Shopsmith Forums

I have a question about planers. I have never owned or used a (power) planer.

I assume that planers can't straighten a board. PTWFE says planers are "not the best for straightening cupped or warped stock", but then says to to use the jointer for this. I don't understand how a jointer could do it either.

I want to get really flat straight boards from twisted/warped stock, and for this I have used a router sled. See prior thread: viewtopic.php?p=290830&hilit=sled#p290830

Router sleds work, but if a planer could be made to do as well, I might invest in a planer. Running that sled back and forth is a lot of labor.

My assumption about planers is: they can't straighten a board. In other words, if a twisted board goes into a planer, the traction rollers in the planer will force the board flat while the surface gets planed, but when the board comes out, it will just un-flatten again and still be twisted.

Is that really true? I guess the answer depends on how the planer grabs and feeds the board, but I dont know if its rollers or belts or how much force they apply.

It is possible to do with a thickness planer and a sled. There are videos on YouTube about how to do it but I will attempt to explain. You take a known flat board and place the non-flat board on top of it. You use wedges and hot glue to hold the non-flat board stationary and in the position you want it. The wedges and hot glue prevent the traction roller in the planer from temporarily flattening the board. Run it through the planer until that surface is flat then remove it from the flat board, flip it over and run that side through until it is also flat.

A joiner has knives under its bed and with multiple passes you can flatten one side of a board. A planer has a flat bed and overhead knives so a board has to already be flat on one side so it will slide on the planer bed when flattening the top of the board and planing it down to a particular thickness.

However, you can use a sled with a flat bottom and mount an irregular board on it and pass the sled and board together under the planer knives. The board is secured to the sled with hot glue or other means so the sled provides a flat bottom to slide on the planer bed.

Woodcraft has a very good description of how a jointer works and how it can be used to straighten a board , flatten it or square an edge. you can see it at the link below.

https://www.woodcraft.com/blogs/cabinet ... ndamentals

Steve, your assumptions are correct. Stumpy Nubs just posted a video today on this very subject. To mill rough stock to be perfectly square in all directions (thus both faces and edges are parallel) you need 3 tools. A jointer, a thickness planer and a table saw. This is the classical way to mill rough stock to be flat and square.

https://www.youtube.com/watch?v=-5RPhgf_eQM&t=322s

jsburger wrote: ↑Wed Mar 26, 2025 6:45 pm Steve, your assumptions are correct. Stumpy Nubs just posted a video today on this very subject. To mill rough stock to be perfectly square in all directions (thus both faces and edges are parallel) you need 3 tools. A jointer, a thickness planer and a table saw. This is the classical way to mill rough stock to be flat and square.

https://www.youtube.com/watch?v=-5RPhgf_eQM&t=322s

Thanks John. Great video by Stumpy. I have posted a short video from Marc before that also goes through the necessary steps for properly milling rough lumber into straight usable boards. Linking to it below just for comparison and because it is a nice short & concise video on the subject. I really like that Stumpy created the 3D drawings to better illustrate the milling steps and why they are necessary. IF anyone has lumber that is crooked, cupped, bowed, etc., it is imperative to have a long bed jointer that is as wide as the lumber you want to mill. This is a key reason why I complain so often about the Shopsmith 4" jointer on this forum. It simply is too narrow and the infeed/outfeed are just too short for many of us for woodworking, but IF you are milling really small lumber, e.g. building miniatures then it may be great for your application.

viewtopic.php?p=312055#p312055

Thanks everyone for your valued and informed inputs.

I asked the question because soon I will be heading outside again for more house-renovation work, much of which needs lots of long (8 ft) lumber. My router sled works OK for cleaning up long lumber but I did want to verify my ideas about planer limitations before I invested in yet another power tool.

I too would follow the classic practice of prepping stock with jointer/planer, but I could not understand how 8 ft bigbox lumber could practically be prepped by those tools. I found that trying to work with long warped-up bigbox lumber was too much of a safety hazard, so I built the sled, and its been OK.

But use of router sled + planer does make sense. Flatten one side with the sled, then planer the other side. Then nail a miter bar to the stock and run it through the table saw to cut square edges. This sled + miter-bar approach has worked well for me.

So I guess the ideal "3 machine" combo is: router sled + planer + table saw. Forget the jointer. Stumpy's video makes this point.

I can't imagine somebody hot-melting wood pieces together to get their planer to flatten stock! That just goes to show what lengths woodworkers will go to get flat, square stock. Maybe router sleds are the woodworking "tool of the future"...

Router sleds are rather slow by comparison to a planer for this same function. Also wonder how the economy works regarding router bit vs. jointer/planer knives. Much easier to sharpen jointer/planer knives than router bits. Most of us see router sleds as being useful for making slabs and they have a niche for example with producing live edge slabs because you want to preserve the sides of the slab. Making straight on all 4 sides lumber is different though. IF you have found a better and faster way to mill lumber using a router sled, I am sure we would all like to hear it. Also what do you do about warped lumber? It must be clamped in some fashion to keep it from moving as the sled is moved across the workpiece - otherwise planarity will elude you. There is a reason that when you want an S4S board that the standard woodworking method is jointer + planer (optionally + table saw) for hundreds of years.

See attached photos.

The 'trick" is to hold the workpiece in place without distorting it. This is done by running "setscrews" into both sides of the board.

The "setscrews" hold the workpiece securely during the cut, with no distortion.

SteveMaryland wrote: ↑Thu Mar 27, 2025 8:47 am
So I guess the ideal "3 machine" combo is: router sled + planer + table saw. Forget the jointer. Stumpy's video makes this point.

I'll just put in a quick good word for the SS jointer here.

A long time ago I learned the acronym FEET as a way to keep track of how to mill a board. The first F is for Face...flatten one face and mark it as a reference surface. As has been discussed, there are many ways to get this first step done. Hand plane and winding sticks was the "go to" method for centuries, which still works, but router sleds, (btw, Steve, those "set screws" are a clever way to hold the stock in your sled ) planer sleds etc as already discussed can get the job done. The chosen method depends on the size of the work piece and/or how many pieces need to be milled.

The next letter, E, is for Edge. With the flattened reference face against its fence, the jointer makes short work of getting an edge at 90 degrees. Even a narrow jointer like the SS one works great for this. For long stock you may need to add shop-made extensions, but this little jointer is a great tool for getting that first true edge.

On to the next E...and this is where I differ by one step from Stumpy...I take the stock to the tablesaw to get the second true edge and the finished width. This is easily done with the flat reference fence on the table and the true edge against the fence. Cutting the piece to the finished width minimizes work for the planer. Finally, the T, for thickness, which is accomplished by the planer. Or hand plane if you are old school.