Dewalt DW735 performance issues

[Assaf Oppenheimer]

Hi folks, I am usually on the Neanderthal forum, the only real power tool I use is my planer...
anyway I was hoping you could help me figure out an issue I have with it.

I have the DW735 with the wings added on.
The planer has been cleaned and the wings and surface have been waxed.
I jointed a board flat with a no.8 and checked its surface for flat (it is)
I then marked the flat surface as reference, scribbled very thoroughly on on the surface I wanted planed, placed it reference surface down and passed it through taking the minimum amount of material off so that the scribbles disappeared. I then placed the board on my bench reference side up, it rocked significantly side to side.
I turned it over (reference side down) it doesn't rock.
I figured I may have not taken a good enough pass so I scribbled a very detailed grid on the non reference side, and passed it through the planer with a 5th of a turn on the depth adjustment. all the pencil came off and I ended up with the same result a board convex along its width

anyone have an explanation?

[Charles Lent]

When you remove the surface of a board, it is quite common for the board to change shape slightly. There are many stresses and tensions in a piece of wood, brought on by how the tree grew, how the lumber was dried, and how it was cut and shaped. Removing the surface of one side has likely removed some wood that was helping to hold the board flat.

Whenever I plane rough cut lumber I plane it to near the desired thickness and then wait a few days before finish planning it. Do you have a moisture meter?
I always use one before and after planning. Wood with a moisture content above about 6% will move significantly as it's cut/finished. Below that moisture content it is more stable. Wood is a living thing and it responds to it's environment. If I want wood to remain perfectly flat I study the grain and moisture content before working it into my project. As wood shrinks with reduced moisture content, the direction of the growth rings can tell you a lot about what it will do as it dries. Growth rings running across the width of a board will tend to curve the board as it dries. Growth rings running top to bottom of a board will likely curve much less as it dries, and the thickness of the board will be much more stable, but the width of the board can change significantly with changes in moisture content. A board with varying grain over it's length will warp and twist.

Study the grain and moisture content and choose a board that has it's grain oriented correctly for what you plan to do with it. Then rough plane it to almost the thickness needed and let it sit for a few days before attempting to plane it to the desired final thickness. If it is still straight, use it in your project.


Charley

[Mark Bolton]

Problem is he says the reference side he jointed flat is still flat. Are you sure the reference surface is flat? I assume you rotated your board end for end on the reference surface to check reference? Knives not registered well?

[Assaf Oppenheimer]

yes I was just about to point that out.
the reference surface is flat. I triple checked. but even if it wasn't it shouldn't cause a convex across the width. I can literally rock it

[mike stenson]

I'd remove the knives, clean the mounting surfaces, reset them and try again. If you happened to have a knife that had an end higher than it should be, that might cause a convex surface across the width.

[Mark Bolton]

Yeah, Mike's response would be the same from me. Even though the 735 registers the knives for you I would be looking for the outbound edge of a knife or both knives to be sitting low (proud of the cutter head) if the knives are new. If they are used I guess there is the potential that the center is worn but that would be a long shot. Not sure how large the convex is (feeler gauge) but I'd start looking at the registration pins/knives first.

[Keegan Shields]

How thick is the board in question? The feed rollers in planers can flatten a thin board out, plane it, then it springs back to its curved shape…

Another option would be to make a simple planer sled, hot glue the board flat side down, so it’s supported at several places along its length, and run it through again. If that doesn’t produce a flat face, then it’s the machine.

[Mark Bolton]

How thick is the board in question? The feed rollers in planers can flatten a thin board out, plane it, then it springs back to its curved shape…

Another option would be to make a simple planer sled, hot glue the board flat side down, so it’s supported at several places along its length, and run it through again. If that doesn’t produce a flat face, then it’s the machine.

One face of his board is jointed flat.

[Keegan Shields]

Is it? I can’t check from across the internet. When something is happening that doesn’t make sense, I like to go back and challenge my assumptions. Usually one of them turns out to be wrong. Just my approach.

[Assaf Oppenheimer]

the board was jointed flat, it was 8/4 stock before I jointed it

[Assaf Oppenheimer]

I shared the approach, I checked it twice. the jointed side doesn't rock, the planer side does.

beyond that though, I understand how a little twist can be introduced but this was a rocking side to side motion - the board was convex across its width

[Keegan Shields]

How thick is the board?

[Keegan Shields]

Better yet, do you know anyone near by with a planer? Have them plane the board and see if it comes out flat.

[Mark Bolton]

How thick is the board?

If one face of the board was planed flat (neander) and has remained flat through the entire process... OP has said he flipped the board end for end, reference surface he is checking the neander face against, is flat... has remained flat. Is not cupped (which would be the condition of the board moved and is rocking on the machine planed face).. he states the neander face is consistently flat.. the only possible issue is the planer? What would it matter how thick the board is? If one face has remained flat checked with straight edge and known surface and has remained unchanged, yet the other side is convex... the thickness of the board is meaningless?

Can you come up with a scenario where one face stays perfectly flat while the other comes out of a machine convex any other way? Unless he is mis-reading flat on the hand planed face?

[Keegan Shields]

“Unless he is mis-reading flat on the hand planed face?“

Bingo. When something goes wrong in my shop, it’s usually the simplest thing and it’s usually my fault. So I start there - not knowing anything about our fellow Creeker.

Sending this strange board through a known good planer would be a great way to verify whether the planer is at fault. Or sending another known flat board through and seeing if the OP gets the same screwed up result as before. Or using a planer sled on the board in question like I mentioned previously.

All good options.