jointer problems

[joe zarnitz]

looking for someone in the crossville tn. area that can adjust my 3 month old 8'' bridgewood jointer---will pay for your assistence---unable to get a flat board or edge--usually they are convex--tried both raising / lowering outfeed table in small increments with unsatisfactory results--- blades set to within .002 of outfeed table with a dial indicator---both tables are flat & parallel----this is my third jointer and never had this problem so i assume my technique is ok---i'm stumped---wilkes answer is my technique & the jointer is ok-----help
tks,joe

[Dev Emch]

Oh Boy! First of all, most companies today dont know enough to really help you. in a nut shell, your tables are **NOT** parallel.

On some older jointers like my Porter 300 and on the new german high end jointers such as the hofmann and the martin, there are provisions to execute what is known as a convex or concave cut. In trade lingo, this is known as a spring joint and is actually a good thing. You have tripped the rift by accident here.

Even though this is a feature on these jointers, it is also used to "adjust" or dial in jointers to a zero position. NO concave and no convex. Right in the middle.

On my porter 300, this is done by raising or lowering the infeed table tip. The infeed table pivots on a pivot pin that sits right in front of the cutter head. A knob on the infeed wedge right at the entry point of the jointer controls this. I can dial the tip up or down. The martin jointer is a parallelogram jointer and the parallelogram pivot pin that is located on the infeed table entry point farthest from the cutter head is actually an eccentric that performs the same function as on the porter.

Jointers such as the newman and the northfield (older ones) do this by raising the tip of the outfeed table. Just about opposite of how porter and martin does it.

Most likely, your jointer has none of this adjustability. Also, if your way off on your cutter head cyclinder adjustments, your going to find you either snipe or your cut is not straight but actually "winds". Your complaint is that the cut is convex. So I am assuming its straight. It just shows light where its not supposed to.

So, this problem can and does occur when the tables are prefectly flat. In order to see how much out of parallel they are, your going to need to get a very long and very accurate straight edge. You can use that clicky clicky method that FWW proposes in their jointer tune up video, but I actually got some old, greasy brown and sharpe camel back machine builder straight edges off of ebay. They probably are not accurate enough to scrape in metal lathes and milling machines but for wood jointers, they work quite well and they were cheap. You may be able to borrow a starret straight edge as well. But you need long and very accurate.

If your jointer has issues with table sag and or out of parallel and its a wedge bed jointer such as an 8 inch powermatic 60, then your going to have to shim to fix this. Unlike Lou's aircraft carrier and my porter, the wedges are cast as part of the table. So we cannot shim between the table and the wedge. Therefore, it may be needed to shim under the rear wedge ways. You can fix this either at the rear or the front but since the front ways are used more often then the back ways, it may be more prudent to shim the aft ways.

Place your straight edge onto both tables. Adjust the infeed table such that its lip is identical to the outfeed lip. The two need to be on the same plane! Now hold the bulk of the straight edge on the outfeed table and let it hang over onto the infeed table. Hopfully the edge spans both tables. Using a set of auto feeler gages, see if you can slide a gage under the staight edge. Your likely to find the greatest gap either at the infeed lip or the infeed front edge.

Now since the wedge is at an angle and this angle error is causing your issues on the flat, you will need to use a bit of trig to translate the feeler gage error into a shim thickness. Once done, shim the jointer as they did in the FWW video and give it a try. You may need a bit of trail and error to resolve this.

Hopefully this diatribe gives you a starting point to attack this problem... let us know how things proceed and what you find in debugging your jointer. The 6 inch and 8 inch wedge beds are known for having issues here due to the fact that the table and wedge are very complex to machine correctly as one piece and to keep this alignment over time. It would really be nice to be able to remove the tables and shim using nothing more than washers!