2

I am trying to smoothen an oak board with a huge gnarl.

enter image description here

I just put in brand new knives and set the difference between the infeed and outfield tables to 0.25 mm, which I think is quite small.

Even so, the board is vibrating quite uncomfortably under my push-blocks. On top of that, I see tiny silvery flakes on the jointed surface, which I suppose were a part of the knives just moments ago.

Am I doing something wrong, or is it better to leave some boards for the sandpaper?

3
  • 1
    Martin, do you know you can also improve surface quality + reduce resistance by dampening a board's surface? It's hard to be sure from the one photo but it looks like there isn't much/any tearout here in the most challenging part of your board around the knots (which is a good result for machine planing) but this is something well worth keeping in mind for the future. It's a trick that doesn't get nearly enough exposure since it can make such a big difference. See reference to it here from 2001.
    – Graphus
    Mar 1 at 12:43
  • But, there will always be some machining evidence from a planer or jointer after milling. It is much less obvious (almost absent) if a helical cutterhead is fitted (one of their many advantages) but every board must have its show face, and maybe one edge, sanded/scraped or planed to remove mill marks after machining. On easier wood mill marks may not be easily visible when the board is dry, but as soon as you wet the surface with finish they will become evident, and even more so if you use stain. Photo.
    – Graphus
    Mar 1 at 12:46
  • In case the Google Books link ever dies, note that "dampening" in this sense means "making slight wet", not "adding mass to reduce vibration". My initial thought was the latter, then the former occurred to me, then I had to read at the link to see which it was.
    – FreeMan
    Mar 1 at 12:55

2 Answers 2

4

Board looks ok to me, ready to proceed to next step.

I see tiny silvery flakes on the jointed surface, which I suppose were a part of the knives just moments ago

Your knives may not be good quality! Oak is hard, and knots are harder, but you should not see chipped edges after only 1 light cut. But maybe these are just flakes of "wire edge" from poor sharpening job.

If edges are chipped I recommend adding back bevel to knives to strengthen edge. Alternative is to make cutting angle steeper with second bevel, but then machines will not work as well on softer woods.

Am I doing something wrong, or is it better to leave some boards for the sandpaper?

Are you trying to produce finished surface?? Then yes you are doing something wrong.

Jointer and planer are to produce flat surfaces, not smooth surfaces.

With normal steel cutters any cut, any feed rate and any wood will not give perfectly smooth surface. You must complete job by sanding or scraping or hand plane.

1

May depend on the machine; I used a schools' wood shop planer on a heavily gnarled oak board. It was about 14" X 8ft. It was noisy but cut fine; a little belt sanding and it looked good. I had a 6" joiner that I did not use much, but I saw no difference with knots in pine, cedar or oak.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.