Newbie Angle Grinder Question


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Old 04-11-06, 05:07 PM
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Newbie Angle Grinder Question

I bought a Makita 4-1/2" angle grinder some time ago. Used it to cut a metal stove pipe roughly 4-inches in dia and 1/8-inch thick. It has been protected in the box it came in and unused for probably 3 to 4 years. Last week I used it to cut two steel bars 1/8-inch x 1-inch. 1/3 thru the second bar and I noticed a reduction in rpmís of the grinder. I shut it off to take a break, as I was perched on the edge of a roof. That was when I noticed smoke pouring out of both ends. The grinder was toast. The brushes look brand new.

The grinder I was using was a Makita 9524NB 4-1/2-inch grinder that I no longer see on the Makita site. No surprise.

The grinder I have my eyes on to replace it is a De Walt D28402K 4-1/2-inch grinder. http://www.dewalt.com/us/products/to...roductID=10939

Iím beginning to wonder if cutting metal like this is not an intended purpose for a light duty 4-1/2-inch grinder? Iíve Googled for info, and can come up with nothing, so here I am asking a newbie question. Can anyone enlighten me on this before I make the purchase?
 
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Old 04-11-06, 05:44 PM
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I probably would have used a reciprocating saw to make those cuts.
 
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Old 04-11-06, 06:28 PM
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I have no problem using such a grinder to cut off a protruding bolt flush with a surface. However, round stock and flat stock are usually cut with:
a. reciprocating saw
b. circular saw with a metal abrasive blade
c. abrasive cutoff saw
The cut is typically across the thin edge of the piece rather than over the wide part, as in the flat stock you had.
The grinder disk on an angle grinder is initially very thick at the edge, causing a wide kerf in the cut as well as increasing the load on the motor.
 
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Old 04-11-06, 07:08 PM
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my 9514NB has a manual reset breaker next to the cord at base of handle. Don't know if your's has this or not. This might be a feature to look for in the next grinder as mine has tripped many times in 10+ yrs and it's still going strong. The hardest job it ever had to do was strip all the paint off my 6X24ft porch deck with a 3" cup brush. This was long and tough taking 7 layers of paint off.
Mike
 
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Old 04-11-06, 11:03 PM
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I never would have thought about using a reciprocating saw to make those cuts. Fortunately, a friend showed up, and went and got a cutting torch, and finished it for me. A circular saw would have been a good idea, but I never would have thought of it. It is extremely rare that I work with metal. Once every few years, so other than cutting thin pieces of metal with a jig saw on rare occasion, Iím just not good with metal working. Iím just wondering, since I smoked the Makita, if this is really not an intended use for a 4-1/4-inch angle grinder. I searched all over the web for info on these grinders, but all I could find was specs on new grinders. I just probably donít know what to search for. Any links someone could provide me with on what these tools are designed to do, other than grinding welds smooth, or body work?

Iím sure the Makita does not have a manual reset breaker, itsí not here at the house, but even if it did, it wouldnít cure this. Thick smoke was pouring out both ends of the Makita, and the rpmís were way down. When I took my gloves off, the grinder was too hot to touch, and remained very hot to the touch for almost an hour. The motor is toast. If I turn it on now, Iíll bet the rpmís donít get over 100, and the motor has a sick sound to it. Itís burnt toast.
 
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Old 04-12-06, 06:48 AM
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I would not apply power to the dead grinder again. If it gets that hot, there is likely a short in it which is not worth repairing.

A light-duty grinder is typically used with either a wire brush wheel or a grinding wheel for surface removal of slag or rounding over sharp edges. The contact area with the work is intended to be quite small. These grinders run at 10,000 rpm and higher to lightly grind to a finished edge.

For heavier grinding, there are small angle grinders at 8+ amps, large diameter angle grinders and bench grinders with 1 hp motors.

Beyond that, it's a cutting or sawing operation:
- plasma cutting
- power hacksaws
- cold saws
- abrasive cutoff saws
- oxyfuel cutting torches
 
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Old 04-12-06, 10:10 AM
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I didnít think the grinder was worth repairing, but Iím trying to figure out if I really want/need another grinder. Iíve had this one for 4 to 6 years, and can count the number of times Iíve used it on one hand.

Would something like this DeWalt D28474W work?

I do have a jig saw and a reciprocating saw, but the jig saw, even tho itís a good one, is probably too light for that kind of cutting. Maybe a circular saw with a metal abrasive blade would be a good idea. Already have 3 circular saws. Cut off saws are way too expensive for my use.

I recently had to cut 3-inches off a wood stove pipe, and used a jig saw. It was difficult to accomplish as the saw wanted to jump all over the place, and it was hard to hold onto the pipe and cut at the same time. Itís just your standard black thin walled 6-inch stove pipe. Would a 4-1/2 inch grinder with a cutting blade on it be good for that?

I appreciate your help. Itís exactly the kind of help I was looking for.
 
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Old 04-12-06, 03:51 PM
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If you don't need an angle grinder then you are finding other ways to accomplish the task at hand. Don't buy one until you need it if that's the case. I find an angle grinder and a sawzall to be some of the first things I reach for, but that's just me.

Thinwall pipe cutting can be tricky. For a 6" I.D. pipe, slide the end to be removed over a 2x6 mounted horizontally with the narrow face up. Mark 3" from the end completely around the outside. Use a hacksaw or sawzall to cut the pipe where it bears on the lumber, then rotate the pipe and continue cutting.
Attempting to use a jigsaw on an unsupported thinwall pipe will pinch the blade creating a lively cutting action as you discovered.
 
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Old 04-13-06, 10:06 AM
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Thanks again. I just went out and stuck a piece of 2x6 into a piece of pipe I havenít used yet to see how that would work. The 2x6 would have to be attached to something, but I can see where that would make it easier to work on. Using the method I used last time ended up with the lively cutting action, and there was no way I could make a straight cut. I guess there is really no easy way to accomplish that task.

The crimped end that fits into the stove is of a larger OD diameter that the opening in the stoveís ID diameter is, so whenever I need to replace that elbow, I need to have the crimped end crimped even more, always ending up with a poor fitting where the pipe comes out of the stove. Itís an old Fisher, and the pipe comes out of the back of the stove, and not the top, so the connection where the elbow comes out of the pipe has always been a weak link in the system. Not much I can do about that except replace the stove, and Iím not sure they make stoves with 6-inch pipes anymore, and replacing the Metalbestos pipe that goes up thru the roof to 8-inches isnít something I want to tackle, and wood heat is no longer my main heat source, as I put central heating in back in 1990. Itís just nice to have a fire on those extra cold winter days. There used to be a hardware store that had a crimper, one with a big handle, and it always did a good job, but nothing like that in town now, so the crimping is an even weaker part of the connection.
 
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Old 04-13-06, 10:47 AM
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Certainly the 2x6 must be well secured to reduce the lively action.

Regarding the larger-into-smaller dilemma, is there some way to insert a sleeve into the stove, then add a bushing to the outside of the sleeve to mate it up to the larger exhaust pipe. This would be substituted for all that crimping. There would be a 1" gap all the way around the sleeve to seal.
 
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Old 04-13-06, 11:36 AM
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This stove hasnít been manufactured for a very long time. The stove was in the house when I bought it in 1980. As for a sleeve, Iíve wondered about that many times, but there is literally no info on this stove that I can find, let alone a sleeve. A sleeve would be the correct fix for this if such an animal existed. The crimping down of the crimped end ends up with the pipe diameter being much smaller, and the crimped end is sloping, causing the crimped part of the elbow to slide out of the stove. It never completely falls out, but I always have to push the elbow back into the stove before and sometimes during use. Kind of a pain, and probably not all that safe. Just a real poor design by Fisher Stoves if you ask me.
 
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Old 04-13-06, 12:03 PM
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I don't know for sure but I think 6" is still standard for most stoves. I replaced my ancient wood burner with a new one [king] about 10 yrs ago and it is 6" pipe. All the 6" stove pipe I have ever seen comes in 2' long sections made from sheet metal. I cut them with tin snips or aviation shears. If it is already put together you can unhook the pipe and lay it flat to cut it.

BTW Wood used to be my only source of heat until installed a heat pump 7 yr ago. I still prefer the wood heat but my wife likes the cleaner HP. A heat pump won't get you warm if you come in half froze but a wood stove sure will!!
 
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Old 04-13-06, 09:33 PM
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Most of the stove pipe I see in hardware stores is 6-inch pipe, but I browsed for stoves once a few years ago, and couldnít find stoves with pipes smaller than 8-inches. Maybe it was an uninformed salesman, or he just wanted to sell what he had. If I was to ever replace the stove, there is no way Iíll go thru the hassle and expense of changing the 6-inch Metalbestos pipe that goes up thru the ceiling, the attic, and the roof to 8-inches. Nope. New stove would have to have 6-inch pipe.

Wood heat is much preferable to electric heat, specially in real cold winter weather, but nothing beats coming home after a long day, and just being able to flip a switch, and have heat.
 
 

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