1. grumpyvette

    grumpyvette Administrator Staff Member

    most guys don,t give a great deal of thought to the drill bits they select,
    and thats a problem in that,
    theres a huge difference in quality between brands and types of drill bits

    Id also point out over heating a drill bits cutting edge, or spinning it too fast for the material its used for cutting in,
    will rapidly ruin its cutting efficiency ,

    and most guys are clueless as to how to drill steel,
    how many times do you see guys try to drill steel that just lean on the drill and try to drill as fast as possible
    , in most cases all that results is a dimple and a burnt out ruined drill bit,
    steady pressure, slow speed and lots of cutting oil is usually a better approach on hardened or stainless steel,
    but the quality of the material the bits made from also effects your results,
    cobalt drill bits, titanium coated, high speed steel?
    you tend to get what you pay for and the better bits tend to be more expensive!
    This depends on the hardness of the steel in question.

    Ordinary twist drill bits are only about 65 rockwell C. (Nearly all steel bits are high-speed steels these days.) Hence they simply will not work on the hardest tool steels, and will wear very quickly on medium-hardness, high strength steels. The most practical option is to anneal the part before drilling or machining.

    Cobalt bits are only slightly harder, maximum 67-68 RC. The advantage of cobalt bits is they have better heat resistance than high-speed steel bits, hence they can be used at somewhat more aggressive cutting rates and are less likely to burn up. For example, cobalt bits work well for stainless steels which have rapid work-hardening properties.

    For drilling tool steels in the fully hardened condition, you need special-purpose tungsten carbide, diamond, or boron nitride tooling. You also generally need a milling machine.

    http://drill-bits.blogspot.com/2008/04/ ... steel.html



    Drill Bits Material: From Carbon Steel to Diamond
    It is important to choose a drill bit made with the right material for your purpose. Getting a softer drill bit than needed will lead to early dullness and uselessness of the tool, leading to endless replacing at best, and a ruined project as one of the sadder scenarios. When picking the material, consider the surface to be drilled into (Soft wood? Hardwood? Metal? Stone?), and the steadiness of the drill itself – a very brittle bit on a cordless drill in the hands of not a very experienced driller is probably not the best idea.

    That said, lets consider the standard options:

    Low Carbon Steel Drill Bits

    This is the cheapest option. Best used only on softwood. Low Carbon Steel bits require frequent sharpening, have a relatively short useful lifespan, and do not hold the edge too well. Buyer beware.

    High Carbon Steel Drill Bits

    These are an improvement over the above, and can be used on hardwood and even some metals. However their low resistance to heat causes them to loose their sharpness relatively quickly.

    High Speed Steel Drill Bits (HSS Drill Bits)

    These have essentially replaced the older Carbon steel bits on the market. HSS is significantly more resistant to heat, and as such these bits are well suited to most wood and metal jobs.

    Titanium Coated Drill Bits

    Titanium coating makes these bits harder and last longer than the common HSS bits. That is because the coating is a hard ceramic material.

    There are a number of different Titanium coatings, most common are Titanium Nitride (TiN), Titanium Aluminum Nitride (TiAN) and Titanium Carbon Nitride (TiCN). TiN can increases the life of a drill bit by three or more times. TiAN is considered even better, and can increase the lifespan five times or more. TiCN is also considered superior to TiN.

    The problem with coated bits, however, is that once dulled, they can’t be properly sharpened – the coating will be gone, and so will all the benefits of it.

    Carbide Tipped Drill Bits

    These are very hard, dissipate heat quickly and hold an edge longer than other types. However, Carbide tipped bits are also brittle and are likely to chip if not used carefully.

    Cobalt Drill Bits

    Cobalt bits retain hardness at much higher temperatures than the HSS ones. However, they are also more brittle than HSS. Cobalt drill bits are most commonly used for drilling stainless steel and other metals.

    Diamond Drill Bits

    Polycrystalline diamond (PCD) is one of the hardest tool materials. It actually consists of a layer of diamond particles bonded to a carbide support. And since diamond is the hardest thing found in our environment (or at least it is the hardest we know of), the diamond bits can be used on the toughest materials.

    Unlike carbide and other types of drill bits, which use sharp edges to cut through material, diamond drills tend to work by grinding away their nemesis on a micro level.

    Diamond drill bits can be used on glass, porcelain, ceramic tiles, granite, marble, stone, fiberglass, etc. They are commonly used in the automotive and aerospace industries, and in other environments where abrasive materials need to be drilled.

    they all have the correct application!
    cobalt alloy steel is hard and cuts well buts its brittle are can,t bend easily
    titanium coated alloy steel is durable but not as hard on average as cobalt drill steel
    high speed steel, cheap, easier to bend and best used on softer metal



    http://www.grizzly.com/products/115PC-D ... Case/H8183






    http://www.northerntool.com/shop/tools/ ... _200343070

    http://www.northerntool.com/shop/tools/ ... _7899_7899


    http://www.harborfreight.com/115-piece- ... 47653.html

    http://www.grizzly.com/products/170PC-B ... izer/H8182

    http://www.grizzly.com/products/Steelex ... -Set/G8866

    http://www.harborfreight.com/29-piece-1 ... 36891.html
    Last edited by a moderator: Aug 4, 2018
  2. Indycars

    Indycars Administrator Staff Member

    Seems you also have to consider if the drill bit can be sharpened. Which materials can be
    sharpened by DIY'er ??? If its a surface treatment, then sharpening will only remove
    what you just paid for.

    This question has come to mind several times for me. Ok, it a test to see if your stash of info
    includes such hard to find details !
  3. grumpyvette

    grumpyvette Administrator Staff Member

    Ive never been an expert on anything, and I,m still learning constantly, but I have used a drill press and MILL for years so I have at least a bit of reference experience with the tools and drills, obviously having a tool designed to sharpen drill bits is going to be far superior to sharpening them on the shop grind stone or using a dremel tool to put an edge on dull bits
    ALL common bits can be resharpened with the correct tool,how long the edge lasts depends on the application and materials and how the bits used, but the basic remains that a bit must be correctly sharpened and drilling steel requires low speeds and lots of cutting fluid to keep the edge cool and clean, and use of a drill press and indexable vise makes cuts far more consistent.
    http://www.northerntool.com/shop/tools/ ... _200320247


    http://www.northerntool.com/shop/tools/ ... _200320241

    Ive been looking into getting one of these for a few years, my neighbor has the cheaper version and even that works really well

    reading thru the sub linked info will help a great deal




  4. grumpyvette

    grumpyvette Administrator Staff Member

  5. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    I was asked how I managed to drill the jack stands....
    as I mentioned in the linked thread above,

    its really no challenge, to drill a 5/8" hole in a jack stand , since I own a MILL,
    and it has a mill vise
    and a coolant pump[​IMG]

    but I can fully understand the difficulty if your limited to a typical hand held 3/8" drill.
    especially if your unfamiliar with drilling steel,
    as its best done with lots of cutting fluid cooling the drill bit or mill bit,
    and slower rotational speed and not the typical new guys route,
    of leaning on the drill and trying to use max rpms,
    and no cutting fluid, with a typical hand held drill.
    first the larger 5/8" drill bit generally won,t fit unless its a deduced diameter shank design,
    and if it is its going to spin in the chuck constantly requiring re-tightening,
    and maintaining a set 90 degree entrance/exit angle,
    will be nearly impossible with a hand held drill

    read the related threads










    Last edited: Aug 17, 2018
  6. Meghesh

    Meghesh New Member


    Tungsten carbide, often called simply “carbide,” is a familiar material around the shop. This compound of tungsten and carbon has revolutionized the metal-cutting world over the decades, enabling increased speeds and feeds and providing longer tool life.
    Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms.
    To fully understand the applications and importance of tungsten carbide, it is important to look at its properties. In its most basic form, tungsten carbide is a fine grey powder. However, it can be pressed, molded and formed into various shapes for use in cutting tools, industrial machinery, abrasives and jewelry.
    The main application for carbide tungsten is machine tools. Carbide cutting edges are frequently used for machining strong and tough stainless steel or carbon steel. They are also used in instances where other tool types would wear away, for example, on top quality high production lines.
    The machining applications and tools in which tungsten carbide tools are used are: turning, drilling, milling, facing, planning, threading, parting off, grooving and deep hole boring. These tools are used for cutting steel, nonferrous materials and cast iron in a wide range of industries including automobile, aerospace, earth moving, oil equipment and heavy engineering.
    The first operation after reduction of the tungsten metal powder is the milling of tungsten and carbon prior to the carburising operation. Here, 94 parts by weight of tungsten and six parts by weight of carbon - usually added in the form of lampblack - are blended together in a rotating mixer or ball mill. This operation must be performed under carefully controlled conditions in order to insure optimum dispersion of the carbon in the tungsten.
    The most common compacting method for grade powders involves the use of a die, made to the shape of the eventual product desired. The size of the die must be greater than the final product size to allow for dimensional shrinkage that takes place in the final sintering operation. These dies are expensive, and usually made with tungsten carbide liners. Therefore, sufficient number of the final product (compacts) are required, to justify the expense involved in manufacturing a specific die.
    A cobalt compact is heated in a hydrogen atmosphere or vacuum furnace in temperatures ranging from 2,500 to 2,900°F, depending on the composition. Both time and temperature are carefully adjusted in combination, to effect optimum control over properties and geometry. The compact will shrink approximately 16% on linear dimensions, or 40% in volume. The exact amount of shrinkage depends on several factors, including particle size of the powders, and the composition of the grade. Control of the size and shape is most important and is least predictable during the cooling cycle. This is particularly true with those grades of cemented carbides with higher cobalt contents.

    Classification of Carbide Tools And Carbide End Mills

    Cemented carbide products are classified into three major categories:
    • Wear Grades — used primarily in dies, machine and tool guides, and in everyday items such as line guides on fishing rods and reels. Used anywhere good wear resistance is required.
    • Impact Grades — also used for dies, particularly for stamping and forming, and in tools such as mining drill heads.
    • Cutting Tool Grades — the cutting tool grades of cemented carbides are divided into two groups, depending on their primary application. If the carbide is intended for use on cast iron that is a nonductile material, it is graded as a cast iron carbide. If it is to be used to cut steel, a ductile material, it is graded as a steel grade carbide.
    Saw tips get dull for several reasons. Abrasion, adhesion, diffusion and fatigue are the 4 reasons for dullness.
    1. Abrasion
    Abrasion or straight wear is countered by smaller, more consistent grain size. What is called abrasion is often thought of a straight wear. However, a big part of it is actually pulling carbide grains out of the metal matrix. Smaller grains have less surface area for wear and less surface area exposed so are also less likely to be pulled out. Grains can also be more tightly packed. Finally, you can add elements to chemically lock the carbide tighter. Instead of ordinary concrete this is much more like concrete reinforced with rebar.
    2. Adhesion
    The materials used in tungsten carbide have an affinity to the materials being cut. This functions two ways. One way is adhesion where the material being cut actually sticks to the tungsten carbide in a sort of welding process.
    3. Diffusion
    The second way is where the material being cut dissolves one or more of the materials in the tungsten carbide. Usually it is the cobalt binder, in the tungsten carbide. This is very readily seem cutting high acid woods. It is also important cutting metals. The solid solubility of nickel in aluminum does not exceed 0.04% while cobalt can have a factor several times that. In addition, nickel / chromium binder chemically locks the nickel to the chrome which makes it much less reactive than elemental cobalt. Right is representation of the electron configuration of cobalt. ((Cobalt 27 (2:8:15:2)). With only two electrons in the outer shell it is highly reactive.
    4. Fatigue
    This is standard metal fatigue. On a large scale you see it by bending piece of metal repeatedly until it snaps or tears. The binder in tungsten carbide work hardens and fails much like any other metal. Its susceptibility to metal fatigue can be changed by minor changes in chemistry and processing.

    Additional wear factors:
    1. Wear – the grains and the binder just plain wear down
    2. Macrofracture – big chunks break off or the whole part breaks
    3. Microfracture – edge chipping
    4. Crack Initiation – How hard it is to start a crack
    5. Crack propagation - how fast and how far the crack runs once started
    6. Individual grains breaking
    7. Individual grains pulling out
    8. Chemical leaching that will dissolve the binder and let the grains fall out
    9. Rubbing can also generate an electrical potential that will accelerate grain loss 10. Part deformation - If there is too much binder the part can deform
    11. Friction Welding between the carbide and the material being cut
    12. Physical Adhesion – the grains get physically pulled out. Think of sharp edges of the grains getting pulled by wood fibers.
    13. Chemical adhesion – think of the grains as getting glued to the material being cut such as MDF, fibreboard, etc
    14. Metal fatigue – The metal binder gets bent and fatigues like bending a piece of steel or other metal
    15. Heat – adds to the whole thing especially as a saw goes in and out of a cut. The outside gets

    The main advantage of using carbide tools is that it produces a better finish on the work piece being worked on. Faster machining can be achieved while using carbide tungsten tools. Ability to withstand high temperatures, in comparison to other cutting tools, is another important advantage of using carbide tungsten tools.
    Tungsten Carbide is about three times stiffer than steel and it is denser than titanium and steel. In terms of hardness, tungsten carbide is equivalent to sapphire or corundum. Carbide has a high melting point and is very hard. In addition, carbide tools have high precision cutting capabilities.
  7. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    thank you for posting interesting added info

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