Harbor Freight Tools that don't suck

   / Harbor Freight Tools that don't suck #3,061  
Good morning Mr Fowler and thanks for the msg. about the grinders and I know first hand about the pipe-lineing, I've done some miles of that back in the 80's in Wyo. dureing the "oil boom" of that time like is going on in N.D. now. Wish I was about 20yrs younger I'd have to get some of that easy money, lol I found yrs. ago that I could do just as good with a 7" as a 9" and not wear myself out. I think the Black and Decker wild-cat grinder weighed about 50# or felt that way after a short time riding one. I found if you put a Pipe-liner disc on the 7" you can cut and grind pretty quick and to me seems like the Pipe-liner last longer, may just be me though. If you have never tried one check it out. They're 1/8th in. instead of 1/4, or maybe 3/16th, just know they are thinner. You don't by chance have kin-folk in W.Va do you? I am kin to some Fowlers up there, ****, we might be kin, lol Have a great day and again, thanks. Eddie
Dont know if I am kin or not. My Dad said the clan moved from out east over to Louisiana. He always claimed that if the name was Fowler, we were kin at some range.
Pipeliner brand discs are definetely the best to use, but high$$$$. That is what they use mostly on pipe lines also (1/8") for grinding beads. They use the 9" disc for speed of cut. The grinder motor turns the same RPM whether it is using a 7" or 9" so the feet per minute is substantial more on the 9" blade so you dont have to use the grinder for as long a period of time and you let the weight of the grinder do the work untill you get on the bottom half, then it is all muscle. That is why the young guys do that work.
For the free grinder blades, I can afford to buy a 9" grinder to turn them with.
 
   / Harbor Freight Tools that don't suck #3,062  
Anyone know if this electric cut-off tool works better than the pneumatic version? The air one doesn't seem to have enough power even at 160 psi. How about this electric one? I have a coupon for $19.99.

120 Volt 3" High Speed Cut-Off Tool
 
   / Harbor Freight Tools that don't suck #3,063  
The motor is only 3 amps, so it can't have much power.
 
   / Harbor Freight Tools that don't suck #3,064  
The motor is only 3 amps, so it can't have much power.

For cutting bar and angle in my own shop I usually use a couple of old 7 1/4 circular saws with abrasive blades. It's an inexpensive solution and usually good enough.
It turns out that the 7" blade gives just enough surface speed out at the edge to do decent abrasive metal cutting, but the downside is that the saw motor has to have enough torque to keep that speed up, and although a hand-held circular wood saw does tend to have that much torque, it is also one big unwieldy thing to cut metal with. Certainly no good under a car, but extrapolating from what we know about using that saw in the shop to cut metal, there is a way we can get an idea of what kind of job a cutoff saw will do.

A typical 7 1/4 circle saw draws 12 to 13 amps. The max. a normal 110v. wall outlet is rated for is 15 amps.

Your question got me to thinking about how to compare the power of various saws. I know about this stuff because I designed motors for various companies for years. Motor technology is pretty mature and the same technology is available pretty much everywhere as far as power is concerned. There isn't anything real expensive in an electric motor, so unless you are at the really, really high or low end of the price range, there's no real benefit in making one that is more or less powerful. All 110V AC motors are basically copper wire wound on a laminated iron core. More copper windings make for more power, but the price of the copper windings is so low compared to the price of the motor that there's little reason to save cost there. Now it's very true that it costs money to beat heat, and so better motors handle heat much better. They may also have features like ball-bearings on the shafts, but the raw power of any motor in the short term is going to be pretty much dependent on how many amps it draws.

Since input voltage (110v) is always the same, what matters is torque. And useful torque out at the edge of the blade comes down to amps and blade diameter.

Manufacturers would have you believe that what matters is HP or horse power, but that just isn't true. Horsepower ratings are an advertising department's best friend. Horsepower is just a popular word for rpm times torque. The problem with comparisons based on high horsepower is that it takes torque to keep the speed up once you start to load the tool by actually doing something with it. But the adv. dept tends to rate the HP by the unloaded speed. Us people who buy and use tools know that only the speed under load counts....but that is almost never mentioned! Trust in this: As long as the rpm is high enough to do the cutting, more torque is what you want.

So one way to think about cutting anything with a circular blade is that doubling the amps also doubles the torque. It is true that doubling the blade diameter gives a longer lever arm and so is another way to give twice the torque AND it gives a side benefit by increasing surface speed which always a benefit in grinding. But there's a catch there. If you double the blade diameter, it requires 2x to 2.4x the amps in order to keep that blade turning at the same torque as the smaller one. So to use the advantages of a bigger blade, the bigger blade had better be turned by a motor drawing twice the amps. Otherwise nothing is gained.

Looking at it another way, if you have ever used a 7 1/4" circular saw with an abrasive blade to cut some steel in your shop then you probably have a mental picture of how that went. And that's handy because a smaller saw like a cutoff saw having a blade half that diameter would only need to pull half as many amps to have similar torque. So for a 3" cutoff saw, it would need to be pulling at least 6 to 7 amps to match the larger circle saw.
Hope this helps some...

Like anything, we can complicate it. If this gets anyone interested in design decisions and motors, or questions about stuff like that, maybe we should start a tool thread on motor design.
rScotty
 
   / Harbor Freight Tools that don't suck #3,065  
Your question got me to thinking about how to compare the power of various saws. I know about this stuff because I designed motors for various companies for years. Motor technology is pretty mature and the same technology is available pretty much everywhere as far as power is concerned. There isn't anything real expensive in an electric motor, so unless you are at the really, really high or low end of the price range, there's no real benefit in making one that is more or less powerful. All 110V AC motors are basically copper wire wound on a laminated iron core. More copper windings make for more power, but the price of the copper windings is so low compared to the price of the motor that there's little reason to save cost there. Now it's very true that it costs money to beat heat, and so better motors handle heat much better. They may also have features like ball-bearings on the shafts, but the raw power of any motor in the short term is going to be pretty much dependent on how many amps it draws.

Since input voltage (110v) is always the same, what matters is torque. And useful torque out at the edge of the blade comes down to amps and blade diameter.

Manufacturers would have you believe that what matters is HP or horse power, but that just isn't true. Horsepower ratings are an advertising department's best friend. Horsepower is just a popular word for rpm times torque. The problem with comparisons based on high horsepower is that it takes torque to keep the speed up once you start to load the tool by actually doing something with it.

But the adv. dept tends to rate the HP by the unloaded speed. ... Thats zero Torque so zero HP

Us people who buy and use tools know that only the speed under load counts....but that is almost never mentioned! Trust in this: As long as the rpm is high enough to do the cutting, more torque is what you want.

So one way to think about cutting anything with a circular blade is that doubling the amps also doubles the torque. It is true that doubling the blade diameter gives a longer lever arm and so is another way to give twice the torque AND it gives a side benefit by increasing surface speed which always a benefit in grinding. But there's a catch there. If you double the blade diameter, it requires 2x to 2.4x the amps in order to keep that blade turning at the same torque as the smaller one. So to use the advantages of a bigger blade, the bigger blade had better be turned by a motor drawing twice the amps. Otherwise nothing is gained. ... You mix Torque and Force and have interchanged leverage intermittently.

Looking at it another way, if you have ever used a 7 1/4" circular saw with an abrasive blade to cut some steel in your shop then you probably have a mental picture of how that went. And that's handy because a smaller saw like a cutoff saw having a blade half that diameter would only need to pull half as many amps to have similar torque. So for a 3" cutoff saw, it would need to be pulling at least 6 to 7 amps to match the larger circle saw.
Hope this helps some...

Like anything, we can complicate it. If this gets anyone interested in design decisions and motors, or questions about stuff like that, maybe we should start a tool thread on motor design.
rScotty
A big reach is required to bring consistency to your explanation. Yes, a thread on T and HP and electrical and mechanical equivalence would be a better place to hash it out. This has been done a few times I think; but in threads not specific to the subject.
larry
 
   / Harbor Freight Tools that don't suck #3,066  
Anyone know if this electric cut-off tool works better than the pneumatic version? The air one doesn't seem to have enough power even at 160 psi.
The pneumatic one is supposed to run at 90 psi, they rely on speed, not brute force for cutting. I have no problem with mine, just need to keep the rpm up. The electric one would be ideal if you didn't have a compressor that would keep up, as the pneumatic one is an air hog.
 
   / Harbor Freight Tools that don't suck #3,067  
A big reach is required to bring consistency to your explanation. Yes, a thread on T and HP and electrical and mechanical equivalence would be a better place to hash it out. This has been done a few times I think; but in threads not specific to the subject.
Larry

Larry, I posted that explanation to help answer a specific question. The way I use terms in my post are consistently based on that goal - which was how to decide if a particular cutoff tool has the power to do the work.
My goal this time was to show how to compare a new tool with something familiar, and with any luck to extend the method of comparison so that it is helpful for more than just one tool. No, it isn't universal. I probably wouldn't try to extend it to airplanes or battleships.

No, I am not interested in starting a technical thread to debate the differences in technical jargon versus the way the terms are used in casual conversation. I am well aware of both worlds, but I participate in these forums for a different reason.
rScotty
 
   / Harbor Freight Tools that don't suck #3,068  
The pneumatic one is supposed to run at 90 psi, they rely on speed, not brute force for cutting. I have no problem with mine, just need to keep the rpm up. The electric one would be ideal if you didn't have a compressor that would keep up, as the pneumatic one is an air hog.


I agree. For all these cutting tools, the problem is keeping the speed up while pushing cutting edge into the work hard enough to get some work done. That takes torque. If it can do that, then the tool has enough power to do the job.
u
Anyway, just letting you know you aren't alone..... I have the same problem. Air tools are neat, but require a big compressor for the air hogs. Or at least a bigger tank. I don't know if the cheaper air tools are bigger air hogs but they seem that way - anyone know that? I

For electric tools, more power simply requires a motor that pulls more amps; wasted amps appear as heat.
For air tools it's supposed to be how much air - cfm - is does useful work. But what happens to the rest of the air that an airhog uses? Compressed air doesn't come in an unlimited supply like electricity from the power plant. It's limited to what's in the tank. It always seems to be time to upgrade the compressor.
rScotty
 
   / Harbor Freight Tools that don't suck #3,070  
Just from the HF reviews I wish I had a place to put and use it. :)

Sounds like it is USA built but not sure that would be the case for all the parts.

If you get it give a follow up please.
 
 
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