Wood Flattening - Planer, Thickness Sander, or Flattening bit

Not an expert, but have been doing hobbyist woodworking for 50 years. I see people talking about the three methods of flattening and thought it would ne nice to have a thread on the pros / cons.

Planer: Probably the fastest, but …
In theory you have to use a jointer to first get the board flat on one side. I don’t happen to have a jointer big enough :frowning:
There are pressure rollers that feed the boards through the machine. This causes two problems, it can flatten the boards before they are cut and the last couple of inches of a board will suffer from snipe. Snipe is when the board goes past the feed rollers and then can cut at a different depth.

Thickness sander: This is slower. You can’t take as much off as in each pass. This also has a tendency to flatten a cupped board just by the pressure of the sanding drum.

Flattening Bit: Admittedly I haven’t used this to flatten a workpiece. Since the workpiece is clamped into the machine and if the machine is trammed properly this is probably one of the best methods. It may require some sanding.

OK, now every one can tell me I’m soft and or wrong LOL.

I used planers (hand electric and BIG planer) and it was insufficient. I’ve also tried various sanding methods. Nothing works.

I’m sucking it up and buying a jointer. I’ve learned through experience that the CNC absolutely MUST have flat material. I’ve run multiple passes with different G code to account for it, but it sucked. I’m a new woodworker, but I did use my Whiteside surfacing bit once with great results. It just took longer than I wanted. And yes, it still required sanding (60, 180, 200 worked fine).

I’ve been able to use roughcut lumber by just surfacing one side (the Tiger Claw clamps are ideal for this) then flipping and using the just surfaced side as the bottom/reference surface.


Here’s my answer to planer versus drum sander from Stack Exchange:
"You’re correct that the planer can remove much more material at a time. With the planer, it is also simple to adjust the depth for removing more material in a pass. With the drum sander, you can change the grit of the paper to take off more material (nowhere near as much as the planer) but that is a more painstaking process.

That said, I own a drum sander but no planer. I used to make acoustic guitars and work with figured wood. In this case the planer is of little use since it will take out chips where the grain angles up. The drum sander does not chip-out the stock and allows smooth and uniform surfacing of wood down to 2 mm thickness, even thinner if required.

So, preference rather depends on what you’re doing. I’ve also used my drum sander to fashion oak window jambs and trim. It required more passes than a planer would have but I would have wanted the drumb sander for finishing anyway, I was happy with my choice of tools."

Since I wrote that, I have also used the drum sander to build a Mission oak dining table, coffee table and corner cabinet. This included some mega stock removal with 36 grit.

Additionally, most non-industrial drum sanders are open ended allowing you to surface material up to twice as wide as the sander. With a planer, you will want a dust collector. With a drum sander, you will need a dust collector.

One trick for flattening a board with either. Use masking tape strips every six inches as needed on one side of the board to present it as flat to the the platten below, then surface the other side first. This prevents the roller pressure from flattening the board only to have the bow reappear after a pass.


I have a 15” 3hp helical head planer, 16-33 drum sander, some hand planes and the shapeoko.

What I do when I have glue ups or rough cut lumber is I set it on my cast iron table saw and find the flatter side. Then I will find what points it rocks on and take off a lot of those points with a hand plane.

Then I will use shims and hot glue to mount it in my cnc and face one side. Then run both sides through the planer (better finish) then run through the drum sander with 220grit to finish.

This will give me a perfect board, but takes time.

I would kill for an 8” jointer but it’s hard to swallow $1800 right now. I would still need to use the shapeoko for larger glue ups but it would save soo much time


WillAdams - I like that idea. I do a lot of work with rough oak - have maybe 800 board feet from trees around my property…


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How noisy are drum sanders compared to planers etc? I live in an apartment and I work in my garage, so not annoying others with noise is a priority for me.

Drum sanders are less noisy than a planer, but not quiet by any means. Still, a jointer is necessary for proper parallel flattening.

I have 16” jointer/planer combo machine. One of the best investments I’ve made for my hobby shop. I only use my drum sander on oversized work pieces.

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There is no substitute for a jointer. A planer and drum sander make a board smooth but not flat. A drum sander and planner only have the board trapped for maybe 6 inches at most. The feed rollers will flatten the board under the head/sander drum but cannot hold the whole board flat. If a board is bowed going through a planner/sander will be smooth but still bowed. If you have a planner only you can make a carrier board and shim the board and get it flatter on multiple passes but you have to start with a pretty thick piece of board it is hard to beat a jointer but there are ways to get a flat board from a planner/ sander but the work around is time consuming. Take a look on youtube for solutions without a jointer.


I agree on the jointer (I do have all 3). The jointer gives me a nice flat side, and if I didn’t have a planer or drum sander, I would use my cnc to get at flat and parallel face to the jointed face. Just my $0.02.

Noise levels: Don’t forget to include the noise of dust collection when using a drum sander. You really need dust collection for that. For the planer or using a surfacing bit, you can always sweep up.

I use Will’s method. shim to get as close to level and surface one side with a surfacing bit. Then flip and surface the other. One option that has not been mentioned is using s DIY planer sled. Place your board on the sled. adjust the supports to level the board as best you can. Once you get a flat surface, you can flip the board and run just the board through the planer flat side down. Essentially turns your planer into jointer. My jointer is only 6" wide so that is how I handle boards wider than 6". I got my plans off a youtube.

I have a 6" jointer, if I need to flatten a board between 6" and 12.5 ", I will first joint as much as I can, then use my planer sled to have the jointed part sitting on the sled while the unjointed hangs of the side. A couple pass through the planer I know have the who board flat on one side, then remove the sled and run the other side through.

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That’s an interesting idea, Jason, I’ve never tried that. Mine is 8” and when I have anything wider, I typically rip it in half (or wherever makes sense), joint both boards, and glue back together so they are perfect before planing. For me, that has worked well because many boards wider than that at my location are not that stable, so putting that extra glue joint in helps to limit the warpage down the road for me…maybe that’s just in my head though ha.

Real cast iron planers require dust collection also, a vac won’t cut it. Just the same as a jointer and a drum sander, all 3 of which will be louder than the dust collector, just like the surfacing bit.

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When you have uneven material, you MUST shim/support it from the bottom, so that the machine wont flex it flat. Even if it is a CNC.

When my material is thin enough for my planer, I use a sled that I made.

When it is too wide, I use my CNC.

In either case, I always support the high areas, surface one side, then flip. Surface the other side as needed for each project.

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