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heavy duty angle grinder

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I am in the market for a new angle grinder for fabrication projects around the shop. I only need it for cutting. I have some 4 1/2" Dewalts that do the trick for everything else but I would like something real durable with a lot more cutting power. What do you guys recommend? Should I go 5", 6", 7"? Metabo? Any experience or advice is appreciated.

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Dear J,

I have an 8" Makita that I picked up at an auction years ago and it really moves metal but it is big and heavy and requires a lot of upper body strength to use it for very long.  Whatever you get look at the size and weight and consider what you can handle (age, strength, endurance, etc.).  I hardly use my big 'un more than once a year.

"By hammer and hand all arts do stand."

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Metabo is a good industrial tool and bigger is usually better though the danger of kickbacks increase with depth of cut. I always used to tell aperentices the quickest way of stuffing your small grinder is by not using the big one. The other thing that is a very good habit to get into is to put the grinder down either upright (disc down) or upside down as if its still running down from use and you put it down on its side then it will suck all the grit etc off the bench and through the motor and then it doesnt matter what brand it is they dont last long before all the smoke leaks out and it wont go any more. My power tool of choice is Bosch or Metabo though I believe that Bosch has moved production to china so not sure about them personally. with care a cheapy may give you a good run if not used in an industrail manner

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I recently picked up a 9" Bosch that has a few features that I really appreciate.  First off, it's got a locking trigger switch that's easily operable while wearing gloves.  Second, the trigger end of the tool has a "D" guard that keeps the trigger, and the trigger hand protected.  One unexpected perk of the "D" guard is that it's a wonderful handle for picking up, and moving the tool around without fear of pulling the trigger.    

That whole end of the tool can be locked in three positions which allows you to use it in different positions without straining your hand.  Prior to this tool, it never occurred to me that a lot of handheld grinders get locked on so the user can shift their grip.  Once the grip is shifted, you can't readily unlock the tool without shifting back.  On a little grinder, that's maybe not a big deal.  On a 9" handheld grinder, that'd give me a pucker factor of 9.3!

It's also got vibration reducers in both grips.  That makes a big difference to the fatigue.  I specifically chose a 9" grinder because the RPM's are lower than the smaller ones, however they all have the same size spindle.  I've found that reduces vibration significantly, without significantly reducing the work output. It's also quieter than a smaller grinder.  Finally, the guard is attached and adjusted with a single throw lever.  I don't need a tool to adjust it which makes it easy enough to live with that there's no incentive to taking it off.

Just like George, I find the big'un to be a workout.  It has enough torque to pull itself around.  That effect is more pronounced when I'm bearing it's weight to grind a vertical surface.  For horizontal work, the tools own weight is sufficient to maintain an aggressive cut.  

The stores around me pretty much don't stock any wheels above 7" diameter so that's what I've been running.  Even so, the bigger wheels are more economical than smaller ones.  That being said, there's a tipping point with this tool.  With a 7" wheel, it takes somewhere between 1/3 and 1/2 the time  it would my 4-1/2" grinder to accomplish the same thing.  HOWEVER, if I've gotta run it for more than an hour at a go, I get so tired that it's not safe for me to use without a break.  Above and beyond that, it's better suited to tasks that can be done standing, with the work between hip and shoulder level, preferably with the majority of the grinding in a horizontal plane.  It's also great for situations where you're trying to maintain flatness, because the diameter of the disk, and the shear weight of the tool make it pretty obvious when you're riding on the flat versus the edge of the abrasive.

With all that said, I think the 9" hand held grinder is a wonderful tool.  I recently completed a project where I'd spent three days grinding.  Two of them were with 4-1/2" grinders, each consuming a flap disk per day and the last day was with the 9" (using a 7" flap wheel).  After each day, I swept up my working area.  I almost couldn't believe how heavy the grindings were on that last day.  I'm guessing that I had 6 lbs of powdered steel in the dustpan, and the flap disk was maybe 1/3 worn.  I had to take a lot of breaks from running the 9", but even with all the down time, I was getting a lot more done per day.

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Basher's comment reminded me of something I neglected to mention earlier.  I've looked for 9" diameter abrasives quite a bit and I've come to a few conclusions.  First off, it's not too difficult to get 9" cutting disks, or the thicker edge/side grinding disks commonly used for cutting out a weld bead.  I've seen 9" stone wheels for sale, but I noticed that virtually all the flap wheels, sanding disks (paper or composite), and backer products are made in 7" only.  

All the 6" and 8" stuff I found is basically made for bench grinders.  

I haven't found any wire wheels in 9", wire cups seem to top out at 5" or thereabouts.  Same story on cup type diamond grinding wheels for stone work.

I still prefer the 9" because it's slower RPM speed means you're got less vibration, noise, and violence with smaller diameter accessories.  That being said, the 9" guard might not offer sufficient / proper  protection with the smaller abrasives.  I believe Bosch offers a range of smaller guards to fit my 9".

I don't know anybody with a "mid-size" grinder to compare mine to, but it wouldn't surprise me if a 7" grinder using a 7" flap wheel was a bit faster cutting than my 9" with that same 7" flap wheel. I just had a quick peek, and it looks to me as though Bosch uses the same size motor for their 7" and their 9" angle grinders.  Obviously the speed's been reduced on the 9" so it stands to reason that the 9" delivers higher torque than the 7" model.  

Being able to jump up to 9" stone wheels is a 38% increase in circumference, and the wheels cost pennies more than 7".  Even if you rigged up a workable guard, you can't safely use a 9" wheel on a 7" grinder because it's spinning too fast.  

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Shocking but true! With this one simple trick you will always be successful!

(Yeah, I hate those ads too.)

But: get out of the hobby mindset. If you want to play with the pros in the major leagues, you can't compete with spotty supplies from flea markets and flimsy big box import tools for a living. I like a bargain as much as the next guy, but get real. Buy once, cry once.

Shop where the pros in the trade shop. The tools may look the same on the outside, but I have seen cheap grinders with pot metal and plastic gears inside when autopsied.

Also, I have never had a problem getting any quantity, size or type of abrasive wheels from a welder supply shop. I might have winced when I handed over payment, but the quality and selection has never let me down.

There are even companies like Unitec that make specialty abrasive tools the likes of which have never seen in a big box store. Mighty handy when you need to polish 3000' of stainless tubing stair rail during a commercial installation. 

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3 hours ago, John McPherson said:

Mighty handy when you need to polish 3000' of stainless tubing stair rail during a commercial installation. 

Or rough grind a Gunther method rebuilt anvil and don't want to burn through 50 or more standard grinding disks. I used a Blue cup stone while the anvil face was still red in the weld zone, then tossed it back into the section off 55gl drum I used to contain the fire to preheat it. Loaded another 10lbs of briquettes on and covered it for the night. 

You can't grind red hot steel with a "normal" grinding disk. 

Frosty The Lucky.

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  • 2 months later...

I concur about the black and decker grinder. I have two from the 1970’s. Both of them burned up and were re-wound before I got them.

First benefit - you can find access to someone with the capability to wind single phase motors they will likely outlast the user.  Second benefit - they make the forearm fatigue of forging seem like a walk in the park.   

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