Every woodworking shop is focused on forward movement — taking raw wood or substrates and turning them into finished cabinets, tables, mouldings, whatever. Having to rework even one piece disrupts the entire operation.

Sanding is a key part of the process, and CWB asked several manufacturers and suppliers of sanding equipment for their suggestions about how to make sure their machines run efficiently and parts are done right the first time. Their responses, covering everything from widebelts to brush sanders and drum sanders, are below:

Widebelt Sanders

Edward Webb, sales manager, Ramco:

“The most important thing that can be done is to ensure that the entire width of the sander is being used. This improves the life of the sanding belts, the contact sanding roll and platen, and the overall life of the sander.”

Timothy Middleton, Sanding Group product manager, Stiles Machinery Inc.:

“Most productivity issues from your sander, regardless of type, can be summed up in two words: service and training. The vast majority of sander problems stem from a lack of one or both.

“Whether the service to your machine is done by you or a second party, the need for proper calibration cannot be overstressed. Whether it is an uneven surface on your conveyor belt or misaligned sanding heads, there are usually so many variables at work during sanding that it may be too much for the operator to overcome. Instead, what generally happens is the operator adjusts the process to the sander to compensate for the machine issue.

“This is where the operator/maintenance training comes in. The number of passes through a machine can increase greatly, while the finish of the workpiece grows steadily worse. The ability to recognize sanding defects for what they are and know which components on the machine to start troubleshooting can prove invaluable. Most sanding defect causes can normally be narrowed down to just a few components simply by using logic — but only if the operator knows what the component is supposed to do and how and when.

“Keeping your sander clean and calibrated with a trained operator can sometimes double your productivity. At a minimum, it will lower the amount of rejects or parts needing rework.

“Lastly, remember that normally all of your labor costs are already in your part by the time it is finish sanded. It is usually the worst place that a workpiece can be damaged. Productivity losses at other machines are of course a cause for concern. But productivity losses at your sander or finishing department can be catastrophic.”

Keith Paxton, product manager, Kundig Sanding Machines, Holz-Her:

“The most basic and important single item any woodworker can perform with his sander is to check accuracy. This is defined as setting the sanding heads within 0.004 inch of parallel to the conveyor.

“A simple test is to sand three consistent pieces of MDF — two at the edges of the conveyor belt and one in the center. Mark them according to position on the belt, as well as infeed/outfeed. Sand at a low feed speed so the belt has time to cut. Measure the sanded parts, compare dimensions and take notes. Adjust accordingly.

“Hold-down rolls or shoes should meet the same accuracy criteria and be positioned so they hold parts against the conveyor belt. Manufacturers have specifications for hold down units to sanding head dimensions.

“The conveyor belt is a critical component of accuracy. Occasionally, it should be lightly ground using an accurately set, concentric, hard contact roll to eliminate low areas, typically located in the center of the belt. The contact roll must be in excellent condition to perform this. Check the contact roll for concentricity and damage.

“If the contact roll has a problem, such as a gouge or concave shape, it will sand the mirrored damage into the conveyor belt. You do not want to grind a taper or create a concave/convex shape in the conveyor belt. Dust collection and compressed air are required to keep the belt clean, cool and eliminate re-grinding any accumulated rubber.

“The set-up system should agree with work-in-process for accuracy. If it is set for a finished dimension, does the part exit at that dimension? If it measures an incoming part thickness, does it accurately measure it? Is it set so the sanding heads perform their selected tasks?

“Accuracy lets your sander perform. If the sanding heads are not parallel, one side works much harder than the opposite side. Machine components and abrasive belts both wear unevenly and create problems and unnecessary expense. Finish, accuracy and the machine all suffer if this is not part of a regular maintenance schedule. If you have doubts about performing this work, hire a good technician. It will pay you dividends.”

Mike Fogel, product manager, Sander Division, SCM Group USA:

“Keep it maintained and calibrated. A machine that is set up and maintained correctly helps production in both the short and long term.”

Mike Johnson, North American product manager, Widebelt Sander Division, Biesse Group America:

“One of the biggest issues that I see across the board is customers not calibrating their machines correctly for grit compensation. This is typical with older-technology machines where it is difficult to adjust the drum height, especially on a one- or two-head model. If they are changing from 80-grit to 120-grit, they do not make the height adjustment on the drum for the difference of the thickness of the abrasive paper. This does not leave them with a true grit scratch depth for whatever particular finish they are looking for. They think they are getting a 150-grit finish, but they aren't.

“The other issue I see a lot is excess chatter mark, left from the joint in the belt, typically running on a hard calibrating drum. Again, customers running a one- or two-head machine typically want to run that drum on several different grits. The problem is that you leave a chatter mark in the joint every time it comes under the hard drum. I feel that customers need a little bit better training in how to truly set up their machine when they are running a limited number of heads. They need more and better knowledge on how to set that machine up, and in the end it reduces the amount of hand work that has to be done to that part after it’s been sanded.”

Tim Mueller, Timesavers Marketing Manager, Timesavers Inc.:

Getting the best possible finish from your widebelt sander requires a number of variables to perform simultaneously. Alignment is a key, but often people forget the importance of using the correct abrasives or the proper abrasive sequence for their specific application. Not all belts or minerals are created equally, they are different for very specific reasons. If you utilize the wrong belt, the finish you achieve and the life of the belt may be drastically affected. Belt and machinery manufacturers are great references to help you “tune in” your abrasives to a level that satisfies both your finish expectations and the life of your abrasives. Don't forget, the machine is simply driving a tool; it’s the tooling that determines the finish.

Brush and Drum Sanders

Bill Schroeder, president, SuperMax Tools:

“Having problems with burn marks when sanding? Try a cooler operating abrasive, such as the “blue” alumina zirconia instead of the standard “red” aluminum oxide. Because the “blue” sands much cooler, it dramatically reduces the possibility of burning/melting, which is especially beneficial when sanding challenging stock, such as hard maple and cherry. The “blue” is a sharper mineral, more uniform in nature and gives a good, consistent sanded finish. The “blue” abrasives can outlast and outperform regular “red” abrasives.

“Stationary brush sanders can effectively and consistently sand sealer on profiles, such as mouldings, raised panel doors and drawer fronts. Brush sanders reduce or eliminate the time-consuming hand sanding, while maintaining the utmost in consistency. The bristles of brush sanders can conform to profiles, effectively sanding at various thicknesses without destroying the profile. Quality brush sanders offer machine adjustments to handle a wide variety of materials and finishes. Many types of brush heads and grits are available, depending on the desired results.”

Dave Gentili, technical service representative, Powermatic:

“When running glued stock through the a drum sander, running it at an angle will help with the burning and excessive loading of the abrasives. When running stock that cannot be angled through the machine, the use of a polyurethane base glue will help diminish the premature loading and burning of abrasives. This glue is more sandpaper-friendly.

“Unlike a widebelt sander, running material through a drum sander will produce an inline scratch pattern in the material. After the material has been run through a drum sander, the scratch pattern can be easily hidden by using a random orbital sander with the next larger grit size. If you stop with a 180-grit abrasive on the drum sander, jumping back to a 150-grit random orbital will help hide the inline scratches from the drum sander.

“Stock removal with sanders in general will be limited to the size of the grit being used. 80-grit abrasive will be able to remove more material than the 220-grit. With 80-grit abrasive, you can remove 0.020; with 220-grit, you can expect to remove 0.002 to 0.003 maximum (depending on type of abrasive) in a single pass. Removing more than this can shorten the life of the abrasive considerably.”

Illustration by Chris Nititham