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How Quality Control Ensures TIR < 0.02 mm on Morse Taper Drill Bits

    How Quality Control Ensures TIR < 0.02 mm on Morse Taper Drill Bits

    Maintaining total indicator reading (TIR) below 0.02 mm is a hallmark of premium taper drill bits.
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How Quality Control Ensures TIR < 0.02 mm on Morse Taper Drill Bits

Maintaining total indicator reading (TIR) below 0.02 mm is a hallmark of premium Taper Drill Bits. This article details the quality control steps manufacturers use: Prussian Blue test for taper contact (≥85% contact), laser measurement of flute concentricity, Rockwell hardness sampling (62–65 HRC), and inspection of the split point symmetry. We also explain how a poorly ground Morse taper leads to oversized holes and reduced tool life in CNC lathes.

Diam
Button
degree
Button Size
Body material
Button Material
Length
38mm
7 Button
11 Degree
7*8
45 CrNiMov
DK05
55mm
36mm
7 Button
11Degree
2*7  5*8
45CrNiMov
DK05
55mm
41mm
7Button
11Degree
2*8 5*9


55mm
32mm
7Button 
12Drgree
2*6.5  5*7


55mm
34mm
5Button
11Degree
2*7  5*8


55mm
32mm
5 Button
12Degree



55mm
Detailed Images


 32mm 5 button 11 degree



41mm 7 Button 11 Degree


32mm 7 Button 11 Degree

FOLLOW QUESTIONS CUSTOMERS MAY CONCERN

Question one:How to use drill bit more correct?

Answer:

1.Choosing the right drill bit is the premise to obtain maximum drilling speed.

2.When open the hole,it should be stable and must lower rock drill working parameters,prevent single button under over load then cause the button broken or lost.

3.According to the drilling condition,timely adjust the rock drill paramaters.

4.After a period of time working,the button and the body of drill bit should be examined.

5.When drilling,for improving drill bit drilling speed,you should ensure that there is adequate hydraulic or air pressure for preventing drill bit from excessive wearing and jamming which caused by bad powder exhaust.



Question two:What if i buy early abnormal scrapped Button Bit
?

Answer:please timely inform our company by written notice.Notify the main contents include:

1.the model number of rock drill,the actual working paramaters(impact pressure,impact powder,impact frequency,driving power and rotation speed)

2.Drill rig model number

3.Drill Rod tail,drill rod and connection sleeve manufacture,specification and usage condition.

4.The rock type and hardness,the construction site(open air,underground,tunneling,production,the anchor hole or others),drilling type(down,horizontal,fan form or others),drilling depth.

5.The failure condition of drill bit:

A.failure type(button broken,button lost,wear off),lifespan,quantity;

B.the button wearing condition(residual height);

C.planned service life;

D.normal average service life;

E.other manufacturers product average service life.

6.We will check whether it is factory duty or end users unproper operation.If that is factory duty,we will fully refund abnormal scrapped buttons bits cost.

The defining feature of a Morse Taper Drill Bit is the conical shank (MT1, MT2, MT3, MT4, MT5). Unlike a straight shank, a Morse taper utilizes the wedge principle. When the male taper of the bit is seated into the female socket of the spindle, the friction bond is so strong that it transmits high torque without a drawbar (though drawbars are often used for safety on larger sizes like MT3 and above).

  • Self-Holding vs. Self-Releasing: Morse tapers are "self-holding." The deeper they are seated, the tighter they grip.

  • Removal: A drift (wedge) is inserted through a slot in the spindle to break the friction seal.

  • A common point of confusion in SEO is the distinction between Taper Shank Drill Bits (MT shank) and Taper Length Drill Bits (long flute length).

  • Taper Shank: Refers to the mounting style (Morse taper). Used for high torque.

  • Taper Length: Refers to the flute length, typically 8x to 12x the diameter (longer than a jobber but shorter than an aircraft extension). 

  • High-Speed Steel (HSS)

  • Standard HSS (often referred to as M2) is the most common material for general-purpose taper bits.

  • Composition: Carbon, Chromium, Vanadium, Molybdenum, and Tungsten.

  • Performance: Good toughness, resists breakage in interrupted cuts.

  • Application: Drilling wood, plastics, and mild steels with a tensile strength

  • Taper Rock Bit (Carbide Button Bits): Used in mining. The steel body is forged, and tungsten carbide buttons are pressed into the gauge. These are designed for percussive drilling in hard rock (granite, basalt). 

  • Tapered Web Thickness: A design variant where the core thickness increases towards the shank. This provides superior rigidity during deep drilling and has been shown to reduce hole diameter errors compared to standard geometries. 

 Cobalt HSS (HSCo/M35)

For high-heat applications like stainless steel, HSCo or M35 Cobalt is the industry standard.

  • Composition: HSS base with 5% or 8% Cobalt.

  • Performance: Retains hardness at red heat (up to 650°C). It is less tough than standard HSS but offers superior wear life.

  • Application: Drilling stainless steel (austenitic and martensitic), titanium, and high-alloy steels up to 1200 N/mm². Premium brands like Würth’s “VaryTap” utilize HSCo for blind hole applications.

Manufacturing Process – Milled vs. Fully Ground

This is the most critical engineering distinction in manufacturing. A CNC ground drill bit is vastly superior to a milled one. The chart below explains the quantitative differences. 

ParameterMilled Taper DrillFully Ground Taper DrillEngineering Impact
Flute SurfaceRough (Ra 1.6-3.2 µm)Smooth (Ra 0.4-0.8 µm)Rough flutes cause chip packing and heat buildup.
Concentricity (TIR)0.03 – 0.06 mm< 0.02 mmPoor TIR causes oversized holes and uneven wear.
Diameter Toleranceh9 – h10h8 (Precision)Tighter tolerance allows for press-fit hole accuracy.
Taper Accuracy±0.01-0.02 mm±0.005 mm / 100 mmPoor taper fit leads to slippage and runout in the spindle.
Relative Tool Life60-75%100% (Baseline)Ground tools last significantly longer in production runs.

The Milling Process (Economy)

  1. Turning: The Morse taper is turned on a lathe. This leaves visible concentric turning marks.

  2. Flute Milling: A rotating cutter mills the helix into the blank. This process is fast but leaves "feed lines" inside the flute, acting as stress risers and friction points.

  3. Point Grinding: Only the tip is ground.

The Full Grinding Process (Premium)

  1. Single Setup: The blank is loaded into a 5-axis CNC tool grinder.

  2. Grinding: A single wheel or sequence of wheels grinds the Morse taper, the flutes, the lands (backing off the Cutting edge), and the point (including split point thinning) in one operation.

  3. Result: Perfect concentricity. The polish on the flutes ensures chips slide out easily, reducing the risk of jamming in blind holes.






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