Bench Grinder losing power.

[Zombifyd925]

Hello all. I purchased a used bench grinder last year and finally got around to rehabbing the garage into a work space. I tested it out and it loses power with any decent amount of pressure applied to the wheel. And if anyone knows anything about it, that could be helpful too.

Thanks

 

[Ole Slewfoot]

1.9 amp motor, it just isn't big enough.

 

[Zombifyd925]

Gotcha. I have lots to learn lol. Ill have to pick up a second one. What would something like this be used for?

 

[exmaxima1]

I live in Geneva IL and never heard of that maker. I suspect it is one of those shaded pole type motors with very little torque. Really only usable for sharpening a screwdriver or kitchen knife, albeit very slowly.

 

[notlob]

HP = V*A*EFF/746

Even if it runs at 90% efficiency (which is unlikely), that motor makes:
115 V*1.9 A*.90 EFF/746 = .26 HP

So that is a 1/4 hp grinder, which, as stated above, is not powerful enough for anything other than the lightest of uses. IME, you need at least a 1/2 HP grinder for serious use, and 3/4 or 1 hp is even better.

 

[evintho]

There's a ton of 'em on your local CL..................
https://albany.craigslist.org/search/tla?query=grinder

 

[Twystd1]

That will barely grind a nail. The smallest grinder I have is 3/4 HP.
All the lesser ones are too inadequate for forcing work onto the wheels. Be it buffing or grinding.
And yea. I like getting things done fast.

-T

 

[6PTsocket]

My old 1/3 hp Craftsman "block" grinder runs fine and have no reccolection of stalling it out. I also don't try and force feed it. I prefer my belt sander for most jobs so I don't use the grinder that much.

Sent from my SM-G900V using Tapatalk

 

[exmaxima1]

HP = V*A*EFF/746

Even if it runs at 90% efficiency (which is unlikely), that motor makes:
115 V*1.9 A*.90 EFF/746 = .26 HP

So that is a 1/4 hp grinder, which, as stated above, is not powerful enough for anything other than the lightest of uses.

Shaded pole motors are rarely more than 20% efficient. That grinder has barely enough power to keep itself spinning. For example, a typical 1/4hp shaded pole grinder of that era draws 7.5 amps.

 

[tool_scrounge]

HP = V*A*EFF/746

Even if it runs at 90% efficiency (which is unlikely), that motor makes:
115 V*1.9 A*.90 EFF/746 = .26 HP

So that is a 1/4 hp grinder, which, as stated above, is not powerful enough for anything other than the lightest of uses. IME, you need at least a 1/2 HP grinder for serious use, and 3/4 or 1 hp is even better.

You forgot the power factor since it is an a.c. power device. For a resistor is is 1, but for an inductive motor it is less.