Why Would That Be a Color Distinction Between Drills?

Jack Lie CNC machining expert

Specialize in CNC Milling, CNC Turning, 3D Printing, Urethane Casting, and Sheet Metal Fabrication Services.

Hole processing is an integral part of mechanical process that accounts for around 1/5 of its total CNC machining process, while drilling accounts for 30% of the entire process. When it comes to the purchase of the bit of drill, there are different colors, and to know if these colors influence any technicality of the bit or not, the following are the details:

Does Drill Bit Color Define its Quality?

Typically, colors cannot wholly describe the quality of the drill since colors only show the difference in the manufacturing procedure. However, a general judgment is easy with the help of color. But again, poor-quality drills can get treated to change their color and look like quality drills. So, drilling with in-depth knowledge helps understand if it is accurate or one with changed color.

Difference Between Various Colored Bits

High quality of drill is an excessive property of the material itself, and the quality of control process ensures the finishing of the surface avoids burning. Meanwhile, HSS (high-speed steel) bits are white and possess much better quality, and rolled bits are easy to turn into white with an outer round on the outer surface of the bit.

On the other hand, the nitride drill is black because of the chemical method of increasing the tool’s life and durability. The tool gets finished with the mixture of water vapor and ammonia after 550 degrees centigrade insulation treatment. Remember, most of the drills in the market are only black because they are colored black to look like nitride drills, but their quality is poor.

In the drilling industry, the cobalt-containing drill usually has a yellowish-brown color changed from the white color. In earlier stages, the color is white instead of yellowish-brown, but later, it changes its color to yellowish-brown (amber) due to grinding and atomization of the drill.

The next one is titanium plated drill, a type of M35 (Co 5%). Mostly, the applications of this drill get found in industrial and decorative plating. Typically, decorative plating is nothing other than being golden and lovely into looks. At the same time, industrial plating is excellent and possesses an improved hardness due to HRC78, higher than cobalt-containing drills.

How to Choose A Drill Bit?

Choosing the right drill is challenging since many copied and poor-quality drills deceive people. So, when you select the drill, the logo of the manufacturing company should be evident on the shank of the drill. Likewise, the marking of the diameter tolerance on the drill also helps you understand if the drill is worthwhile or not. Nonetheless, if the words on the drill’s shank are blurred, the drill is of lousy quality.

Secondly, the cutting tip of the drill helps ascertain the quality of the drill. Open edge and spiral face fulfillment are good quality indicators, while the lousy back corner face shows poor quality.

Simultaneously, white is generally a fully ground HSS drill and should be of the highest quality. And the quality of the drills of gold and black colors keeps changing.

Drilling Accuracy

Drilling accuracy gets determined by multiple factors like the size of the hole, roundness, accuracy, surface roughness, orifice, coaxiality, etc. Along these lines, here are the factors that affect the accuracy of the hole while drilling: cutting and accuracy settings of the drill (cutting speed, cutting fluid, tool holder, and drill bit), size and shape of drill bit along with its edge shape and length, and shape of the hole, its thickness, and other properties of the hole.

1. Reaming

While drilling, the oscillation of the drill bit causes the reaming. Bore diameter hugely depends upon the clamps’ fluctuation. Thus, new clamps should get placed in time to avoid diameter alteration if the holding clamps are not in the proper condition or worn out.

Drilling small holes leads to more difficulty in the measurement of oscillation. Hence, a coarse shank small-edge drill bit with reasonable coaxiality is placed between shank and edge to avoid it.

2. The roundness of the hole

Vibrations in drill bit cause polygonal holes that tend to be pentagonal and triangular. Typically, the two centers of rotation of the drill bit cause a triangular hole, and they vibrate at the frequencies that keep on interchanging at 600 intervals. Mainly, the cause for these vibrations is an imbalance of drill and cutting force triggered by the rough roundness of the hole. And once the drilling depth achieves a certain degree, friction between the hole wall and ribbed surface of the drill edge increases while decreasing vibrations, bettering roundness, and disappearing rifle line.

The orifice gets shaped like a funnel when seen in a longitudinal section. Similarly, pentagonal as well as heptagonal holes may show up in the cut. To control this phenomenon of extra vibrations, the rigidity of the drill bit should be low, feed per revolution should be higher, the back angle should be lower, and the cross edge must get repaired.

3. Drilling holes on inclined and curved surfaces

The tool’s life reduces when the drill is out of the proper function, like it has poor positioning accuracy or beveled. Following are the measures to improve positioning accuracy:

  1. Bring the feeding rate to low.
  2. Use end mill to milling the hole seat.
  3. The bit should be able to penetrate deeper and show good rigidity.
  4. First, perform the drilling of the central hole.

Treatment of burrs

While processing thin plates and tough materials, burrs might appear at the entry and exit of the hole. It is because of the plastic deformation of the material. For that reason, the triangular portion to get cut by the bit close to the outer edge of the drill bit is subjected to axial cutting force and bent outward. It is further curled under the action to chamfer the bit’s outer edge.