Replies

1. 
   JohnWW | Mar 16, 2007 02:15am | #1

   I am not sure what you mean by the piece developing a ramp, so some additional explanation of the condition would help.

   Try this, and let me know what happens:  Take two reasonably straight and flat 30" or so long boards, 4" to 6" wide and around 3/4" thick, and joint the edges of both, taking about a 1/16" cut.  Heavy pressure on the outfeed table shouldn't be necessary. 

   Now, place the two jointed edges together and see how they meet.  Is the joint open at the ends, open in the middle and touching at the ends, or are the two boards touching over their whole length?  If the boards don't touch over their whole length, what happens when you take three passes on each board and then place them together?

   It would help to know what make and model of machine you have and what you have adjusted so far.

   John White 

   
   

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   Edited 3/15/2007 7:19 pm ET by JohnWW

1. 
   m71 | Mar 16, 2007 02:47am | #2

   Thanks for the quick reply

   Further explanation:

   I'm using a grizzly G0593 8" w spiral cutting knives.

   For set up I have made sure that the blades are level with the outfeed table. That the outfeed table  is level with the infeed table and that the fence is 90 to the outfeed/infeed table.

   If for instance I take a 4" wide board with perfectly flat edge then joint it i end up with a tapered(ramped) board.  3 3/4" where i started to joint the piece and 4" at the end of the piece.

   I'm thinking it might be that I'm concentrating on too much pressure on the outfeed and not enough pressure on the infeed?

    

    

1. 
   JohnWW | Mar 16, 2007 04:03pm | #3

   It sounds like your problem is being caused by the outfeed table being set wrong.

   It is a myth that the outfeed table on a jointer is set at the height of the blades.  It will be close, but the best setting for the outfeed table height is achieved through the procedure outlined below: 

   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 1/2 to 2/3's 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 work with hardwoods, this adjustment will be more accurate if the test boards are also a hardwood.  Never plane MDF or plywood on a jointer unless it has carbide blades, the glues in them will dull steel blades very quickly. 

   Start by dropping the outfeed table so that it is approximately 1/16 inch lower than the top dead center height of the knives in the cutting head.  In this position, the outfeed table will definitely be too low.  Also set the infeed table for a 1/16" cut.

   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. 

   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.