When a horse is a horse

[Richard Dooling]

In my maddening quest to purchase a drill press I've come across two 8 amp motors on two 15" drills.

The Home Depot site gives the Ridgid 8 amp motor a 1/2 hp rating.

The Lowes site gives the new Porter Cable (Delta) 8 amp motor a full 1 hp rating.

PC specs (http://www.lowes.com/pd_78742-46069-PCB660DP_4294857557+4294962151_4294937087?catalogI d=10051&productId=3162489&Ne=4294937087&currentURL=%2Fpl_PORTER-CABLE_4294857557+4294962151_4294937087_&N=4294857557+4294962151&identifier=PORTER-CABLE&langId=-1&storeId=10151&ddkey=http:ProductDisplay)

HD Ridgid specs (http://www.homedepot.com/Tools-Hardware-Power-Tools-Drill-Presses/h_d1/N-5yc1vZ1xh7Zarc7/R-100037270/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053)

If I use a very basic approach and not accounting for thermal inefficiencies and such:

8 amps x 120 volts = 960 watts
960 W x .00134 = 1.29 hp

Anybody???:confused:

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[Harvey Melvin Richards]

I was just notified that a lawnmower I bought was in a class action suit because of a false horsepower claim. You'd think these companies would get their act together and quit making false claims.

[Nathan Callender]

It would be nice if the companies actually posted the motor efficiencies, but I don't think they are going to do that any time soon.

[Neil Brooks]

It's not so simple, really.

What's missing from the equation is the efficiency of the motor.

At 100% efficiency, then ... a 6.5 amp draw, at 115V WILL equal a horsepower, but ... motors do NOT tend to be 100% efficient.

Then there's the "power factor (http://en.wikipedia.org/wiki/Power_factor)."

To calculate HP, use this formula:

I x E x Eff x PF
746

Where:

I = Amps
E = Volts
Eff = Efficiency
PF = Power Factor

Have fun :D

[Richard Dooling]

Still this seems to be a heck of a disparity - 1/2 to 1 hp. Even if you mess around with how efficient the motor is and use calculations based on 115v as opposed to 120v - twice the power rating seems very odd. I guess one would have to be privy to the exact testing and tea leaf reading and wishful thinking formula the labs use.

"Quick, go find me an expert witness! No, no!! One who thinks I'm right!":rolleyes:

.

[Van Huskey]

Bottom line forget horsepower, 1/2hp "rated" from any reputable brand will be enough for most any woodworking application. Buy based on how tight the quill is at full extension. If buying a new DP this is my biggest criteria and suggest you even consider being able to hand "test" the particular one you are buying first. A sloppy quill will make all the HP in the world rather useless.

[Jeff Bratt]

In my maddening quest to purchase a drill press I've come across two 8 amp motors on two 15" drills.

The Home Depot site gives the Ridgid 8 amp motor a 1/2 hp rating.

The Lowes site gives the new Porter Cable (Delta) 8 amp motor a full 1 hp rating.

If I use a very basic approach and not accounting for thermal inefficiencies and such:

8 amps x 120 volts = 960 watts
960 W x .00134 = 1.29 hp

An 8 amp motor is around 3/4 HP. A good rule of thumb for motors is - at 120 V it takes 10 amps to get 1 HP. Of course, this will vary depending on motor efficiency. This looks like an induction motor, and the efficiencies of these are generally in the 60-80% range - towards the lower end for smaller motors. That additional efficiency factor is important...

If you actually go to the store and look at the drill press, these motors nameplates usually have accurate HP ratings.

[Chip Lindley]

There is always LOTS of hype among BIG BOX store brand tools. No way is an 8 amp, 115v motor an honest 1 hp. It IS however, an honest 1/2 hp. *Real* 1 hp. motors are closer to 13 amps @ 115v.

[Dave Verstraete]

"A horse is a horse, of course, of course unless its Mr. ED!:D

[Frank Guerin]

The one good thing about a drill press is a drill press is a drill press. It's not like other machinery that really needs to be super accurate. If it has some variable speed and the slop in the shaft is not to much it will do what I want it to. It drills holes. I bought a Crapsman and it drills holes where I want them. I really would like an old Rockwell with a variable Reeves (sp) drive but just for an ego boost. Mine has variable speed. I just change the belt on rare occasions and it does what it is suppose to do. It drills holes. I do center punch to start. I'm sure there are those with much more knowledge than me but in my opinion a drill press is the one piece of machinery that can be put on the bottom of the list as far as a needed close tolerance piece of equipment.
Of course I'm old and slow and don't know much.

[Richard Dooling]

A horse is a horse of course of course
Unless it’s a horse from a big box source
And if it’s a horse from a big box source
You can’t be sure where you’re led.:rolleyes:

Thanks for everyone's inputs. I am finally getting close to a decision and I have to admit that the 1 hp claim for an 8 amp motor has left me a little cold.

I also must say though, that I do not see that 1 hp power rating on the Porter Cable (Delta) site - just the amp rating. The blue borg is the only place I've found the 1 hp claim.

And I guess I'm being a little unfair to the blue borg and the orange borg. Everyone pushes the figures and that's one reason why sites like this are so great - real world user opinions.



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[Josh Bowman]

Here's what I've read and understand. An amp is an amp, but a horse does not have to be a horse. Something about the rules, but manufacturers have to give the correct running amps. Many (like craftsman) will give the stalled (they call it brake) motor horse power, like anyone really cares what HP a motor achieves right before the motor burns up. That's how my 3 hp craftsmans saw motor can look like something out of a washing machine, but my 3 hp powermatic with a Baldor motor, looks like the whole washing machine.

[Joe Jensen]

With induction motors it's easy to calculat the true horsepower. The motor plate on each motor will have all the numbers needed to do the calculation shared above in this thread. I've seen cheap import motors with efficiency as low as 50% and I believe you can buy premium efficiency motors that are as high as 84% efficiency. If the motor is only 50% efficient, then 50% of the power consumed goes to heat. If it's 80% efficient, then only 20% is wasted as heat.

If two motors draw the same current the one with higher effiency will deliver more HP. If two are rated at the same HP and one is less efficient, the less efficient one will draw more amps.

I recently replaced a pool pump. Around here they run 4 hours a day in the winter and 8-12 hours a day in the summer. I don't remember the exact specs, but with the 1.5HP pool pump motor I think the standard efficiency is around 60% (cheap import motors) and the "Premium Efficiency" motor I bought was higher than 80%. It was $80 more but the payback was less than one year in energy savings. It's like getting 1.5HP for the cost of running a 1HP motor. I don't remember the exact numbers but with my duty cycle the payback was less than a year. You can't just look at amps and determine the HP. Compare two cheap motors and that will work, compare two high end motors and that will work.

In the case of a drill press I doubt either matters. I have a 40 year old Rockwell with a 6" stroke and a 1/2 HP motor. I've never come close to needing the 1/2 HP. I have wished for more HP on my 3HP shaper. the workload on a drill press for woodworking is just not that high. Also, I doubt you would run a drill press enough for the efficiency to matter cost wise.

If you want to buy based on the motor, go look at each and write down the motor spec details and do the calc. All other things equal, I'd rather have a more efficent motor.