Moving too slowly while sanding will leave lines on both sides of the sanding path. Adjustments to your sanding speed should be made accordingly. Sometimes a new drum's edges are not beveled. Beveling the edges is a simple cure.
Reasons You Get Swirl Marks Using Random Orbital Sander
You're using the wrong technique. The sandpaper you're using is of low quality. The sander is malfunctioning. Dust and debris are clogging up your random orbital sander.
Bad sandpaper alignment, uneven wheels, incorrect drum pressure, imbalanced drums, loose V-Belts, failed bearings, or even poor subfloor construction are all common issues that could produce chatter marks on the floor.
Here are a few things you can do to counteract the excessive heat that causes burn marks: Finer grits require a reduced depth of cut. If you need to remove more material, switch to a coarser grit. Also, at slow feed rates, finer grits could start to burnish the wood, causing heat buildup.
Most times, I have either 80 or 120 grit paper on the drum. This grit is perfect for removing milling marks from the planer. And although I recommend against heavy thicknessing, these lower grits will certainly allow you to sneak up on the exact thickness you are looking for.
If wood gets over-sanded in one spot, it starts to become uneven, with a distorted sort of appearance. This can happen to even the most experienced woodworker. Usually this starts simply by attempting to sand out a discoloration, defect, scratch or gouge.
Be sure to only sand as much as is required to get the wood nice and smooth again. If you sand off too much wood, your grain might pop again when applying the finish. Once you've popped the grain and re-sanded, you're good to apply your finish.
How will I know when to change the abrasive? The abrasives we sell at Pete's have very distinct lifespans; drum sander belts should last between 250 and 300 square feet each and edger discs should be changed every 20 linear feet.
Wipe With a Clean White Cloth
Use a clean cloth to wipe the rest of the dust from the surface of your wood after using specialized equipment. This helps you pick up any extra dust particles to ensure the wood is clean and ready for stain or paint. Use a white cloth so you can see how much dust you pick up.
Sand closed grain woods with no finer than 180-grit. Sand open grain woods with 120-grit followed by 150-grit, then 180-grit.
Fine grits close up the pores of the wood, so if you sand to too fine a grit, less finish will soak into the surface. Generally, if you're using an oil or clear finish, you can stop sanding at 180 grit. Continue on to 220 grit if you're using a stain or dye.
Wet sanding is a sanding process that uses water or another liquid as lubrication to wash away grit particles. Without the liquid, the sandpaper can build up with material, causing scratches that ruin the finish. In general, the best liquid to use for most materials is water with a little bit of detergent in it.
Wet sanding is a process where we use special sandpaper that is supposed to be wet with water. Very wet. The water acts like a lubricant plus helps remove tiny particles so that the sandpaper does not get clogged and create deep scratches.
These back marks are called metallic discoloration, or iron stains, caused by elemental iron reacting with phenolic chemicals in the wood, forming black iron tannates. Iron stains require the presence of iron, water, and wood and will not occur if one of these elements is absent.
To remove deeper burn marks from wood, scrape away the burned material with a utility knife and sand it down. Then, fill in the gaps with wood epoxy and apply a stain or paint on top to blend the repaired wood in with the rest of the finish.
Use a 200-grit or 220-grit sandpaper (the finer the better) and remember to be super gentle when sanding at this stage, especially if you don't burn very deep. If you have any shading or surface burn lines, they may come off, so really; go light and slow here. Watch how I sand my wood slices before I burn on them!
18" drums should have a motor running at 1725 RPM (the balanced drive system will cause the speed to encrease to 2250 RPM). the 24" and 30" drums require a 1/2 HP motor running 1725 RPM. Under NO circumstances should the 24" or 30" drums run any faster.
For a floor in better condition, you should get three P80 grit sheets. These numbers are for an average sized room, so if the room is exceptionally large, you should consider increasing the amount of sandpaper to four or five sheets.