Kowboy:
Thanks for the paragraph tip. Will do.
For me this is not about trade offs it about developing and using a method that is effective and repeatable. Based on my expirience I would advise against sending a "relatively low-skill operator" to core holes on a finished project. At that point you have way too much time and money into the project to take that kind of risk. Doing things right the first time is far more profitable that fixing mistakes.
This is probably more appropriate in the post asking about coring holes a customers home, but here goes anyway. This is the method we have developed after literally thousands on-site core holes:
Tools:
-Variable Speed Grinder brand is your preference, I like Makita. I like one that
runs 2700-10500 rpms.
-1 3/8 wet/dry core bit. I like the DIAREX PRO SERIES TURBO CORE from Gran
Quartz they run about $65 bucks off the truck and we've had good luck with
the quality. I like bits with diamonds on the sidewalls, this reduces the wear
on your tool as well as the risk of binding up the bit. You can definitely get bits
cheaper and sometimes they work but I would rather pay a little more for a
diamond matrix that is consistent.
- Suction ring $5-8
-Shop Vac
Process:
-Mark your holes using a white pen or tape (your preference) If you are
having difficulty keeping the bit from skipping a few layer of masking tape can
be cheap insurance but not fool proof.
-Have someone hold the shop vac. If your alone get creative.
-Holding the grinder with both hands brace your elbows on the deck and
make contact with the front edge of the bit. Gradually add pressure until the
bit is stable and begin rolling the bit back to level. Once you are about 1/8th
deep stop.
-Apply suction ring and add enough water to fill about an 1/16th inch about
the surface of the stone.
-Make contact with the stone and then turn your tool on. While using a rolling
motion gradually increase downward pressure until you find the "sweet spot".
-Stop occasionally to add water as the hole dries out. Adding too much water
will make a mess, not enough can build up heat that may crack the stone and
diminsh the effeciveness of your bit and shorten it's life.
-As you approach the end again brace your elbows and lighten the pressure
so that when you cut through your tool does not bang the surface.
Notes:
-Wear ear and eye protection. If you are having trouble controling the dust a
carbon filter mask may be necessary.(nssthan this is for you:)
-Every stone is different you may need to adjust the speed and
pressure to find the "sweet spot" you will know when you find it. If you are
having a hard time, keep practicing on sink drops. Know your stone before
you work a finished piece.
-Start the speed on the lower end as higher speeds (especiallly 30K)
will generate more airborn dust, even with a shop vac. Excessive speed and
heat are the main causes of glazing. If your bit is glazed simply dress it in a
fire brick.
For a demonstration of this check out Nssthans Video
-The main purpose for using water is to act as a lubricant and control heat,
a nice side effect is that it also controls dust, prolongs the life of your bit
and reduces the need for dressing.
Video:
Had a few extra minutes at lunch and shot this demo with a cell phone. If you
don't tear me up too bad, and/or anyone finds it beneficial I'll bring in the HD
camera and film other topics. Let me know what you'd like to see.