Replies

1. 
   hotglass | Mar 16, 2003 03:45am | #1

   I saw an add for a waterfed grinder in a recent finehomebuilding magazine for 300 and something dollars. Did anyone try it? I want to get one, but am on the east coast and it seems all the suppliers are in the west. I'd be willing to order one if the price was right and it was a good quality grinder.

1. 
   KARLSTER | Mar 30, 2003 05:31pm | #2

   Look up Alpha Professional Tools in New Jersey. I have used their old style water fed polisher (aep 158???) and it is ok.  It tends to need a lot of servicing if used for hours on end, week after week so I switched to a pneumatic water fed polisher with much better reliability (It required purchasing a Large Compressor)

   Alpha just came out with a new electric water fed polisher that seems to be set up especially for flat polishing surfaces (has guide wheels to keep it level).  The good news is it seems much lower priced, the bad news is I just noticed it was recalled.

   Alpha has a great track record for customer service so you can feel confident about follow up support.

   Be aware that concrete  is far more abrasive than most stone so the grinding/polishing media alpha sells are not correct for concrete unless they tell you otherwise.  The grinding/polishing media needs to have a much harder bond between the diamond particles to resist the abrasiveness of concrete.  As a general rule the softer the surface to be ground, the harder the diamond bonding matrix needs to be.

   Harbor Freight sells some diamond polishing pads that are so cheap you could get away with using them on concrete.  They are five bucks or less per disc.  Alpha's start around 40 bucks.

   karl

1. 
   TRIGGER | Mar 31, 2003 03:23pm | #10

   Karl,

       Will the diamond disks @ HF take care of my granite slab polishing task? I have a 4" angle grinder, a 5" ROSander, 6" air ROS, and a 7" grinder. It's about 50sq.ft. of slab I need to polish. Thanks,

   Triggerski

1. 
   KARLSTER | Mar 31, 2003 04:33pm | #11

   Triggerski, When you say 50sq ft needs to be polished it gives the impression you want to polish the surface of the slab.  Any flexible polishing pad (from HF or anyother supplier) is not suited to polishing large flat areas.  They are designed for polishing edges, such as a bullnose.  You can buy rigid polishing cups for handheld polishers from the better supply houses that are suited to limited surface polishing.  By "limited" I mean I wouldn't want to polish more than a few square feet with them.

   In addition to this any polishing medium for granite needs to be run at 2000-3000rpm.  It sounds like your arsenal of tools run at higher speeds.  It is possible the RO sanders might be ok but most granite polishing pads are only 3, 4, or 5".  I have never seen a fabricator use a random orbit sander so I assume there must be a reason they don't.  Some guys apply water with a sponge as they work and get adequate results but they have a lot of experience than guides their technique.  I would tell any beginner attempting to teach themself to use a center feed wet polisher.

   Finally different stones require different polishing techniques.  A gold colored stone like Giallo Veneziano is relatively easy to put a shine on.  A deep green like ubatuba requires a lot of care with each grit or you will get a hazy shine that won't match the polish created at the quarry.  Cheap pads like harbor freight sells are presumably adequate for easier stones like the gold ones but if I am polishing a finicky color I always use Alpha Professonal Tool's pads which run $40 or more a piece and I use at least five different grits.

   Without both the right tools and getting some one on one coaching from an experienced fabricator polishing stone is not very realistic.  I am not saying you can't do it but there is a reason the pro's charge what they do.  It takes knowledge, time and practice to get consistent quality results polishing stone.

   There is an outfit that I believe calls themselves Regent Stone Products in Virginia that offers classes/workshops in stone fabrication.  This is probably the best option for an individual who lacks a mentor yet desires to develop skills in stone fabrication.

   So the answer to your question about the HF pads is NO.

   Karl

1. 
   TRIGGER | Apr 02, 2003 03:20pm | #12

   Karl,

   You have confirmed what others have tried to tell me. I'm gonna pass on this task, before I *^#@ som'thin up.

   See Ya! Thanks.

   Triggerski

2. 
   KARLSTER | Mar 30, 2003 05:33pm | #3

   Braxton Bragg is a low price mail order house that sells Alpha products.  Look them up on the internet for contact info.

1. 
   ndege | Mar 30, 2003 05:49pm | #4

   I'm also trying out a concrete countertop for the first time. A fellow builder told me he'd seen some tops "peeling." What do you think that is? I thought maybe a bad concrete mix or some kind of surface treatment that was peeling off? Is that a common problem?

   Do you think you could grind with non-water-fed grinder and just keep running water over the surface by hand?

1. 
   KARLSTER | Mar 30, 2003 08:08pm | #5

   Unfortunately my experience is limited to cutting and polishing stone.  I am strictly an amatuer when it comes to concrete. 

   I don't see much need for a water fed grinder unless you are doing narrow edges and can't keep the water pooling on the surface.  I even will attach a "loc line" articulated hose and nozzle to a dry angle grinder to convert it to a wet grinder.  Most of the water fed polishers run at a maximum of 4000 rpm and for concrete I don't see any inherent hazards in running at 10,000 rpm.  The only reason to go slow speed for polishing is the flexible diamond wet pads will overheat at higher speeds.

   I go with a wet grinder to protect my lungs.  Chronic exposure to silica dust is a big worry for me.  Those with less paranoia for their longevity seem content to run silicon carbide grindstones at around 4000rpm.  If you want to merely flatten and smooth concrete in limited amounts you could try a 36 grit, 60grit and a 120 grit Silicon Carbide 5" stone on a slow speed grinder.  I like the Makita pistol grip sander (9218SB) which runs at 4000 rpm.  You will need to develop a technique for balancing a brand new grinding stone with a wheel dresser as they frequently vibrate until you have done the initial balancing.

   Good luck, Karl

2. 
   Mongo | Mar 31, 2003 07:01am | #9

   A fellow builder told me he'd seen some tops "peeling." What do you think that is? I thought maybe a bad concrete mix or some kind of surface treatment that was peeling off? Is that a common problem?

   I'd bet that the peeling was a cured, or film ,that was applied to the countertop.

   Why did it peel? The slab could have been improperly prepared. The film finish could have been improperly applied. All coould have been done properly, but the end user could have damaged he film in eveyday kitchen use.

   I advocate penetrating finishes over film finishes.

2. 
   wallyo | Mar 30, 2003 11:26pm | #6

   You may have looked at it already but I picked up Tauton's  concrete countertops.  Have not read it yet but it goes into great detail on how tov polish. Just a thought.

1. 
   ndege | Mar 31, 2003 12:54am | #7

   Yes, I have this book and have found it helpful. He suggests renting a grinder. I'll look at it later and post some of the specifics.

1. 
   ponytl | Mar 31, 2003 03:08am | #8

   last concrete countertops i did... i built a mold (3/8 flat smooth steel with 2" polished surface angle iron sides 2" foam board glued in place for sink openings where they were to fit agaist a wall i made em long and cut em with a diamond blade... oh yeah this was top side down... they could not have been any smoother... i use RV antifreeze for a release agent sprayed on with a windex bottle... i had a huge stack of that 4"x4" display grid 1/4" rod they use in dept stores to hang stuff on (fished it from a dumpster) used it instead of rebar... with the 2" angle i could adjust my sizes pretty easy ... one piece was fixed (welded) the others clamped to L & W...

   pony

   started out with nothing... and have most of it left