in woodworking drill bits are for small holes usually up to a half of an inch and larger holes are usually bored with hole saws or spade bits or forstner bits we can make a whole video about when to use one of these over the other because there are times when i prefer a hole saw or even a spade bit but most of the time i prefer forstner bits because they cut cleanly with less tear out they leave a nice flat bottom if you need it they may be used to make overlapping or elongating holes or slots or you can use them just to remove waste around your joinery in this video i'll give you some tips and tricks that will help you get the best results from your forstner bits the most important feature of a forstner bit is its guide rim this is what severs the fibers around the perimeter of the hole to produce a clean entrance without tear out choosing the right guide rim can also help your bit stay sharper and last longer the most common styles are usually sawtooth continuous and wavy sawtooth rims produce less heat because only the points of the teeth cut into the wood around the perimeter of the hole this means that you can run a sawtooth bit at a slightly faster speed and cut a little more aggressively with it without overheating and dulling your bit but those saw teeth tend to chatter a bit or shift a little bit on the surface of the wood at the beginning of the cut and this may mar the fibers around the hole sawtooth also make it more difficult to work at an angle and they produce a rougher cut when boring overlapping holes continuous rim bits solve many of those problems they sever the surface fibers and enter the cut more cleanly and they perform well for angled boring and for overlapping holes but that continuous rim does generate more heat especially on larger sized bits so you really have to watch your speed and not be too aggressive with the continuous rim bit or you may dull it quickly wavy rim bits are my favorite because they bridge the gap between the aggressive friction reducing teeth of a sawtooth bit and the crisp cutting knife-like edge of a continuous rim bit wavy rim bits produce clean holes in pretty much all situations they also seem to better break up the chips within the hole so they may be ejected more efficiently to further reduce heat build up i'll link to the wavy rim bits i prefer below this video but regardless of the rim that you choose you do have to slow your drill speed down when you use larger bits your drill press should have a speed chart under the belt cover if not take a screenshot of this one and print it out if you're working with a handheld drill use one that has a variable speed feature keep in mind that partially pulling the trigger may slow down the bit and help keep it cooler but it can overheat your drill motor so give your drill some time to cool off every few minutes keeping the hole free of chips will also keep the bit cooler so make it a habit to raise it up out of the hole from time to time to help clear those chips another key feature of a forstner bit is that spur point and you can use it to your advantage in several ways for example you may be boring a hole that will be seen on both sides of the work piece to be sure you don't just force the bit through and blow out the fibers on the back side as it exits slow your cut as you near the bottom of the hole and stop just as the point of the bit protrudes from the other side this isn't difficult if you pay attention then flip the work piece and you can use that little hole on the back side to locate your spur and finish from the opposite direction suppose you need to make an existing hole larger how do you center a large forstner bit over a smaller one one way is to place tape over the hole then use the center spur of a bit that matches the whole size to puncture that tape now that you've located its center point you can bore a larger hole over it with your larger bit this method works best in a drill press that can keep the bit from drifting as it enters the cut with nothing but tape to keep it centered with a handheld drill i recommend another method which is to bore a hole with your larger bit in a scrap of wood then use the tip of that bit to center the scrap over the original taped hole clamp the scrap down and it will guide your large bit as you re-bore over the smaller hole a similar tip applies to any time you use a forstner bit with a handheld drill since it can be difficult to keep a bit from shifting and marring your work piece as it enters a cut you might first bore a hole in a scrap then clamp it on your work piece as a guide for boring the hole that really matters this will also help support the fibers on the surface of the wood and create a tear out free hole very large bits can be especially challenging to handle in a hand-held drill they may bog down your motor or they can catch and jerk the drill from your hands consider stepping up your cuts to reduce the workload on a large bit this involves boring a small hole stopping just as the point exits the back side then flipping the work piece and using the larger bit to remove the rest of the waste in the opposite direction this process of removing the bulk of the waste with a smaller bit can also keep the large bit cooler after all large bits are not only more prone to building up heat but they're also the most expensive to replace when they get dull i hope these tips help you get better results from your forstner bits and save you some money by keeping them cool and sharp for a long time see you next time for the last several years i've been replacing my cheap drill and forstner bits with quality bits from fish tools they're a family-run company that still forges their bits the old-fashioned way try replacing your most used bits with fish bits using the links in the notes below this video and you'll see why i love them so much
