Planers can't flatten boards....really?

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Blog entry by pashley posted 04-10-2008 06:18 PM 23836 reads 1 time favorited 13 comments Add to Favorites Watch

The common wisdom to flatten raw stock, is to first plane a face flat on a jointer. To get to opposite face paralleled and flat, you run that newly flattened side face down in a planer to your desired thickness. Sounds familiar, I’m sure. Hard to do that with 8” stock when you have a 6” jointer though.

The common wisdom also states that if you just try to run that raw stock through a planer, flipping it each time until you get it flat on both sides, you’ll end up with anything but. Supposedly, the planer rollers will flatten the board temporarily while it takes off stock…so what you end up with is a smiley-face shape board.

I’m currently breaking down some thick raw stock – about 5/4 oak, 8 inches wide. I only have a 6” jointer, so I can’t go the traditional route of jointing, then planing.

Thinking back to the conventional wisdom, I found it difficult to believe that rollers in a small planer had enough strength to flatten a board that thick.

So, I put a piece of this 5/4 raw oak through the planer, skipping the jointer. I put it in so that it would like like a frown, if viewed from the side, with a high point being planed off first. When I finally planed it down enough to reveal smooth wood on that side, I took it out, and a straight edge told me it was dead flat!

Flipped it over, planed down the other side….and now i have two flat, parallel sides!

Having said that, I think conventional wisdom would be true for thin stock, or soft wood.

My neighbor, an older man who makes great stuff, said he hardly ever uses his jointer, and does basically what I described to you.


-- Have a blessed day!

13 comments so far

View Russel's profile


2199 posts in 4180 days

#1 posted 04-10-2008 06:22 PM

It seems reasonable for this to work providing your cup doesn’t have any twist in it. A little twist in the board and all bets are off.

-- Working at Woodworking

View Damian Penney's profile

Damian Penney

1141 posts in 4232 days

#2 posted 04-10-2008 06:27 PM

This won’t work if the piece is a lot longer than your planer bed/infeed/outfeed either.

-- I am always doing that which I can not do, in order that I may learn how to do it. - Pablo Picasso

View Bob #2's profile

Bob #2

3810 posts in 4263 days

#3 posted 04-10-2008 06:28 PM

It will work for bowed boards but you may run into trouble with wany ones.
I’d be thinking of building a sled for your planer if I were you.




-- A mind, like a home, is furnished by its owner

View GaryK's profile


10262 posts in 4229 days

#4 posted 04-10-2008 06:43 PM

This is very rare. Any twist or bow lengthwise and it can’t be done.

-- Gary - Never pass up the opportunity to make a mistake look like you planned it that way - Tyler, TX

View Scott Bryan's profile

Scott Bryan

27250 posts in 4063 days

#5 posted 04-10-2008 06:58 PM

I agree. I have tried this same approach to speed things and the planer simply followed the curve of the board, like it is supposed to. A sled works well.

-- Challenges are what make life interesting; overcoming them is what makes life meaningful- Joshua Marine

View Brad_Nailor's profile


2539 posts in 4198 days

#6 posted 04-10-2008 07:09 PM

My friend owns a successfull cabinet shop that I work at part time on the weekends. As long as I have known him (over 25 years) he has never face jointed a board. He insists that the plane and flip method gets the boards flat and parallel. We have gotten in many arguments over this. I agree with Gary, if it’s twisted or bowed over a long length it just isn’t going to get flat. If you eyeball each board you can get away with not jointing the flat ones.


View Blake's profile


3443 posts in 4115 days

#7 posted 04-10-2008 08:26 PM

It is true. This will only work for cupped boards. But if your board is also twisted or bowed in either direction it will just follow it’s own curve through the planer and stay curved/bowed.

-- Happy woodworking!

View ww_kayak's profile


70 posts in 3966 days

#8 posted 04-10-2008 08:56 PM

Been there, thought that. I also got lucky the first couple times, but once I had a piece with a twist in it, I saw it for myself. In the end I had a very parallel twisted piece of wood :)

That’s not to say you can’t use the planer:

Planer Sled Video

-- Tom, Central New York

View Karson's profile


35154 posts in 4641 days

#9 posted 04-10-2008 09:49 PM

The only way to do it 100% is use a jointer and then a planer.

If the jointer is too wide then you need to construct a sled to hold your board flat and you run it through your planer. Of build a tray with sides that you can build a router to slide over one surface and make it flat and then run through a planer.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Appomattox Virginia †

View motthunter's profile


2141 posts in 4040 days

#10 posted 04-10-2008 10:12 PM

lucky that this board worked.. good luck on a twisted and cupped one. I suggest finding a friend with a wider jointer or a local mill that can help you out. I have an 8” jointer and when I need more, I pay a mill to do the work for me.

-- making sawdust....

View Lip's profile


158 posts in 4291 days

#11 posted 04-10-2008 11:52 PM

If you go over to The Woodworking Channel and watch Sam Maloof basically cut a piece of wood freehand on the band saw … you’ll hear him freely admit that his technique is both incorrect and very dangerous. While he’s been far more successful than I’ll ever dream of being and probably forgotten more woodworking techniques than I’ll even know … I would never in a million years think of going against “common wisdom” and advising someone else to even attempt what he does with a band saw … heck, he even goes out of his way to warn the audience against it in the video. Yes, he gotten away with it for more years than I’ve been alive … and I think it’s fair to say that each of us probably has that little thing or things we do that goes against common wisdom … but that’s not to say that “common wisdom” doesn’t have it’s place … from safety concerns to simply saving yourself a lot of aggravation … there are reasons why these things have become “common wisdom”

Yes, I’m pretty sure you could successfully get away with only running a board through the planer … as I can think of more than a few folks who have been successful with less … but my advice to the fairly inexperienced woodworker or the “weekend warrior” ... would still be to stick with “common wisdom” until you’re comfortable enough with the tools and wood you’re working with to know when you can and can’t get away with something.

-- Lip's Dysfuncational Firewood Farm, South Bend, IN

View Peter Oxley's profile

Peter Oxley

1426 posts in 4115 days

#12 posted 04-11-2008 12:11 AM

motthunter suggested having the mill deal with wider boards, but that doesn’t always work – I paid a mill 20% extra to provide 200BF of hard maple 13/16” S3S (rather than 15/16” H&M). I figured I’d save some wear on my tools – hard maple is really hard! Apparently they have a planer with cutterheads top and bottom so they remove stock from both faces at once. They didn’t flatten the stock – they just ran it through the planer. It was all wavy. One board out of the whole order was usable at 3/4” – I had to flatten the rest, and most of it was usable at 5/8”, although some of it had to go down to 1/2”. Oh, and the “surfaced” side looked like it had been cut with a chainsaw – it was relatively straight, but far from “surfaced”. Why didn’t I return the order?? They wouldn’t take it back because having it surfaced made it a “custom order”. So I made drawer boxes out of 200BF of clear hard maple, and had to buy another 200BF (H&M this time) for the project.

If you have a rabbeting jointer, you can double the width capacity by removing the guard and running the board twice, flipping end-for-end between passes. Before anyone tells me how dangerous it is to remove the guard … yes, I know it is dangerous, but you have to remove the guard to make rabbets on a rabbeting jointer, so I guess it is accepted practice when necessary.

-- -- --

View lightweightladylefty's profile


3277 posts in 3953 days

#13 posted 04-12-2008 05:15 AM

Still another viewpoint: The vast majority of lumber we use is cut from our property. We have found that if the board is so twisted or bowed that it can’t be planed flat, then it is probably too stressed to be used successfully in its full length and would need to be cut into shorter parts to alleviate problems later. You should also allow time for the lumber to acclimate to your shop after it has been flattened. Twisted and bowed boards are generally twisted and bowed for one of two reasons: improperly stacked when drying or stressed lumber. Your best answer is to choose another board! (Or you might wish you had after spending hours of time on your project, only to have it split or twist later. :-( )

Just my viewpoint! :-)

-- Jesus is the ONLY reason for ANY season.

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