Archive for August, 2012

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Different Types of Drill Bit Materials

It is sometimes critical that the “drill bit” you choose is the proper type for the job.  You can often use a higher quality tool for a lower difficulty job, but doing the opposite can lead to tool failure, ruined parts or even personal injury or worse.

A softer drill tool can dull more quickly. When picking the type of “drill bit” you need, consider the surface to be drilled into. Some products that can be drilled with automatic drill machines might be:

  • Different types of wood (soft, hard, abrasive like Ipe, etc.)
  • Plastics (HDPE, Phenolic, PVC, etc.)
  • Fiberglass (Or fiberglass impregnated materials)
  • All types of Metal
  • Stone (how do you think they make holes in counter tops for faucets, etc?

Also consider the mass and steadiness or stability of the drill itself. A very brittle bit such as carbide on a small, lightweight drill can actually dull prematurely because of the micro-vibrations caused by a poor mounting system, a lack of total mass, etc.

Materials Drills Are Often Made Of:

Low Carbon Steel Drill Bits: This is the cheapest (or more properly the least expensive) drill tooling generally available. Best used only on soft woods, some plastics, etc. Low Carbon Steel bits need to be sharpened more often and have no place in a reputable shop.

High Carbon Steel Drill Bits: These are better than Low Carbon Steel tooling. They can often be used on hardwood and even some very soft metals. Typically, they have no place in a shop that calls itself professional.

High Speed Steel Drill Bits (HSS Drill Bits): These have essentially replaced the older Carbon steel bits on the market. HSS is much more resistant to heat and wear. They are the most common type found at a supply shop serving professionals such as McMaster-Carr or MSC Direct, etc. These bits are suitable for most wood and metal jobs. There are exceptions such as Ipe which is a wood with very hard particles inside it. It will dull HSS very quickly even though it drills easily.

Titanium Coated Drill Bits (TiN, TiAN, TiCN, more…): Titanium coating makes these bits harder and last longer than the common HSS bits. That is because the coating is a hard ceramic material. If you are having problems with excessive heat build-up or dulling of HSS tooling, you can try this type if drill to solve the problem. For production drilling, using this type of tool allows you to run at a faster RPM and thus lower your cycle time.

There are a number of different Titanium coatings.  The 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 challenge with coated bits is that once dulled, they can’t be properly sharpened. The coating will be gone. So will all the benefits of the coating. They generally revert to being HSS tooling at that point.

Cobalt Drill Bits: Cobalt bits retain hardness at much higher temperatures than HSS ones. However, they are also more brittle. Cobalt “drill bits” are most commonly used for drilling stainless steel and other difficult metals as well as when you need to run at a significantly higher RPM to save time or when coolant is not available because of a part that needs to be painted in the very next step, etc.

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. For instance, some carbide bits work well on a multi-thousand pound drill press or milling machine such as the Bridgeport but do not work well in an AutoDrill or other selffeeder drill unit. There simply isn’t enough mass to protest the tooling from vibration. AutoDrill suggests testing the tooling out on a standard drill press prior to buying a large batch for use on a self-feeding drill machine.

Carbide tools are often used in fiberglass reinforced plastic drilling processes as they hold up to the abrasive nature of Fiberglass Drilling much better. Some customers use diamond for even better results.  See the next entry for diamond drill tool information.

Diamond Drill Bits: Polycrystalline diamond (PCD) is one of the hardest tool materials available to the average person. It actually consists of a layer of diamond particles bonded to a carbide support in most cases. Since diamond is the hardest thing found in our environment that we know of, the diamond bits can be used on the toughest materials.

Diamond is carbon. Carbon is flammable.  Keep those diamond tools cool!  They WILL be ruined by heat.

Diamond drills are generally used to grind away material on a micro level. They are the favorite tool of masons trying to drill precision holes in stone, concrete, tile, glass, etc. With that in mind, Diamond “drill bits” can be used on glass, porcelain, ceramic tiles, granite, marble, stone, fiberglass, etc.

They are also commonly used in the automotive and aerospace industries. Basically in any environment where abrasive materials need to be drilled.

AutoDrill suggests that you speak to a reputable tooling distributor before making any important tooling purchases. If you are drilling a few holes here or there, then a standard drill set will likely meet your needs. If you are drilling a million holes a year like some of AutoDrill’s customers do, tooling choices become much more important. Do it right the first time no matter how much of a rush you are in because you will always find the time to do it right the second time.


How to Drill and Tap Metal

Tapping a hole in a metal part can often remove the need for a nut. Rather than passing the bolt through the metal part and putting a nut on the back side, you can sometimes tap the threads right into the metal part and simply tighten down the fastener. Tapping metal creates threads in the metal. You can then put a threaded fastener into these threads.

To create proper threads in metal, you need to drill the correct size hole in the metal. To determine the correct size hole to drill into the metal, you will need to reference a drill and tap chart such as the one at this link:


Basic Tapping Instructions

Locate the size of the fastener you need to install in the metal. Identify the thread size and pitch on the drill and tap chart. (The fastener size is generally displayed on the left-hand side of the chart.)

Place the piece of metal on a stable work surface. Keep in mind that a properly secured work piece is a safe work piece.  When drilling and tapping, pieces can spin, move or even rise up on the tooling causing damage or worse – personal injury!

Select the “drill bit” from the set that matches the size recommended on the chart we have provided. Secure the tooling in the drill motor and put on your safety glasses and other safety equipment.

Drill the hole into or through the metal, depending on the type of metal and the application. Liberally apply cutting and tapping fluid to the “drill bit” while you drill to lubricate and cool the drill bit. Remember that slower RPM rates are better than faster ones.  Too fast and you will damage the “drill bit” or maybe even your part.

Select the tap from the tap set that matches the size of the fastener you will be installing into the metal and secure the tap in the tee-handle tap wrench.

Coat the tap with cutting and tapping fluid. Place a bit of fluid on / in the hole to be tapped. Align the tap with the drilled hole in the metal. Start threading the hole in the metal by turning the tee-handle tap wrench clockwise for a right-hand threaded hole or counter-clockwise for a left-hand threaded hole. Make sure that the tap is straight with the hole to ensure that your fastener will seat correctly.

Reverse the direction you are turning the tee-handle tap wrench if and when you feel the resistance from the tap increase. This will break the shavings and chips coming from the metal. This makes the process of threading the metal easier.

IMPORTANT: Make sure to keep any and all pressure on the tap to a minimum. you only want to press down when starting the tap.  From that point forward, you want to make sure you are only turning the tap and not leaning it from side to side or pressing down.  Some taps are hard and brittle to cut difficult metals. This means that they will snap very easily – especially smaller diameter taps.

The smaller the t-handle tap holder, the better.  Using a larger one causes broken taps often.  As long as you can comfortably turn the tap, you are good.  Look for flexing or twisting in the tap while you go.  If this happens, add more fluid, reverse the rotation for a turn or two to remove chips and continue down.

Remove the tap from the metal, wipe the cutting and tapping fluid from the surface of the metal and turn the threaded fastener into the newly threaded hole in the metal to ensure that the threads are cut correctly.

If the threaded fastener will not thread into the hole, look for debris or metal shavings in the hole and clean them out. It is almost never necessary to re-cut the threads unless your tap is the wrong size or extremely damaged.


How to Drill Through Stainless Steel

Drilling through stainless steel is much like drilling through any other type of metal but with a few key differences.

Using high-speed drill bits or better is mandatory. There are also other steps to drilling this material that will make the process easier. Many people have drilled holes into plain old steel with satisfactory results. Although drilling through stainless steel is different from drilling mild steel, the basic technique is much the same. Here’s how to get those holes drilled without ruining “drill bits”

Things You’ll Need

  1. Variable speed power drill
  2. Gloves
  3. Eye protection

Basic Instructions

Hold it secure! Clamping the part down is critical.  If it is not properly clamped down, you may see it move, spin, or even lift up causing damage or even injury while drilling.

“X” marks the spot. Locate the exact spot where you want the hole and mark it with a permanent marker or even use a center punch to mark the location. Use heavy-duty tape to mask the area around your mark if you are worried about the chips scratching the surface as they spin. The best way, by far is to use the center punch to make a sharp depression in the metal. Holding the punch firmly on your mark, rap it sharply with your hammer once or twice to set the tiny puncture. Make sure it does not move between the hammer blows. This will prevent the drill bit from sliding away from your target as you drill.

DO NOT DRILL YET, but if the hole is larger than 3/8″ diameter or 8mm, use a two-bit process. Unless you have a drill press, hand drilling in metal is most easily done with a two-step process when you go above those sizes. To begin, install a “drill bit” roughly half the size of the hole diameter you need. For example, if you need a 1/2″ hole, start with a 1/4″ inch bit. Once you have drilled the 1/4″ hole, install your 1/2″ bit and drill again to finish the job. Thinner metal, for example less than 1/8-inch thick, may allow the use of a single bit to accomplish the task but has a much higher risk of “grabbing” as the tool breaks through the material.  The “drill bit” turns into a screw-like device.

Put several drops of lubricating oil into the depression you made with the center punch. With your gloves and eye protection on and hearing protection in place, hold your drill perpendicular to the bracket, insert the tip of the bit into the punched hole and begin to drill.

Slowly pull the trigger until the bit gains rotational speed being careful to keep it on target. Ultimately, the drill bit will win the contest and you’ll have bored that hole. Switch bits and begin again if needed to finish off the final hole.  Add more lubrication often.  Stainless does not conduct hear well so the tip of the “drill bit” will get very hot, very quickly.

Clean it up. Once you’ve drilled the hole, wipe off the excess lubricating oil with a rag. As you do, you’ll notice that the back of the bracket is fairly rough. Using a metal file, take down the ragged edges of the hole being careful not to damage the bracket. If necessary, apply more heavy-duty tape to mask the area.

BONUS TIP: By using an even larger drill bit, you can de-burr the hole on both sides if desired.

Consider using some sort of plastic or felt on your clamp if the surface will be easily damaged.

Drill slowly and allow the bit to do the work. Some will tell you that if you apply too much pressure, friction will cause your drill bit to redden with heat which will ruin it or your piece of stainless steel. If you are spinning slow enough and have enough lubrication, then this will not happen. In fact, more pressure can sometimes cause the drill to stay cooler as it travels through virgin metal below the last cut surface on every rotation.  Let off on the pressure as you break through to avoid spiraling into the hole.

Overheating the tool can happen if you engage the drill to its full speed. The trick here is to find a happy medium, that “sweet spot” at which the drill, the bit and the metal cooperate fully. If it appears there’s too much smoke from the lubrication, back off immediately. Allow the bracket to cool for a few minutes and start the process again. You’ll save the “drill bit” in the process. When in doubt, drill slower.  Also, the larger the hole diameter, the slower you should spin the “drill bit” to reduce heat.

Once you’ve removed shards and burrs, you can sometimes finish smoothing the area with steel wool as long as the marks left by the process are desirable.

Eye protection is a must as are gloves! Work safe!!!

Don’t touch the bracket or the drill bit with your bare hand until they have cooled. Changing bits during the drilling operation should be done with gloves.


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