My Machine is Leaving Chatter

Photos courtesy of Lägler North America unless otherwise noted.

The term “chatter” is one we are quite familiar with in the wood flooring industry. In my years of involvement with wood floor sanding machines, I have had plenty of dealings with chatter, and the many potential causes. In this article, I am going to offer up why those of us working in the world of “solving floor sanding problems” might be able to better approach getting to the bottom of what actually is causing the chatter, so the next time we hear, “My machine is leaving chatter,” we will have a better pathway to investigate the root causes.

One could hardly argue that chatter isn’t a fitting term for all unwanted features of the big machine’s work. It normally is identified as a repeating series of marks, usually transecting the wood’s grain at a width that is often more or less the width of the sanding drum that was used. Most would agree what chatter looks like, but very few take the time to investigate the root cause of why these marks are being left behind.

I have all-too-often witnessed big machines in service centers with tags on them that read things such as “leaves chatter” or maybe just “chatter.” I wonder if the conversation between the mechanic and the service center begins and ends with “my machine is leaving chatter,” without any further questions. Not asking for enough information can be an easy habit to get into. Letting “chatter” be an end-all to the conversation is an example of a bad habit. Maybe it’s because the term is just so common in our industry that many believe they know what chatter is and let it go without further thought. We need to gain the understanding that there is a glaring flaw in the term “chatter,” and when it is left on its own, it lacks a true landing spot when we break down what a floor sanding job really is.

To get there, we must first recognize there are two central goals in floor sanding:

SAND JOB TOPOGRAPHY – Referring to the SHAPE of the floor’s surface as a result of the sanding that was done: Is it flat or something other? In wood floor sanding, we aim to get it FLAT.

SAND JOB COMPLEXION – Referring to the wood’s ability to express its unique character after sanding: Is it free of visible scratch pattern signatures that otherwise would interfere with its visual value. (This typically has nothing to do with how flat the floor surface is.) In wood floor sanding, we aim for a clean complexion.

Understanding the concepts of sand job topography and sand job complexion as separate criteria proves to be key in navigating the causes and cures of bad results. Once this approach is applied to a complaint of chatter, it doesn’t take long to realize that problems left behind from big machine use easily can fall into either category.

When diagnosing “chatter,” you are faced with two questions:

Is the problem a matter of sand job topography? (Did the big machine’s work actually dig in repeatedly and deform a surface that is supposed to be flat)?
Is the problem a matter of sand job complexion? (Is the surface flat as one would expect, but the big machine’s scratch pattern features visible bars that transect the boards)?

This is a critical diagnostic step, since the potential causes for each involve lists of usual suspects that are quite different from each other. To understand how all of this works and fits together is to understand how chatter is truly non-specific to either category. From here, we now can begin to ask for more information.


You are not being rude or appearing to be a novice by asking for more information. Photos of the floor are in the “Must Ask For” category any time a machine complaint comes in. Everyone takes photos of their work these days. If the person you are trying to help is serious about getting your help, they will have no issues getting you photos of the affected floors.

If it so happens that there just aren’t any photos available, don’t give up on fielding more information. Consider showing some photos of your own and ask which most resemble the results they’re experiencing. Do this several times to build certainty. To an experienced equipment repair technician, photographs can offer enough information to decipher between topography-related, and complexion-related “chatter.”

You also should ask a few targeted questions:

  • Initially, ask for a description of how the problem can be best viewed. Listen for clues that can indicate if they are describing topography or complexion. Asking follow-up questions should be expected, but be careful not to coach your subject into a direction they aren’t moving toward on their own.
  • Asking how far apart these chatter marks are can be useful. Generally speaking, marks of one inch apart or more will lean toward topography, while those that are less than one inch apart will lean more toward complexion.
  • Ask if the machine is behaving any differently from normal – unusual vibrations and noises often will (but not always) bring complexion issues to the floor. Poor dust pick-up also can hold some clues. Accumulation of dust in the machine’s drum and upper roller unit can affect the machine’s abilities to dampen vibrations that will compromise its performance in the complexion category.
  • Ask if this chatter is the type that can be buffed out with some extra screening. If the chatter is a scratch pattern (complexion) issue, it normally will buff out with extra screening. If it is a topographical issue (waves or ripples), the idea of it buffing out with a screen is pretty much off the table. (Don’t get this confused with a guy going nuclear with a sanding disc – keep the idea based upon the limitations of what a screen can do.)

Remember that we all see things, perceive things, and describe things differently. Many times, a verbal description will contradict what a photograph is showing. Nevertheless, getting yourself a good body of information up front will serve you well in accomplishing your first critical goal. Don’t let it all come to a crashing halt with the mere utterance of one word.

Before inspecting a floor to determine the cause of the chatter, consider NWFA standards for Evaluating a Wood Floor (Problems, Causes, Cures on page 2). NWFA states wood floors should be evaluated from a standing position, on the floor being assessed, in ambient lighting. Glare from direct light sources must not be used during evaluation. Inspection may take place from floor level, using direct light sources, through magnification, or through destructive testing in order to determine the cause of a problem, but not necessarily to determine acceptability.


When the sand job is complete and the final coat of finish has dried, that floor’s “flatness” is a huge factor in how it is judged for quality. Since wood floors are merely a floor covering, it must be considered that the installed wood is only going to be as flat as the shape of the subfloor structure below. With this being the case, there is no reasonable goal of sanding a floor truly flat. Allowances for subtle subfloor effects to the surface shape need to be made for when it comes to judging the result of the floor sanding. This is why we call it “sand job topography” as opposed to just plain “topography.”

The main thing to bear in mind when properly examining the sand job topography is to find and focus on the reflected ambient light and the glare off the floor surface. This will reveal what the surface looks like. Have you ever searched the side of your car for door dings? If you have, and were the least bit effective at it, you undoubtedly utilized reflected ambient light in the process. The very same holds true in examining the surface of a wood floor. The focus must be placed upon the fact we are limiting all of our judgments of that floor’s appearance on what its surface looks like. It is vital we position ourselves so that relatively large expanses of the floor can be viewed at gentle angles (standing position) to focus on the reflected ambient light. These regions of reflected light are where we can best see the existence of any irregularities of that floor’s surface plane. As we walk upon that floor, the reflected light moves as well, providing us with a sort of scan in what the floor’s surface shape is as we search for irregularities over an even more broad surface than what a photo bears. While scanning what’s revealed in the reflected light, we continually ask the question, “Do I see a flat surface here, or do I see something other?”


If there were no goal for a clean complexion in our wood floor surfaces, there would be no need for any sanding beyond what initially gets the surface flat. Given that up to 70 percent of the investment of time and materials in total sanding and screening is devoted to these processes, it’s a sure bet that sand job complexion is taken quite seriously. Finish sanding is an upward progression of finer and finer sanding grits used upon the wood floor surface until it is ready for finishing. Judging the floor’s sand job complexion is all about whether the sand job succeeded in a sort of “leave no trace behind” campaign in regards to any vestiges of the sanding process left behind that interferes with that expression.

Sand job complexion flaws come in a number of forms, including bar-like marks transecting the boards. These marks clearly are not a natural feature found in the wood; they are merely a function of scratch pattern. Picking out these features as opposed to those of the topographical sort differ in a couple of ways:

Reflected light, in many cases, is not utilized in picking these features out. In fact the glare only will make them harder to see – especially when there is a finish on it. However, there are some cases where the visible bars are seen best in the glare of the raw wood. A little practice is all it takes to know what’s in the glare: surface disruption “chatter” or a “chattered” scratch pattern.

When there is a presence of scratch pattern chatter upon the floor, you usually can kneel down to that floor’s surface, place your hands around a section, and still see it. Conversely, if you were to try the same test with topographical chatter, the feature often disappears.


Big Machine

Any time someone shows me photos that clearly depict chatter as topographical issues (commonly called “waves” or “ripples”), I will never advise to NOT have the machine looked at. Out-of-round wheels, arthritic suspensions, drum pressure, and suspension issues all heavily factor into how flat any floor’s sand job topography is going to appear when the floor is finished. We call this the “Ride of the Machine.” If you shut down the motor, roll the machine up and down the floor while raising and lowering the drum, you are working the Ride of the Machine.

Jobsite Conditions

All floors are not created equal. Structural integrity among the floors getting sanded can vary by a large degree. If the floor is flexing during the sanding process, any expectation of its sand job topography not being affected is probably quite unrealistic. Harmonic vibrations involve listening to what the sander is saying while sanding. If adjustments aren’t made, a good sand job topography could become an over-lofty expectation.

Three Red Flags

The following red flags represent aspects of the sand job that will make a floor more difficult to present a finished product that is pleasing to the eye from the topographical perspective. When any of these red flags are present, all precautions must be taken to avoid bad topographical results. Using a big machine that is well-tuned, sanding at angles, not skipping too many grits, and utilizing a multi-head sander in the finishing stages all are going to offer advantages in the finished product from the topographical perspective. These red flags are as follows:

1. Floor composition: When a wood floor surface is comprised of materials that carry a wide variance in material hardnesses equating to differential resistances to the eroding down effects of sanding, it should be deemed as a “topographically challenging” floor. Common examples include multi-species lay-outs, multi-directional lay-outs, and open-grained species floors that contain a good number of flat-grained boards.

2. Refinished floors: It’s no secret that the sand job topography of any floor begins to suffer a bit more with each successive sanding job over its lifetime. The more material removed from that wood’s wear layer, the less it resembles those flat faces that were cut into the boards with the planer. If there is anything that was less than ideal done on the previous sand job, chances are good that topographical issues from the last sand job could be amplified on the current job. Couple that with an added challenge of breaking-through the existing finish, it is not hard to see why refinished floors belong in this category.

3. Light source positioning: Sliding glass doors, big floor-to-ceiling windows, etc., positioned at the end-match wall should spell it out for any experienced hardwood flooring pro that any of this topographical chatter left behind on the floor is going to be especially visible.

Operator Error

Operator error is a much bigger subject for topographical chatter than it is for complexion chatter. Getting the floor flat and keeping it flat throughout the sanding process is truly one of the biggest challenges in floor sanding. Getting the proper training and adhering to sanding procedures aimed at achieving the best results is critical. All operators of big machines should strive to move their machines about the floor smoothly and at uniform speeds. No jerky motions, keeping your hands off the operating levers while sanding, and most importantly, letting the machine do the work.


Big Machine

Once we have determined that a chatter complaint is a matter of sand job complexion, the big machine performance becomes a major consideration for its cause. Repeating marks in the scratch pattern almost invariably means there are vibrations occurring while sanding. Sometimes these are felt and/or heard by the operator, and sometimes they are not. With the “Run of the Machine,” we mean the big machine’s motor and motor-driven moving parts. To see these in action, ready the machine just as you would begin sanding, turn it on, and step away. Everything that is moving, or better yet spinning, is the Run of the Machine. Virtually all of the involved parts are subject to wear and face replacement once its service life is over.

Understanding the concepts of sand job topography and sand job complexion as separate criteria proves to be key in navigating the causes and cures of bad results. Once this approach is applied to a complaint of chatter, it doesn’t take long to realize that problems left behind from big machine use easily can fall into either category.

A big machine that conclusively is leaving this scratch pattern chatter is very likely to require a visit to the shop. At the very least, a thorough examination and testing will be made of the big machine’s drum, pulleys, V-belts and V-belt tuning, upper roller unit and its components. It can’t be stressed enough that keeping the machine clean and well-serviced is one of the best guarantees for keeping complexion chatter from adding profit-killing time to the sand job.

Jobsite Conditions

A poorly constructed floor can vibrate back to the sander and result in complexion chatter also. Often there will be accompanying noises and vibrations that will tip the operator that something isn’t going so well. Testing a small area with some stain or sealer often can reveal the effects on the floor, and decisions can be made as to whether a multi-head sander or more screening might be more efficient.

Operator Error

Provided the operator keeps the big machine clean, in a good state of tune, and uses quality abrasives that are stored properly, there is very little effect his or her sanding aptitude would have in the creation of complexion chatter. It is pretty much a marriage of big machine tune, sandpaper quality, and substrate integrity.

Electrical Issues

Big machines that are exhibiting effects of electrical issues certainly shouldn’t be eliminated as causes for topographical or complexion issues with the floor. However, these machines usually are brought in for acute complaints of the electrical nature as opposed to what might be the effect on the floor. If no electrical performance complaint is noted by the operator, it’s very unlikely electrical caused quality issues.


LOFT (Low On Fundamental Talent) (LOFT) issues in sanding nearly always result in sand job topography problems. Drum digs can be common in such cases. These often can be remedied with more training and more practice.

The next time someone comes to you with the complaint that, “My machine is leaving chatter” identify whether the chatter is of the sand job topography, or if it is of the sand job complexion. And please don’t forget to ask for pictures.

Russ Watts is in sales and service for Lägler North America in Denver, Colorado. He can be reached at

HFM Subscribe

Leave a Reply

Your email address will not be published.