Replies

1. 
   johnhardy | Aug 10, 2004 05:21pm | #1

   The only time I've seen this is with blades which were nicked and in need of replacement or sharpening.

   If this is new, I'd either return it or demand a replacement set of blades.

   John

2. 
   JohnWW | Aug 10, 2004 06:18pm | #2

   If the marks are actually gouges, look for a burr in the machine's table or a chip of wood caught in the gap between the main table and the infeed or outfeed table.  The chip or burr is sticking up enough to scratch the underside of the stock as it slides through the machine.

   Another possibility is that you have nicks in the knives which will create slightly raised lines down the length of the stock.  Unless somebody used the machine and put it back in the box, the most likely source of the nicks is some problem with the first boards you ran through the machine.

   Nicks are caused by something harder than the steel of the blade being embedded in the the wood.  While a stray screw or nail in salvaged wood is a possibility, the probable cause is sand or a small stone. 

   I always sweep off rough sawn wood with a wire brush and look closely at dings, cracks, and gouges.  Fairly often I'll find a grain of sand or even a small pebble pushed into the wood.  Brushing off the wood will also get rid of much of the fine grit that will speed up dulling the blades.  

   Knots and highly figured wood from burls and crotches can also have grit embedded in them.  Some knots, especially in tropical woods, can be hard enough on their own to chip steel.  Knots in any case are tough on blades, I always try to remove as many as possible when cutting up the stock before running it through the jointer and planer.  If the knot isn't going to be incorporated into the finished piece there's no reason for running it through the machines and beating up your blades.

   A third source of nicks are glue lines.  Almost all wood glues are considerably harder than steel, so running a glued up panel through a jointer or planer will damage the blades.

   If the problem is a nick in the blades, you can salvage them by loosening one and shifting it to the left or right a little bit to throw the notches in the two blades out of line with each other.  Most of the disposable blades have slots where they go over their alignment pins so the blade can be shifted a fraction of an inch to the side.

   Hope this helps, John W. 

     

    

   
   

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   Edited 8/10/2004 11:22 am ET by JohnW