Concrete Drilling and Coring

Started by glenn-k, November 23, 2004, 12:06:49 AM

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Holes can be made through concrete fairly easily with a rotohammer ( a rotary percussion drill).  They come in many sizes from small drills with a little hammer built in to larger ones made only for percussion drilling or chipping.  

Some do not stop rotation so cannot be used for chipping or demolition work.  Many of the larger ones do not have reverse, so the bit may have to be reversed with a pipe wrench if stuck on something such as a rebar.  The larger drills will drill a 1" hole in concrete at the rate of about an inch a minute and smaller holes faster.  My personal favorite is a large Bosch rotohammer but there are other good ones out there also.  The SDS max size I have has a clay bit like a small shovel or with an adapter you can use SDS drills and chisel.  If you stop rotation it makes a great hammer using an old bit to drive anchors in or pound things on the old truck much faster than hammering with a sledge.  It makes a great small demolition hammer or jack hammer for hard digging or chipping concrete.

For bigger holes you can buy fairly inexpensive diamond coring drills that will fit on a standard 5/8 x 11 thread grinder shank.  The big portable hand grinders work best for this.  A 3" core drill cost around $130 and will go through a 10" concrete slab, depending on the model or manufacturer.  They can be used wet or dry but some water makes them cut faster and keeps the dust down.  We just finished a job with a gas powered one and drilled 32 three inch holes 8 inches deep in about 4 hours.  The grinder powered one is a little slower but gets the job done.  Probably about 10 to 20 minutes for an 8 Inch deep hole.

Something for those times when you would just like a nice round hole through your slab!  Core drills come in a wide range of sizes.  A local contractor supply is a good place to find them.  Here is a link I found on the net.  

Glenn :D