7" grinder questions

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Looking to buy one, looking at the Dewalt at Home Depot for $149. It's first job will be sanding a lot of rust off my 4x5 welding table top that I just built out of salvaged materials. It's 3/8 plate with plenty of rust, I tried my 4.5" grinders but it is taking forever, so heres my excuse to get a 7". Will a 7" grinder with a sanding kit do just about as well as a 7" disc sander? I don't really want to buy a disc sander because I don't think I'll use it much.Built a torch table and a welding table over the holidays, pics coming soon!Miller Challenger 172Miller Thunderbolt AC/DC 225/150Miller Maxstar 150 STLVictor 100CVictor JourneymanOxweld OAHarris O/ASmith O/A little torchNo, that's not my car.
Reply:You want to keep your table top level and flat. What I have done in the past when I want a flat table is spread naval jelly down with a paint brush, let it sit, it will change color after 15-20 minutes. Then take a putty knife ( or wide wood chisel ) and scrap the naval jelly off ( use paper towels as its nasty and trashes shop rags ). This might need a repeat. Then take penetrating oil and really soak the top and any wood sander ( power prefered, a block of wood will work by hand ) and sand it wet with penetrating oil. Wipe it all down.You will probably need to repeat some spots. After that I hit it with penetrating oil again and let it soak overnight, light sand once again with 220-400 grit, wipe dry.If you have pits the above is not going to fix them. If you use a grinding wheel you are going to cup and scar the top. A flap disk on your new grinder will work better and not scar up the top as bad. If you have a wood belt sander on the first wet sanding  ( above ) with the penetrating oil will get most of the pits, I use my belt sander every so often to dress my bench, its quick just cleans up weld splatter, and I have the tool.
Reply:Grinder with a 7" backing pad can be much more aggressive than a 7" DA. Good and bad point to that. Besides regular grinding wheels, I have both flap wheels for my 7" as well as a backing pad and various grits of paper to fit it. I generally go with the backing pad and heavy grits if I need to get aggressive with the surface, and the flap wheel when I need a lighter touch. I generally try not to use my belt sander for steel too much, since I primarily use it for wood, but for large flat surfaces it works quite well except the "standard" belts don't hold up as well..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Belt sander for smoothing and de-rusting a steel work table top - great idea.  I never could figure out a reason to own a belt sander, but now I have one.
Reply:A twisted knot wire wheel on that 7" grinder will take care of your rust
Reply:Well fred I tried what you said today on a 18x18 section, made some pretty good progress but I didn't have much Liquid wrench for penetrating oil so I soon ran out. It tends to get hot and burn up pretty quick. I am using 60 grit for starters on my old US made Milwaukee belt sander (going to have to give it a good cleaning after this!).You are right it doesn't do much for the pits, almost wish I'd sprung the $300 for a new piece of plate, but then what will the pits really hurt?I just thought with a 7" Sanding disc I'd be able to keep the disc flatter than a 4.5" and cause less gouging, but we'll see how the belt sander works. I think a lot of what I have is mill scale, the rust seems to disappear pretty quick then it's just black scale except for the pitting.Miller Challenger 172Miller Thunderbolt AC/DC 225/150Miller Maxstar 150 STLVictor 100CVictor JourneymanOxweld OAHarris O/ASmith O/A little torchNo, that's not my car.
Reply:I knew I forgot to get something today. Try PB Catalyst in the spray can, it breaks down at a higher temperature. Its also a spray can which makes it easier to cover your area.Pits unless they are deep serious craters ignore them, the end result is a flat level and true top small pits won't mess up clamps, sqaures, and levels, a cup from a sander or gringer will.If the pits are real deep and not too many you can fill them, I would use my mig at a low setting. Then get the belt sander on it again.If your going to use rotory sander test on a scrap first.
Reply:A belt sander will always sand faster than a disc, and will level better if you keep it moving.Try the blue belts (zirconium).  The outlast anything else for steel.
Reply:Mark the top with a sharpie, just scribble all over it.Run the belt sander or other sander in one direction over the entire thing, then move to the opposite direction and do it all. This will do two things. The remaining sharpie marks will show your low spots so you can decide how to deal with them. Going one way, then the other removes metal faster than just randomly sanding. Even after using the power tools, wrap some sandpaper around a straight edge and go over it by hand to keep track of your progress.On my table which is 1.25" thick I added a 1/4" plate to the top and it is screwed down to the top. When it gets messed up I can flip it over or replace it. The main table top stays in perfect condition.
Reply:If you are set on buying a 7" grinder I would definitely consider looking at a Metabo.HammerFile Big Hammer------------------------------Here, let me Google that for you...
Reply:Originally Posted by rlitmanA belt sander will always sand faster than a disc, and will level better if you keep it moving.Try the blue belts (zirconium).  The outlast anything else for steel.
Reply:I just got a Ridgid 7" and it seems good to me and it has a lifetime warranty, but i am no expert and it is the only bigger grinder i have used.
Reply:" big orange store "When I think of orange and tools I am thinking Fien, and I know we aren't on the same track. Are you talking Hoe Depot?Yes its one of the very few things ( square D Electrical parts, wire ( expensive ), desperation nuts and bolts, and odd ball hardware that doesn't PO me. I don't like Home Depot tools, looked many times, never bought don't like the quality.But simple answer is they do have good grinder belts, as long as your not on a odd ball size.
Reply:Originally Posted by fredschrom" big orange store "When I think of orange and tools I am thinking Fien, and I know we aren't on the same track. Are you talking Hoe Depot?Yes its one of the very few things ( square D Electrical parts, wire ( expensive ), desperation nuts and bolts, and odd ball hardware that doesn't PO me. I don't like Home Depot tools, looked many times, never bought don't like the quality.But simple answer is they do have good grinder belts, as long as your not on a odd ball size.
Reply:"  I will say wet sanding with PB Blaster makes one royal mess "Agreed !!!!!Hows it working for you? Do you like the PB better than the Liquid Wrench?OK once you get the hard part done I will give you another tip. Get all finished, clean, oiled, ready to use ? No...clean all the oil off completly I use ether like to clean out a distributor or a start a motor ( doesn't have to be ether just whatever you have ) then get a can of paste wax, If you have some car wax it will work also. Wax your table and polish it out like a car....why the wax protects the table, weld splatter doesn't stick as easy, with the oil penetrated into the steel, and the wax on top it won't rust agian. Once steel has rusted it rusts again easier, ask somebody else why, a material science guy maybe, but I know it for a fact.
Reply:You can ghost on a very light coat of black paint too, and use it as a guide coat. It works very well for auto body work when taking out dents. It'll show any dips and peaks.
Reply:More great tips, thanks guys. I remember using the glossy black paint to get Bondo repairs perfect, and parking another car behind the project car using the headlights to show any imperfections along the sides. I have a feeling some of you have welding table surfaces way better than my standards!The wax is a good idea cept the table will remain indoors in a very dry climate, don't know if it will rust much but I'll probably wax it anyway just so it looks good.Had to sideline the sanding for now, got work to do at rental property.Miller Challenger 172Miller Thunderbolt AC/DC 225/150Miller Maxstar 150 STLVictor 100CVictor JourneymanOxweld OAHarris O/ASmith O/A little torchNo, that's not my car.
Reply:Got some time tonight to sand on it. Industrial supply didn't have any zirconium belts but I was amazed Home Depot had some Diablo belts with a "patented zirconium blend". They did cut real nice. Got to stay away from the edges with those expensive belts, shredded a couple. I found some Deere belts in my stash that work very well also.Now that I am through the mill scale and into shiny steel the cutting is going faster. Tonight I started sanding the opposite direction and most of the pits are now disappearing. I couldn't stand the slop any more and I am now dry sanding.I am thinking of rounding the corners a bit, they could be dangerous the way they are.Miller Challenger 172Miller Thunderbolt AC/DC 225/150Miller Maxstar 150 STLVictor 100CVictor JourneymanOxweld OAHarris O/ASmith O/A little torchNo, that's not my car.
Reply:Here's a couple pics, I still have a bit of sanding to do but meanwhile I had to put it in service as I needed to build a gate and a rack for my van. It is very flat and I was able to make the gate nice and straight. As far as all the surface pits and imperfections, I probably won't be too picky so long as the top is flat enough for my purposes. I already nicked it with the grinder today.I still need to sand the rust off the salvaged framework.The table was not tall enough for me so what you see on the bottom is 1/4" angle extensions, two per leg, one inside and one outside, then a 3/8" pad welded to both and drilled for the 6" casters. I welded all the 1/4" with 6011 stick burned in deep then I capped it with 7018 just for looks, and practice! The top I tacked underneath to the channel which runs every 14" using Mig solid core, skipping around and keeping the tacks short to prevent warping of the top.The top overhangs the frame by about 3" all the way around. This was real handy for clamping the gate down.Still deciding if I want a lower shelf or not.Last edited by bigb; 01-15-2012 at 11:36 PM.Miller Challenger 172Miller Thunderbolt AC/DC 225/150Miller Maxstar 150 STLVictor 100CVictor JourneymanOxweld OAHarris O/ASmith O/A little torchNo, that's not my car.
Reply:"  Still deciding if I want a lower shelf or not "You do so you don't need to pick up a bunch of stuff to clean under it or move it. I liike grating for that .Looks good, instead off sanding and more work on the legs why don't you get some of the Rust converter from Napa. Stuff works good, it stops the rust and the base will end up black, done maybe 1/2 hour, couple of hours to dry.