Motor information please

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natenaaron

Member
Long story short, All my fun when I was young has caught up to me and unless I can find suitable wrist braces forging is out and building a press is not economically viable right now. That being said, a grinder is. It will have to be home made, I have the know-how and based on some plans I have found I have all the steel I will need. See I'm not a hoarder, I was storing it until I needed it.

I am stumped on the motor though. This will either be scavenged or bought new but in my reading I see different suggestions.

one place said 1HP was enough, a couple other places said 1.5 was enough and some said 3 was perfect. I plan to use belts and pulleys for speed to begin with.

My inclination is to go with a 3hp motor but not sure if that would be overkill.

I learned a long time ago to figure what I need and buy bigger. I have no idea if this applies here though.

What are your recommendations?

Oh, I will be buying wheels from Oregon Blade Maker.
 
check out the DVD on the Grinders Page at www.WayneCoeArtistBlacksmith.com. There is also a video there that you can watch. I strongly suggest that you get a 1.5 or 2 hp 3 phase motor and an appropriate VFD. If you go with a single phase motor and step pulleys you will soon determine that you need variable speed and will then have to buy the 3 phase motor and VFD. The other motor and parts will then be expense that you could have saved.

Let me know if I can help you.
 
I built one of Wayne's grinders (the guy that posted before me). Contrary to his advice, I used a 1hp 3phase motor with a VFD. It works great, I've never felt like I needed more power. But, if you go scrounging for a single phase motor, you would want more than 1hp. First off, I think the hp ratings on a lot of cheap motors are exaggerated. Then, even if you have a decent motor, you're going to lose some hp in the pulleys and belts. Single phase motors have a lot that goes wrong too, caps, centrifugal switches, start windings, etc. I understand if you can't swing a VFD and 3ph motor, but Wayne is right. You'd be money ahead to build it variable speed now. Good luck whichever way you go.
 
The maximum size motor that you can run on a 120V 20A circuit is about 1.5hp. This is what many consider to be the bare minimum when building a grinder. That said, I'm running an Esteem grinder with a 2hp motor and a KB Electronics model KB27d variable frequency drive (vfd). However, I have the vfd hooked up to a 120V circuit but its smart enough to run the 2hp Leeson motor as if it were only 1.5hp. Eventually, I'll wire in a 220 circuit for it so I can take full advantage of the motors torque. To tell you the truth though, I've never had a problem with power just running it the way it is, but it is a direct drive as opposed to using a pulley system. Pulley systems themselves take some power to run and will also add some vibration to the system. This is why most knife makers prefer a direct drive. Now then, if you're just starting out and on a budget then you do what you have to do. Find yourself a 1.5hp motor, one or two step pulleys so that you can change speeds and you'll be off to a good start. Eventually though, if you're like most of us, you're going to want to upgrade to a vfd and direct drive system so you may want to keep that in mind for whatever machine you plan on building.
 
If you only have 110V, then 1.5hp is gona be the max. If 220V is available, the sky is the limit. Personally, I'm at the point in my career where all the grinders have 3 hp motors. I'm actually in the process of updating the motor on my KMG from a 180V DC motor/controller to a 3hp/3 phase and am going to use my existing KBAC 29D VFD to run two grinders that sit side by side on the bench.

These are the two motors that I generally purchase when I need a grinder motor....

For direct drive applications (drive wheel connected directly to the motor shaft..... http://www.electricmotorwholesale.com/LEESON-113890/ along with this drive wheel: http://www.beaumontmetalworks.com/shop/item.aspx?itemid=78

For a belt drive/shaft setup for the drive wheel, this motor: http://www.electricmotorwholesale.com/LEESON-116107/

Both are the same motor...... the first one is a 56C frame (face mount), and the second is a 56CH (has both "feet" and a face mount). In order to run either you will also need a KBAC 29D VFD: http://www.electricmotorwholesale.com/10001-KBAC-29D/

I started out years ago with 1hp motors, and found that they quickly became "too whimpy" for me, then went to 2hp....and the same thing happened within a year or two. Been running 3hp motor on my grinders for about 15 years now..... and haven't yet found the need to "move up"...... but that's not to say my mind might change some day. :)
 
Just to clarify a little about what Ed just said, those motors would work fine with the KBAC 29D vfd. If as the OP mentioned that he's going to use a belt and pulley system to start things off he won't be able to use these motors as they are 3 phase and require the vfd. Which ever motor you decide on, make sure its rated TEFC (Totally Enclosed Fan Cooled). Sometimes these are referred to as agricultural (farm) grade motors and you can indeed pick them up at a local farm supply place quite easily. To summarize, if you're going to use a belt and pulley system you need single phase motors rated for either 120V or 220V. For 120V you can go up to 1.5hp assuming a 20A circuit. For 220V, you could run a 3hp motor on a 30A circuit, although the actual current draw is closer to about 20A, you have to leave some head room on the circuit by code. If you're going to purchase a variable speed controller (vfd), which is very highly recommended at some point, then you're going to need a 3 phase motor. The vfd actually converts your single phase power (120 or 220) into 3 phase power for these motors.

And you thought all you need to learn was how to make a knife. :biggrin:
 
I would also like to point out that the KB Electronics VFD's are highly regarded and have a price to reflect that...around $350 or so. Many guys start out with an offshore VFD widely available on ebay for around $120 if memory serves. I haven't heard any complaints about these vfd's other than they're susceptibility to burning out due to power surges. As with anything of this nature make sure you unplug them when not in use...even the KB's. Point is, why invest in the pulleys and single phase motors when eventually you're going to want a variable drive. If you can put together enough to cover the cost of a cheap drive, then go that way. You can always upgrade later. You know the old saying...pay once, cry once.
 
Yep! If you go "belts-n-pulleys" those motors I listed won't help you. But, if you grind blades for any amount of time, you'll quickly learn the usefulness of speed control on a grinder.

Many guys start out with an offshore VFD widely available on ebay for around $120 if memory serves. I haven't heard any complaints about these vfd's other than they're susceptibility to burning out due to power surges.
Click to expand...
pay once, cry once
Click to expand...

Thats the reason I strongly advise the KBAC controllers...... those cheap ones have people "crying" all the time. I just hate them. I've spent countless hours trying to help people who have either burnt those controllers out, or had some other issue(s) they were trying to correct. I've had so many instances of people calling for help that, it's gotten to the point that when someone calls me asking for help with one of those cheap controllers..... I just tell them "sorry...you REALLY need to just get one of the KBAC controllers, and then you won't have all the problems."
 
Ed speaks from years of experience and is very knowledgeable in knife making..... AND knifemaking tools. I listen to Ed. With that said, those Chinese VFDs are a good buy for a hobbyist type user. They are widely used in desktop CNC use and many of us are using them for 2X72 grinders. They do have a different learning curve than do the KBAC VFDs. I've got a Telco VFD on my 1hp lathe, and am very happy with it, and a Chinese VFD on my grinder. Just does what it's supposed to do for the last yr or so. BUT - with that said, Ed will put more hours on his grinder in a week than I do in several months.

Allow me to add a bit for my opinion on variable speed vs belt drive. Here I've said it all:
http://knifedogs.com/showthread.php?38839-New-Grinder-for-me

Down toward bottom of page is a link to a 3ph 2hp, TEFC motor for $127 shipped. If you have to purchase the shafts, pulley's and belts for a belt setup, you'll find the VFD setup not much more expensive... Less than $300 total cost if using a Chinese VFD. When ("IF") the $116 shipped Chinese VFD goes bad, then you can purchase the expensive VFD.

Ken H>
 
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You folks are great. I will take a look at those. I am just starting this and hobby is the operative work. At this point I don't need the big bells and whistles. If I stick with it, I can upgrade later.

I have 220 wired to the shop so a larger motor is doable. and those chinese VFDs might workout also. Electricity and I do not really see eye to eye and I have a hard time understanding why a 3 phase motor is important. There is no way for me to get 3 phase to my shop side of the property.
 
That's the cool thing, you don't need 3 phase power with the VFD, it converts your 220/110 volt power to 3 phase power. 110 volt is good to about 1.5 HP, and 220 volt is good to at least 3 HP. The VFD needs a 3 phase motor to be able to control the motor speed variably. I think it does so by altering the frequency.

[video=youtube_share;KaMqXra7aew]https://youtu.be/KaMqXra7aew?t=155[/video]

Check it out at about 2:30......

YMMV
 
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Jax is absolutely correct! It would be extremely rare for anyone in the U.S. to have 3 phase power dropped to their house....none of us have it. The vfd performs that bit of magic for us, converting either 120 or 220 single phase into a 3 phase output which is sent to the 3 phase motor. Speed control is much simpler electronically when dealing with 3 phase motors which is why vfd's do what they do.

Here's the gist of the magical part. All motors work by creating a rotating magnetic field. This is accomplished via the stationary stator windings on the outer most part of the motor. The rotating magnetic field drags the rotor (the rotating part thats attached to shaft) along with it. With a 3 phase motor there is one stator winding, at a minimum, per each phase. This, because of some advanced electrical theory that we won't get into now, naturally causes the field to rotate. With a typical single phase shop motor we have to use capacitors to get the field rotating, this makes speed control of single phase motors difficult.

Another piece of the puzzle is that the speed of the rotating field is dependant on the frequency of the source. Its not easy to change the frequency of a single phase motor because the capacitor thats involved also changes characterisitics with frequency....its a can of worms. Anyhow, since 3 phase motors do not require capacitors to get the field rotating, we can easily change the frequency being applied to the motor which then changes the rpm of the rotating field which in turn changes the rpm of the rotor being dragged along by the field.
 
natenaaron said:
You folks are great. I will take a look at those. I am just starting this and hobby is the operative work. At this point I don't need the big bells and whistles. If I stick with it, I can upgrade later.

I have 220 wired to the shop so a larger motor is doable. and those chinese VFDs might workout also. Electricity and I do not really see eye to eye and I have a hard time understanding why a 3 phase motor is important. There is no way for me to get 3 phase to my shop side of the property.
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go on ebay and find a decent 220v inverter/VFD and 3 phase motor. the inverter/VFD use single phase 120 or 220 input and has 220 3 phase output and allows you to vary your speed. i would suggest a 1 or 1.5hp motor, but get whatever you want. the bigger the motor, the bigger the VFD, the bigger the power cables, the bigger the cost. I would suggest find a grinder plan that uses the motor direct drive, you eliminate pulleys and belts and the safety hazard they present. if you really in hobby mode, try a 1x30 or 4x36 size belt sander(less than $150) and see if you like making knives with a grinder. chinese VFDs cost less for a reason, they are poorly made. KB makes an ok VFD, but also look at Allen-Bradley, TECO, Leeson, or Siemens; truly industrial grade units.
 
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