Laguna planer depth changing during planing

[Alan Lightstone]

Don't know if this is normal, or whether I'm just seeing tiny changes due to my installation of a DRO, but here's my issue:

I have a 16" Laguna jointer/planer. When in planer mode, if I set the digital readout (DRO) for, say 1.00" and plane a board, after planing it the readout has decreased to 0.95. Seems relatively consistent at 0.05 inches drop with each pass from where it is set.

Is this normal behavior for a planer that I am only noticing due to the DRO? Is there something loose that I need to tighten? Seems like a pretty big discrepancy from where it is set.

[David Nelson1]

Did you mic it just to see if the DRO is messing up?

[guy knight]

my pm did that it was caused by dull blades

[Alan Lightstone]

I'll run another board through tomorrow to see if the DRO is accurate.

How could dull blades cause it? They are spiral cutters, FWIW. A couple of years old, but haven't had massive use by any stretch. How do you tell when they need rotating (often wondered about this)?

[Scott T Smith]

On my straight knife combo machine, it does this when the blades get dull. If you've run many "dirty" boards through the planer, then it may be time to rotate the carbides. You can feel them with your finger and compare the ones near the perimeter of the cutterhead with the ones in the middle. If you can feel a significant difference, then rotate.

[Mike Wilkins]

In addition to dull blades, make sure to tighten the height lock knob to keep creep to a minimum.

[johnny means]

You may be dealing with backlash. If you're adjust down to 1.0 try adjusting up to 1.0 and see what happens. If it cross in the opposite direction, got that much skip in the adjustment mechanism. A little sloop has to be designed into these mechanisms in order to avoid seizing. My JP which has power depth adjustment accounts for this by going slightly lower in it's travel than backing up to my desired setting.

[Alan Lightstone]

The backlash possibility was interesting.

I tightened down the height lock knob, and it still decreased by 0.05.

Tried adjusting up and down to see if it was backlash (and some is evident on the height control knob), but nothing changed - still decreased 0.05 each run through the planer.

Now the dull knives might have potential. They didn't seem razor sharp. On the other hand, neither do the other sides of the spiral knives. At least when I try to cut paper with them.

I think my next step (sigh) will be to rotate the blades. Not a quick procedure, I would imagine. There sure are a lot of them.

Unless anyone else has any other ideas...