Planing or clamping?

Hi Everyone

This is perhaps more a question to the woodworkers than the cnc-gurus!
I have noticed that my stock wood is sometimes slightly warped. I use a type of oops-clamp combined with tape and superglue to fix my stock to the wasteboard. But on large stock pieces the wood might be raised by 1mm or 2mm in the center of the stock, therefore I always have to set the bottom of the cut a bit deeper.

I also trammed my cnc and have slight tolerances of 1mm on either sides of the 1OF, but I can live with that.

Before I drop a few hundred bucks on a planar, I was wondering if it is not better to clamp the stock down with bolts through the wood wherever possible, or screw it down.

The objects I make tend to be small, and I dont think the natural warping of wood would be a massive issue for the final pieces I cnc cut. I was just wondering if people out there, first plane their wood to get nice flat pieces or do you all just clamp the stock to death, that it cant budge or show any signs of warping.

Thanks in advance

Hey Fred,

it is not a solution to screw or clamp the wood so that the warping disappears, because if you loosen the workpiece, then it would warp back.

The fact that wood warps after being cut into boards has been a concern of woodworkers for thousands of years and there are proven solutions for this problem. When it comes to glueing together larger areas of wood that you want to remain flat later, even when the wood is exposed to changing humidity levels, you have to maintain a certain alignment of the individual wood strips before glueing. This is shown here:

Compensating warping of wood. Above: wrong. Bottom: correct.
– Image source: Spannagel, Fritz: Der Möbelbau. Otto Maier Verlag, Ravensburg, 1954.
Reprint: Th. Schäfer im Vincentz Verlag, Hannover, ISBN 3-87870-666-9

This is also often mentioned in woodworking videos, e.g. in this video or in this video.


Still, most woodworkers will say before you clamp a piece of lumber into a CNC, it should be dressed. Lumber, after all, is often not only warped, but can be twisted as well. The dressing is done with a jointer (called planer in the UK) or a combined jointer/thickness planer like the Felder Hammer A3. At least that’s how it’s done nowadays. In the early days, trueing was done with a jointer plane or trying plane (shown here), which is of course still a possibility, especially if the warping is not that extreme, but to use it you also need a proper planing workbench to hold the workpiece while planing. A Workmate may wander away while planing.

You can of course leave the warping in, but then some clamping methods might not be suitable. Clamping from the sides with eccentric lever clamps can of course increase the warping and with the tape and glue method you may not have enough contact surface.

1 Like

If they called a jointer a planer in the UK, what do they call a planer?

Hey Ken,

a thicknesser :wink:

(See also: Jointer)

PS: You can see this also when the same combined device is referred to as “jointer-planer” on the US website and as “planer-thicknesser” on the UK website :slight_smile:

1 Like

Here is what I do to overcome the problem of “spring-back” if you were to screw down a warped panel before planing. I lay the panel on the wasteboard of my CNC and find if one side lays better than the other (usually, the panel is cupped “up” on one side and “down” on the other. I place the panel so that the cupping is oriented tall face upward. Then, if there are significant gaps anywhere around the perimeter of the panel, I may use a few small wedges to occupy that space. Using small blocks of wood at least a bit thinner than the panel and a hot melt glue gun, I glue blocks to the edges of the panel in several places - I glue only to the panel, not to the wasteboard, but make sure the glue blocks are flush to the wasteboard surface. I do not apply any pressure onto the panel, I want it to sit ‘naturally’ on the wasteboard with no pressure forcing the panel in any direction. I then use my clamping system only on the glue blocks to hold everything in place and then proceed to use the cnc to flatten the face of the panel. Because I introduced no deformation when placing the glue blocks, the panel will remain flat on the surfaced side when I am done. I then flip the panel over and flatten the remaining side.


Hey John,

the perfect method to level with the CNC, and a jointer is superfluous. The idea with glueing and clamping only the blocks on the edges is great.

A method with wedges and hot glue is also known for being able to level warped and twisted boards if you don’t have a jointer but only a thickness planer, as shown in this video or in this American Woodworker video (=the “jointer sled” method)

1 Like

If the back does not matter I attach with tape/super glue or edge clamp and just use my surfacing bit to flatten the top, and then I get an even carve.
If both sides matter… I put backside up and use wedges and side clamps along with surfacing bit. Then tape/super glue the flat back down and surface the top. carving right after. If I want it to be a specific thickness I just set Vectric to work from machine surface measure the high spot and let the machine do the work.
It does not usually take too long with a 1" surfacing bit. Leaves a smooth surface and if it does warp a little after, it’s not usually a big deal.
That’s for live edge pieces, for dimensional lumber I cut join, plane, glue, scrape glue and then flatten on the CNC.


I use a lot of thinner stock for most of my projects so far. i Joint and then resaw my boards. Lately i have been using wood for coasters that is .360 thick and even after jointing, resawing, and then thicknessing on a 48 inch by 5-inch board the board will not always lay flat on the onefinity, but since the item itself is only about 4.5 inches in diameter the slight cupping is not noticeable. that is the usual routine i follow jointing with the concave side down / toward the jointer blade (till flat) then 90 degrees to that edge joint again till straight. then resaw jointed edge to the fence then thicknessed planed till you reach your desired thickness.
If the wood is the correct dryness, you should be fine and flat and stable. Always when finished whatever you do to one side of the wood do also to the other side or the wood will absorb moisture on one side more than the other and you will introduce warpage yet gain.


You can use your machine to flatten.

-Shim the piece and clamp making sure your clamps are not taking the twist out.


I have a DEWALT 735X planer. When trying to flatten a 3/4” pine board due to cupping, the rollers flatten the board as it goes through and comes out the other end still cupped. 2X stock not an issue. I’m interested in applying some of the tips in this thread for securement and then trying a surfacing bit. I also have a 6” jointer, which might be a better play but most of the 3/4” stock I want to work with exceeds the width capacity of the jointer. With thin, soft woods, additional tools like I have really don’t help, unless you want to rip, glue, and then surface. The 1F when all the tips and tricks are learned should be a 1 step operation. Proper securement of the material, whether flat, cupped, etc., flattening operation if needed, and start creating your project. Sounds like a quality hot glue gun will be coming to my arsenal of tools as I now can see alternate securement methods without destroying the wasteboard. Thanks all!


You can “joint” the boards by shimming and attaching to an adjacent board (underneath) on your planer as well. Although an additional step, the planer is much faster than the CNC to flatten say - 10 pcs of 1x6x10.

I have a 735 as well, and I find slighter passes, do tend to correct cupping, but I agree pine, softwoods, and thin material, its hit or miss.



I run into the same issue all the time. I mostly make toys, so a small cup in the wood isn’t an issue.

You mentioned having to set the bottom of the cut a bit deeper because of a cup in the wood. Rather than doing that, I like to zero my Z axis at the level of the table rather than the top of my wood. Then no matter how thick or thin the wood is it will always cut just to the table and no deeper. I blows my mind sometimes how accurate this machine is. I’ll zero to the table, tape my pieces down, and when the cut is done the tape will be cut, but there won’t be a mark in the table. Pretty freaking impressive!

Anyway, just zero to the table instead of the wood and you’ll be good!


Thanks! Again, explained, that makes perfect sense. I have a lot of 1x8’s, 1x10’s etc. that due to cupping, they would be practice pieces. This has the wheels turning on how to flatten them in an efficient way. I learned early on how DOC affects the finished design, and anything short of a flat surface to carve on, doesn’t work.

Brian Lindell

1 Like

Phil Thein, of “Thein baffle” fame, invented a planer-sled technique that uses nothing but a flat base board, painter’s tape, and hot glue. I’ve used it for years with my thickness planer, and it works wonderfully well.

To summarize the method, you apply matching strips of tape to both the flat base board and the workpiece, put blobs of hot glue on the tape on the workpiece side, flip it over, and simply lay it on top of the base board. The hot glue then sags down and forms pillars in any gaps between the workpiece and the base, creating shims of the perfect thickness when cool. The base board doesn’t even have to be particularly stiff, as long as you do the glue-up on a flat surface, as the resulting structure is basically a torsion box. After planing, you just peel the tape & glue sandwiches off and throw them away.

Phil has a great detailed writeup on the technique here.

I haven’t yet used this technique with my Journeyman, but I see no reason that it wouldn’t work just as well for flattening with a CNC. I’d use the spoilboard as the base board of the glue-up, making the process simpler yet.


If you’re doing smaller stuff, a thickness sander works pretty great for this. I bought a Supermax 16-32…not cheap but I use it constantly. It’s a necessity for what I do (guitar making). I do sometimes do a sled technique with it.

Sometimes though I just start with a really skim pass with hand pressure to put the board in the plane I want it. Once it takes off the high spots I flip it over and then it will usually give me a flat surface. Then I flip it again and boom…perfect board. But this is for stuff 4’ or less.

1 Like

I couldn’t do it with a planer though…I’m usually using figured wood and the planer would tear it out horribly. So the sander works pretty amazing.

1 Like

Tape and ca glue are good for quick projects that are flat and dry in my experience. So far tape and ca glue has faiked me many times ruining ling detailed carves. Sign making lije these welcome signs etc ca glue and tape is fine.
Xlamps whole nother issue from making material rise up slightly from the waste hoard to interference with dust shoe bolts and bits lol
Ive been just using xonstructiin grade 2x12 etc to do carves in working out any deffects etc and i have even dried it in the over for cpl hrs to try to reduce warp cupping twist etc
Ive had moard cup while planing it sucks to chasr your tail
I notice alk the furus who have been doung this a long time always use screws brad nails etc to secure their work. Yes it damages the spoil board but thats why its a spoil board and replaceable. Just part of the process you accept in your hobby.
Or usr sacrificial material but even that is an exspense added to your overall hobby business and enjoyment
Quality lumber atacked and stickered properly and kept in a controlled enviroment and only plane the thickness when you get ready to make the project and use screws and yes youll have more waste material to avoid cutting screws with bit etc
Clamps again ok but you can warp your material with them
Ive come to the conclusion each work holding has it own olace and use but to be really secure its my reccomendatiin to stick witj tje pros and use screws brad nails etc fir long detailed fine work
If i make a welcome sign ah a small defect no one worries about but you do that witj a 3d carve and see what they say
Idk its a good thimg we have options as not all things have a solation to work with all we do
Versatility is key and having more tools is nevwr a bad thing in my book
Just love the fun of battling witts with mother mature and what we take from her to enjoy the hobby
Good luck
Keeping the chips big and flying
Nothing like a 5 ft rooster tail of chips blowing out a channel during a profile cut. Lol
Chips and smiles take care

1 Like

Three techniques apply.

  1. You said small parts, warp doesn’t matter. In the case, I draw screw in my software and have the CNC drill the holes. This helps to mis the screws. I am also practicing with zero at table surface, so the small variation in thickness does not cause cut through issues.
  2. I use M700 George method.
  3. I have built a flattening jig for my 4 post planer. It is 48” long, bottom built like a torsion box, and the top has adjustable resting bars. It does the same thing as M700 George method, but done on the planer instead of the CNC.
1 Like