Shopsmith Forums

Hey kids,

I noticed you were talking about my post concerning running the reverse rainbow on the jointer and thought I would jump in.
This jointer technique does work great and it is fast and easy. Honestly, sometimes I run 500 bd. ft. of lumber in a day running both a face and an edge on the jointer to make sure everything is straight before it goes through the planer or table saw. You know how wonky lumber can dry and this method works with even the craziest lumber as long as you don't run out of wood. If it is that crooked, you will need to cut the board in two to produce straight lumber no matter what method you use to straighten it.
One of the posts mentioned using a bandsaw to straighten the edge and then finishing on the jointer. That will work too, but it isn't necessary. Just try this once and you will see how well it works. Keep feeding the lumber into the jointer with the front of the lumber on the outfeed table to start and eventually the back of the cut will drop right in line with the back of the board. The bow will be gone and your edge will be perfectly straight.
This method works great for both the edge and face. When working on a face, pay attention to the bow, not the cup. The bow should be run the same way. Start with the leading edge on the outfeed table and hold the pressure on the out feed. Keep doing this until the tail end of the board drops into line, then finish with one full long pass starting on the infeed table to make the face perfect. The only time that cup comes into play for me is on boards that are wider than my jointer. I have a 12" jointer, so say I was jointing the face of 18" wide board. In this case I would like to also do a reverse rainbow with the cup up, so that the part that got jointed was on the table and ran over the knives. The outside edges of the board would hang out beyond the jointer bed, but they wouldn't matter because they weren't getting cut anyway. If you did the same thing in reverse, with the cup down and the outside edges of the board touching the bed you would have no support on the side that hangs off of the jointer.
Another post mentioned that the jointer wasn't really for doing faces of lumber. I would disagree, otherwise jointers would only be up to 4"-6" wide. Wide jointers are common and used on a daily basis for flattening the face of lumber quickly and accurately.
If you have any other questions post them. I love to talk about wood and look forward to sharing thoughts about this.

scottwunder wrote:Hey kids,

I noticed you were talking about my post concerning running the reverse rainbow on the jointer and thought I would jump in.
This jointer technique does work great and it is fast and easy. Honestly, sometimes I run 500 bd. ft. of lumber in a day running both a face and an edge on the jointer to make sure everything is straight before it goes through the planer or table saw. You know how wonky lumber can dry and this method works with even the craziest lumber as long as you don't run out of wood. If it is that crooked, you will need to cut the board in two to produce straight lumber no matter what method you use to straighten it.
One of the posts mentioned using a bandsaw to straighten the edge and then finishing on the jointer. That will work too, but it isn't necessary. Just try this once and you will see how well it works. Keep feeding the lumber into the jointer with the front of the lumber on the outfeed table to start and eventually the back of the cut will drop right in line with the back of the board. The bow will be gone and your edge will be perfectly straight.
This method works great for both the edge and face. When working on a face, pay attention to the bow, not the cup. The bow should be run the same way. Start with the leading edge on the outfeed table and hold the pressure on the out feed. Keep doing this until the tail end of the board drops into line, then finish with one full long pass starting on the infeed table to make the face perfect. The only time that cup comes into play for me is on boards that are wider than my jointer. I have a 12" jointer, so say I was jointing the face of 18" wide board. In this case I would like to also do a reverse rainbow with the cup up, so that the part that got jointed was on the table and ran over the knives. The outside edges of the board would hang out beyond the jointer bed, but they wouldn't matter because they weren't getting cut anyway. If you did the same thing in reverse, with the cup down and the outside edges of the board touching the bed you would have no support on the side that hangs off of the jointer.
Another post mentioned that the jointer wasn't really for doing faces of lumber. I would disagree, otherwise jointers would only be up to 4"-6" wide. Wide jointers are common and used on a daily basis for flattening the face of lumber quickly and accurately.
If you have any other questions post them. I love to talk about wood and look forward to sharing thoughts about this.

Thank you for joining the forum and responding to the post. Your technique is so counter to what every "authority" recommends that I had my doubts. But I did have a chance to try this out on the edge of a slightly bowed piece of oak about 24 inches long yesterday and it did work.