qquake
Member
Can anyone tell me the differences between cobalt, titanium nitride, and uncoated HSS drill bits? And what about 135 degree split point?
Drill bit questions
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Skie_M
Member
Of the three, the uncoated HSS is the cheapest option. It will cut fairly well through a very wide variety of materials, but not very well through extremely hard materials like granite and higher carbon content steels.
Titanium Nitride (T/N) coatings on HSS bits give some extra heat dissipation and increase the usable life of the bit by keeping it cool. No other properties ... having it on the tip can enhance the life of the cutting edge, but if you try to cut extremely hard stuff it's pointless.
Cobalt alloy bits are extremely hard, and should allow you to cut the extremely hard stuff that can't be done very well with HSS and T/N coated bits.
The difference between 135 degree and other angle bits is how aggressively the bit chews into materials. 135 degree is better for harder materials, like metals. It takes a smaller "bite", so the edge doesn't wear as quickly. More aggressive bits go through softer items quite a bit faster without nearly as much wear ... this is common for general purpose and wood cutting bits.
The "split point" performs as a pilot function, allowing one to more easily keep the bit in line for drilling without "walking" or wandering over the work surface. You may also want to go ahead and center punch hard materials to assist in this. Brad point bits also perform in similar manner ... there are several such gimmicks to assist in drilling a hole where you want it to go.
Titanium Nitride (T/N) coatings on HSS bits give some extra heat dissipation and increase the usable life of the bit by keeping it cool. No other properties ... having it on the tip can enhance the life of the cutting edge, but if you try to cut extremely hard stuff it's pointless.
Cobalt alloy bits are extremely hard, and should allow you to cut the extremely hard stuff that can't be done very well with HSS and T/N coated bits.
The difference between 135 degree and other angle bits is how aggressively the bit chews into materials. 135 degree is better for harder materials, like metals. It takes a smaller "bite", so the edge doesn't wear as quickly. More aggressive bits go through softer items quite a bit faster without nearly as much wear ... this is common for general purpose and wood cutting bits.
The "split point" performs as a pilot function, allowing one to more easily keep the bit in line for drilling without "walking" or wandering over the work surface. You may also want to go ahead and center punch hard materials to assist in this. Brad point bits also perform in similar manner ... there are several such gimmicks to assist in drilling a hole where you want it to go.
CREID
Member
Price.
Curt
Curt
KenV
Member
High speed steel is the basic machine tool material. It handles heat and cuts many steels. Often called M2 HSS. General Purpose is a good descriptor.
Cobalt HSS is an alloy with Cobalt added. It adds more toughness and is used for things like drilling cast iron. Often called M42 (or M35). Cost a bit more, but probably not needed for softer thing. Holds an edge well. Specialty drill may be a good descriptor.
TIN is a coating on tool steels. Commonly put on HSS to increase durability. It all gets ground off on the first sharpening with the diamond wheel on a Drill doctor. Used to extend tool life. Commonly use as a sales pitch. Marginal value for a drill bit that will be sharpened. Good value if you use and pitch (especially when paying labor costs).
Makes real sense to use on thing like taps and dies - Specialty treatment.
In the machine tool world there are a number of different cutting tip configurations and the 135 degree angle and 105 degree are common. Both will work for pen turning, but I use the 135 with my drill doctor as being a bit less aggressive.
Split tips skate less, but I am in the habit of using an automatic center punch or center bit (or even a long tip of a skew) to start holes, so not especially important. I generally use split tip with the Drill Dr.
Cobalt HSS is an alloy with Cobalt added. It adds more toughness and is used for things like drilling cast iron. Often called M42 (or M35). Cost a bit more, but probably not needed for softer thing. Holds an edge well. Specialty drill may be a good descriptor.
TIN is a coating on tool steels. Commonly put on HSS to increase durability. It all gets ground off on the first sharpening with the diamond wheel on a Drill doctor. Used to extend tool life. Commonly use as a sales pitch. Marginal value for a drill bit that will be sharpened. Good value if you use and pitch (especially when paying labor costs).
Makes real sense to use on thing like taps and dies - Specialty treatment.
In the machine tool world there are a number of different cutting tip configurations and the 135 degree angle and 105 degree are common. Both will work for pen turning, but I use the 135 with my drill doctor as being a bit less aggressive.
Split tips skate less, but I am in the habit of using an automatic center punch or center bit (or even a long tip of a skew) to start holes, so not especially important. I generally use split tip with the Drill Dr.