I don’t trust people who like sanding. To me, that’s a sure sign of a serious character flaw. I’d rather clean a public toilet than spend a day sanding. That’s the truth, and I’ll bet there are lots of woodworkers out there who would agree. It pays to sand as little as possible then, right?
Sanding is almost universally viewed as a necessary evil, so it makes sense to sand as little as possible. Any bonobo can rub rough paper on wood, but there is actually quite a lot going on between the sandpaper and the wood. If you become knowledgeable about sanding, you will find it is less painful and your results will be much better. Win-win.
Equipment
First, buy good sandpaper. Reasonable people don’t expect a $20 plane from Lowes to perform like a $300 plane from Lie-Nielson. Same for sandpaper. I like 3M Pro Grade No-Slip Grip. This paper cuts fast and lasts a long time. The backing is almost as tough as fabric. The no-slip grip has pros and cons. It’s really nice if you do a lot of fingertip sanding. If you do a lot of profile sanding with folded sandpaper, the heat generated from sanding will glue the paper to itself. When attaching this paper to a block, you must be careful that the tacky backing doesn’t pick up any debris that will create a high spot on the block (and a low spot on your project). These characteristics are easy to get used to. Bottom line- find a high quality sandpaper you like and lay in a lot of it.
https://www.amazon.com/gp/product/B00M12MTGI/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
Next, get the right sanding tools. Make or buy good sanding blocks, good profile sanders, and make or buy a good sandpaper cutter. Invest time and effort in eliminating fuss and drama around sanding and it pays big dividends when you’re sanding your way down the home stretch of an exhausting project. My favorite sanding block is the Preppin’ Weapon, and I have four of all different colors. Yes, they’re expensive, and yes, they’re worth it. I load each of my weapons with 4 layers of sandpaper (a full sheet cut into 4 strips) so I can tear off a dull sheet and keep on sanding 4 times as long. Each of my 4 weapons has a different grit- 100/120/180/220- which is my preferred sanding sequence for most projects. Having all of my typical grits available at once adds a level of speed to the sanding process that rivals a power tool. In the photo you can see my four Preppin’ Weapons. There is also a shop made Melamine sanding block with cork on the bottom, a pile of rubber profiles sanders from Rockler, a couple pieces of PVC covered with self-adhesive sandpaper, and a strip of sandpaper with painter’s tape backing and a couple matchsticks to be used like a shoeshine rag. The tape mitigates tearing and the matchsticks enhance grip.
My sandpaper cutting station is as simple as it gets. I have a piece of ¼” MDF about 18”X18” to back up my cuts. I have another piece of ¼” MDF the exact width of a ¼ sheet of sandpaper and about 12” long I use as a template. I have a utility knife dedicated to cutting sandpaper (because it goes through blades fast). I align my template piece on the edge of a new sheet of sandpaper, cut it on my backer board, repeat thrice, and I’m ready to load 4 fresh layers of sandpaper onto a block. Simple, fast, accurate, dirt cheap and easy to store.
The Physics of Sanding
Like most woodworking, effective sanding requires a combination of knowledge and skill. Let’s begin with a little information about how sandpaper works.
Sandpaper is a cutter. It is made by gluing an abrasive material to paper. Each grain of abrasive on a given sheet of sandpaper is similar in size, and the number of pieces of abrasive in a particular area (like a square inch) establishes the “grit”. The lower the grit number, the coarser the paper and the more aggressive the cut.
There are two different grit scales- CAMI and FEPA. CAMI paper is marked with a “C” and FEPA paper is marked with a “P”. While it may be helpful to understand there is a difference, I am giving you permission not to care. Take a look at this chart and you’ll see what I mean. For woodworkers, there is very little difference between CAMI and FEPA at the grit grades we use. I think of CAMI like miles-per-hour and FEPA as kilometers-per-hour. The difference between the two is marginal at slow speeds. The faster you travel, the more disparate the scales become. The difference in grit size between C and P is marginal up to about 220, then things begin to diverge. The difference between 2000C and P2000 is almost 3X (P2000 is roughly equal to 700C). Now you know far more than you ever needed about CAMI and FEPA.
Sandpaper is self-sharpening. Each grain of abrasive on the paper is friable, and the grains are constantly breaking and revealing new cutting edges as the paper grinds against the work. Eventually, you exhaust the paper of cutting material and the paper stops cutting.
Don’t be fooled into thinking that sandpaper becomes smoother with use. Worn-out 100 grit paper does not effectively become 120 grit paper (or higher). You do not get smoother results from well-worn paper as if you changed to a higher grit. If you’ve done this (and I think we can all admit that we have), it is time to acknowledge that you were fooling yourself, like cheating at Solitaire. If the paper stops cutting efficiently, it is worn out. It has not become something different.
Take it easy. Using moderate pressure and a moderate pace will help get the longest life and best result from your sandpaper. The adhesive that holds the abrasive to the paper does not like heat. Heat will build up faster if you push hard, or use dull sandpaper, or sand at the pace of a twitterpated bunny rabbit. As with any cutter, let the cutters do their work and temperatures will stay low, grains will fracture, dust will clear, and you will sand away more stock in less time and with less effort.
The Sanding Process
There isn’t a great deal of skill involved in sanding, but mastering the basics takes much of the drudgery out of it. Sure, you need be able to hold a tool level and keep pressure even over the length of a stroke, but sanding is really more of a process than a skill. Like any good process, it needs to be followed. You can’t cheat the process without introducing inefficiency, frustration, and poor results. Honor the process and sanding becomes easier and the results are better. I’m not saying you’re going to love sanding. I wouldn’t trust you if you did.
In broad strokes, sanding is the process of removing mill marks and scratches on wood through the use of progressively finer grits of sandpaper until the project is smooth enough to finish. An efficient sanding process begins with the most aggressive grit necessary to remove mill marks reasonably quickly. Note I said mill marks and not defects. Chips, tear-out, dents and dings are better addressed before sanding. Sanding is rarely the best option for stock removal. Prep projects properly for sanding and the sanding process will go more smoothly (ha!).
Step One is to mark up your project with a pencil. I use a wide construction pencil and make a tight sine wave wherever I’m sanding. Starting with my coarsest grit, I sand until all of the pencil has been erased. Check for mill marks and if any remain, mark up the project and repeat Step One. I know I’m done with the initial grit when all mill marks and pencil lines are gone. Mark up the project with a pencil between every grit to manage your progress and minimize time and effort spent on each grit. If this is new to you, try it. I think you’ll be astounded at how quickly you can proceed.
My milling machines consistently deliver a surface I can quickly sand flat with 100 grit paper. Lots of folks start with 80 grit. The big grit paper is the workhorse. It is a fool’s errand to use finer grit papers to remove mill marks. Let the big workhorse do the heavy pulling and the journey through the higher grits to your final surface can be reduced, literally, to a few strokes of each grit.
Your project is probably at its least smooth after milling and jointing, so the bigger grit paper has to remove more stock before it reaches the point where it is reproducing the same surface as you sand deeper and deeper. Stop sanding as soon as the mill marks are gone (along with your pencil lines), joint seams are level, etc. The only work you should leave for the next grit is to remove the scratches left by the bigger, previous grit. The goal is the same for every grit- stop as soon as you have removed the scratches from the grit before, as indicated by the removal of your pencil marks. Eventually, the routine emerges: Mark the work with a pencil. Sand away the marks and stop. Clean the surface. Change to a higher grit. Repeat. Don’t skip grits. I’ll bet you’ll be surprised how little time and effort it takes to advance through the grits if you’ve done a good job at 80 or 100.
I usually take each surface, like the sides of a box for example, through all the grits I’m going to use before re-positioning the work and starting again. On some projects I sand the entire thing with 100, then 120 and so on. When that’s the approach, I always mark the next grit to be used on each surface so I don’t lose my place.
The work needs to be cleaned between each sanding grit. As you sand, the broken bits of abrasive get intermingled with wood dust. Realize that 100 grit abrasive is still 100 grit when it is fractured from the paper and mingled with wood dust. If you don’t clean all that abrasive off the work, then you will still be sanding with 100 grit abrasive bits when you change to 120, 180, 220, and so on. Put simply, if you don’t clean between grits, you aren’t changing grits. I use my shop vac with the brush attachment and thoroughly vacuum all the dust between grits.
I rarely need to start rougher than 100, and rarely exceed 220 on the smooth end, often stopping at 180 depending on the finish. It is a lot of work to advance through 4 grits of sanding, but each grit goes very quickly. For example, one side of a square table leg shouldn’t take more than 20-30 seconds of sanding at the 120, 180, or 220 stage. It takes longer to secure the work, mark it and clean it for each grit than it takes to sand it.
Sanding hard-to-reach surfaces is inevitable sometimes, but good planning goes a long way. Finish sand everything you can before you assemble parts that will render some areas hard to reach. Take care sanding around joinery before assembly so you don’t queer the fit or open a gap. One change I’ve noticed as I’ve gained experience in woodworking is that I do a lot of finish sanding just after joinery and before assembly, and oftentimes a lot of pre-finishing, too. Over time it has become intuitive and nowadays I rarely find myself trying to sand or finish inside small spaces. I’m also getting more intuitive about sanding some components before joinery, as some joints are more apt to get spoiled by sanding than others. A perfect dado joint can be rendered useless by a few strokes of the sanding block. Rabbets are more forgiving.
Sanding fancy profiles, edges and corners takes care so that you don’t break an edge you want to remain crisp. Even a fine grit can remove enough stock on an edge profile to make a once-stunning shadow line disappear. This type of sanding work is best done with profile sanders to back up your paper. Sanding blocks and holders are available in typical molding profiles, but it is also easy to make your own. Shop-made blocks work best with a semi-rigid backing like cork or leather. I keep a roll of real cork shelf liner in the shop for this.
Power Sanders
Sanding techniques change a little if you introduce a power sander. Power sanders include dedicated spindle sanding machines, drum sanders, drill press-mounted sanding drums and random-orbital sanders (ROS). I may get into sanding with other power sanders in future posts, but I’m only going to cover the ROS here.
An ROS is likely to be the first power sander most woodworkers acquire and for many, it is also the last. An ROS is very good at what it does and most woodworkers simply don’t need anything more. ROS’s are not the “jitterbug” sanders of old. Jitterbug sanders simply aren’t capable of producing the result you need for a fine finish. If you’re in the market, check the multitude of tool reviews available for ROS’s and get a good one. Quality counts extra when you’re doing finish work.
As the name implies, an ROS sands in random circular patterns. Sanding in circles obviously means sanding cross-grain half the time. ROS’s solve the problem of cross-grain scratches by making them too random and too fine for the eye to perceive. The randomness scatters light and tricks the eye into perceiving a smooth surface, but make no mistake, ROS’s leave circles and swirls and sometimes you can’t tell until you apply finish. Surprise!
Many woodworkers will use their ROS to work up to their last grit, then sand the last grit by hand to sand away the ROS’s circles and swirls and align final sanding scratches with the grain. This is a fair way to get the best of both worlds if you love your ROS.
As far as the physics go, sandpaper works pretty much the same whether you rub it against the wood by hand or by machine. Grains fracture and material is removed with successive grits until the desired surface is created for finishing. Paper wears out and must be changed. One advantage over hand sanding is that if you are using good dust collection, the ROS cleans as it goes. You can forego cleaning between grits, although a quick wipe of the hand is never wasted.
Sanding with an ROS takes more care than hand-sanding to protect the work from damage. These machines are powerful enough to seriously mess up a project before you can stop them. Here are a few rules that will help you sand effectively and safely with an ROS:
- Always start the ROS in contact with the work. Never drop a running ROS onto the work.
- Take care lifting a running ROS from the work. Lift straight up. Better yet, turn it off before lifting.
- Set the ROS aside on a safe, secure surface, or allow it to stop completely before setting down.
- Use dust collection with an ROS.
The jury is out whether using an ROS has any real advantage over hand-sanding. I used to believe it was a lot faster to sand by machine, but I have developed doubts after refining my sanding process. I have an ROS, and I use it based on the project. I’ll grab it to sand something big and flat like a dining table except, perhaps, for the final grit, but it isn’t a big deal to sand a large project by hand if you follow the process. I don’t like the noise and I always wear ear protection when machine-sanding. Machines do not perform elegantly like hand tools and I don’t find woodworking by machine to be as soul nourishing. If I sand up to an edge or inside corner with an ROS, I don’t like how much work is left to be done by hand and how difficult it can be to blend the work. On the bright side, I really like how clean it is to sand with an ROS. Bottom line, I judge an ROS to be a useful tool, but not critical. When I bought mine, I thought it was a borderline requirement to produce good results in a reasonable amount of time. Now, if I didn’t already own one I might think hard about making the investment.
Conclusion
I dislike this idiom, but sanding is what it is. Sanding is not sexy but fine finishes are, so maybe sanding is sort of like pregnancy. We aren’t likely ever to free ourselves from having to sand, but that doesn’t mean we are powerless to do anything to make it suck less. That’s why it’s worth it to:
- Better understand what sanding is and what it does.
- Refine the process and thereby, sand easier.
- Learn how to sand less (Yay!).
- Bring something beautiful into the world by sanding well.
Nice article. You might have given a clue to your age with the “shoeshine rag” reference.