Selecting the Right Concrete Core Drill & Diamond Core Bits

I apologize in advance for the dry material but we get lots of questions about concrete core drilling and hopefully we can clear it up a few of the basics in this post. There are lots of options when it comes to coring drills & rigs in terms of price, quality, size, power source, etc. Each type of drill has its place and it’s not always easy to select the right one and not make the decision totally based on which is cheapest. Ohio Power Tool offers a wide range of different types of core drills to cover the majority of needs out there which we’ll look at but obvious there are dozens of other brands out there that could be matched up.

Power Source – Air, Hydraulic, Electric

The most common type of core drill is electric using standard 110-120v power but in some cases air or hydraulic could be necessary or more convenient. The Air Core Drill CP0315 is a good hand held option for job sites with trailer compressors but it can suck down up to 44cfm of air so you really need a large compressor. Hydraulic can be another good option for situations where there is high flow hydraulic equipment around to tap into and power the drill. Hydraulic is the best option for underwater drilling for the few out there do that kind of work. You might also see hydraulic used for the large diameter drilling for diamond bit up to 72”. For the electric core drills mounted on rig or stand it is very important to also have a meter box to regulate power and protect the drill motor.

Hand Held vs Rig Mount Core Drills

If you are interested in proving your manliness handheld concrete coring all day would do it in my book. It takes some torque to power a drill in concrete and sometimes the drill is more inclined to turn you than actually remove the concrete. It’s no problem drilling with small diameter coring bits but when you get to 2” or 3” bits it can be taxing. Anything about 3” is not recommended to ever use a handheld core drill but of course some people do it anyway. It is much easier to use a hand held unit than lug out the rig mount and try and fasten it to something so people tend to go with easiest solution. The Weka DK12 & Weka DK13 and the best hand held units in the business, 3 speed, built solid, just all around great units. Of course if you are looking for a more cost effective solution Diamond Products also imports a CB500-HH ($460, Ohio Power Tool). All these handheld units can also be used in the M-4 Rig Stand so you can have the best of both worlds and the Weka handheld drills will be able to handle up to 6” bits when mounted in the rig.

Concrete Core Drilling is a much safer endeavor when using a stand that is secured to the work surface with either anchors or a vacuum pump. At this point you can core holes several feet in diameter if you so choose. A complete Rig Coring system can be as inexpensive as $899 with a basic anchoring unit like the M1-AA-15 single speed, best for repetitive smaller single size holes like installing hand railing for instance. A very popular electric coring motor option would be one of the Milwaukee motors; used by several other manufacturers in their rigs these 2 speed motors are very durable and economical. Weka also makes coring motors for rig mounts which are extremely well engineered, versatile with 3 speeds but fetch a higher price. The Weka motors are also available in larger sizes such as the DK32, DK42 & DK52 which are available in 230v & 480v 3 phase for large diameter drilling.

Diamond Core Drill Bits

Possible one of the most important aspect to the core drilling process is the Diamond Core Bit itself. The production and use of diamond core bits can be incredibly scientific. Similar to selecting a Diamond Saw Blade (previous article). It is very easy to have a bit fail or wear out very fast if you are using the wrong “diamond cocktail” in the core bit. Concrete is made differently in different parts of the country even within different parts of the state you can have much different aggregate.

For instance a core bit in Florida is going to zip through the soft shelly concrete so you want a harder bit that will hold the diamonds and last longer however up in the tip of the pan handle the aggregate is completely opposite, on the very hard end of the spectrum and you will need a very soft bit to release new diamonds more often. A general purpose bit will not get the full potential in either situation because it will release diamond to early in soft concrete whereas the same bit may overheat and be ruined in the hard aggregate because it can’t get new diamonds released. The jobs may be less than 50 miles away and could be working on the same day.

Each core bit grade has different options for hardness, for instance Heavy Duty Orange Core bits come standard as HOL but are also available at the same price as H33F (Hard Aggregate) or H64L (Aspault/Block). In addition to these options with in a single line/grade/color there are also multiple different lines/grades/colors of bits. The different grades  determine the cutting quality of the diamond chunks inside. Gold, Orange, Black & Silver (2” cost: $82, $96, $140, $169 respectively) are the wet diamond core bit grades available from Ohio Power Tool which should cover most of the different needs. The Orange bits are by far the most common also the black bits are popular for those who are working in the same material and know exactly what they need in their diamond mix. Silver Bits are an even higher quality bit for small diameter drills mostly used with handheld units. The less expensive Gold core bits are only available in the single general purpose formula and are more for mixed use applications where they may be run by an operator who most likely did not purchase the bit and has little interest in longevity of the bit, if you know what we’re talking about here.

The best option if you have any questions at all would be to contact the professionals at Ohio Power Tool, who have years of background in helping match the right diamond core bits to the right coring machines for many specific applications across the country. Call them at 800-242-4424 or email your questions to [email protected].  


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