Choosing the right sandpaper for your woodworking or metalworking operation can be difficult and recommendations can vary from person to person. There are some basics to keep in mind when determining what process might be right for you. Things you need to take into account are grit, grain structure, type of backing & what material. If you are woodworker or do any kind of wood fabricating and you want to learn a few of the basics of sandpaper as it pertains to your craft – give this article a read!
Know your grits
One of the most basic components of choosing the right sandpaper is figuring out what grit and grit sequence is right for you. Before you can decide the sequence it is first important to know what “grit” actually means. Grit is defined by the number of abrasive particles per square inch on any given piece of sandpaper. This also means that the small the number the courser and larger the grain particle is. For example – a 36 grit grain is much larger and courser than a 120 grit grain.
As a general rule of thumb, sandpaper is generally referred to as course between grits (24 – 80) , with medium being in the (80-150) range, fine being in the (180-220) range & Very Fine being in (240-280) range.
A normal grit sequence in wood fabrication for sanding belts will be grits 80, 120, 150 & finish with 180. Generally, from these 4 grits the woodworker or fabricator will then blend the finish with either a jitter bug or orbital sander using 220 grit. It is important to know that as you progress along your grit sequence from a courser grit to a finer grit what you are doing is removing scratches left behind by the previous grit. When hobbyists or woodworkers fail to properly blend in an even finish along the work piece, you will be left with ripples or an inconsistent finish when you go to stain the wood.
Grit Structure – Half Pregnant?
Lets break this down:
Closed Coat Sandpaper – This essentially means that a almost all of the surface area of the belt is covered in abrasive grains, with almost no space between grains. This obviously means that there is more grain on the belt which leads to longer life & more aggressive cuts. This should be the material of choice if you are sanding hard woods such as pine, cedar, douglas fir, redwood, ash, birch, cherry & mahogany. This is always recommended as well if you are working with metal.
Open Coat Sandpaper – Open coat sandpaper means that there is more space between grain particles on the surface of the abrasive sheet or belt. The reason why this particular material is engineered this way is because when you are sanding soft woods such as araucaria, cedar, celery-top pine, cypress, hemlock etc. is there is sap and wood debris that will clog the surface of the belt and the space between grains. This is problematic because as the space between grains gets packed with wood & sap the belt becomes a smooth surface prevent the grains from creating any grab or friction along the surface of the material you are sanding. We do stock open coat material and I recommend you give us a call if you think this might solve some clogging issues you are experiencing.
Semi-Open Coat – Semi open coat generally means that there is roughly 30% less grain on the surface of the belt. This is our standard material that you will find on our woodworking belt pages and we find that this is a great standard because it will fit almost all cases and still give great life.
I will never forget a conversation I had with our old Hermes abrasives rep back when I first started here at Maverick…I asked him do you have any products that are semi-open coat for wood? His reply was “there is no such thing as semi-open coat! That is like being half pregnant!” Needless to say he was wrong…kind of. While semi-open coat VS full open coat is largely arbitrary I will never forget his response & needless to say he didn’t last very long with Hermes Abrasives haha!
Types of Backings
Backing types can always be a confusing thing to someone unfamiliar with sandpaper. There are two main types of backings – Paper & Cloth.
Paper – Paper backings are generally most common on two types of products in woodworking, sanding discs & wide belts for timesavers. Paper sanding discs almost always will come in gold or white and are usually 5” diameter or 6” diameter with no holes or various hole patters, a common one being the festool hole pattern. One other important distinction that can be made here is that these discs can also come in two types of applications, PSA which means pressure sensitive adhesive (sticky back) or Hook & Loop (Velcro) which there are advantages to both.
Paper abrasive products can also come in stroke sanding belt form or more commonly for wide belts. The wide belt paper material we carry here at Maverick is widely regarded as one of the best woodworker paper belts on the market in the B317 which is manufactured by Sun Abrasives and is an E/F weight paper. Woodworkers generally go with paper wide belts for their time saver because of a few advantages: Thinner splice which means less chatter, Cost-effective (cost less than cloth), & the paper belt will leave a better finish on the final pass (Pro tip: Use paper belt on last head or last grit of sanding). Obviously the down sides of using a cloth X-weight belt is that they are more expensive & the splice will be thicker and can lead to more chatter issues, although it is still relatively uncommon.
Cloth – Cloth belts are by far the most common types of belts used in almost all industries such as woodworking, metalworking, glass fabrication etc. This is because cloth belts are made from a sturdier, more heavy duty backing generally made from a blend of polyester and cotton. Because of the polyester that is in these backings, these belts are very versatile and can be run in wet applications when warranted. Although you don’t see this in wood applications it is very common in metal fabrication. The advantage of having a polyester backing in woodworking is that you can power wash or clean your belts of any sap or debris that might be clogging your belts. This little trick will extend the life of your sanding belts by 15-20%…HOLY COW!!! J
Material – Aluminum Oxide? Zirconia? Ceramic?
Choosing between Aluminum oxide, Zirconia & Ceramic is rather straight forward. Since Zirconia and ceramic are hard structured grains and do not break down easily, they are almost exclusively used for stock removal. Zirconia and Ceramic are only available in grits 24, 36, 40, 50, 60, 80, 100 & 120. While zirconia and ceramic and not that common in woodworking & dimensioning, you do see it in some industries such as the particle board industry where large blocks of wood or particle board need to be ground down. Additionally – zirconia & ceramic will last longer for stock removal and generate less heat…thus less loading from resinous & oily wood as well as glue. PRO tip: you will have less of a chance of burning maple and cherry if you go the route of zirconia or ceramic on your grinding & timesaver operation.
Aluminum oxide is by far the most common abrasive material used in woodworking and depending on the operation you can use anywhere from 60 grit all the way up to 220 grit although if you prefer less aggressive line grains than a zirconia you can go all the way down to 24 grit as well. The reason it is so popular for woodworking is because of how well it fragments under heat and pressure in whats called “friability.” Chances are if you are wondering what material is the best for you in starting your woodworking project, aluminum oxide is the way to go.