Milling - why can't you plane the first board face?

[Scott Casko]

Hey folks,

I apologize in advance - total NOOB question here. I'm just starting into woodworking, and my question is about milling.

Everywhere I read and watch, people say to flatten one face on a joiner, and then either plane the other face flat or join an edge. My question is why can't you flatten the first face on a thickness planer?

My only thinking on that is because my mobile planer (Delta 22-540 I picked up used) has the cutting head floating over a fixed base. Is that why - because the cutting head floats, as opposed to the fixed cutting head of a joiner? I don't see that, if you were to feed the board in "frowning", with two planar points of contact, how it's any different than on the joiner.

I'm hoping for a good technical explanation here, so I can finally put my mind to ease.

Thanks all,

Scott

[Matt Day]

Because though in small lengths the board may be flat, it will likely be waves over he entire length. Think about it in an extreme way - what if your board was 1/2" at one area, 3/4" in another, and back to 1/2".

a jointer makes it flat and complainer, and a planer simply references off the opposite face.

Trust us, you need a jointer! :-)

[John TenEyck]

That's right, a planer will press the wood down so that it is flat on the bed plate. Whatever variations there are on the bottom side of the board will be reproduced on the top surface after planing. If you are able to buy really flat wood then you can plane them w/o much problem. Most of us, however, get wood that has twists, cups, and bows in it. To make those boards flat you need to use a jointer or hand plane, or you can build a sled for your planer that will support the bottom of the board so that the top surface will indeed be flat after planing. In the end, a jointer is the most efficient way of accomplishing the process.

John

[Scott Casko]

Because though in small lengths the board may be flat, it will likely be waves over he entire length. Think about it in an extreme way - what if your board was 1/2" at one area, 3/4" in another, and back to 1/2".

a jointer makes it flat and complainer, and a planer simply references off the opposite face.

Trust us, you need a jointer! :-)

Thanks, Matt - that makes much more sense than the $.02 i had before. Oh yeah, I picked up one a jointer used as well - a Craftsman 6" model. I was just wondering what to do with stuff wider than 6".

Also, thanks to advice on this site, I was able to clean the rust off of the joiner top and put a coat of wax on it. I think this was a good deal.

IMG_1658.jpg

[Scott Casko]

That's right, a planer will press the wood down so that it is flat on the bed plate. Whatever variations there are on the bottom side of the board will be reproduced on the top surface after planing. If you are able to buy really flat wood then you can plane them w/o much problem. Most of us, however, get wood that has twists, cups, and bows in it. To make those boards flat you need to use a jointer or hand plane, or you can build a sled for your planer that will support the bottom of the board so that the top surface will indeed be flat after planing. In the end, a jointer is the most efficient way of accomplishing the process.

John

Thanks John- I think that ties it up for me. So essentially whatever cross-section goes in is what comes out, just a bit thinner because the head floats. That's why you won't get anything flat out of it. Right?

Thanks again!
Scott

[David Hawxhurst]

Thanks, Matt - that makes much more sense than the $.02 i had before. Oh yeah, I picked up one a jointer used as well - a Craftsman 6" model. I was just wondering what to do with stuff wider than 6".

my first choice would be to make a jointing sled for the planer. some say you can remove the guard and joint up 6" then flip it around joint the remaining inches (up to 6" more). so in theory you could joint up to a 12" board with a 6" planer. i have never done this just heard about it. does not seem like a safe thing to me, but each to there own.

[Alan Schwabacher]

So essentially whatever cross-section goes in is what comes out, just a bit thinner because the head floats.

This is not quite right. A planer references to the bottom surface and cuts at the top, with the head at a constant height throughout the cut. The board you get has a constant thickness (and cross-section), but it may not be flat. To add detail to the example provided above, if you have a board that varies in thickness, it could be flat on one face and wavy on the other. If you put the flat face down on the planer bed, you will make the board flat and of the same thickness throughout. If you put the wavy side down on the bed, you will cut the board to become wavy on both sides, but of constant thickness.

A planer sled is a device that holds a board so it travels straight through the planer, so it cuts a flat face on top. The sled is essentially a removable reference face.

A jointer has an infeed table that leads to a cutter at the bottom of the board, and an outfeed table that serves as the reference. If the just-cut face is held to the flat reference outfeed table, and the cutter is properly aligned with that table, you will get a flat face. A warped board could wobble on the infeed table. To make a bowed or twisted board into a flat one that is maximally thick, you need to think about where you want to take off wood before you run it through.

The jointer references the same face it cuts, and can make it flat, while the planar references the opposite face and can only cut a face parallel to that.

[Prashun Patel]

This all may be true in theory, but i almost always run rough stock through the planer first, flipping on each pass. You can get darn near flat , or at least flat enough for a good panel glue up or apron. To each his own. The jointer shines when working with narrow stock or edges for me.

[Alan Schwabacher]

That is a good point: if the stock is already flat enough, you can plane it smooth and parallel. If you need it flatter, then something else is needed first: a jointer, handplane, or planer sled.

[Jim Andrew]

I started out with a cman 6" jointer, and mine didn't have enough power to plane a board flat. If yours doesn't either, don't give up on woodworking, just buy a bigger jointer. You ask what do you do about planing boards wider than 6", you get a bigger jointer.

[John TenEyck]

Unless your boards are flat to start with they won't be flat no matter how many times you flip them. "darn near flat" isn't flat enough for many uses, and I have several painful reminders of that when I tried to plane boards too wide from my jointer. A jointer shines at making stock flat; not just narrow stock, any stock. If you have not been pleased with your results on wide stock you just need a little more practice - or maybe a new jointer ! My little 10-1/4" wide Inca does an amazing job.

John

[Matt Day]

Unless your boards are flat to start with they won't be flat no matter how many times you flip them. "darn near flat" isn't flat enough for many uses, and I have several painful reminders of that when I tried to plane boards too wide from my jointer. A jointer shines at making stock flat; not just narrow stock, any stock. If you have not been pleased with your results on wide stock you just need a little more practice - or maybe a new jointer ! My little 10-1/4" wide Inca does an amazing job.

John

I agree John.

If that rough sawn board has a bit of of a twist in it, that's coming with it out of the planer. I don't plan on ever bringing a board to the planer first unless it's on a planer sled (less than ideal results) or ideally through the jointer.

There's another way to use a 6" jointer to joint wider stock. With the guard removed (proceed at your own risk yada yada) you should be able to run say an 8" board over the cutterhead and joint 6" of the board to be flat. Now with that jointed face down and a 6" wide piece of plywood in filling in the jointed section, run it through the planer to plane the full width of the board. Once that's done, flip it over and finish plane the jointed face. This may not work on your particular jointer.

[glenn bradley]

I think we have it covered here. Jointers make things flat. Planers make the planed side parallel to the already jointed (flattened) side. The planer will also make the other side paralllel to a warped or bowed side so, you of course need to flatten one face first. That is the first step in your milling process for squared stock.

planer jointer.jpg

I got by with a version of Keith Rust's planer sled that I still use when I need to "joint" really wide stock.

[Prashun Patel]

Like i said, to each his own. It has worked for me. But i am a hobbyist and a hack.

[Alan Schaffter]

The point that many have missed in this thread is that "flat" has two directions- across the width of the board and along its length. Unless the board is thin and so flexible that it springs back to a cupped shape when it exits the planer, or the planer has strong pressure rollers (most do), a planer can do a fair job "flattening across" the board.

A planer will do little or no flattening along the board if the ends are on different plane than center few feet. You could plane a board that is shaped like a shallow "U" when viewed from the side and make it flat across the board, but after it exits the planer the edge will still look like a "U." If you feed such a board across a jointer with light pressure you will take a little off each end on each pass until the board is flat end-to-end. (Obviously you can't do this with a board that is really a "U" or more correctly a board that is bent end-to-end more than the thickness of the board. That is why you always want to make sure you start with a board that has sufficient extra thickness.