Drilling Methods & Some Advice For Diamond Drills

When you need to drill with diamond drill tooling, there is a fine balance between method and specifics and the specific situation’s needs.  Here are some very simple tips:
  • First, you should make sure that you choose the proper drill tooling.
  • Second, you should make sure that you know exactly what equipment that you will need for the project
  • Third, you need to understand the importance of coolant and lubricants in the process
  • Forth, you need to figure out the proper drilling RPM and thrust for the process
Always Think About the Safety of Your People First!
  • Eye protection. Many people don’t wear it, but ask the guy walking around with blurred vision or the loss of eyesight whether it would be worth the hassle of goggles when working and you will get the true perspective on wearing them AutoDrill strongly recommends that you wear safety goggles that wrap around your face to stop even the most determined piece of debris! Our warning labels say, “Eye protection is required to protect personnel from chips produced in the process.”  In the case of diamond drilling, it would be slurry, liquid or dust, but the concept is exactly the same.
  • Loose clothing, baggy sleeves, ties and similar articles are dangerous near rotating machinery.   Period. That’s also on our warning labels.
  • Diamond tools require coolant. Most people simply use water. Most of our drilling equipment is sold with electric motors so extreme care must be taken. Washdown rated motors are available for situations where an AutoDrill Self-Feeding Unit is being used. when drilling by hand or with a drill press, you should be very careful where the water goes, where the electric lines go, etc.  One mistake and your diamond drilling days are over…  One excellent tip is to make sure machines are powered by a properly grounded and tested outlet. Never override the grounding system or modify the plug.
  • The manual provided with your AutoDrill, drill press, etc. is there for a reason.  Read it at least once and make sure anyone else who uses the machine does so.  Understanding the proper set-up and operation of your machinery is extremely important. Most injuries are caused by those using machines in a way that they were not designed to be used.
  • Always make sure that your set-up is as good as it can be.  Taking short cuts in the set-up process can lead to poor hole quality, premature tool wear or even dangerous situations. Consider things such as rigidity, coolant migration and flow from the work area, the height of the set-up in relation to the most common user(s), lighting, guards, clamping mechanisms, etc.
Choosing the Correct Tooling:

Drilling quality hole(s) in any material requires choosing the correct type of drill “bit” for the job. Some things that need to be considered are the material, the size of the hole, the machine that will be driving the tooling, etc.

  • Diamond Tooling: Typically this type of tooling is used for drilling in stone, glass, tile, ceramic, and similar mineral materials. The diamond can be attached via electroplating, sintering, or brazing the tool together. The method of manufacture often has to do with the intended use of the tool and desired cost and lifespan of the tooling. There are suppliers who make standard tooling and there are suppliers that make custom tooling. Some may offer diamond tooling with different grits corresponding to the coarseness or fineness of the diamond used.  Diamond bits are not recommended for steel or other ferrous metals although they are used in applications drilling products such as fiberglass.
  • Carbide Tooling: Tungsten carbide and some other carbide tooling is generally available as either solid carbide or carbide tipped tooling. They are suitable for drilling iron, steel and other ferrous alloys as well as some other metals, fiberglass, wood (especially woods like Ipe that have silica in the grain), masonry, tile, and glass, etc.
  • Twist Drills: Are used to drill holes in just about any material you can find. They come in various grades and hardnesses depending on their intended use.  For the average user, quality High Speed Steel (HSS) tooling is adequate. However, for high RPM rates, coolant-free drilling in some materials as well as high volume jobs where tool changes cost money, there are higher quality tools available. Here are some simple charts on twist drills:
The Equipment You Will Need:

The first thing you want to make sure you have is a drill machine that is the proper size. You do not want to use a hand drill for a very large hole or a high HP machine for a small hole.

For small drills, up to about 0.500” diameter, a hand held drill will work in some cases. A better option is a drill press.

For drills, especially core type, 0.500” and larger and/or when drilling in thick materials, a drill press or an AutoDrill Self-Feeding Unit are highly recommended. It is very difficult to properly control the drill and material.

When Drilling More Than One Hole At A Time, a high quality drill press, a multiple spindle head with a guide rod set-up or an AutoDrill Self-Feeding Unit are needed. There are special custom set-up options where motors can be used to spin the tooling, but we would need to discuss that application with you in order to determine the best set-up possible for you. You can get additional information by CONTACTING US.

The Importance of Coolant:

The easiest way to destroy a diamond drill when trying to drill a hole is to run it dry or with too little coolant.  Coolant is absolutely required to cool the drill tips and surface and to flush out the debris (called swarf or slurry) generated during the drilling process. Water is the most common coolant used due to it’s availability, low cost, etc. There are high end coolants on the market but unless you are in a very high volume application and have recirculating coolant with filters, etc. It generally isn’t needed.

Water provides excellent performance at a very low cost. Think of it this way – It is a green or true organic coolant option.  One of the major benefits is that water does not leave an oily or greasy residue on or absorbed into the material you are drilling.  There are additives you can purchase to the water to help increase the lubricity and protect your diamond tool investment. Occasionally mineral oil or other oils are also used but can be messy to clean up and are generally not used on surfaces where the final finish is critical or food service use is in the material’s future, etc.

Not many people realize this, but a diamond is flammable.  Given enough heat and oxygen, it will burn slowly the same as a lump of coal. Drilling without proper coolant produces enough heat to “burn” off the tips of diamond tooling and dull or even destroy the tooling.

  • You should use more coolant when the hardness of the material increases. Sparks or a dry, crumbly residue while drilling are a very bad sign. These indicate insufficient coolant and you need to make sure that the set-up is immediately changed so that coolant reaches the drilling area.
  • Proper use of coolant increases the diamond drill efficiency. It also reduces heat which in turn lowers the chance of cracking or otherwise damaging the drilled material or tooling.
  • Proper use of coolant will help flush away debris and help guarantee proper lubrication of the drill. Sometimes using an up and down motion while drilling keeps fresh coolant flowing into the drilling area. AutoDrill often offers a thru-the-tool coolant option so that there is always a fresh supply of coolant at the tool.
Diamond Drilling Set-Ups:

Below are a few ideas to make sure that enough coolant is getting to your tooling in simple drill-press or similar set-ups.

  • “Cake Pan” Method: Some people who do low volume drilling literally use an old cake pan and place a couple sheets of cardboard in the bottom to act as a drilling board or back stop and prevent you from drilling through the tray bottom. What you want to do is place your material on top of something similar to a soft sheet of wood or plastic and fill a tray-like container with water just high enough to cover your piece.  This method is suitable for small to medium size pieces and although many people simply hold the piece in place by hand, we would suggest a clamp on each side of the piece to keep it from moving. Your fingers and hands are worth the time to set it up right each and every time.
  • Clay Dam Method: If the material is too big to fit inside a “cake pan” type set-up, you can build a dam from materials similar to modeling clay around where the hole will be drilled and fill the dam with coolant.
  • Other Options: For an automated drill process, you can supply coolant via a manual squeeze bottle if you have to but setting up an automated method of providing coolant is almost always a better idea.
  • IMPORTANT: Don’t forget to think about where all that coolant will  go when you have drilled through the part! When there is a hole in the product, the coolant will drop through and land on whatever you have below.  Think electric wires, your expensive drill press table, under your fixture stand, your new shoes, etc.
Drilling Speeds and Pressures:

Drilling speeds are determined by the hardness and abrasiveness of the material, the size of the hole you are drilling, the quality of the tool you are using, and the amount of pressure and coolant used.  The speeds listed below are suggested guidelines only. Experience will help you develop the right drilling speed and pressure for your application. Make sure to test on disposable materials first.

General Guidelines:
  • Generally, diamond drills run at faster RPM rates when the material gets harder. Remember all that talk about coolant? It’s especially important when you are spinning fast.
  • In drill press operations and/or when a Multiple Spindle Diamond Drill is being used, you should begin with low pressure and extra coolant to prevent damage to the diamond tooling.
  • Use light pressure or a slow feed rate and let the diamond do the work for you. Unlike standard twist drills, diamond tools require only light to moderate pressure for the best results. Allow the bit to drill at its natural speed. Too much pressure can fracture the material and prematurely wear the diamond. On AutoDrill Self-Feeding Units, the feed control should be set properly to allow the drill to rapid up to the surface, take a very controlled feed through the part and then stroke a bit farther to insure a clean hole process. the AutoDrill will then rapid retract and be ready for the next hole process regardless of whether it is a single or multi-hole process.
  • If you do not have coolant through the tool, use an up and down or “peck drill” motion when drilling to allow coolant to move around in the hole and flush out the slurry or swarf. This will allow fresh water/coolant to penetrate to the surface that is being drilled. This is especially important when drilling through thick materials.
  • When drilling completely through an object on a manual drill press,  you will need to decrease the pressure as the drill is about to break through. If you do not do this, you will chip out the back side as it emerges or pops. On an AutoDrill, the feed control will handle this important step for you.
Basic Drilling Speed Chart:
.75 – 2.5 mm 0.125″ to 0.500″ 0.625″ to 1.500″ 1.750″ 2o 2.740″ 3″ to 4″
30,000 TO 18,000 rpm 2,400 -1,000 rpm 1,250 – 1,000 rpm 1,100 – 850 rpm 850 – 200 rpm

NOTE: AutoDrill Multiple Spindle Drilling Heads generally can not be run faster than 4000-5500 RPM depending on the size of the components and the hole spacing. Some very large heads have a maximum closer to 2000 RPM. Please check with AutoDrill if there is any question as to whether you will be running above the rated speeds for your device.

General Tips For Better Drilling:

  • If a white powder forms as you drill, stop, remove the drill, clean and add more water/coolant. Never drill materials with diamond drills dry unless the manufacturer of the tooling allows for or suggests it.
  • When drilling by hand or with a manual process such as on a drill press, use drilling boards or a back stop of expendable material. This will protect your work surfaces and your tooling.
  • For the very best results, bring the drill down at a right angle to the hole and keep it that way the entire time during the drilling process. You do not want the part or the tooling to rock back and forth or move in any other direction other than the stroke direction during the drilling process.
  • When manually drilling, always use light pressure until you become familiar with your tooling’s natural cutting speed. With a hand drill, the weight of the drill machine itself should provide sufficient thrust and pressure. You want to allow the diamond to do the work for you. Too much pressure can fracture the material and prematurely wear the diamond. On an Self-Feeding Drill, the feed control will handle this important step for you.
Manual Drilling – Prevent The Drill From “Walking” When Starting The Hole Process by Make a Drilling Template:

Make a guide by either drilling a pilot hole in a piece of thin plastic, a thin piece of wood or even sturdy cardboard. Some people stabilize the tool by cutting a “V” in the edge of materials like this and cradling the tooling from one side. It is AutoDrill’s opinion that a hole template works best. However, the “V” template is easier to make and can be used with many sizes of core drill bits. For higher volume manual drilling, a plastic or Plexiglas template will last  the longest because the water and wear affect it the least.

Make sure the template is held on the surface of the material being drilled. Place the pilot hole or “V” above the target hole area. It will hold the drill tooling in place as it starts drilling.

A few revolutions of the drill will create a shallow hole, or groove if using a core drill. That will now hold the drill in place and the template can be removed.

Manual Drilling – Create Some Friction For The Drill To Grab:
  • Mark the center of the hole using an easy to see indelible pen. Make sure to write only on parts that will be scrap later on.
  • Layer several pieces of clear tape over the mark until you build up a “pad”.  If needed, re-mark the hole location on the tape if the original mark becomes hard to see through the layers. The layered tape pieces will give the bit a place to bite into as you start the hole and are easy to remove.
  • Similarly you can use a piece of masking or duct tape over the area and then mark the hole location but this may not be precise enough for some jobs.
  • Use a glass or stone scribe to create a small round divot or scratch where you want to drill to give the bit a place to bite as you start drilling the hole. Again, make sure you do not damage anything other than surfaces that will become scrap later on.
Make a Pilot Hole:
  • Drill a pilot hole using a much smaller tool first.  This will allow you to center the tip of the larger diameter tool and then accurately drill your final size hole. This often keeps the larger tool from jumping all over the surface when it first touches the material. Obviously, this method only works for wire and twist type drills and is not suited for core type drills unless they have a center pilot drill as well. Most diamond core drills do not have a center pilot drill though.
Tips Just for Core Drill Tools:
  • If you are using small (less than 0.500″ diameter) core drill, start with core drill held at a 45˚ angle to the material. Obviously, this only works on manual processes with hand drills, etc. As drilling proceeds and the drill begins to bite into the material, then slowly bring it up until it is at a right angle to the material.
  • Frequently remove the core drill from the hole during drilling to flush out the ground material and allow fresh water or coolant to get to the surface you are cutting.  Also rinse accumulated material from core drill itself as sometimes built up material will block coolant flow.
  • You must remove any slugs and debris from the inside diameter of the core drill tool. Remove by pushing a nail or stout piece of wire through the hole provided in the side of the core drill or on larger drills, through the back of the tool.

AutoDrill welcomes any questions that you may have. You can get a free Self-Feeding Drill or Multi-Drill Spindle Head quote by simply CONTACTING US.

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