Kurt Hertzog gives his best advice on drilling better holes.
As woodturners we are often cutting holes, but there are many occasions where drilling holes is the method needed. Whether it’s a pass through for fasteners, locations for assembly dowels or one of the many other purposes, the ability to drill a proper hole is a skill.
In this two part series I’ll share with you 10 tips to creating drilling better holes.
Sharpness is paramount
Like your turning tools that will cut well and cleanly when they are sharp and properly presented, it’s the same with your drill bit. In this day of throwaway, few people outside of the trade have ever learned to sharpen a drill bit freehand. It’s that sad fact that ensures the drill bit purchased at the home centre will get dull quickly, and continue to be used regardless of the quality of the hole it cuts.
It will continue to be used until it becomes so woefully inadequate, but the turner rarely goes to purchase a new one to replace it. You will need a sharp drill bit to cut wood, plastic, metal or other materials – whether they’re new from the package or just re-sharpened.
The calibre of the drill bits available, other than the industrial trades, are so poor that two things typically happen: firstly, they don’t sharpen extremely well and even once it’s done to their best, they don’t hold a usable edge for long. In spite of that, don’t be afraid to learn to sharpen or, as I did, buy an inexpensive drill sharpening machine.
The home hobbyist versions are very modestly priced and it won’t take long before it has paid for itself. Now, a sharp drill is only a minute away. Like your tools, keeping an edge sharp is easier than sharpening, so don’t be afraid to touch up a drill after some use. It’ll be fresh and keen for your next needs.
Give your drill a good start
It may seem unnecessary, but I can’t recommend this more highly, create a starting location for your drilling. Are there times you might do okay without it?
Sure, but like any process, if you make it rote and do it as a matter of course, you’ll find the seconds it takes is shorter than thinking whether it is necessary or not. I give every hole I drill a starting location by using either a centre drill, spring loaded centre punch, prick punch, hammer or even a nail and rock. That impression in the surface allows the nose of the drill to seat a bit below the surface of the wood and begin drilling without wandering or skating.
Regardless of whether you use a pistol drill, a drillpress, your lathe, or other mechanics to execute your drilling, precisely locating your centre point and giving your drill the opportunity to get a good start will give you a better quality drilling.
Select the correct drill type
To say ‘drill bit’ really doesn’t narrow it down very much.
There are more types of drill bits than most of us are aware of. Like most of the tools, there is a reason for any particular style and type. Their design, size, shape, material, sharpening characteristics, length and more are all for a purpose. Most of us will be using the standard jobber length-type twist drill in either 118° or 135° nose angle. These in either angle will work quite nicely for our typical needs.
For most holes of a quality nature, you’ll need to use a twist drill or Forstner bit. Spade bits are inexpensive in the larger sizes, but they cut a brutal hole. Carbide tipped drills aren’t needed for wood and will not take as keen an edge.
Besides, sharpening carbides requires a special wheel. Titanium Nitriding (TiN) is a wear resistant coating applied to cutters in industrial applications to extend life between changes, which is a ‘not needed’ capability in our type of applications equidistant between the wing cutters. Not a good recipe for straight tracking of the drill.
If you buy and use bradpoint drills, be certain the centre spike is truly dead centre and accept the fact that you probably won’t be able to sharpen the drill. None of the drill sharpening units I’m aware of will deal with them. Getting good quality, high-speed steel twist drills will serve you well unless you have very specialised needs. Getting good quality, high-speed steel twist drills will serve you well unless you have very specialised needs.
Bradpoint bits are nice for cutting into face grain, but have little benefit in drilling the end grain. Most bradpoints I’ve seen are so poorly ground that the centre point isn’t even.
Use appropriate speeds and feeds
You’ve certainly heard the term ‘speeds and feeds’ from me before.
It is the catch-all term that says, how fast are you turning? And how hard are you pushing? It applies to nearly any kind of cutting, and drilling is a perfect place to use it. The rpm you select to drill is based on two key items: what is the material being drilled? And what size is the hole being drilled?
Denser woods require a slower speed, and less dense woods can be drilled at a higher rpm. The size of the hole also has a huge impact on your rpm choice. A 3mm hole can be drilled at a fast speed, while a 25mm hole needs to be slowed down. It is simply surface feet per minute (SFPM) at the outer edge of the drill bit.
The SFPM of the 25mm drill is far higher than that of the 3mm drill running at the same rpm. Good technique for drilling involves getting the hole centre established using a start point, advancing the drill to just touch that location and get properly located. Apply some drilling force, drilling slowly enough to avoid chatter and breaking the chip.
Breaking the chip involves relaxing the drill forward force a bit to let the chip break and exhaust out of the flutes. This process is repeated until near the breakthrough point. At that point, relaxing the forward force will provide a better-quality hole at breakout.
If the exit hole size, shape and quality are key, they provide a sacrificial backing material to support the material being drilled as you break through, even with your relaxed pressure. Some other helpful ideas for minimising destruction of the entry or exit surfaces are using packing or painters tape over the wood. These can help minimise damage when combined with a backing material.
Eject the chips
The only spot that really does any cutting work is the two edges at the nose of the drill. All else involved is solely as a support mechanism. Those sharp cut edges that twist up alongside the flutes are there as part of the process of making the drill flutes. The flutes, their design and their functionality are exclusively known for getting the already cut debris clear of the cutting edges so they can continue to cut.
Depending on the species, drill size and technique, you may have a nice, continuous exhaust of cut material from the flutes. This is especially true with proper breaking of the chip. If you don’t have debris being thrown from the drill flutes as you drill, retract the drill, turn it off and clean the flutes. Many times, the flutes will become clogged with material and not continue to self-feed upwards and out.
If you continue to drill with the flutes plugged, you’ll negatively impact the quality of the drilling. Not only will things overheat and probably smoke, but you will have debris preventing the cutting edges from working correctly. It only takes a moment to stop and clear the chips. There are some species where it needs to be done repeatedly. Take the time to do it to drill the best holes possible.
Summary
These tips make a good foundation for drilling better holes. Remember to choose the right drill bit for your material, and keep them sharp with regular maintenance. In part two I will continue to talk about how to drill in different materials, and share more tips and tricks that I’ve learnt from my many years in woodwork.