Abrasives - Best Cost to Grind Time Ratio

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Alright what are your opinions? I started out using the good old fashioned hard grinding disks for all my weld grinding because labor time = $0.00/hr as I was just a hobbiest. Since then I've gone to flap wheels. In my experience, they grind at least 3 times faster than hard disks, but wear out probably 5 times faster. Cost of flap wheel is about $3/each and I have them rated at about 80-150 welds ground per disk (1-2" welds). So in yall's experience, what's the best grind time/cost/life ratio of abrasives? If it matters, assume employee pay and overhead rates at $30/hr. Are pneumatics any more efficient than electric grinders? One of my guys claims that a right angle die grinder with 2" fiber grinding wheel is the best option, but I wasn't too impressed when I tried it out.John 3:16(2) Miller Pheonix 456(2) Millermertic 252Dynasty 210DXHobart 210MVPDoringer D350 SA Cold SawScotchman 350LT Cold SawWebb 10x50 MillWebb 15x40 LatheGeka Bendicrop Ironworker
Reply:Pneumatics are very inefficient. Figure that an electric random orbit sander draws about six amps or so on 120V. The equivalent pneumatic sander will consume 13-15 CFM, which is pretty much maxing out a 5 HP 80 gallon air compressor drawing 30 amps at 240V. That's like drawing 60 amps at 120v, so in a nutshell, pneumatics require about ten times the power to accomplish the same task. I've never done a cost to grind time analysis on abrasives, I usually compare the cost to effectiveness ratio. I'm a fan of Klingspor flappers, decent pricing, impressive performance and excellent service life. Their 36 grit flappers really move some metal.
Reply:I was all bent out of shape trying to find an exact stripper type disc that someone had raved about and while it works the ones I used from 3 or 4 different makers all seem to be very, very sensitive to edges, particularly sharp ones, like the just cut ends of tubing.  Even if I was very careful about only spinning them at the correct angles so they go "off" the edge they seemed to wear very quickly for what I was getting done which was typical prep for welding and later painting.  They seem to work far better for subtle types of surface blending.I think you may find that your search will be influenced by different brands/makers than by the exact process or tool used.  Not sure how this relates to overall cost, I've found some slightly cheaper flap wheels very  very good lasting longer than known brands but did not track well enough to say precisely.I think it also depends a lot on the grit and job matching.  I had some 3M very coarse grit on one of those lock on discs using an electric die grinder and was almost scared to use it as it cut so much faster/better than others I had used.  Still trying to decide if the products with the little plastic (?) fingers like a brush that have imbedded abrasive in them are worth the high cost, very very sensitive to edges.Last edited by RussZHC; 02-07-2015 at 05:02 PM.
Reply:You have any idea how many grinds you get out of a disk? And beside the point, I'm not sure I agree with your compressor ratings... My 5HP, 80 gallon compressor puts out about 19cfm at 175psi, closer to 35 at 90psi and draws 14 amps peak. It's 3 phase though, so a little different, but still...John 3:16(2) Miller Pheonix 456(2) Millermertic 252Dynasty 210DXHobart 210MVPDoringer D350 SA Cold SawScotchman 350LT Cold SawWebb 10x50 MillWebb 15x40 LatheGeka Bendicrop Ironworker
Reply:Estimating mind you, towards the upper end of the range you gave...120 to 150 welds.  Your 3 and 5  relative numbers for hard discs and flappers is pretty close too IMO, IF, if the hard discs don't get clogged with crap from mill scale, I prefer them, they seem to load sort of at random though, sometimes very quickly, sometimes a long time but I would not be sure if it is the steel supplier/maker or more related to the disc maker.
Reply:You probably won't like my advice but it is free so all it costs is your time to read it. Go to a reputable abrasive supplier like Walter( http://www.walter.com/documents/1019...6-62ea7c6160b2) or Norton( http://www.nortonindustrial.com/DepressedCenter.aspx ) and buy the wheel that best suits what you are doing. If you really want to remove metal buy a bigger angle grinder. We start with 9" and bump the wheels down as they wear to 7" and then 5". Never had one explode (rpm increase as diameter of grinder gets smaller). I have used both Walter and NorZon and liked them both. Labor is far more expensive than good grinding wheels so save your time and buy the right wheel and the right machine to drive it. I like my 9" and 7" grinders. We have a 5" but only use it for something "delicate" or where I can't fit a larger machine. I have a box full of discs worn down to 5" and rather than use them up I take a new 9" and start again.Saves time and money. Nobody I know (including me) likes to grind but I have spent 100's possibly 1000's of hours doing it. Big good grinders are heavy and if you are not careful they will hurt you bad and quickly but if you have metal to remove there is no comparison to tiny, light. underpowered toys. Matching the wheel to the job at hand is absolutely necessary. Just try grinding aluminum with a wheel designed for steel and you will see.---Meltedmetal
Reply:There are too many factors to consider to answer this question. I think you just need to buy some and compare for yourself.
Reply:big fan of walter flappers, but im not the one paying for them. the 40's take metal off like nothing, and dont glaze over when over heated on stainless like others dobosses stuff:trailblazer 325maxstar 200my stuff:sa 200fronius transpocket 180100 amp Lincoln w/f97 f350 DITKevin
Reply:While flaps are great and i have used a lot of them on my 9" and 4 1/2 " and on my die grinders ...Yes they do make small ones with the roc loc but i have had those plastic studs break off and send the little bugger flying like a shuriken at full speed...hit the guy who was working with me in the throat ..He was grinding a weld in the trunk of a race car we were doingBut for major weld or metal removal i use these...They last forever but heavy Attached ImagesBacked my CATMA over your CARMA oops clusmy me  What would SATAN do ?? Miller Trailblazer 302 AirPakMiller Digital Elite  Optrel Welding HatArcair K4000Suitcase 12RC / 12 VSHypertherm PM-45Rage 3 sawRusty old Truck
Reply:Rondellor wheels work very well too. It all comes down to what you are trying to accomplish. For heavy grinding use a hard wheel. Flap disc flex are good for blending. Generally you get better performance the more you spend but a lot of people just look at the initial cost and then complain the cheaper option isn't as good.
Reply:Find what works for you. I only use 36 grit flap discs, once they wear a little they're like 80 grit. So if I need to do fine removal I grab an old glazed up one. I did pick up a few 41/2" sand discs for use with a backer but haven't tried them yet. Ak weldshop has a video on one of his threads about 3M cubitron discs, them suckers cut fast, by the looks of it anyway.
Reply:For blending I used to like the walter flex-cuts. About twice the cost of the flap disks but more than double speed and didn't need a different wheel to move from steel to Stainless or Ally. It was also about the only thing that handled blending stellite (Cobalt/Chrome) or stuff like Colmonoy56 (Ni/Cr/B) on extruder screws with any speed. If you tried to edge stab those things they would bow enough to climb up & over stuff (pretty cool).They later came out with another one "just for mill scale". I never tried one, but I believe it. Find them here-> http://www.walter.com/en_CA/products/abrasives/blendingLike killdozer said about the heavy removal - nothing keeps up with the type 11 cup wheels. Looks like sombody set up a small milling machine when you look at the swarf the put out.Good luckMatt
Reply:My experience with flappers is the more expensive ones last long, and usually grind faster INITIALLY, but after a dozen or two grinds, they're all the same. And the $10 flappers do no last 5 times longer than the $2 ones. I may try one of those cup wheels. Never seen anything like that before. I'd say 99.9% of my grinds are grinding/blending. I have a 6" grinder, and that's pushing it when it comes to operator fatigue. I think we can all agree when it comes to hours of grinding in various positions, every ounce of less weight makes a huge difference!John 3:16(2) Miller Pheonix 456(2) Millermertic 252Dynasty 210DXHobart 210MVPDoringer D350 SA Cold SawScotchman 350LT Cold SawWebb 10x50 MillWebb 15x40 LatheGeka Bendicrop Ironworker