20" planer giving tearout

[Bob Cooper]

I'm trying to figure out why my new Jet 20" planer is giving me tearout. I can take the same piece of wood and run it across my Delta DJ-20 and not get tearout and then take it to the planer and i'll get pretty bad tearout.

i've tried taking very light cuts...doesn't seem to make much difference. Also i am running the planer as it's minimum feed rate. The DJ-20 performs 275 cuts/second and the planer does 333 cuts/second and a feed rate of 24 fpm thus about 833 cuts/foot

So if i take about 3 seconds/foot through the jointer then the cut rates are about the same.

Naturally the tearout happens where the grain changes direction but it seems to be much worse than acceptable -- seems like 1/8th to 3/16...but i haven't measured it yet. It's definately not something you can sand out.

There is a gear reduction kit for this planer that'll slow it down some and that may help but i'm not optimistic that'll solve the problem.

My only guess is to have the knives sharpened. Any other thoughts?

BTW, the woods i'm using are ash (hard) and alder (soft). Both have the problem.

I called WMH and talked to their technician but he didn't have any suggestions.

[Joe Jensen]

1) How sharp are the knives
2) Are they set to cut within the same cutting arc? When I had straight knives I would get them +/1 0.0005" with a dial indicator. I found that knife setting guages and magaset would not get close enough.
3) It's possible that the angle of the knives in the planer cutterhead is different than the angle of the knives in the jointer.

[Ed Labadie]

In my experience Ash is very prone to tearout, a slower feed rate is better but not always the answer.
It's been bad enough before I've had to use the drum sander to get to final thickness. :(

Ed

[Bob Cooper]

Joe...i'm not sure nor am i really sure how easy it's going to be for me to determine this...though i need to look into it. The finish though doesn't really appear to be wavy. Good point about the angle of the knives.

The other curious thing is the wood coming out of the dust shoot seems like it was cut w/a sharp knife...ie slivers as opposed to saw dust.

[glenn bradley]

I am working an ash project right now and although prone to tearout, I am having only minimal problems on a small DW734 planer. I vote for sharpening. Not that it helps, but I get no tearout on my spiral head machine, just the three knife ;-)

[Chip Lindley]

Joe...i'm not sure nor am i really sure how easy it's going to be for me to determine this...though i need to look into it. The finish though doesn't really appear to be wavy. Good point about the angle of the knives.

The other curious thing is the wood coming out of the dust shoot seems like it was cut w/a sharp knife...ie slivers as opposed to saw dust.
Bob, I know it's disheartening to have such bad performance from a new machine! A new sharpening may be in order. I have sharpened my own blades for 20 years, held in a hardwood fixture, and passed under a cup wheel held in my drill press. It is not high tech but it WORKS! You need to determine the angle of your planer knives in this cutter head as opposed to that of your DJ20. The angle of attack may not be optimal for planing hardwoods. In this case, a different grind angle or a "back grind" on the knives can be helpful to minimize tearout in wild grain hardwoods. Old issues of Fine Woodworking magazine contain all this information but I can't put my hands on them at this moment.

It's time to purchase a dial indicator and magnetic holder. Grizzly and others sell decent ones. I rely on the dial indicator to set my knives on my old Rockwell/Invicta RC33 13" planer (no jack screws) I make sure all 3 are within .001" of each other, as referenced from the cutterhead surface, and protruding no more than .020" above the cutter head. Knives set too high could be your problem.

The chip breaker should be checked to see if it is adjusted correctly. Few machines are perfect out of the box. Fine tuning is often needed to make them perform as they should. Quality control on some Tiawanese / Chinese products is "iffy" at best. If you contacted a Tech Rep who could give you no help, call again and complain firmly to speak to a Manager. Keep after them until you talk to the company president himself if necessary! It's Your money, and Their reputation! Finally, my planer chips are never sawdust, but look like small cornflakes, which is normal! Best of Luck!

[Bob Cooper]

ok...i will do that. It's one of those tasks that i've avoided since it seemed pretty involved but i'd really like to get this working as intended...which i don't think it is.

Also i'll compare the angle of attack.

[Joe Jensen]

Joe...i'm not sure nor am i really sure how easy it's going to be for me to determine this...though i need to look into it. The finish though doesn't really appear to be wavy. Good point about the angle of the knives.

The other curious thing is the wood coming out of the dust shoot seems like it was cut w/a sharp knife...ie slivers as opposed to saw dust.

It sounds like from the way the shavings look, the knives are sharp. If one is lower than the others, it is doing all the work, and effectively tripling the feed rate.

I'm very picky on planers and I had a straight knive cutterhead for 16 years. All the cut quality issues I had were due to planer and knive adjustments. It is pretty easy to tell of they are sharp. Sharp knives will cut you almost as easily as a razor blade.