Jointer Problem

[Darrin Davis]

I've given up. I have a 6" delta jointer that doesn't want to put perfectly flat edges on the wood. When I go to put the pieces of wood to glue together there is a very small gap (like the picture below) in the middle where the boards come together. On boards 3 foot long, I would say that I could slide a birthday card between the boards. Any ideas on what's wrong? do I need to sharpen the blades? Any help will be greatly appreciated. It worked perfect until about a couple of weeks ago and now it is doing this!
132556

[Tom Hintz]

Generally, the "bow" can be caused by the outfeed table being a little low. take a look at the link below for a story on my site that has been VERY popular. This is actually an update to my original story but with newer photos and updated formating. the inforamtoin remains the same though. It looks at common jointer problems (including the bowing) and what to do about them. Keep in mind that these are general fixes and you could have a combination of more than one problem. Check the machine over carefully as you go to be sure you eliminate problems as well as identify them.

http://www.newwoodworker.com/jntrprobfxs.html

[glenn bradley]

Some people actually prefer a "sprung" glue joint but getting one by default is not a good idea. Tom's link looks very helpful and I agree with his stressing that technique can be a factor so eliminate that before you go down the long and painful road of adjusting what I assume is a dovetail way machine.

Once there is a reasonable amount of material past the cutterhead, your downward pressure and forward feed efforts should all (or almost all) be focused past the cutterhead. That is; once there is enough machined board surface to register against the outfeed table, use it.

A too-low outfeed is generally given away by the presence of snipe. Are you getting snipe at the end of your cut or do you feel the material "drop" off the infeed as it leaves it? You can simply try raising the outfeed tiny fractions of an inch at a time and watch for an improvement. I'm sure much more advice will follow so I'll stop here for now.

[charles lewis]

I had the same problem as you have experienced and found it to be my technique had changed , once that was corrected low and behold straight edges , though I was really frustrated until I realized what I was doing wrong ....................

[Darrin Davis]

I figured it out. It was the outfeed table was just a little too high. I lowered it and the problem was solved.

[Peter Quinn]

Glad you figured it out. I was going to suggest your out feed table might be too high, but it looks like you beat me to it! My boss actually prefers we spring the joints a bit for edge glue ups on long counters and such, so seeing a little day light in the middle is not a bad thing. Not so good for face jointing however. Some older jointers have a stop going each way on the out feed table so you can kick it up a hair to spring joints, and back down for true flatness.

[Jason Hanko]

What are the advantages to creating a "sprung" glue joint like that?

[Keith Gwin]

The advantage, as I understand it, is to keep force on the ends of the boards by creating a very small gap in the middle. If the boards edges are perfectly flat the ends will tend to separate after a period of time. I have read where you can put more downward force on the board as the middle passes over the cutter-head in order to do this.