The miracle of sharp planer kinves and quietness

[Zachary Hoyt]

A recent thread (which I now can't find) here on SMC got me thinking about how long it had been since I put sharp knives in my DeWalt 733 planer. I built the building where it lives now in 2015, and it moved in there in December of that year. I was quite sure I had not changed the knives in the current location, and I don't know how long before I moved it in there it may have been. During most of those years I had an old generic 15" planer that did the heavy work and since 2018 I've had a drum sander for thin pieces or figured woods, but I still used the DeWalt for all my instrument wood planing and such. I had noticed that while it still left a good surface on the wood it was a lot louder when I ran wood through than when it was just running empty, and after I put the new knives in today it is almost as quiet while planing as not, plus it doesn't bog down when taking a bigger cut like it did. I need to remember to change them more often, and maybe the noise will be a clue next time.

[Jim Becker]

Yes, sharp edges can make a notable difference in sound levels. The big challenge is the ability to perceive that it's changed because that change tends to be gradual. So it's probably still a good idea to have a system for keeping track of how long an edge has been in use. For your application and the nature of the fine material you work with, I'd also probably err to the "newer edges sooner" because it reduces risk for tearout, etc.

[Bill Dufour]

Do any modern planers have onboard grinders for knife sharpening? I see them for older rockwell and powermatic 18-24" planers designed around 1930.
Bill D

[Jim Becker]

I honestly don't remember that being a feature of most modern planers, Bill. One reason may be that the steel used for knives "today" stays sharp longer. I suspect that those old school machines "back in the day" had knives that needed constant resharpening just because of the metal they were made from.

[Bruce Wrenn]

I honestly don't remember that being a feature of most modern planers, Bill. One reason may be that the steel used for knives "today" stays sharp longer. I suspect that those old school machines "back in the day" had knives that needed constant resharpening just because of the metal they were made from.
I suspect that industrial planers still come with sharpeners onboard. In 1967, worked in a plant one summer that made laminated wooden arches. They had a 60" Powermatic. On each shift (two shifts) they sharpened the knives at least once. Took less than 30 minutes. Often done during meal breaks to save production time. Some of these arches were over 100 feet long. Used over head gantry cranes to feed them thru planer. With arches supported on steel saw horses, we would get on them, and use a floor sander to sand them prior to applying finish. Sander had to be lifted up by gantry crane. Also use a tool called a "German Jointer of missed spots. Think about using a 16" wide hand held power planer and you get the picture. I was a 129 pound kid, handling a 70 pound power tool.

[Zachary Hoyt]

That sounds like a fascinating process to build those arches. I've been living for the last 20 years in a converted barn that is built with smaller versions of them, and have often wondered what the manufacturing process would have looked like. I wonder if the knives had to be sharpened so often because of all the glue, or would the excess glue have been knocked off prior to planing?

I do need to come up with a schedule for knife changes. I'll be planing a few hundred board feet of maple and cherry for the house I'm repairing this year, so probably I should plan on sharp knives by next winter if not before.

[Frank Pratt]

I just change out the knives on my jointer. Wow what a difference. I also bought a second set so it doesn't get put off so long next time.

[Bill Dufour]

I think a amp gauge, like used on belt sanders, would be a good indicator of sharpness.
Bill D.

[Jim Becker]

I suspect that industrial planers still come with sharpeners onboard.

That may very well be true. We don't get a lot of exposure to that kind of machinery here, of course.

[Tom Bender]

The 733 has resharpenable blades. I have a spare set and swap them out pretty often, maybe after 40 BF of hardwood. They get sharpened when I get into sharpening. William Ng has a terrific video.

[Zachary Hoyt]

Thanks for the suggestion. I've got a few sets of dull knives and have been meaning vaguely to find somewhere to send them for sharpening, or get a machine to do it myself, but William Ng's way is much better. I'll just have to get a water stone or two. It is indeed a terrific video.