Dry Core Bits Offer Better Options!

When drilling holes through masonry walls (brick, block, stucco) dry core bits offer a tremendous advantage over carbide bits. It has been my experience over the years on numerous jobs sites to witness contractors employing a variety of tactics when penetrating masonry walls. Whether an electrician needs a two inch opening or an HVAC contractor needs a four inch vent, or even a plumber needs to run a six inch pipe, or maybe the fire sprinkler contractor needs to run through block fire wall; they usually grab their hammer drill and start drilling a series of holes followed by some maul and chisel work. This type of drilling makes quite a mess and leaves behind a hole a bit larger than the one intended due to the “blow-out” produced by the hammering action of the carbide bit.
When I see this I hop on their scaffold after receiving permission. In my hand is a dry core drill machine with the core bit required to drill the hole needed. One of the first things I have to verify is the hole size. Most contractors are so used to a hole that winds up much bigger than prescribed, I also need to point out that a diamond bit at two inches for instance will have a hole in the wall of precisely two inches. For this reason, the contractor needs to measure the o.d (outside diameter) of his pipe or duct and account for any escutcheon or flange or grill to be attached.
My hand held drill has a variable speed trigger which helps to start the bit without walking on the wall. Provided there is no steel in the wall, these contractors are amazed at the speed at which an average brick and block wall can be drilled. There is generally very little clean up as the “cored” masonry remains inside the bit. Insulation and or fire caulking costs are greatly reduced as the hole is only slightly larger than the pipe.
You wouldn’t believe how many of those contractors now ask me to drill such holes when I am on the job site doing my other drilling and cutting jobs.
Try this on your next job and I am sure you will be satisfied.

Does it pay to step cut when flat sawing?

In a word, yes. Many contractors shy away from step cutting when cutting through a slab in preparation for breaking and removal. The typical excuses run from not wanting to change saw blades to time constraints to basically not thinking it makes any difference.
However, it really pays to do the job right. I once worked for an old contractor when I was a young man and he would often recite: “be the jobs, big or small, do it right or not at all” I grew quite tired of hearing his rhyme but it stuck with me because he had a good point!
First of all, let me explain the concept of step cutting . Let’s say we have a ten inch thick slab to cut and remove. The top is two inches of asphalt over eight inches of concrete with number five rebar mats throughout.
Our first cut will be with a fourteen inch by quarter inch thick Asphalt Blade. An asphalt blade has a hard bond mix and undercut protection. In order to cut one slot one quarter inch wide, we sometimes use a blade that thick (.250”) or we often use two blades mounted side by side on the spindle of standard thickness (.125” each) With the initial slot open and the highly abrasive asphalt cleared out of the way, we make the second cut with a twenty inch concrete blade with a thickness slightly lower than our initial slot (.187”). The advantage of using a narrower diamond blade on each successive cut is that it doesn’t have to re-cut the sides of the previous cut. In this case we use a concrete blade and avoid the asphalt. The twenty inch concrete blade cuts a depth of seven and one half inches. Depending on the hardness of the concrete we take this depth in one or two passes. Always be sure to match the bond on your saw blade to the aggregate of your concrete. Last, we need to use a concrete blade of at least twenty six inches in diameter to cut the rest of the way through the slab. The thickness can be either the same the previous cut (.187”) or thinner (.175). If you decide to go with a larger blade, like a thirty six inch one, just be mindful not to drop the blade too deeply
under the slab. Even though the temptation is to cut way under the slab in order to account for variations in depth, it results in a tremendous waste of a very expensive diamond blade. Because the sub grade can be either sand or rock, cutting through it wears the diamond blade but actually accomplishes nothing.
The greatest advantage to step cutting is through reduced blade wear. The larges blades are significantly more expensive than the smaller blades . In the long run using your blades is this manner reduces cost. Our company actually cuts concrete every single day, so we know what we are talking about. Try step cutting for yourself on your next big job and you will never go back to the single blade approach again.

Proper Set Up Is The Key To Successful Core Drilling

Many contractors shy away from doing their own core drilling because they have had bad experiences in the past renting rigs and allowing their workers to drill holes with little or no prior core drilling experience. Most of these contractors believe that operating a core drill machine is no different from other drilling operations performed with 1/2” drills or rotary hammers.
Even though, core drilling is very different from other types of drilling, it isn’t really hard to master. The first thing to know about core drilling is that the set up is vital to operator’s success. The set up may take thirty minutes while the actual drilling operation is completed in just ten minutes. The steps to a successful set up for core drilling are the following:
1. Site Preparation:
Be sure to have your holes clearly marked by the contractor and well in advance. Water must be available and a regular garden hose spigot is fine to provide the proper flow however, make sure it is not further away than 150 feet. A power source providing the proper amperage for your machine must also be available. For that matter, please use a dedicated line for your machine. Do not use jumper extensions for drills, lights etc… Always run a single core (10 gauges) from your machine to the power source (should never be longer than 100 feet). You must have a flat surface on which to anchor your machine. Most machines have leveling bolts, the purpose of which will be explained later because it takes an advance drilling expert to successfully drill on uneven surfaces.
2. Anchoring:
Although some operations require the use of a vacuum pad in lieu of anchoring, I always set an anchor when possible. The exception would be when drilling short penetrations such as 3” depth for epoxy set railings. I have found that drop in anchors work best because they are flush with the surface and usually are acceptable to the contractor when left behind after the job. I also believe that 3/8” is sufficient unless drilling over 10” cores. Once the anchor is in place, I position the machine over it so that the anchor is visible through the slot in the base of the machine. I like to use a threaded bolt with extra length. On the bolt, there is a thick, wide washer more than sufficient to completely catch the base of the stand. Above the flat washer is a slit lock washer and above it a nut threaded between the washers and the top end nut on the bolt. First, the bolt is threaded with washers and second put the nut firmly in place onto the anchor. Then, I spin the inner nut snugly against the two washers and against the base of the core rig . This is a hand tightened action only at this point

3. Leveling
The next point is hard to over emphasize. I wish I had a dollar for every time I approached core driller who said “this core bit must be stuck on something”. The very first question I ask them is: where is your level? In most cases they do not have one! A level is a must for every driller! Some of the better machines are equipped with levels however I still like to use my own because I can use it in several different positions. Get a magnetic bullet level then place it on the column of the rig. Now is the time you use your own leveling bolts. Because you have already hand tightened the anchor bolt, only a slight adjustment is possible. And that should be enough to level the rig. In extreme cases, the anchor bolt may need to be backed off a little. Once you achieve a level base, you can now tighten the inner nut on the anchor bolt with your crescent wrench! You should now be on your way to performing outstanding core drilling .

What is a diamond core drill?

From Wikipedia, the free encyclopedia
Diamond core drill bits are used to bore large holes in brick, concrete and stone. They are not generally used in other materials. The bit consists of a metal cylinder, usually relatively soft steel mounted on an arbor. Industrial diamonds are embedded at the open end of the cylinder. In the image, the diamonds are on the metal segments attached to the end. The segments are thicker than the cylinder wall, so most of the bit does not rub in the hole being bored. The sloping slots in the cylinder wall help carry the dust out.

Diamond core drills can be used with or without water lubrication. The drill shown can cut a 115 mm (4.5 inch) diameter hole through a single-thickness brick wall in less than a minute, running at about 300 RPM. The resultant hole is very cleanly cut. Another obvious advantage over conventional masonry drills is the core bit’s efficiency — since very little of the removed core must actually be abraded, the power and operator effort required to drill a very large hole is reduced enormously, and the capacity of a given portable drill greatly increased.

This form of core drill wanders hopelessly when presented to a flat surface, and needs a centering mechanism. The arbor can carry a masonry bit to bore a centering hole. (The version shown has a plain 10 mm (0.4 inch) rod; a 10 mm masonry twist drill must first be used to drill the centering hole for the rod.) A wooden or stone template, a close fit for the cylinder, can also be used to guide the bit at the start of the cut. After the first few millimeters of cut, the centering mechanism may no longer be needed, although it will help the bit to bore without wandering in a deep hole.

Diamond core drill bits for use with portable drills are commonly available in diameters from 20 mm to 130 mm. The only limit on length of the cylinder, and thus depth of the hole, is the need to remove the bit from the hole to clear dust. 300 mm (11.8 inch) cylinder length is not uncommon, although shorter bits are usual. By breaking the core off from time to time and using a shank extension, a diamond core drill can drill to depths many times its length.

Some disadvantages quickly become apparent when using these bits:

• The portable drill used must be capable of producing considerable torque at low speed
• They tend to bind if choked with dust, or if allowed to wander away from the central axis of the planned hole
• The kick-back from a powerful drill may be severe under some conditions, and long side-handles should be used, preferably with two operators for very large holes. Careful consideration should be given to this when using such equipment at height or in confined spaces, for obvious reasons.

Diamond Blade 101

What is DIAMOND BLADE?

A Diamond Blade is a circular saw blade for cutting a wide variety of materials with special cutting equipment. It consists
of a Steel Core containing special Diamond Segments. There are several different types of Diamond Blades: Segmented Diamond Blades, Continuous Rim Diamond Blades, Turbo Diamond Blades (Serrated Continuous Rim), Turbo Segmented Diamond Blades (with serrated segments).

The core of the diamond blade is made up of precision steel and may have several gullets (spaces between segments) depending on the usage of the blade. These gullets allow a cooling process through air and water circulation between the segments. They also allow the blade to bend under high tension cutting.

The diamond segments are a mixture of diamond crystals and metallic powders. The diamonds used in the blades are synthetic or natural industrial diamonds of several different grain sizes, shapes or qualities.

How Do DIAMOND BLADES Cut?

A diamond blade doesn’t cut like a knife, it grinds. Through the fabrication process, diamond crystals are exposed on the surface and the sides of the segments. These exposed diamonds do all the grinding. The bond of metal powders hold the diamonds in place throughout the cutting process. Behind each diamond crystal, there’s a “tail” (like a comet) which helps hold the diamond crystals in place.

Through the cutting process, the operator will push the blade through the material. The blade will begin to cut through the material, and the material being cut will begin the wearing process of the diamond blade, at the rate of which the blade advances.

The exposed diamond crystals will break into smaller pieces while cutting. Harder, Dense materials will fracture the diamonds faster. As this happens, the material being cut also wears down the metal bond through abrasion. Highly abrasive materials will wear the bond faster, exposing new diamond crystals to continue cutting.

How to Select a DIAMOND BLADE?

Before you begin. The contractor should decide which is more important: whether it’s the initial cost of the blade or the cost per foot/meter. For smaller jobs or occasional use, you may prefer a lower priced blade. For larger more important jobs the cost per foot/meter is generally much more significant than the initial cost of the blade.

Identify what you will be cutting. This is the single most important factor. The majority of diamond blades cut only a specific variety of materials. For more efficiency (of cutting speed and duration), you should be sure to select the best type of blade for your application.

Choosing between dry/wet cutting. Using some equipment you may not be able to use water due to electricity. For floor saws (walk behind) it is preferable to use water to reduce dust levels and act as a coolant for the blade.

For high speed saws, dry cutting blades are recommended, however sometimes water may be used to control dust levels.

While wet cutting blades and core bits must be used ONLY with water, dry cutting blades on the other hand can be used with or without water (depending on the job situations or the equipment).