 rpm, and calculated 11.6 scallops per inch, which is about what I measured on the test piece. I guess I have a high (or low) knife. Good luck.
Be seeing you...
Wow, I just got my homework for the weekend. Thanks for the input this gives me a lot to look into. I'll let you know what I find.
Dave
Dave, you should be achieving a very clean edge with this jointer. Given that you've taken a lot of care in setting the knives, even using two different time-proven, relatively easy techniques, I'd have to say that the knife set is not the problem.
The next place to look is the cutterhead bearings. If one of the bearings is bad, it will produce exactly what you're experiencing. Essentially, it's radial play that wreaks havoc under the dynamics of cutting. Be sure to give these bearings a good look.
Best of luck,
Dick
Edited 9/27/2002 6:10:36 PM ET by Dick
Any chance that you may have vertical movement in the cutterhead itself? May only evidence itself while running at high speed unless you go looking for it. Bearings.....mounting...????????
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