I bought rough Quarter Sawn Oak for my first big project (the boss needed a new buffet for our dinning room). I have tried to dimension the lumber by jointing it on my 6" jointer but no matter what I do it comes out bowed. In some cases I have even thought it was better of before I started. What am I doing wrong. Is there a specific technique for this.
The main cause for what you are seeing is that your jointer tables are out of whack. When you have them set for 0 cut they should be flat from end to end. If not then you will get the problem you have seen. Check your owners manual for adjusting the tables.
If the tables are set right and you still have the issue make sure that you are appling the majority of pressue on the outfeed table as you move the stock across The jointer. Also flaten the face with the cup side down. That way you won't just follow the existing bow.
As Lou suggested, make sure your tables are co-planer, then check for parallelism.
You don't mention if you are getting "bows" while edge jointing, face jointing, or both. Sometimes "bows" can result from trying to run boards that are too long; they can sag a tad.
Once I receive my stock, I'll put together a cut list and mark each board for the various components I want to mill out of it. Once that's done then I'll cross cut to rough lengths, then move to dimensioning operation; it's easier to handle smaller boards.
At this point, given the information provided, I can't really tell if it's technique, misaligned jointer, or both.....
Dan and Lou,
Thanks I checked for co-planar and they seemed OK, my "straight-edge" was not the most accurate. I got a good one now and will check again. What do you mean by parallelism?
The problem manifests itself upon face jointing more readily. Dan, I suspected I was exceeding the maximum length I could join with my jointer. If I remember correctly the total length of the tables on my jointer is 46". I think I read somewhere I could accurately joint a board up to a maximum length of 1.5 x the combined length of the tables. Is this correct? I am trying to joint a 60" board.
60" should be ok. If you were talking about 12 ft then it might be the board. The two tables need to be in the same plane and when you adjust the infeed table for a cut of say 1/64 th then the whole table needs to be 1/64 th below the outfeed table.
Place the cupped side down and apply pressure on the board to keep it as flat as you can on the infeed table. Move the board smoothly across the cutter shifting your hands/push blocks to the outfeed table as soon as you have a stable base of wood on the outfeed table keeping the board flat on the outfeed as you move the stock through the rest of the cut.
The key is how you shift your weight as you move the stock through the cut.
The wood will have a bend to it one side concave or cupped, and the other side is convex or bowed out. So you want to put the stock on the jointer so that the ends are the lowest pints and the middle is higher.
As you push the wood through the end gets planed and then the middle might not be cut and the far end get sut. AS the board gets flat you get a even cut across the whole board. If there is a large bow or cup to the board you might want to use it for sshort items on your cut list and cross cut it to limit the amount of stock that needs to be removed.
As I mentioned last night I got good straight-edge and sure enough the tables are not coplanar, across 24" inches there is a difference of .0006". This seems a bit much to me but I don't know what the tolerance is for these machines. I have no idea how to correct this and could not find any reference to this issue in my manual. I will call tech support tomorrow.
Regarding the technique you suggest I was doing the opposite. I was putting just enough pressure on the infeed to eliminate chatter. My reasoning was that if I flattened it out I would be doing the same thing the rollers on the planer would be doing. I will try your technique once I get the coplanar issue resolved.