4.2mm drill bit
If you are buying a 4.2mm drill bit for metal it is important to buy one made of the correct material.
Metal drill bits come in a large variety of options in terms of material they are made of.
You can choose from HSS, titanium, tungsten, carbide and cobalt, to name just a few.
Ultimately the type of metal you intend to drill and the amount of money you wish to spend will determine which you chose.
HSS (High Speed Steel) would be considered entry level and will drill through most softer metals without a problem. Carbide would be considered extremely expensive. But will cut through very hard metals. However they would be best used in a pedestal drill setup.
Are you looking for a high performance drill bit at an affordably price? Then cobalt is the way to go.
Cobalt drill bits contain a percentage of cobalt (typically 5% cobalt or 8% cobalt).
8% cobalt drill bits will drill some harder metals than the 5% cobalt bits. However they are more brittle. Therefore 5% cobalt drill bits are favoured as they will drill most metals including stainless steel with ease.
Conventional 4.2mm drill bits come in a length of 75mm.
However extra long drill bits can be got from specialist suppliers.
Drill Bit Size Comparison
4.2mm drill bit to inches
4.2mm is approximately 0.165354 inches.
If you are drilling though a metal with a 4.2mm drill bit it is important to drill at the correct speed.
A drilling speed chart will tell you the correct speed for the type of metal you are drilling. In addition it takes into account the size of the drill bit you are using.
Drilling at too high a speed will result in overheating and can make the drilling task harder and can even damage the drill bit.
You should not be overwhelmed by the speed chart. You will not be able to measure the speed your drill bit is rotating at unless you are using a precision pedestal drill. If you are using a hand drill it is advised to use one with a variable speed. And if in doubt start off at a slow speed.
When you buy a drill bit that has been certified by a testing agency you will be able to see the hardness it is rated for. Anything above a rockwell hardness of 63 is very good.
If you buy from a company which offers a 100% satisfaction guarantee then you know they can stand over their product.
When you are drilling any metal it is very important to use a metal lubricant. This can be either a liquid or a paste.
A good quality drilling lubricant will make the job of drilling metal much easier.
It will reduce friction thereby helping to prevent overheating. This will not only assist in the drilling but will also help increase the life of your drill bit.