Drill Bits For Metal
Drilling through metal can be daunting enough. But when you go to choose a drill bit for metal and are faced with a sea of choices the job can seem very confusing.
There are many drill bits on the market suitable for drilling metal ranging from basic HSS (High speed steel) drill bits to solid carbide and many in between including diamond coated and carbide tipped.
Many of the metal drill drill bits are best suited to either specific metals or particular processes. Cobalt drill bits are generally the preferred choice for drilling hardened metal or stainless steel as it performs the job well and at a reasonable price. Although Solid Carbide drill bits will drill harder metals they are very expensive and can chip easily.
Common Metal Drill Bits
Because many of the metal drill bit types are for speciaist jobs or are best suited to use in a very controled applications we will not be covering them in this article. We will however explain briefly the difference between 5 of the common metal drill bit types used by both professionals and home improvement enthusiasts. Hopefully this will allow you to decide which is the best drill bit for your current application.
5 Popular Metal Drill Bits
1. HSS (High Speed Steel)
HSS or ‘High Speed Steel’ drill bits are considered entry level drill bits for metal. They are made from a tool steel and can drill mild steel and softer metals. They are not suitable for drilling harder metals or stainless steel.
2. Black Oxide
Black Oxide drill bits are essentially HSS drill bits which have been subjected to heat. This gives them the black ‘oxide’ coating. Similar to standard HSS metal drill bits these will drill milder steels and softer metals. The black oxide coating gives a degree of corrosion protection and extends the life of the drill bit somewhat.
3. TiN (Titanium Nitride)
Nitanium Nitride drill bits are HSS drill bits with a coating of Titanium Nitride. They are capable of drilling milder steels, Magnesium and iron. The coating increases the life of the drill bit. However as with any ‘coating’ once it wears off the benefits it provided will be gone.
Cobalt drill bits are a mix of metals plus either 5% cobalt (M35 drill bits) or 8% cobalt (M42 drill bits). The addition of the cobalt allows for the drilling of hardened metals and also stainless steel. Although 8% cobalt drill bits will drill harder metals than 5% cobalt drill bits it is important to note that the additional cobalt makes the drill bits more brittle. It is for this reason that 5% cobalt drill bits are often favoured. Coablt drill bits unlike coated drill bits can be sharpened.
5. Solid Carbide
Solid Carbide drill bits are capable oif drilling most metals. However they are extremely expensive, can break or chip easily and are only available in certain sizes and from from specialist stores.
Which Drill Bits To Choose
In deciding which metal drill bit you choose you will need to consider a few factors.
The two most important factors to consider should be:
1) Type of metal you are drilling
You may not always be able to identify the metal you wish to drill. However it is worth trying to find this out as it could prevent you spending more on a drill bit or drill set than you need. On the other hand if you know you need to drill stainless steel you will be aware that you probably need a good set of cobalt drill bits or better.
2) Type of drill you are using
If you are using a pedestal drill in a workshop you will have great control of stability, alignment and also probably speed. This should reduce your fear of braking or chipping some of the more expensive drill bits like 8% cobalt or Carbide.
Other obvious factors will include your budget and how often you intend to use your metal drill bit or bits.
Taking Care of Your Drill Bits
Once you have bought your drill bits there are some measures which you can take to protect them and extend their life. By employing the following guidelines you should prevent unwanted damage to your drill bits.
- Always use a metal cutting paste or lubricant when drilling metal
- Drill at the correct drilling speed or if in doubt drill at a slow speed
- Only use required pressure
- Drill in stages and allow short breaks between drilling sessions
All of the above are designed to prevent excessive heat build up which is one of the major contributors to drill bit damage.