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Variable Speed Bench Grinder + Coote or Kalamazoo?


mpc

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I have an idea and I’m wondering if it will work. 

I have access to a variable speed bench grinder (5 amp Delta). Is there any reason I couldn’t slap a pulley for a v belt on that sucker and use it to run a Coote, Kalamazoo, or a Grizzly?

 

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Assuming it's running on 110 V; that would be less than 1 hp.  My 2x72 would like 2hp.  Note that 5 amps does not identify the size of the motor---watts are what HP is measured at. (And as they started to use the "stall amps" for ratings---where the motor is a second from self destruction, instead of constant running amps it's a pretty useless number anyway.)

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In my opinion 3/4 HP is a little light for running a 2" wide belt, but the torque you will get will depend to some extent on the "gearing" you adopt using different pulley sizes.  Not sure what your RPM is on your delta, but if you can tolerate slower belt speeds at the platten (and some stalling under heavy grinding) it might be barely acceptable.  Personally I prefer at least 1.5 HP for 2" belts.

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6 hours ago, Latticino said:

 

I have a question about the jump from 1 hp to 1.5 hp. Both Pheer and OBM sell a 1 hp setup with a VFD and a 1.5 hp setup. I’m thinking of just getting an OBM but I want to know how big of a difference I’ll see if I just get the 1 hp with the KBAC-24. 

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The difference is perceptible, but not necessarily critical.  I recently switched from a 1.5 HP grinder up to a 2 HP grinder after cutting my teeth on a 1 HP Grizzley.  It all depends on the kind of work you will be doing, but you will never regret having a larger motor if you can swing it financially.  Also please recall if you are planning on running your grinder on 120 V single phase rather than 220 V dual phase the VFD will do the conversion, but the power output of the motor will be decreased for the former option.  You should also factor in the power source available to you.

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Unless he lives on the edge of NJ an Pennsylvania   NO ONE has dual phase power out side of that ONE area in the WORLD, (2 ph is a 5 wire system) and I am not sure its even used there anymore.  Also rated Hp is the same HP no matter where the power is coming from. Motors work from watts.  If he has it wired at 240 volts it draws half the amps that the same motor would have with 120 volts,  ANY 1HP motor does 1HP of work unless its windings are damaged no matter if single phase or 3 phase  at 120 volts or 240 volts or even 480 volts, and no one has made 2 phase motors in many years

for more info : https://en.wikipedia.org/wiki/Two-phase_electric_power

 

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My apologies,  I'm a mech eng and always getting that wrong and my boss the EE gets on my case. I meant normal household power with two hot legs out of phase with each other, a neutral, and a ground. 

As regards the power loss I was referring to the specific application in the OP regarding use of a VFD to convert either 120 or 240 household sources to three phase for a 3 phase motor to drive a belt grinder. My understanding is that under those conditions you give up a bit of brake horsepower if you use the 120.  I'll certainly check into that further to be sure, if you feel that strongly that it is in question. As I'm sure you are aware, brake horsepower available  is often quite different than rated horsepower. 

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14 hours ago, Latticino said:

...use of a VFD to convert either 120 or 240 household sources to three phase for a 3 phase motor to drive a belt grinder. My understanding is that under those conditions you give up a bit of brake horsepower if you use the 120.  

On both the OBM and Pheer websites they list the 2 hp motor as only getting 1.5 if you’re running on 110. 

As an aside...  Why do some folks refer to 120 and others 110? In the USA they are often used interchangeably in informal conversation but I live out west and it has always been 110 or 220 out here. Is it still 120 in some places? 

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the transformer at the pole produces 125 volts to each side (leg) of the output. US Electrical Code allows 5% voltage drop to the mast/meter, and then another 5% to the source.  So while most outlets will have 120 volts available, some poorly maintained systems will only have maybe 110 volts. This is why equipment is designed to tolerate that low voltage to operate.

I  have no idea why the Hp change, except that 2HP is pushing the limits of a 120 volt circuit capability, so maybe they choke it to allow safe operation? I dont know

a 1.5 Hp motor can draw up to 20 amps a 2Hp up to 24 amps at 120 volts, so a 2hp can run on 120 volts IF you have a 30 amp circuit for it, as in a factory setting, most houses are not set this way.  its only half the draw at 240 volts because the load is shared between 2 power lines, which is why mot homes just used 240 for motors

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Upon closer review, the “1 hp” motor is actually only pushing out 3/4 hp if you’re running on 110. 

From the OBM website::

  • The VFD is wired for 110V so the motor produces 3/4hp at 3600rpm which is ample for knife grinding but it can also be rewired for 220V if you wish for the motor to produce 1hp (original instructions for the VFD enclosed).

 

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that is the VFD circuitry not the motor fault ask them why, as I said I dont know why VFD are weird things, maybe its reduced due to the "ghosting" of the 3rd leg to get the 3phase power, that amperage has to come from somewhere. cant run the peak 14.7 amps for a 1 HP safely on a 15 amp circuit there is no head room. most home  lines are 15 amps not 20.  A 20 outlet has one horizontal tab and one vertical looks like this -.|  a 15 has both vertical and looks like |.|   power conversion is not 100% efficient. so there is loss there as well

 

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