Router Bit Care
In conversations with other woodworkers across the country I am constantly surprised by the number of problems they have with their routers that could be eliminated with some routine maintenance. Do away with problems caused by heat and dust with a regular maintenance schedule and your router will provide years of trouble free service.
Remove and clean the bearing
Scrub the bit with a brass brush
Sharpen the cutting edges
Tighten and lubricate the bearing
Lee Valley Bit Holders #16J03.61
DMT Diafold hone
As with many of the tools in a workshop, it is at the cutting edge where the actual work happens. When the carbide edges of router bits cut the wood (does anybody still use high speed steel bits?) they are subject to a build-up of pitch and resin. Certain woods, like pine, are worse in this regard than others and can gum up cutting edges after routing several dozen feet. Other species, such as oak or ash, may not noticeably affect the bit for months. As the pitch builds up on the bit, it will increase the temperature on the cutting edge and the body of the bit, and this begins the degradation of the bit. When the cutting edge loses its ability to remain cool in use, the carbide edge is placed under additional stress, and this will ultimately affect the integrity of the bit and the sharpness of the carbide edge.
If you are working with a piloted bit, one with a bearing on top, remove this bearing with an Allen key. Bearings are one of the first things to fail on a bit. They guide the bit along the edge of a work piece and must spin freely to avoid marking the wood. As the bit is used, minute particles of dust will get trapped in the bearing and will slowly reduce its ability to rotate freely. When the bearing spins relative to the wood along which it is moved, it will start to leave a faint shiny surface behind. If the dust prevents the bit from rotating it will leave a burn mark on the surface. Remove the bearing carefully as some brands have small brass washers or shims under them that can easily get lost. Place the bearing into a small sealable plastic container (my favourite is an old 35mm film canister), add a little Varsol, and then shake it vigorously for a few minutes. Remove the bearing from the solvent and place it on a piece of paper towel to wick out the excess solvent. I also use compressed air to blow out the bearing as well. Never hold a small bearing in your fingers and then direct a spray of compressed air at them, as this is a dangerous practice, instead, wrap the jaws of a cheap set of pliers with electrical tape to protect the surface of the bearing and then use this to hold the bearing when you blow it out. If you can’t restore the bearing to new condition using these methods, replace it with a new one. Before treatment with the Bostik bearing lubricant I can hold a bit by the bearing, and when I spin the bit freehand, it will make about 4 revolutions before stopping. After treatment and cleaning, the same bearing will spin at least a dozen times before stopping.
With the bearing removed you will be left with a solid bit of steel to clean. Several companies make proprietary cleaning solutions for edge tools and these can make the job easier. Products such as Blade and Bit from Boeshield (boeshieldcanada.com), and Freud’s Fresolv (freud.ca), are designed to dissolve the pitch and make it easy to remove. It has been common practice for some woodworkers to spray their bits and blades with oven cleaner and then to attack them with a brass brush. However, research by Freud has found that oven cleaners are very corrosive (you are not told to wear gloves during use to make a fashion statement!) and that it will degrade both the carbide edges as well as the brazing that holds the carbide to the body of the bit. Pay particular attention to the stud on top of the bit that the bearing mounts to and clean this area thoroughly. Be sure that there is no debris inside the threaded hole before you reinstall the bearing or you may never get it off again.
The point of contact between the router and the bit is the collet and shaft and these should receive careful attention as well. Any build-up on the shaft or on the collet will cause your bit to either slip during use or, more likely, to seize in the collet making it impossible to remove. Clean and inspect the shaft every time you change the bit. I use some cleaner and coarse steel wool to remove stubborn residue and just some medium steel wool in between major cleanings. Give your cutting edge a quick visual inspection every time you change the bit, but if you are doing a major clean up of your bits, inspect the cutting edges with a loupe. The loupe will magnify the edge allowing you to check it closely for nicks and dulling. If your bit has major chunks missing from the edge, then the damage may be too severe to repair by sharpening. For edges that are not badly chipped you can use a small folding diamond hone to dress the back (flat) edge of the profile. I prefer the Diafold hone, (leevalley.com), from DMT, (dmtsharp.com). This foldable hone has 600 grit on one side and 1200 grit on the other. A couple of stokes is all it takes. This diamond hone is meant to be used dry so there is no mess to clean up.
Reinstall the bearing and tighten the Allen screw completely. Check this screw after using the bit a short while to be sure it is still tight. Before using the bit, apply some bearing lubricant to the bearing if it has one. This lubricant will keep the bearing spinning freely without attracting and trapping dust, which will ultimately destroy it. I also spray my bits (and other cutting tools for that matter) with DriCote cutting lubricant. It does a good job of inhibiting glue, pitch, and resin build-up on cutting surfaces, and reduces cutting friction, and hence heat build-up.
Invest in some decent storage for your bits. Keeping them loose in a drawer is sure to damage the edges. Drilling holes in a piece of wood to store them is not the best option since moisture from the wood may cause corrosion on the shafts, which will ultimately cause them to stick in the collet. I prefer to use the composite bit holders available through Lee Valley that can easily be screwed to any surface where they are needed. Whether built into a cabinet or a wall, proper bit storage will safeguard your investment in these expensive accessories.
Whether your router is used free hand or used in a table, unplug it before performing any maintenance. As you unplug the router, inspect the power cord for damage. Look at the end and check each of the blades to be sure they are still firmly attached. If one or more is loose, or if you are missing the ground blade on a router that came with one, replace the end. Use a good quality cord end from Hubbell or Arrow Hart (westburnedirect.ca), that will stand up to the abuse it will see in the shop.
I can’t stress this point enough. If you have your router mounted in an enclosed router table you absolutely must have it connected to a decent dust collector or you risk shortening its life dramatically. When I designed and built my router table (Issue #47, AprMay ‘07) I contacted the product engineers at Delta/Porter Cable to confirm that the airflow I was allowing for would be sufficient to cool the big Porter Cable 7518 monster I was going to put in it. They agreed that it was critical that a table-mounted router be connected to a dust collection system and that it should not only draw air from around the bit, but also from around edges of the front door to keep the router cool. In practice, my enclosed routers are always spotless, free of dust and cool during use while the one in an open table is constantly in need of cleaning and runs considerably warmer.
Use your shop vac to vacuum any loose debris from the air vents at the top and bottom of the router. With the larger debris clear, use some compressed air with a precision blow gun to clean the fine particles from the router motor, plunge mechanism and collet. Dust on the inside of your router will reduce its ability to cool itself, which will raise its operating temperature. When dust builds up on the bearings they begin to have more resistance to rotation and this also builds up heat.
Most routers have brushes that are easily accessible through ports on the side of the router. A sure sign that your brushes are nearing the end of their useful life is the loss of power when the tool is used and excessive sparking visible from the motor area. Open the access covers and pull the brushes out. Inspect brushes and replace if necessary; the minimum brush length should be in your owner’s manual or available through the manufacturer’s website.
The collet should receive a thorough cleaning as well. Pull off the retaining nut and collet and drop them into a solvent bath. Use a brass or stiff nylon brush to scour the inside of the end of the shaft. Any debris in here will make it very difficult to remove the collet and bit. To clean the collet use a small brass or nylon brush on the inner section and then take some kraft paper (any paper shopping bag would be happy to help out) and fold a strip over lengthwise until you have something that fits into the gaps but still gives it a good scrub, and work it back and forth. After doing this, run the brush up the center to remove anything that may have been deposited in the center. Use a brush to clean the threads on the router and on the inside of the collet nut. For plunge routers, consult the owner’s manual for your specific model for instructions on how to clean the plunge mechanism. Inspect the bases for burrs that may mark the surface of the work piece.
The little bit of time spent on maintaining your router and router bit investment will pay off over the long haul in reduced down time, longer life and lower frustration.