Flattening a benchtop along the length

[Michael Sobik]

Lots of workbench threads lately, but I'm a little confused with one aspect of flattening the top. I understand how to using winding sticks to remove twist, and how to flatten across the top (from front to back), but how do you flatten the top along the length? Say there's a hump in middle of the bench along the long axis. Without a straight edge as long as the top, how do you remove the hump? Does this happen as a matter of course when planing diagonally across the top? Any info would be appreciated. Thanks!

[Mark Roderick]

One way to see and measure unevenness on large surfaces is to string a fishing line taut from end to end, secured by eye-hooks or something. I've done that when hand-flattening a large table top.

[Wilbur Pan]

I used a 4 foot level to check for humps along the length of my workbench. What I did was to start at one end, and mark any high spots, and try to get them level over a 3 foot span. Then I slid the level over about 2 feet, and repeated the process. Since I was overlapping the areas, the whole length eventually becomes level.

Planing diagonally does help a lot with this process as well. If you look at the pattern of planing, you'll see how the diagonal pattern leads to leveling out the planed surface across both the length and the width.

[Mark Berenbrok]

I leveled my benchtop last week and considered using this method at Highland Hardware (www.highlandwoodworking.com/library/makingitplane.pdf) that uses a router in a sled to level the top. At the end I just got lazy and used a #7 jointer instead. Didn't feel like making the jig and didn't want to hear the router scream for however long it took. I did use the string trick they discuss and it worked well after I figured it out. Planing the 24" X 82" SYP top took a little more than an hour.

[Mark Roderick]

I think you made the right choice. There's just about nothing I weould enjoy less than listening to a freaking router flatten a whole benchtop!

[Michael Sobik]

Thanks for the ideas guys. I definately don't want to do the router sled thing. By the time I build it, I could have it done with a jointer plane.

[Robert Rozaieski]

Flat across the width is much more important than flat along the length. Just get the length flatness close enough.