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Old 03-12-2010, 01:10 PM  
Quattro
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OK, I'll post up some options I'm looking at. BTW - what's the difference between an angle grinder and a hand grinder? The photo of the Bosch is what I'm referring to.



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Old 03-12-2010, 02:30 PM  
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Quote:
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an angle grinder
The operator has to oppose the torque generated by the grinder in operation. The angle gives him/her a lever arm to make this easy.
With no angle gear drive, the operator would have to grip the body of the grinder very tightly to constantly oppose the torque. Arm and body muscles are stronger than the forearm muscles that control the hand grip.

Not to set off another nerd alert, but:
For 32 lb-in of torque and a handle 8 inches long, the operator has to use 32/8 = 4 pounds of force at the end of the handle to control the tool.
Stall torque is higher, and the operator has to then cancel out this sudden, higher, force or he/she will lose control of the grinder.

If you're expecting a lot of stalling I'd use large hose clamps to fasten a 24" pipe or stick to the grinder body. The force is then 32/24 = 4/3 rds pounds.


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Old 03-12-2010, 03:07 PM  
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Dude, I get it, you're smart. But, you don't answer questions very well, honestly.

I asked: What is the difference between a hand grinder and an angle grinder?

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Old 03-12-2010, 03:32 PM  
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An angle grinder has a 90 degree mesh gear configuration.
A hand grinder is simply a straight rotary grinder without the 90 degree angle to it. These are most commonly air driven whereas an angle grinder is electrial. However a hand grinder can come in the 90 degree variety also.

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Old 03-12-2010, 03:53 PM  
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Quote:
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Dude, I get it, you're smart. But, you don't answer questions very well, honestly.

I asked: What is the difference between a hand grinder and an angle grinder?
Dunno'. The only grinder pics I could find were of angle grinders. Sorry.
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Old 03-12-2010, 04:32 PM  
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Quote:
Originally Posted by Quattro View Post
Dude, I get it, you're smart. But, you don't answer questions very well, honestly.

I asked: What is the difference between a hand grinder and an angle grinder?
Sorry, it was me that caused the confusion. The original post in this thread said that Quattro was looking for a 4 1/2 inch ANGLE grinder. The angle grinder stuck, but the 4 1/2 inch didn't, so I was thinking the guy was looking for a 7 or 9 inch grinder.

Basically, an angle grinder is a portable grinder that has the arbor at a 90 degree angle to the tool. A "hand grinder" is one that's small enough to be held in one hand. So, a "hand grinder" is simply a small angle grinder, and so a 4 1/2 inch angle grinder IS a hand grinder.


A DeWalt 9 inch angle grinder.


A DeWalt 4 1/2 inch angle grinder (aka: 4 1/2 inch "hand grinder")
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Old 03-12-2010, 04:46 PM  
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I've had both a Bosch 4 1/2 inch hand grinder and a DeWalt 4 1/2 inch hand grinder, and:

What I liked about the Bosch was that it seemed to be smoother, and didn't vibrate as much when using it. Also, I found the paddle switch on it to be very convenient. What I didn't like about the Bosch was that it required a special tool to tighten and loosen the nut holding the grinding wheel in place. Also, I didn't like the fact that the paddle switch made it easy for the grinder to go one whenever it was plugged in, even when you didn't intend it to. So, if you buy the Bosch, ALWAYS unplug it when it's not in use or when you're replacing blades or whatever.

What I like about my DW400 4 1/2 inch DeWalt hand grinder is that it seemed to have more power than the Bosch. Also, it has a little arrow molded right onto the housing showing the direction of rotation of the arbor, and that can be convenient. And, I can use an ordinary wrench to replace a grinding wheel in it. What I don't like about the DeWalt is that it seems to vibrate more than the Bosch. Also, the on/off switch is close enough to the business end of the tool that if you're using without the safety guard, it's possible to have your finger hit the grinding wheel on the other side of the tool.

(Normally, on the DeWalt, the guard around the blade prevents your fingers from coming close to the blade. However, when I'm using a handgrinder fitted with a thin masonary blade to cut Wonderboard, I actually like to take the safety guard off so I can see better from both sides. And, no I don't recommend other people do that, but I have noticed that when I've done it, the on/off switch is a little too close for total comfort to that spinning blade. The paddle switch on the Bosch allowed me to turn the grinder on and off with my hand well away from the blade at all times. But, when you're using a masonary blade, it doesn't have sharp teeth that will tear flesh off you like a great white shark, and you're just more likely to skin your finger rather than lose big hunks of it. Still, no one recommends people use any equipment without all it's safety features in place. I just mention it because it's something I did notice that I didn't like.)

I liked the Bosch better. It simply struck me as a better built tool. In my case, I only bought the DeWalt because it was on sale. Price isn't normally that much of a consideration for me because tools are tax deductable in my case, so I'm buying them with before tax dollars, not after tax dollars. But, before I'd buy any grinder, I'd check that the arbor on it is 5/8 inch diameter and has 11 threads per inch. Some tools, notably Makita, have a metric size arbor, and so you might have difficulty finding grinding wheels, rotary brushes and accessories that'll fit, which can be a pain. Everyone in North America makes grinding wheels and rotary brushes to fit a 5/8 inch 11 thread per inch arbor. At 12,000 rpm, "close" doesn't count. It has to fit properly.

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Old 03-12-2010, 06:39 PM  
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Thanks for sharing your experiences...that's exactly what I'm looking for.

I do appreciate the knowledge here (Wuzzat?, Nestor, others), sorry if I came off sounding otherwise.

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Old 03-12-2010, 07:28 PM  
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Here's several brands from Grainger

4.5" angle grinders
price amps price/amps
$69 7 9.9
$95 8 11.9
$95 10 9.5 best ratio [DeWalt]
$99 10 9.9
$99 5.5 18.0 worse ratio [Milwaukee]
$105 10 10.5
$139 12 11.6
$159 12 13.3
$159 13 12.2
$159 13 12.2
$159 13 12.2
$159 12 13.3
$105 8.5 12.4

You pay about $12 more for each additional amp.

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Old 03-12-2010, 08:53 PM  
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Quattro:

Also, I'd spend a bit more and see if you can get a grinder with variable speed.

I did some pretty scary things with my Bosch hand grinder, and having it variable speed would have been a lot safer. I bought a Makita 4 1/2 inch diameter wood cutting blade meant for their mini-circular saw and used it at 12,000 rpm to cut wood in some very tight spots. The blade was rated for that speed, but that little blade had big sharp teeth, and if I ever lost control of the grinder, I expect I woulda lost a sizeable chunk of flesh somewhere. Also, I used a really worn down masonary blade (that was rated at 5500 rpm) from my 7 1/2 inch circular saw and used it at 12,000 rpm in my hand grinder. It was worn down to about 5 inches in diameter so it would just fit in my hand grinder and I figured the smaller the diameter of the blade the higher the rpm it could take. It was purely good luck that it stayed in one piece.

I look back on those things, and I figure I'm lucky I didn't hurt myself. But I also realize that both stunts woulda been a lot safer if I could have operated the grinder at a lower speed. So, spend a few dollars more, and get one with variable speed if possible. That way, if you do end up doing something stupid with your grinder, like lots of us do, at least you can control the speed of the grinder and thereby have some control over the danger you're exposing yourself to.

The 5/8-11 tpi arbor and variable speed would be the trump cards if I was in the market for another hand grinder. I'd look for those features more than the name of any particular manufacturer in making your purchase decision.



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