Even though sanding with a pneumatic random orbital sander may seem like a pretty simple activity, challenges can definitely arise – causing frustration, along with flaws in the work piece. As with most aspects of woodworking, getting the best results in your work comes down to a combination of using proper techniques in the various applications and processes while properly maintaining your equipment. So, if you’re experiencing issues with your pneumatic sander or with your sanding results – such as swirls or other visual defects, blotchy and uneven finish, inefficient removal rates, or otherwise – the tips in this article are a good place to start.
1. Check Your Air Pressure
If you notice that your air sander is not performing consistently and perhaps you’re seeing swirls or other sanding marks repeatedly, the first thing to check is if your compressor is providing sufficient air pressure for your sander to reach the ideal rotations per minute (RPM).
In general, Uneeda’s air sanders require 90 PSI to run optimally, so if you only have the one machine attached to the compressor, simply check that you’re set to 90 and that the full 90 is reaching the sander. While it is possible to run the sander on less than 90 psi, the sander will not perform as well and your results may not be ideal.
t becomes more complicated when multiple tools/machines are running from the same compressor, at the same time. In that case, it’s possible that while the compressor may technically be putting out 90 PSI (or more), with other machines attached and turned on, all machines in operation would be sharing the air pressure output, meaning that each machine might not be reaching its required PSI levels. So, if multiple tools are in use simultaneously, make sure that your compressor is set to output enough pressure to meet the minimum requirements for each tool.
2. Check your RPM
Random orbital sanders are designed to run at 12,000 RPM and 10,000 RPM for 3×4 orbital sanders. While it is possible to achieve a good finish at 10,000 RPM, anything less will cause significant sanding marks. As sanders age, if not properly cared for, they will lose RPMs. Most operators will not realize this is happening and will continue to use their sanders, only to find rejects escalate over the same time frame. Checking your sander’s RPM is a simple way to maintain a consistent finish and keep the subpar work pieces to a minimum. You can use a Vibrating Reed Tachometer to check the speed. If you find it is not spinning at the proper RPM, try oiling the sander and testing again.
If you’re a Uneeda customer and you do not own a tachometer, we offer a technical service to check our customers’ hand sanders for proper operation.
3. Don’t remove the filter cap on the back of the pneumatic sander
When looking at your pneumatic sander, you may have noticed the two cylindrical areas on the rear – one where we connect the air line from the compressor, and the other with a grated cover. This cover is a filter cap that covers a small nylon filter. The filter cap plays an important role in the proper functioning of the sander: keeping the inside of the sander clean from all the particles and debris created from sanding.
While it may be tempting to remove the filter cap under some circumstances, this is a bad idea and is never advised.
As we operate the sander, air is forced through the sander causing the moving parts to spin, which creates heat and liquifies the grease in the bearings. When the lever is depressed, we drive the air through the sander, however when we release the lever, this opening becomes a vacuum, allowing any debris to enter the sander motor and bearings. As the bearing grease hardens, the debris becomes like sand, and the wearing on the bearings is unrepairable. Once the ball bearings are not free to move, the bearing will lock up and the bearings will need to be replaced.
4. Make sure to oil the sander regularly
What’s worse than trying to sand with a sander that won’t move? Maybe only being forced to sand everything by hand … without the help of a machine.
But, when you start to notice the sander not spinning well, what will you do? Probably you would naturally try to compensate by pressing harder on the sander to add more pressure. In this scenario, essentially, the sander has become useless and you might as well be sanding manually without the tool. Trying to get better results in this manner will likely cause worse sanding results, uneven scratches, swirls and more – not to mention more soreness in hands, wrists and forearms.
The fix for this is to make sure to oil your hand sanders daily. This keeps the housing and bearings lubricated and moving freely. As we sand, we create heat, which causes friction. This friction is not a friend to the sander, as it will dry out the phenolic vanes to a point they get dis-lodged in the housing, stopping the motor from turning.
If you use your pneumatic sander regularly, the best way to keep it operating well is to keep it lubricated. Simply put about 2 drops of machine oil in the air intake area at the end of the day and run the sander briefly to spread it around. This regular practice will keep your sander lubricated and prevent it from locking up – and keeping your projects moving smoothly.
5. Keep backup pads fresh and maintained
Another often ignored or actively avoided area of maintenance on orbital sanders is the backup pad. While replacing them is easy, it can often go overlooked when trying to save money or otherwise conserve on tools. But, when your backup pad is bad and left unchanged, you will see the results in your finish.
Firstly, to lengthen the life of your backup pads, practice proper sanding techniques and routinely clean your backup pads well.
With vinyl face pads for PSA/sticky back discs and sheets, make sure to clear the adhesive residue each time, and clean it well. While cleaning will help, any residue left on the pad will cause an uneven sanding surface, meaning, the next sheet/disc will conform to the unevenness underneath – leading to sanding issues. In addition, take note for other signs of damage on your pads, such as torn edges.
When it comes to the hook face pads, excessive heat and overuse can cause the hooks to straighten out. When this occurs, your discs/sheets will no longer stay properly attached. The only fix for this is to change the backup pad.
Although time will vary between changing backup pads, and the best is to keep them well maintained, for heavy users, backup pads can be changed roughly every other month and lighter users may be able to go roughly 3-4 months between changes. However, make sure to keep an eye out for the signs and don’t be shy about replacing.
Clearly there is not much that is more frustrating when trying to get your sanding done than having a temperamental pneumatic sander. However, just as with our own health, prevention is the best medicine. When it comes to sanders, keeping them well maintained in the first place is the best way to ensure you’ll have reliable results every time. This means, keeping them well-oiled and clean/free of debris with a fresh backup pad and running them with the appropriate 90 PSI.
If you are a Uneeda customer and are experiencing another issue with your pneumatic sander, or would like to get a replacement backup pad, please contact your Uneeda rep.
If you’re not yet a Uneeda customer, but would like to know more about our air sanders, visit this page.