Replies

1. 
   DennisS | Jan 15, 2004 05:55am | #1

   Scott -

   The other day I noticed I was having the same result. I checked the outfeed table and found that somehow it had gotten lowered to below the level of the knives. The way I was taught with respect to jointer technique is to start the piece into the rotating knives with most of the pressure on the infeed table but held tight against the fence. Then as the first portion of the leading end of the piece begins to bear on the outfeed table, pressure is transfered to this leadng end and onto the outfeed table. Using that technique, if the outfeed table is below the arc of the knives, it doesn't take too much imagination to visualize how you get a convex bow as the end result.

   I re-adjusted the outfeed table so it was just a hair *above* the arc of the knives and the bow was gone.

   Unplug the jonter. Take a straight rule, something like the blade of an adjustable try square and carefully slide it on the outfeed table up to the cutter head. Rotate the cutter head by hand being careful of the sharp knives (that's why we unplug the machine) and see if the knives are indeed flush or just slightly, like a coupla thou higher than the outfeed table. If not, make it so. Then try jointing another board and see if this solves the problem.

   Lemme know if that's what was causing the bowed board .... curious.

   ...........

   From Beautiful Skagit Co. Wa.

   Dennis

1. 
   rslatm | Jan 15, 2004 03:45pm | #6

   "I re-adjusted the outfeed table so it was just a hair *above* the arc of the knives and the bow was gone. "         I think you need to look closer look and re-evaluate the situation.

   Ideally you want the outfeed table at the same height of the knives at top dead center or the knives a few thousandths higher than the out feed table. I use a dial indicator to set planer and jointer knives. Also I've done it professionally so I've done it hundreds of times. I've measured the height of dull knives on our planers just to see how much the edge changes from wear and typically find it .005" lower than the original setting so having the knives a bit higher than the outfeed table on your jointer is best.  If you have an adjustable outfeed table drop it down until you get snipe and slowly raise it up until snipe is gone. If you went too far and the table is higher than top dead center of the knives the jointer will cut at the beginning of the board and taper off untill the knives are not cutting at all resulting in a tapered board . Further proof of this is if the outfeed table is too high the board will stop dead because it's hitting the outfeed table.

1. 
   DennisS | Jan 15, 2004 06:31pm | #7

   Rich -

   You're quite right - too much typing too late at night. When passing the straight edge across the knives while sliding on the outfeed table, one should be able to just barely turn the cutter head with the friction of the straightedge on the top edge of the knife, or conversely, rolling the cutter head by hand should move the straightedge just a fraction of an inch.

   My mistake and thanks for the correction.

   ...........

   From Beautiful Skagit Co. Wa.

   Dennis

2. 
   kensshop | Jan 15, 2004 06:07am | #2

   Your outfeed table is probably too high.  This can be remedied by adjusting the outfeed table down then slowing adjusting it upward between trial passes, use something other than your project wood.  

   Another possibility is that either the infeed or outfeed table is too high near its edge furthest from the cutterhead.  This can be checked with a quality straight edge.  If this is the problem you can usually adjust the table(s).  

     http://forums.taunton.com/n/main.asp?qu=outfeed+table+height&webtag=tp-knots&ctx=search&cl=632359&af=10000&o=relevance&be=0

   Go to the topic that starts with gsg, assuming....     Good Luck, Ken

   
   

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   Edited 1/14/2004 10:22:53 PM ET by Ken's Shop

   
   

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   Edited 1/14/2004 10:30:47 PM ET by Ken's Shop

1. 
   oldsub86 | Jan 15, 2004 06:45am | #4

   I would start by raising both tables up to a level above the cutter head and then laying a long straight edge accross both tables. You may find that something has sagged a bit and that they are not straight. This happened to my jointer and I had to put some shim material on the outfeed table "tracks" (can't recall the technical term for the table slide thing). A thin shim of paper in my case solved the problem. Some machines may have a means of adjustment. My machine did not. It does not seem worth the cost to have it machined. One might do it with a file given it is obviously a small amount but the shim seems to work fine. It has now been like that for a number of years.

   Randy

3. 
   notDusty | Jan 15, 2004 06:43am | #3

                Hi scott ,                      

       On a fixed outfeed table model, the knives get set to the hieght of the out feed table , since you can't adjust the table .

4. 
   mlbfreestyle | Jan 15, 2004 10:04am | #5

   I agree with what has been said.  Now let me add my two cents worth.  I just purchased a Grizz 0500 and was having the same problem.  Very frustrating.  Stock under 36" was dead flat, but once I ventured longer, it became convex by a few thousandths.

   Here was my remedy.  First, the table extensions (5" on each end) were tilted up slightly (perhaps .003").  I fussed with them some more using aluminum foil as shim stock to get them coplaner with the bed.

   Second point.  I agree that the outfeed table must be at the correct height.  Here is how I do it.  Use any method mentioned by the others here to get it close or inch a flat peice of stock backwards on the table until it passes over the blade.  Drop the outfeed table slowly until it starts to knick the board.  Now do a normal pass with a flat board.  As the workpeice arrives at the outfeed it will do one of three things.  1. pass above it, which will result in end snipe at the tail end.  2. Be perfect.  3. Hit the leading edge of the outfeed table.  I slowly adjust the outfeed upward until I get the third condition.  I then can back it off slightly so that I can feel the drag of the outfeed when the stock first comes on to it, but it does not hit the edge.  You will have to play with this a bit until you get it.  I prefer my last move to be upward to take slack out of the screw.

   Here is the other point related to what was also said previously about technique.  I found that I had developed a bad habit.  As soon as the workpeice was 4 or 5" over the outfeed, I was maintaining my pressure point just past the cutterhead.  I have gotten better results if I allow my pressure point to travel to the middle of the outfeed table and maintain it there until the stock has cleared the head.  This is not so critical if face jointing stock prior to surface planning, but it has given me much better results when jointing prior to edge gluing.

   I used to do all my jointing by hand, leaving a slightly concave surface, which I think is best for durability of the joint.  My machine method leaves it nearly dead straight.  On critical peices, I may still follow up with the hand jointer to reintroduce this slight concavity.

   Let me add that even with the adjustments to machine and technique, two 48" boards adge jointed and butted up to each other will still leave a gap at each end of about .001".  It is not perfect.

   
   

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   Edited 1/15/2004 2:06:56 AM ET by mlbfreestyle

5. 
   JohnWW | Jan 15, 2004 10:24pm | #8

   Scott,

   This is an answer I wrote to someone with the same problem:

   Assuming there are no mechanical problems, the blades are sharp, and the tables are flat and coplanar, the most likely problem is that the outfeed table isn't set at exactly the correct height.  Setting the outfeed height is a simple procedure, so I'd start out trying to adjust it before trying anything else.

   To set up the outfeed table height, you'll need two test boards, each about 2/3 as long as the overall length of the jointer, these boards should be close to perfectly flat on their wide faces with no large knots.  If you primarily plane hardwoods, the adjustment will be more accurate if the test boards are also a hardwood. 

   Start by dropping the outfeed table so that it is slightly lower than the highest point in the path of the knives on the cutting head.  In this position, the outfeed table will definitely be too low.  Take a pass with each of the test boards and place them together, planed edge to planed edge.  With the table too low, you should find that the planed edges are concave when placed together and each board's trailing edge will have a small snipe over the last inch or so.  The test cut should be fairly shallow, removing no more than a 1/16th of an inch from each board. 

   Next start to raise the outfeed table by small increments, taking test cuts on both boards after each adjustment.  As you bring the test boards together after each height adjustment, you should see the midpoint gap diminish and the trailing snipe disappear.  Keep adjusting the outfeed table upward by small amounts until the edges mate perfectly and you'll be all set. 

   If you overshoot the setting, the boards will be touching in the middle and gapping at the ends of the joint.  If this happens, drop the table to below the correct height and try again to get the correct setting by raising the table. 

   If this procedure doesn't solve your problem, I'd replace the knives with a freshly sharpened set, and repeat the above adjustments on the outfeed table.  If you are still having problems after that, then it is likely you have some problems with the alignment of the tables with each other, which will be harder to diagnose and fix.

   John W.

1. 
   user-3207593 | Jan 16, 2004 12:55am | #9

   Thanks for all of your help!

   After tweaking the outfeed table and still getting a bow I decided to look at my jointer and make sure everything is where it should be.

   I have found that the infeed table on my jointer is tilted slightly inwards towards the knives. I observed this when I placed a 4 foot level across the entire top. I took the infeed table off(as far as I could) greased the sleds and generally refreshed all of the bolts. I took another look at the level and it seems much much better.

   I hope this will fix the problem, but I can't test it until later this evening. Otherwise, I'm going to review all of the great suggestions on aligning the blades with the outfeed table. Starting first with lowering the outfeed so the knives are proud then incrementing the distance until the gaps between my boards dissapears. Or so I hope.

   Thanks again to everyone for all of their great suggestions.

   Scott Suess

1. 
   Tao | Jan 16, 2004 04:08am | #11

   Good advice all.  

   Just acouple of observations: 

   I recently bought a 50 year old long bed planer.  The tables were not coplanar.  I took off the tables, cleaned everything, and re-adjusted the gibs.  Perfect joints.  Point is, when jointers are manufactured, the tables are usually machined flat with the tables on the jointer, so if they are out of line, there can be only two causes: either something's loose or the casting has warped.  Something loose is a lot more common, and easier to fix. Wear just isn't much of a factor on jointer ways, unless it gets adjusted a LOT over a lot of years.  Also, shimming might not be the best answer when just cleaning and tightening might suffice.

   The other thng is that a good jointer, properly set up and sharp, will give amazingly close joints where you can't even see a dark line when you put the edges together dry, much less see any light through the joint.  This assumes, of course, that you have good straight-grained wood with no reaction wood or case hardening.

   Michael R.

2. 
   VeniciaL | Jan 16, 2004 03:57am | #10

   John,

   That's a concise and coherent description of jointer adjustment. It defines precisely the end point in knowing when the outfeed table is the right height. That height is NOT easily obtained by any measuring technique and even can vary with wood. Although, as you say, if done with a hardwood, it will suffice for another hardwood. But swiching to a softwood may alter the result, so be prepared to adjust if ultimate accuracy is the goal.

   I would like to add two points. First, take less than 1/16" at each pass. 1/16" is actually a lot of wood to remove. Second, perfect flatness of the jointed pieces is not necessarily the only end point. It certainly is, if one is preparing a board to be a straight edge as for a face for a rip fence. And straight edges are obviously desirable for gluing. But the slight concavity of the two mating edges just before the last adjustment of the outfeed table gets the machine cutting absolutely straight is actually a better cut for a glue joint.

   That way, the ends of the boards touch first. The clamps pull the center of the boards together, closing up the hairline gap and the ends are minutely tighter that the middle. The normal tendancy of the ends to loose moisture faster than the middle, resulting in glue lines opening there, is counter acted by the extra compression exerted by the boards themselves. They are their own, permanent cauls.

   VL

6. 
   steven_woodward | Oct 29, 2019 08:15pm | #12

   Check your blades to make sure they are straight. Hold a straight edge against the sharp edge and check for light. I found my blades came back from the sharpening shop not very straight. That made it impossible to set the outfeed table to the correct height because a portion of the blade would be above the outfeed and another portion below the outfeed table. The only solution was to set the outfeed table to the low point of the blades and accept some snipe. I now sharpen my own blades with Makita 98202 and can get the blades straight within 0.001 inch, which is an improvement - see photo.