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I have several home improvement projects that would be made enormously easier if I had a decent angle grinder with both grinding and cutting wheels to attach to it. But I've never used or bought one before. Arbitrarily, going to Lowes (not that I am endorsing Lowes in any way shape or form here), and arbitrarily picking Dewalt as a brand:

http://www.lowes.com/Search=angle+grinder?storeId=10151&langId=-1&catalogId=10051&N=0&newSearch=true&Ntt=angle+grinder#!&N%5B%5D=0&N%5B%5D=1z136s7

Some models seem to focus on amps, and some seem to focus on voltage. This is confusing to me, as I would have expected the main rating on a grinder to be, say, torque or RPM. So I ask:

  • When does one care about the amp rating on an angle grinder, and why?
  • When does one care about the volt rating on an angle grinder, and why?
  • Are these the only two quality metrics that really matter for angle grinders?
smeeb
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3 Answers3

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Electric angle grinders are very useful tools, they can also be extremely dangerous. First and foremost, select a tool with as many of the latest safety features as you can afford:

  • an integral clutch that disengages the drive-line upon wheel bind
  • a "slow-start" or "soft-start" feature
  • NO "lock-on" button
  • a "deadman" trigger or lever feature (shuts off if you let go)
  • an easily adjustable guard (no tools required)
  • auto-braking

Buy gloves, goggles and dust mask when you buy the tool

Amps indicate the power that the motor draws during use and generally indicates the size and power of the motor (higher is "better"). I personally think a well built tool with the features I want and which is comfortable for me to hold and use is more important than the amp rating. If you are routinely grinding and cutting thick heavy hard metal materials you might consider a bigger/more powerful machine.

Voltage should be whatever your household current is (220-240vt angle grinder would not be practical for home or general shop use, pretty much industrial only)

Jimmy Fix-it
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    The "voltage" rating in the product list you posted is for cordless battery-operated units. Corded units will almost always be 110 - 120 V from house mains. – John Apr 03 '15 at 19:06
  • @John Not everywhere in the world has 110-120V mains... – David Richerby Apr 03 '15 at 21:20
  • The question mentions Lowe's hardware store, a store that can only be found in countries with 120V mains. – sleblanc Apr 04 '15 at 03:43
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Volts should be irrelevant - normally only even mentioned on battery powered tools, and an angle grinder is not a good choice for battery power. Since you mention Lowes, presumably any grinder you look at with a cord will be 120VAC, end of that story. Elsewhere in the world, 220-240 VAC, still end of that story. Buy an extension cord if needed, or a generator if you have really remote uses for it.

In that context, more amps either means more power (power out of the wall = volts times amps), or a less efficient motor (power out of the wall that just turns into heat does no useful work.) No good way to tell, for sure, really. So one is prone to making the assumption that it SHOULD mean more power, if efficiency is assumed to be similar.

Quality of bearings and gears matters more than either of the above, longevity-wise. Rotational speed is mostly something to pay attention to not exceeding when you buy discs, brushes, or other attachments, so that you do not put a 10,000RPM attachment onto a 13,000 RPM grinder (the other direction is fine.) Getting a widely-interchangable arbor size helps to keep your attachment and disc options open .vs. weird proprietary sizes.

A usage tip - if the grinder begins to bog down, ease up the pressure - the JOB gets done faster with the tool running full speed. If you apply so much pressure that the tool bogs down (labors, is not running full speed) the cutting or grinding process is slower, not faster. Let the tool work, don't force it.

Ecnerwal
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  • And make sure your extension cord is also rated for the amps you're planning to put through it. – GalacticCowboy Apr 03 '15 at 20:05
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    Eleven or one hundred and eleven, (or three hundred) if you push it til it complains, the job is done slower, worse and with more broken discs. The complaining point will come sooner on the horrible fright unit (main source of eleven dollar grinders) but I find it a lot cheaper overall to spend the hundred and not have to return to the store over and over (got about 20 years on my hitachi at this point) – Ecnerwal Apr 04 '15 at 01:10
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    Not to be too contrarian, but I have to speak up on behalf of my battery powered grinder. If I know I'm going to be doing a whole bunch of grinding, I'll try to remember to pack my corded one, but for simple jobs, it's a dream. (That said, I'm heavily invested in batteries, so will always have 1/2 dozen available... the grinder is a bit of a pig where power consumption is concerned.) – Aloysius Defenestrate Apr 04 '15 at 16:29
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When does one care about the amp rating on an angle grinder, and why?

Models that list amps as a primary specification have cords. The amps are directly related to the machine's power.

When does one care about the volt rating on an angle grinder, and why?

Models that list volts as a primary specification are battery operated. The volts are sort-of related to power, but more related to how long it will run. Battery capacity is a function of amps vs time, and as volts go up, amps go down for the same power.

Also, once someone chooses a battery-operated tool they tend to stay with the same voltage for subsequent tools as the batteries and chargers are interchangeable.

Other comments:

a "slow-start" or "soft-start" feature

unless the tool is industrial / contractor size it doesn't make much difference

NO "lock-on" button

Your finger will get very tired, and that prompts users to do silly things like a string or tie-wrap around the switch which is far more dangerous than the lock-on button.

a "deadman" trigger or lever feature (shuts off if you let go)

Same, unless it's very well designed.

auto-braking

noisy (not that the tool itself isn't deafening, but...) and on battery operated tools makes a noticeable difference to the run time. Can also loosen the disc clamp, turning it into a high-speed frisbee.

Not everywhere in the world has 110-120V mains

Quite true, but Home Depot in country A tends not to sell power tools for country B's electricity. The plug is also different.

paul
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