Wood Finishing
Wood Pre-Finishing
Post assembly the real work starts what I so called in beautification which goes along with the characteristics of the wood. It is so important to understand this beautification in the context of nature of wood, that one may make or break the efforts been spent to bring wood from its basic state to semi-finished product. This last leg of generating best possible value out of wood is an important stage. The finishing of wooden product requires a unique skill to understand the nature of wood, usage of wood etc.
The important feature of bringing finishing coats to the wooden product is to protect the wooden products/surfaces from external environments. Finishing of wooden products/components contributes towards 5% to 30% cost of the finished products. Finishing being a final stage of production in woodworking industries, this gives wooden components/products desirable characteristics with required durability, enhanced appearance, increased resistance to moisture and environmental agents. Finishing influences other wooden properties such as hardness in wooden flooring, tonal qualities of musical guitar etc. Finishing also enhances the intrinsic value of the wooden product where it can turn a normal wood into a high-value final product.
Though finishing is the last stage in woodworking, planning for finishing should start way before we start manufacturing. The design phase of every woodworking product should identify all available finishing options for a final product. The factors contributing to wooden product finishes are attractiveness at given price, performance and durability in usage and safety and environmental requirements. Wood being designed in the different way for different products it is important to understand the focus areas in such products ex. – round/curvy edges in case of furniture’s, inner areas in case of musical instruments. Finishing should bring strength to the wooden product by ensuring design and joints should not open up in service and crack the overlying finish.
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Wood Filling
The wood filling is being done post assembly to cover up the small hairline cracks, nail holes, knot areas to achieve a good quality streamline finishing. The filling is an essential part of the final step in getting a right quality of finished products. By its nature, wood tends to leave small hairline cracks or knots like areas during its final stage. Those are unavoidable and good to identify during finishing stage of the product.
We have multiple options for filing available such as paintable, stainable, water base, epoxy etc. The filling material in wood depends on factors such as the type of wood, usage of internal or external. The usage area of the final product decides whether we paint the wood or stain the wood. If we decide to use wood internally and paint the finished product the fillers may be water or oil based. Usually, the fillers are overfilled on the area which will shrink down and leveled up by sanding the filled-up area. To make this filling more efficient, sometimes sawdust will be mixed with the glue to have an efficient color match and bring extra strength into the filling. A mixture of sawdust and glue mixed up together on the crack which will force this mixture to sink up inside the crack. Post which a sander will be used to level up the area which will disappear the affected area on wooden surfaces. The sawdust of same wood will help to stain the filler naturally which eliminates the use of specific pigments to match up the wooden color.
In other cases, to stain a specific wood we need to have a stainable filler which may be solvent base or water base. A pigment needs to be mixed with these natural color fillers to match up with the wood color for consistent finishing. We also have oil based paddies available in the market in different final color which can be mixed together to achieve the desired color.
For a comparatively bigger crack in wood and if the final product is being used in the interior area of the home, we may use auto body filler. In these cases, the final product must be painted instead of natural polishing. The reason we need to use auto body filler for interior products is, auto body fillers don’t expand or contrast with wood which brings up the possibility of the possible break due to misalignment with wood. Interior wood moves or varies very less with an environment in comparison with the exterior wood which is directly exposed to the external environment. For interior products with the paint can be filled up with PVC based fillers. These fillers come in a nicely packed huge injection type of equipment’s which upon injecting mixes two internal components together to fill up an affected area on wood. All such fillers are filled above the surface area to allow them to sink in the wood which then will be removed/leveled using sanding machines.
My recommendation for filler in natural finishing and for exposure to external environments is to use epoxy based or synthetic latex wood fillers. These fillers are used to fill cracks, holes, and surface imperfection. It is a smooth, buttery paste that spreads and feathers easily and dries to match the most light-colored wood. Interior/Exterior Wood Filler can be sanded, stained, painted, varnished, drilled, nailed, and screwed. It will not shrink or crack up to an 18 mm (3/4”) application. Interior/Exterior Wood Filler has a low odor and wet product can be easily cleaned with soap and water. It is weather proof and mold and mildew resistant.
Sometimes the filling may need to be done post sanding and buffing activities over the assembled product. Sanding done at 150 grits or above have high chances of small damages at the edges of wooden components. The paste fillers which are made smooth, creamy batter mixed up with right base either water or solvent. The density of mixer depends on the open pores, length/width/depth of the crack in assembled product. The wider the pores/gap, thicker will be the mixer. Usually, the mixer is being applied with the brush of blades specifically designed for the same purpose. The advances chemicals are available in injected tubes which can be applied directly as needed.
Water based fillers are quick to dry in comparison with the solvent based fillers. The filled area should look clean and along the color of the wood. The dull haze spots are a result of non-removal of excess filler from wooden surface. Sanding must be done to remove these dull haze effects and to prevent clouding in finishing.
Using router is one of the essential process steps to get the finished product just before final finishing. The sequence of routing process in relation to Sanding and Buffing processes may vary depending on the final product and organizational preferences. I personally prefer sanding done before routing and then buffing of the product. Post routing, some of the wooden edges may chip off which required being filled in before final finishing. The filling after routing demands manual sanding and buffing with sand papers which again depends on the design and complexity of routing area.
Routing in majority used to shape up the internal sharp edges of the final product. The external sharp edges may be shaped up on Spindle Molding as needed. The routing machines are available in the market with various capacity and capability. The newly designed and invented CNC machines are used in the mass repetitive production of same/similar components and final products. Routing machines are used to put the internal groove on wooden panels as a design on the panels. The size shape and design of routing bits are different based on different design needs in final wooden components or products.
For usual routing machine, the subject is usually static where routing machine will be moved along the edges of the wooden product. The routing machine usually moved by two hands where operator ensures all safety majors which includes the pair of hearing and eye protections prior to operation. The router bit which needs to be installed into the collar of the router upside down. One of the important safety aspects again is to ensure router is not yet plugged into the power socket. Some of the routers come with very sensitive on/off switches. Usually while locking a router bit into router collar a space of coin or normal size of the washer is kept between collar and router. This will ensure an expansion in router due to heat is considered while into operations. Height adjustment is an important aspect in all these punch routers. Most of the punch router comes with a height adjustment pins along with a movable truant at the bottom of the router. The recommended approach to set a height of router is to use the locking lever which comes with most of the new generation routers. To set the right height of router depth is to drop the router down to the required depth, lock the lever where router stays in that position. Post locking router at the required depth set the adjustment pin on the front at the required height and lock that pin to height locked by the lever. Post locking pin at the front of the router, release the locked lever at the back of the router. This way when we start the operation, the depth of router will be restricted to the height set at the front pin.
While starting operations on wooden edges, it’s always recommended to start with the edge grains first because at the start bit is going to blow out or tear out the wood. Edge of the Wood grain is the right area where tearing of wood will not impact much on the finishing or designing of the final product. The direction to push router on the wooden edges is very important while operating routing machine on wood. Every routing bit has a face and a back which repeats twice in a bit. The face of router always wants to get pushed into the wood. Usually, from router machine, we know the direction in which router is traveling which determines the face of the router which is going to push against the wood.
Router bits come in various profiles which need to be determined based on the shape of the cutting edge. Straight router bits are used to do grooves or dados. They also can be used on wooden surfaces for mortises and decorative inlays in the variety of sizes. Routing bits are guided by the pilot bearing at the tip and which can be bought along with routers in different diameters and thickness. Rabbeting router bits are used for designing various shoulders in different sizes. Flash Trim router bit is used to make the edge of one material even with the edge of another. We use this sort of bits to trim laminates plus the material underneath. These bits are used to route multiple identical pieces with the same pattern. Flush Trim bits come with a pilot bearing which usually of the same diameter as that of the bit cutter. Edge forming bits come in different profiles and are used to cut a decorative edge. These include Chamfer bit, Round-over Bit, Ogee bit, Edge-bidding bit, and Cove Bit. All these bits come with a pilot bearing on top of the bit cutter. There are also verities are bits manufactured for special applications. We can use sections of multi-profile molding bits to cut different decorative edge patterns. By using Rail and Stile bits and Panel raising bits we can build small door panels.
Some of these routers are comparatively larger which is recommended to be used in table routers. The router shanks come in two sizes, ¼ inch & ½ inch. Most the routers come with collar suitable for these two sizes. Whenever possible it is recommended to use a bit with ½ inch shanks, they will give less vibration and produce smoother cuts. Most of the routers have solid carbide tip cutters which are harder than high-speed steel and holding edge lot longer. But they are also more brittle which needs to be handled very carefully. A drop of the router on its carbide tip cutter’s edge may result in damaging in carbide tip. High-quality routers come with carbide blades which are sharpened with diamond abrasives. The router bit must be precision balanced to avoid unwanted vibration which results in uneven cut and maintenance of routing machines. High-end routing bits comes with Nonstick coating at the back face of the bit to prevent resin build up.
For best Quality fully finished solid wood Doors & Windows
Sanding is an important element of wood finishing. Sanding is carried out before final finishing of the wood to remove uneven or unwanted small layers, strains, or defects. Sanding will remove an adverse effect on the appearance and performance of finishes that are subsequently applied to the wood. The defects may be due to cutter marks, burns, scratches and indentation, filler spots and raised grains. The planner ripples, joiner ripples are visible in an assembled product which needs to be removed through sanding prior to polishing the wood. Sanding cannot be used in replacement of wood planing or thickness planer.
A sanding schedule usually begins with sandpaper that is coarse enough to remove larger defects (typically 80 or 100 grits), but sometimes higher if the surface is already quite smooth), and progresses through a series of sandpaper grades that gradually remove the sanding scratches created by the previous sanding steps. A typical sanding schedule prior to wood finishing might involve sanding wood along the grain with the following grades of sandpaper, 80, 100, 120, 150 and finish with 180 and sometimes 220 grits. The precise sanding schedule is a matter of trial and error because the appearance of a sanded surface depends on the wood you are sanding and the finish that will subsequently be applied to the wood. According to Nagyszalanczy, coarse-grained woods with large pores such as oak hide sanding scratches better than fine-grained wood and hence with such species it may be possible to use 180 or even 150 grit sandpaper as the final step in the sanding schedule. Conversely, sanding scratches are more easily seen in finer grained, harder woods and also end-grain, and hence, they require finer sandpaper (220 grit) during the final sanding stage. The sandpaper selected for the final sanding stage affects the color of stained wood, and therefore when staining is part of finishing avoid sanding the wood to a very smooth finish. On the other hand, according to Nagyszalanczy if you are using an oil-based finish, it is desirable to sand the wood using higher grit sandpaper (400 grit) because oil tends to highlight sanding scratches. Similarly, for breaking an edge i.e. to have around edges of wooden component a higher grit sanding paper is recommended. The rounding edge is required when we need to have a final polishing material required to stay on the wooden edges. For plywood and veneer’s sanding with 220 and above grits are recommended.
Below are different variety of Sanders –
1) Orbital Sanders – The pattern of the pad on the bottom of the sander does little tiny circles. The part of the reason this is not so favorite is because some of the circles within sander pads may be going against the grains of the wood.
2) Finishing or quarter sheet sander – This sander goes in only one direction. The pad of this sander goes back and forth only in one dimension with the grains. These are not widely used in market being legacy or out of technology sanders.
3) Random/Orbital Sander – Instead of making circles it does a random pattern where it starts to make a circle but then moves out. With these kinds of Sanders, it is very difficult to see consistent sanding patterns. The pads in these sanders are easily replaceable in comparison with previous two Sanders with the availability of multiple grits in circle pads. The sanders work well with flat grains.
4) Belt Sander – If we have a very rough surface or if we need to take off a lot of material from the wood surface a belt sander may be the best choice. A variety of width are available in these belt sanders, few are available in 2.5-inch & 3-inch width. These sanders work well with flat grains or edge grains as they took off lots of material. We must be a bit cautious in operating with these sanders as sometimes they can be too aggressive. If we don’t hold them flat, if they rock just a little bit, they can often damage the wood. So, we should be very careful in using belt sanders.
5) Surface Sander – These are advanced sander with static sander with a conveyor which will feed the object below static sanders. At a times, depends on the object we are manufacturing the width of the object may be bigger than the actual surface sander. We should be cautious in these scenarios where the object needs to be fed twice ensuring that both top and the bottom surface of the object are flat and we do not have any joinery misalignment in feeding through these sanders. The Sanders have a width running from 19-inch to 36-inch.
6) Drum Sander – These sanders are mainly used in plywood industries, where a wider plywood needs to be surfaced out with bulky production quantity. These sanders are specifically designed with automated feeder and height adjustments which need to be equipped with the right belts for consistent plywood sanding.
7) Floor Sanding – These are the Sanders with a capacity to roll on the floor as these are mainly used in sanding wooden floors. We have almost similar varieties in these Sanders as component sanders. The advanced Sanders have a control panel in the hand grip of these sanders.
a. Drum Sanders – These sanders have an inbuilt drum inside of the floor sanders. These sanders move in a direction where a replacement of paper should be done in the same direction. The control panel of these sanders is on the removable handle of these sanders. These removable handles bring more efficiency in transporting these heavy Sanders from one place to another.
A good quality finish in woodworking can make or break the wooden product. The precision in woodworking is been bought by the enhanced machine working on wooden components and final products. Applying a superb finishing technique will enhance and raise the overall perception of the product. Very few manufacturing companies engage themselves in using buffing technology to bring good finishing to wooden products. The overall color, texture, character, figure, stroke etc. in the wood will be enhanced by using buffing technique prior to final finishing on the wood. Wooden products color, texture, luster, and finished tactile surface quality all combine to produce the intended perception of a final wooden product. No matter which final finishing products we use, buffing will enhance the look and feel of wooden products. The purpose buffing is to bring an enhanced finishing on the wooden surface, hence buffing should not be used for removing uneven wooden surfaces. Buffing must be done only post sanding where the wooden surface is fully flat to the final expectations.
There are various tools available for buffing in current enhances manufacturing world. The dedicated buffing equipment’s offer the option of varying speed of the buffing wheel in use. The same machine can be used interchangeably between sanding and buffing as needed. Dedicated buffing wheels are used with electrical variable speed polisher. The polisher needs to be attached with a rubber based backing pad to which buffing disc can be mounted for flexibility in buffing on wooden surfaces.
A general buffing technique used in a larger area is an overlapping pattern. In the overlapping pattern, the initial step is to move buffing machine in the horizontal direction. Following which buffing machine will be directed in the vertical direction. The buffing pads manufactured with woven microfiber structure quickly clean and remove scuff marks and enhance the overall wooden appearance. Buffing pads which come with web construction mean these are washable and reusable. These pads resist clogging and loading. Comfortable fiber provides maximum pad to floor contact. Quickly cleans and remove stuff marks and enhance overall wooden finishing and appearance. These buffing pads enhance the grain structure by reflecting it nicely on the wooden surfaces.
Buffing product prior to final finishing is one of our key winning edge in delivering a high-quality product.
