June 2010

Well this has been the month for jointers. I purchased somewhat new “Scratch & Dent” jointer from General Industrial a week ago. I carried it home in my van and set it in my roll-around base. Apparently “Scratch & Dent” means you the buyers are responsible for rust removal --- AND --- any setup / calibration that is required. There are a few “Golden Rules” for jointers that any one who owns a jointer and has had to change the blades has learned:1. The knives must be set parallel to the outfeed table surface and each knife at TDC (total dead center) must be at the exact same height of the outfeed table. Once set it is advisable not to change the outfeed table height until a blade change is made. Use the locking screw to lock the table.2. The infeed table and the outfeed table must be parallel to each other or “Coplanar”. and the more out of coplanar they are the greater amount of taper you will introduce each time you make a pass across the knives. Coplanar is checked using a “good” straightedge or two accurate framing squares back to back on each table and looking for gaps between the vertical arms of the squares. The problem I had was I have a four foot carpenters wooden level with brass runners on each side. In it’s day I’m sure it was accurate but after years of bouncing around in a pickup toolbox I have my doubts. My framing squares are old and even though I have calibrated them for square but I’m still not sure they’re accurate enough. That said I checked my jointer for coplanar tables and found that in relation to the outfeed table the infeed table was 20 mils (0.020 inches) high on the outboard end. Not wanting to cry wolf and look stupid, I purchased from Lee Valley a precision straight edge - steel - 3/8” thick and 1 1/2” wide and accurate to within 1 mil (.001 inch) over it’s 36” length. I had called Jet tech service to find what the Jet spec was for coplanar and told that 8 to 10 mils was OK. That's too darn much from my point of view. The guy told me to just play around with the gib-screws till I got it coplanar. When my straightedge arrived I found that with the gib-screws snug or loose, I still had 20 mills out of coplanar so I started playing around with the gib screws and low and behold I managed to get it coplanar to within ½ mill (.0005 inches ) and it repeats in any position of the infeed table. Without a precision straight edge I would have been chasing my tail. There are many times where a good straightedge would be handy but a 5 pound steel precision straightedge is over-kill but a good wooden one will sufice. I have since cut two 44 inch pieces of mesquite and glued them together with the grain reversed to counteract any movement of the wood. I believe that mesquite is the most stable wood found in North America and chose it accordingly. I now jointed and planed my new straightedge and checked it against my precision straightedge and found it to be straight. I made a wooden case for the good rule and it will be placed out of harms way while I use the new wooden rule around the shop. Jet places two springs under each knife while Delta uses jackscrews. A piece of glass and two rare earth magnets made a good knife setting jig for the Delta but with the Jet I don’t use the magnets. The trick is getting the knife edge to TDC and holding that position while you set the knife’s. I will have to design a holding clamp for the cutter head when I get some time to think about it. Now all this gets me to wondering how many jointer owners have ever checked for coplanar tables or are still using it the way it was delivered. Just a thought! Jay