^{I recommend and use kerosene to remove the grease and coating.  I then wipe the tables down with paper towel followed by a cotton cloth.  I then apply a good coat of wax.  I use Johnson’s paste wax.  I keep a can handy and buff out the tables frequently.  Helps keep the tops looking good, fights rust, and makes the material glide across the tables.}

The way you are describing the problem, it sound like a convex cut problem. Here are the 4 basic problems that can happen and how to correct them.

            TROUBLESHOOTING JOINTERS

Concave cuts, the boards that you run through your jointer end up shallower in the center than at the ends.

·        One or both ends of the table sag some

·        Slide fence off table

·        Remove guard and raise infeed table to match outfeed

·        Straight edge across length of table and check for sag

·        Tighten gib screw until no light appears under straight edge

Convex cuts, your jointed edges prove slightly narrower at the ends than the center.

·        Exact reverse of the concave problem

·        Check for this in the same manner outlined except look for light under the middle of the straight edge near the cutter head

·        Loosen gib screw on one or both tables to correct the problem

Out of square, the face and the edge don’t meet at an exact 90% corner.

·        Fence is not set at 90% to the table

·        Use a drafting square to correct this problem

·        Reset fence

Snipe, jointed boards that show a small hollow cut at their end. Out feed table nolonger supports the workpiece after it passes the cutterhead.

·        Correct poor alignment by raising the outfeed table.

·        First lower the outfeed table slightly

·        Slowly feed a piece of stock about 1” across the cutterhead

·        Unlock outfeed table and raise it until it just touches the workpiece, then lock it down

Is there a formula to determine the longest board that can be edge jointed on a jointer of X" in table length?

Like: Max Stock Length = (Infeed table length + outfeed table length) * X

I have a Delta 6" Variable Speed Bench Jointer (Mod 37-070) which works fine on cabinet doors and the other small projects I use it for.  I've even had great results on 6' long (yeah feet) rails/stiles. 

Table tops are the problem.  I can't get the invisible joint I am used to on cabinet doors when trying to make a table top.  None of the Delta's jointers (that I looked at) said what the maximum stock length was.  (Telling me an 8" jointer can joint up to 8" wide boards was not especially useful).

The longer the bed the better!  The 6” bench top is designed for smaller work.  I would suggest lengths up to 48” would be manageable.   There is no maximum length for any jointer, it is determined on how much length the operator can control and support through the cut.  Even with support rollers you will find a bench top jointer a challenge for longer stock.  I can accurately joint 96” boards on my 8” jointer by myself.  Anything longer requires help from an assistant.  Thanks for a great question.

I have two questions.  The first is regarding a jointer.  I need to buy a new jointer and am undecided between a 6-inch and 8-inch.  It seems like every time I take the least costly option I end up being sorry.  The disadvantages to getting an 8-inch are; it requires 220v, it takes up more space in my basement shop, moving something that heavy down the basement stairs, and cost.  The obvious advantages are the longer bed and bigger fence.  It is difficult to purchase straight and true lumber and the larger machine makes straightening lumber easier.  Please share with me your insights.  I do woodworking as a hobby and foresee that I would use the jointer 20-40 hours per year.

Eight vs Six……As a hobby woodworker it is some times difficult deciding and justifying the investment in large power tools.  You have raised some very valuable points of discussion on the size needed in a jointer.   If you mainly build small crafts and occasional a piece of furniture I would suggest going ahead and purchase a six inch jointer.  If you are going to build pieces of furniture, tables, and larger cases goods, I suggest the eight inch would serve you better.  Let the projects that you want to build make the decision for you.  You can always trade up; as many woodworkers do.

I believe that you can find an after market replacement 1 micron filter bag for your Jet

1 1/2hp dust collector.  Using only one machine at a time your Jet unit should serve you well at this time, and by replacing the existing bag with a 1 micron bag you will capture that fine nuisance dust.