OK so i've got a conundrum. I'm looking to buy a drill press and I've come across 2 thats are incredibly similar. except one has a 1/2 hp motor that uses 8 amps, and the other has a 3/4 HP motor and 6amps.

I've done my research and i'm more confused then ever, it says that HP should determine the load applied to the motor, obviously more HP can handle more load. but it also says that HP is determined by the wattage it can consume (which makes u wonder how one motor claims to make more HP then power it consumes).

the big question is that if i'm primarly drilling metal, do i want more amperage, or more HP?

I read up on this site
http://www.iprocessmart.com/leeson/l..._reference.htm
http://www.iprocessmart.com/leeson/l..._reference.htm
^^ those are 2 different pages

 

are both motors you list 220 v
or is one 120 v
and the other 220
?

 

On my consumer devices, HP is simply a marketing number. For example, I own a "1 horsepower" Shop Vac that draws 5A.

5 * 120 = 600W

Or 145W less then 1 HP.

Keep in mind that a 1HP motor running on 240V will consume half the current as a 1 HP motor running on 120V.

A 1/2 HP motor that is pulling 8A at 120V is pretty inefficient, but realistic.

A 3/4 HP motor pulling 6A at 240V is drawing 1440W, or twice the current it should.

At 120V, it's pulling 720W, a more reaslistic number.

 

all the presses i looked at are 120v, and the 3/4hp 6amp press is the only one with such a low amperage. The others i'm concidering are 1/2hp 8amp, or 3/4hp 12amp.

but if 12amp * 120v = 1440watts, then y is the motor rated for 3/4 hp instead of the 2hp (or 1.5hp with 85% efficiency) it should be? wouldn't they try and market any product to have more power?

 

It's a very inefficient motor, or has a very inefficient drivetrain. Either way it's a good way to judge a more realistic measurement then the unit that claims 3/4 HP and draws 6A.

 

I'm no expert but it seems as if under a certain load the 1/2 horse will draw 8 amps and the 3/4 will draw 6 amps. Meaning the 3/4 will be under less load to achieve the same result. 6 and 8 amps isn't how much it uses, but how much the motor needs to draw to maintain it's RPM. Buy the 3/4 horse.

 

Amperage refers to how much is needed at startup (full load Amps). It's used to id the proper breaker to use in a circuit. It means nothing. 3/4 will give you more torque, which is what you want.

 

so having the motor rated for higher amperage, is a bad thing?

 

The amperage rating of an electric motor is generally the amperage it draws at it's full rated load at supply voltage. The startup current will be many, many times higher.

That "supply voltage" is an important part because you can control how much current the motor draws by varying supply voltage, and thus controlling the power the motor produces. Thus, current rating (and therefore power rating) is almost arbitrary. The motor is designed to draw a specific current at a specific voltage at full load, and will be most reliable at that point. However electric motors like anything else can be operated out of their design specifications. How far out depends on the quality of the motor and what you expect from it. While the motor will run at it's ratings continuously, it may run on twice the voltage (producing twice the power assuming it can suck twice the current) at a 25% duty cycle. Do this continuously and the motor will burn up.

Thus, a 6A 120V motor will pull 6A on a 120V supply at maximum load (generally stalled). The startup current will be 40-60A but only for a few microseconds. You could safely run this example motor on a standard 15A circuit.

 

True, I'm trying to remember my school days unsuccessfully. The startup spike will be much much higher than the Amps rating. I think time delay fuses and breakers are sometimes requires for a motor circuit because of the spike. The service factor (SF) is also a good point to make. You can find it on the motor's nameplate and can be a good measure of quality. The higher the service factor, the more you can overload the motor without failure. 1.15= 15% more 1.25=25% more

 

No. I honestly think there are too many variables to make an educated decision, though. These ratings are given by the manufacturer who are obviously going to inflate the ratings or modify a test in some way. A 1/2 horse 6 amp motor could outperform a 1/2 horse 8 amp motor and vice versa depending on what the manufacturer wants to tell you. An 8 amp Milwaukee drill will rip your arm off if you let it. An 8 amp JobMate drill, at the same RPM, won't even come close.

 

so i'm buying the press based on how much i can trust the manufacturer.... that sucks, b/c all the presses i'm looking at, i don't have any experience with. pioneer, ridgid, powerfist.

 

If you aren't using it in an industrial or manufacturing environment, it won't make much of a difference. I have a Power Fist from Princess Auto. It was cheap ($70 lol) and it does the job very well. Remember that with a drill press chances are that it won't be used continuously and if you do overload it the belt will slip before the motor stalls and overheats. The only other problem with the cheap ones is that the bearings might wear out and your holes might end up a little bit bigger than the drill bit but if you want that accuracy you should be using a milling machine and a reamer anyway.

 

what do u put ur power fist through? 1/2 plate? thats abotu what i'd be doing, drilling flanges.

 

Half inch plate should be no issue for almost any press. I regularily drill stuff like that with my hand drill.

More important then the drill are the bits. High quality bits with a good cutting oil will make all the difference.

Also, get a Drill Doctor so you can resharpen bits anytime you need to. The Drill Doctor kicks ***.

 

i keep breakign off drill bits b/c i can't hold my hand still enough to use a hand drill, although i love the one i have. the 3/4hp 12amp press had a coolant system on it but i kidna laughed cuz it was just a bottle with a hole and hose poked in the bottem of it.