Diamond Core Drills, High Tech Application

Precision Industrial Diamond Core Drills are manufactured by Braemar using our exclusive metal bond developed for high strength and longevity. Braemar can build your Diamond Core Drills to suit your exact needs with a quick turnaround that today's industries demand. Our Diamond Core Drills sizesrange from .026" to 36" diameter with tolerance of (±.001") on 2" and under. We have the ability to mount Diamond Core Drills to your needs or the standard that is used at your facility.

Quartz, Ceramics and many man-made modern materials, because of their brittle and abrasive nature, pose serious machining problems, especially when drilling straight, clean holes. Chipping, cracking, drill burn-out and excessive wear will occur unless

great care is taken. Braemar can build your diamond core drills to suit your exact needs with a quick turnaround that today's industries demand. Our diamond drill sizes range from .026" to 36.000" diameter with tolerance of (±.001") on 3" and under.

Braemar diamond core drills can be made with natural or synthetic diamonds, sieved to the desired grit size, mixed with a metal matrix and bonded to a steel core. The depth of diamond is usually 1/4", or 3/8", other depth sizes can be made upon request. The standard wall thickness on drills that are 3” and smaller is 0.030”. Most of our drills are made with synthetic diamonds that are uniform in grit, shape, and size: than natural diamonds. Diamond size can range from 20/30 to 270/320 grit. Coarser grit sizes are used for faster stock removal without much concern for surface finish.

There are two basic drill types: solid and core. It is universally accepted that diamond core drills are superior in performance to solid drills because of the importance of through coolant in drilling. With a core, .025 inch (.65 mm) or smaller, however, it is

1) Metal Bond Diamond Core Drills (or sintered) diamond drill. The diamond section consists of a prescribed quantity of natural or synthetic diamond, sieved to the desired size, mixed with a holding matrix and bonded to the steel shank. The depth of diamond is usually 1/8,1/4, or 3/8 inch.

2) Electroplated Diamond Core Drills. A single layer of diamond particles, either natural or synthetic, is plated with nickel or another material to the end of a metal shank. The diamonds are more exposed than those in impregnated drills and, consequently, cut faster. Once the layer of diamond wears off, the drill must be discarded. It should be remembered when using plated drills, that only the top, or crown, of the drill does the actual cutting. Although diamonds may be visible on the side of the drill when the crown area is worn clear of diamond, the drill will no longer cut. Some machine operators look at the drill and, seeing diamonds on the side, attempt to continue drilling and are usually puzzled when the drill fails to penetrate the workpiece

3) Electro-Formed Damond Core Drills. Here, the diamond section is built up in layers on a ceramic core by means of an electrolytic process. The disadvantage of these drills is the loss of controlled sizing and the brittleness of the diamond section.

In the past there were only a few machines capable of quality drilling small holes (under 1/8 inch or 3.18 mm). Then CNC milling centers were developed that are capable of drilling holes down to .025 inch with coolant moving through the drill center. With the manual machines we had always recommended drilling by the pecking method, where the operator constantly lowers and raises the drill to ensure a steady supply of coolant at the cutting point. Now, with the automatic CNC machines, we can drill straight through the workpiece. The operation is faster and the drill lasts longer. This only applies to core drills, because it is still necessary to use the pecking method with solid drills

When the goal is to drill chip-free holes consistently, every component in the drilling process is important. The basic equipment required is a sturdy, vibration-free and well-made machine, capable of developing the proper speeds and, at the same time, allowing sensitive feeds. The machine must be mounted on a firm base and its spindle must be periodically checked for run out.. The workpiece should be securely held in position. Moreover, the spindle bearings must be in good condition and the feed sensitive enough for precision down feeds.

Diamond grit is available in sizes ranging from a coarse 20/30 to a fine 270/320 grit. Choice of grit size is largely determined by the size of the drill and the material being drilled. It is highly important that the correct grit size be used. A coarse 20/30 grit diamond grill will not give the same performances as a 150 grit drill. Generally speaking, coarser grit sizes are used for faster stock removal (i.e. Higher productivity) without much concern for surface finish.

Coolant is as important as the drill bit itself. We do not recommend drilling dry with diamond core drills. Coolant serves two purposes: first to keep drill and material cool; and second, to flush away abraded particles that could otherwise impede the operation of the drill. With the use of an additive, coolant flow is increased, thus aiding in carrying away the abraded material. The ideal procedure is to supply coolant under controlled pressure through the center of the drill. With solid drills, an abundant flow of pressurized coolant to the outside is good. The practice of squirting coolant onto the workpiece and drill point is utterly e smaller the drill, the greater the coolant pressure should be. As a rule of thumb, we recommend a pressure of 80 psi for a 0.025” core drill. For a 1 inch drill, 20-30 psi is adequate. There are CNC milling centers that provide through the spindle coolant that can cost thousands of dollars for this feature. The alternative for this is the use of the Water Swivel that Braemar manufactures.

Experience has taught us through the years that there is not set speed for diamond drilling. Drill speed depends on the material, the operator, the pressure and other variables. Today, we recommend a variable speed control on your machine. The operator will soon determine the best speed for the specific job he is doing. A further point to be dealt with is the recommended speeds for drilling. We hesitate to generalize since so many variables are involved. Speed may range from 2000 to 8000 ft/min. Depending upon the drill type, operator, and operation. It is important and indeed essential for the user to observe closely the tool at work, if he/she is to obtain an improvement in the tools work capacity by skillfully altering speeds and coolant as the tool is adjusted.

Truing a tool is the operation of squaring a tool so that it runs within required tolerances. This is done with a hard stone that will knock the high diamonds out of the metal matrix, or by using a Brake Dresser with a Silicon Carbide wheel. Braemar will ship drills ready to use and a small break-in period may be needed.

Diamond Core Drills that are correctly dressed are directional and should always turn in the same direction with the leading edge of the diamond cutting into the workpiece. Using the correct dressing sticks will expose the diamonds for optimum cutting performance. After each dress give your drill the “Thumb Nail Test” by snagging your thumb nail on the diamonds. This will give you an indication of how free cutting your drill is and will be a good reference point on how often this process should be repeated. After using your Diamond Core Drill it may seem to drill slower or may begin to chip your material, diamonds may not be exposed. Do not force the tool, stop and dress the drill.

Care, experience and good equipment are required to minimize chipping. The most successful method of avoiding chipping is to flip-drill. This, however, is not always feasible. It also presents additional problems, such as realignment of the workpiece. In some instances, drilling with an undersized drill followed by reaming with a reamer of finer grit size not only enables you to hold tight tolerances but also removes any small amount of chipping that might occur at break-through. The application of facing plates will also reduce chipping. But this application is costly and is not always practical

This is an important subject. Core hang-up generally takes place just at the point of break-through. As the core breaks away from the workpiece, especially when the workpiece is not properly supported, there is usually a rim of unground or unabraded material at the very bottom of the core. Being unground, it is wider than the core drills 1.0. This unground rim causes the core to stay firmly within the drill.

By waxing down the workpiece with a minimum of wax adhesive and by properly supporting the workpiece under the drilling point, it is possible to drill completely through the workpiece, have the core remain in position and also obtain clean holes. Remember, good coolant pressure, a suitable coolant type, and a minimum of Pressure, at break-through will help to prevent core hang-up problems. Whenever possible, a dial gauge should be used so that the operator knows exactly the point of break-through, and so can reduce the downward pressure of the quill and ease the drill through its last few thousandths of an inch of travel.

Braemar manufactures drills to a plus or minus 0.001” tolerance on drills that are 3.000” or smaller. Tighter tolerances can be obtained on request. It is nonetheless often found that while the drill measures on size, the resultant holes may be oversize. This is brought about either by bad drill alignment, machine run-out or a badly ground drill.

First, check the machine spindle head to be sure there is not run-out. Check that the drive belt is not too tight or too slack since either condition affects spindle motion. Also be certain there is no foreign matter on the drill seat, to cause misalignment of the drill. Check the drill for head concentricity. If the head is not absolutely concentric with the tail or mounting portion of the drill, it will produce oversized holes. The fact that the head size mikes correctly means little.

A single high diamond will also produce oversize holes, but may not be detected when the drill is measured. So it is prudent to check the drill head with a loupe. If a high diamond is found, switch on the machine and lightly touch the drill head with a fine file, to chip off the high diamond without damage to the drill surface You have, no doubt, often heard it said, just drill into a scrap piece of glass and your drill will align itself. This is correct to some extent. The drill appears to be running true. But to be certain place a dial indicator against the head of the Drill and rotate the spindle by hand to be sure there is no run-out. Be sure the dial indicator is fitted with a nylon-protected finger.

Finally, if you must drill straight through with no backing, drill carefully! Watch your dial gauge, and when you come near the end of the hole, ease up the pressure and increase your drilling speed. There is no substitute for experience. An operators first holes can be ragged and drill life short. But as he or she proceeds and gains an understanding of speeds and pressure, the quality of the holes improve and drill life is lengthened

Tapered drills have also been successful. Here, the drill portion of the head is below required finish size, while the section immediately behind or above the head tapers out to the correct finish size. This results in a hole reamed to finished size while at the same time removing any chipping. With this type of drill a catchment is required beneath the workpiece to trap and return the coolant to the outside of the drill during the remaining action.

Finally, a disintegrating core drill with the drills ID. Offset to one side (of the drill) also helps to prevent core hang-up. With this type of design, the actual core material is smaller than the drills internal diameter, and can easily be washed away by coolant pressure. Be sure to tell us what you will be drilling. We can then deliver the correct diamond size and matrix. Also ask for the drill to be made to your largest tolerance - i.e., if ordering, say, a 1 inch drill with a given tolerance of +/.001 inch, request that the drill be made 1 inch + .001 inch and - .000 inch. This will give you longer drill life.

Duel core drills can increase production by drilling the ID and OD at a single pass. There is a learning curve when using these drills, we have had many successful applications with this style of drill. Typically we can hold both dimensions by ± 0.001” on drills that are 2.000” or smaller.

Concentration is a measure of the amount of diamond used in the drill. A 100% concentration drill would contain 25 volume percent diamond or approximately .72 cts. Per cubic inch. The majority of drills (90-95%) contain 100% concentration. Finer grit sizes and other drilling variables might lower this concentration The true measure of a drills performance is not the amount of diamond, but rather is a complete performance evaluation. Today, virtually all drills are made with synthetic diamonds. There are special types that have been engineered for this purpose. For plated drills many manufacturers use GE synthetic diamonds of the MBS (t) type in 120/140 grit or De Beers ECD type synthetics. For impregnated type drills De Beers SDA or GE MBS is used.

Braemar Diamond Core Drills can be permanently mounted on standard or custom mounts precision machined from brass. Our stock mounts are: 5/8-18, 3/4-16, 1-14, 1/2 gas -Belgium Mount, & Winter Mount. For best optimum performance it is highly recommended that drills are permanently mounted.