Pneumatic Angle Grinders

[doojus]

Hi Fellas,

Anyone have any experience with pneumatic angle grinders? I'm using a dewalt electric 4 1/2" angle grinder to remove millscale and it gets damn hot after a while (sidenote: I just got an 80 gal compressor so I'm looking for an excuse to buy more air tools).

From looking at the reviews of the Ingesroll Rand 3445MAX it seems a common complaint is that it falls apart and is underpowered... Moving on, Chicago Pneumatic has a 5" model CP9121BR that can accept the standard 4 1/2" wheels and it seems like it reviews favorably, so I'm leaning towards that one.

Anyone on GJ switch out their electric grinder in favor of pneumatic? Or is this a solution in search of a problem?

 

[sam.coll]

Its my understanding that air angle grinders are an air hog and you would need a size able compressor to get the benefit

 

[MatBirch]

I run a Chicago Pneumatic (not CENTRAL Pneumatic) at work often. I usually run a dewalt as well, but for long grinding tasks. I was getting a tennis elbow sort of pain. I needed something that had a smaller diameter barrel. It works great, has pretty good torque and no load rpm. It's not as strong as the dewalt, but different, and very usable. I like it very much. Interesting that you are working to alleviate heat, as this thing will freeze you out! Without a drier, it will eventually ice up inside. The only other cons are:
You must use a wrench, there is no arbor lock
The guard is large and does not rotate freely, it locks into only a few detents.
Both have been more than manageable for me!

 

[sberry]

Electric is way cheaper to operate. But here are my 3 bargains and go to tools. I have 3 of the 4 inch right angles and ran them hard, never so much as had to tighten a screw on one. I have used quite a few of these, several that cost in the hundreds, this one impresses me and outlast them.

 

[Kenskip1]

Being new to the air grinder myself I have found it to be a very useful tool, especially on small engines.My compressor is 30 gallonz and handles it without a problem.Grinder, an Air Hog! Get a grip.Do we have to limit the volume of air to meet government standards? I mean no disrespect however what good is a tool that has to be restricted? Now unless their is a shortage of air someplace, then this would be a bad thing. Ken

 

[Hammer1963]

I have been using a Blue Point low RPM high torque model for 20 years with no issues. Unfortunately this model has not been available for many years. I believe Florida Pneumatics was the producer, so may look into Aircat/FP

 

[plinker]

At work I have two 4" air angle grinders, main reasons are compactness and it's always easier to find an air hose then an extension cord. They do get ****** cold after a while when using them. I do like the air grinders a bit better as there seems to be less vibration.

 

[dr_clyde]

Being new to the air grinder myself I have found it to be a very useful tool, especially on small engines.My compressor is 30 gallonz and handles it without a problem.Grinder, an Air Hog! Get a grip.Do we have to limit the volume of air to meet government standards? I mean no disrespect however what good is a tool that has to be restricted? Now unless their is a shortage of air someplace, then this would be a bad thing. Ken

That is an angle die grinder, not an angle grinder. There is a huge difference. The CFM requirements of a proper angle grinder is way more than anything other than an industrial compressor can supply at a regular volume.

 

[sberry]

Right, not a problem where air is plentiful and free. I use them, have a lot of different wheels attachments that replace a machine shop,,,, hahahaha They are like impact, used where the cost of manpower is hi and it becomes a small expense to get real work done quickly.

 

[sberry]

A real 5 hp will run one pretty well, about like a big DA. I like right angle for cut off and wire wheel, so variable in speed. Regular 1/4 x 4 1/2 we use electric due to operating cost.

 

[Ign]

I've got a 4" Top Cat (TC Service). This is industrial stuff. It's awesome for tight spaces and less vibration. Once you get used it, it's so small that going back to electric feels like holding a small boulder in your hands. My 80 gal Craftsman runs it fine.

That said, I never use it. Electric - and now cordless when the job warrants - is just more convenient for me. I also just don't like air hoses.

Note mine is a true 4", ie 3/8-24 spindle. So it's more compact than most 4.5". I'm surprised at how powerful it is, but certainly you can stall it if you get carried away.

 

[rlitman]

That is an angle die grinder, not an angle grinder. There is a huge difference. The CFM requirements of a proper angle grinder is way more than anything other than an industrial compressor can supply at a regular volume.

The CP9121BR mentioned by the OP claims 13CFM. That's well within the reach of any 80 gallon compressor I've seen, and many 60 gallons. It's also a bit less than my DA uses (the second biggest air hog I own, which lags way behind my 4-bolt rivet buster). Still, Kenskip1's 30 gallon compressor will not run any of these things continuously.

It will be lighter than a comparable electric 5" grinder, but less powerful (looks like it's closer to the power my 4 1/2" puts out). Less feature-full (no quick disconnect nut, or easy adjust guard), but will outlast your grandchildren with continuous abuse.

Aside from the advantage of running cool, air tools do not breathe in abrasive dust, so cutting stone won't wear out the brushes, and they're totally safe around water, so feel free to wet cut stone.

I've got a cheap $20 4" chinese air angle grinder (3/8" spindle like above). While it's really weak power wise, it'll still cut granite quite easily (I used it to cut the perimeter of a circle into a 1" pool table slate to make my kitchen table), and I love the fact that it's so easy to one-hand (the small barrel, the light weight, and yes, the limited power too; no big kickback risk). For bigger grinding tasks, I've got a good compliment of electric grinders (a Metabo 4 1/2" and several 5" Feins). Maybe if I were buying new today I'd have a bigger air grinder in the mix...

For grinding mill scale, where you're not really making hogging cuts, the reduced power compared to a good electric grinder of the same size will not be a problem for you. And for continuous use, nothing beats air tools. Yes, electrically, it will cost you 10x as much to run as a proper electric tool, but we're still not talking about a lot of monetary difference here. Not enough for that to slant your decision.

 

[doojus]

So it sounds like if you have an adequate air supply it's all good with no downsides, so I went ahead and ordered the Chicago Pneumatic CP9121BR. I'll try to update the thread with my thoughts after I use it a little. It has the same arbor size as my dewalt so all of my old discs should fit it.

I'm using an 80 gal/5 HP 2 stage compressor so it should have no problem staying ahead of the grinder.

 

[dr_clyde]

I hadn't looked up the CFM of the CP. Besides, an 80 gal. tank with a decent pump should keep up with most tools anyway. I was simply commenting on the difference between a die grinder and an angle grinder.

I'm used to 7'' air angle grinders, and let me tell you, they really hog the air. Our IR T30 has trouble keeping up with that thing. It makes sense that a 4.5" grinder uses less. I just didn't know the numbers.

 

[Kenskip1]

That is an angle die grinder, not an angle grinder. There is a huge difference. The CFM requirements of a proper angle grinder is way more than anything other than an industrial compressor can supply at a regular volume.

DC, thanks for pointing this out.It never dawned on me the difference until you pointed this out. Thanks, Ken

 

[crewchief888]

i use air at the shop, and in my service truck,
20+ year old bluepoint

all electric at home.


every place i've worked has plenty of air power,

at home not so much

 

[1967lemans]

I'm a welder in a ship yard and I was issued the Chicago Pneumatic CP9121BR. Our company also issues an IR. (not sure what model number it is) We've have had more issues with the IR. Im happy with my CP. It does feel a little bit heavier than the IR but It is a little shorter which helps in getting into tight areas.

Since we got on the subject of 90 degree sanders/die grinders. I was issued the IR 3102B. It worked great for years but the housing finally cracked. It was replaced with an import made by Florida Pneumatic. So far it has held up well. I brought my harbor freight 90 in (so I wouldn't have to waste time change froms discs to brush) It worked good for about 5 years. Not bad for $9.99.

For the straight die grinders, I was Issued some huge Chicago CP3000-520R
. works great but hard to get into some tight areas. I also picked up an Ingersol Rand 307B which works great in tight areas. It's a tiny guy.
I Had a Cp 860 and when that broke got an IR 308B. Out of the two, I preferred the CP 860. It just seemed to have more power. Overall I have been happy with the IR and CP die grinders.

A few of the guys had the HF die grinders and they just wouldn't hold up in an industrial setting. The biggest issue was the roll pins working loose allowing the motor to come apart.

 

[dnschmidt]

These tool simply don't make sense unless you're in an industrial setting with unlimited air supply. Why continuously run a 240 V 30 amp circuit to power an air compressor when you can run an 8amp 120V circuit to run and electric grinder having far more torque. Use the side handle on the electric and it's easier on your arms than the pneumatic.

I love air tools and have a million of them but purely rotary tools like air grinders and polishers are simply not a good replacement for electric rotary tools. Impact wrenches, air ratchets, paint guns all make sense pneumatically. Grinders don't

 

[johninct]

I have a Snap-On (I think it is a PT450). I was in the market for some die grinders on Ebay and the air grinder was listed like a die grinder so I got a really good deal on it. I have used it on only light duty jobs and I really like it so far. I do not think it will ever replace my electric 4 1/2" grinder but a lot of my jobs are light grinding where the air grinder is easier and quicker to use because it is so much lighter than an electric.

 

[RedF]

If you are working a 4 1/2" grinder until it's hot, buy a 5" electric grinder.

 

[doojus]

I had a chance to use the Chicago Pneumatic grinder last night cleaning off some millscale, and wow is that thing an air hog. My 5 HP compressor kept up with it, but never cycled. I'd consider 5 HP the _minimum_ if you want to run an air angle grinder.

That being said, I definitely felt more comfortable running it for an extended period than my electric angle grinder. It was quieter, cooler, vibrated less, and was lighter. I didn't feel like it wanted to stall out on me at all. With a flap disc and a bristle disc I sped thru the millscale removal in no time.


Looking at 7.5 hp compressors now...



Doing the math on the increased electricity costs, power is about $0.12 kw/h here, so if I ran the compressor continuously for an hour a day every day of the week, it'd cost me about $15/month... In reality i'll be running it much less than that (probably an hour a week at most) so it seems like something that's not even worth worrying about given the increased comfort of the tool...