2X72 grinder build. Need validation/recommendations

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MitMo303

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May 2, 2018
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I am planning on putting together a 2x72 grinder based on the Oregon Blade Maker Chassis. What I was thinking of getting the Kbac-27d vfd so that I can run a 1.5hp motor on my 110v outlets. how well do you think this will work? (im planning on having a lower rpm motor direct drive with a 6inch drive wheel). Im sure it will be better than my craftsmen 2x42. I will eventually have 220v ran to my garage but the way my house is set up im getting quoted $1500 for the job. Maybe one day when I have it I can use the same vfd and upgrade to a 2hp motor...someday. Also, do any of you have a suggestion for a good 1.5 hp motor in the 1400-1700 rpm range? Any input/suggestions will be greatly appreciated.
 
You might wish to consider a 4" drive wheel - that will still give you around 4,000 SFPM which should be plenty, and your 1.5 hp motor will still pull it ok. Start getting up to 6" it will load the motor. I'm sure other folks who have more experience than me will chime in on this idea -
 
Your most common 1.5HP 3 phase motors will be either 1800 or 3600 RPM. IronHorse is probably the best "new in box" deal on the market, if you're on a budget. If money is no object, then Baldor makes a good motor. Whatever you choose to go with, make sure it's rated for "inverter duty", or has at least class "F" insulation. You'll also want a TEFC (totally enclosed fan cooled), and probably want to stick with a 56 frame. If you think you'll ever upgrade to a face mounted motor style grinder, I'd get a 56C, as this will work for both the OBM grinder chassis, as well as a mountable chassis.

FWIW, this motor meets all of the requirements:
https://www.automationdirect.com/ad..._(0.33_-_3HP)_TE,_Footed_Rigid/MTRP-1P5-3BD18

You will of course need some 14/3 and 14/4 cable (first for the wall connections, latter for the motor to vfd connection, SO cable is best for this), a couple of cable glands (2 for VFD, 1 for motor), a plug end, and maybe an extra switch or two, depending on how you want your VFD set up. If you don't have the VFD already, I'd recommend adding the power switch and FOR/STOP/REV switch option.

I think that should be most of what you need to get going...
 
Awesome advice, I really appreciate the parts list as I was assuming that all those items, if not partially, would be included. Thanks again. Am I understanding right that I can double my rpm by reconfiguring the kbac vfd?
 
I'm going to recommend the 6" drive wheel, even an 8" if you can find one for a decent price. I say this because ceramic belts really shine in performance and longevity when used 6-7k sfpm. A lot of guys are figuring this out, especially when grinding post ht. Get an 1800 rpm motor so you can double rpm when/if you feel ready. Definitely get f/r switch. I know it might up the cost and change your plans, but I also recommend at least a 4" tracking wheel, and only one 2" platen wheel. Make the other a 4". I say this because if you do decide to grind fast the bearings last longer in bigger wheels. I run an 8" drive 2hp on 2x jumper and I wouldn't mind it being even faster. If you haven't seen it, watch the "Entrek knives-grinding the blades" video on YouTube.
Also, when you build, make sure your belt tension system is strong enough. A lot of guys who build try too weak of a spring at first. You want about 30-40 lbs of pressure pushing against the belt. If you run a gas spring, and can get it vertical, 30 lbs is good. As the angle changes from being a straight up push the spring loses power.
 
if you get a 3600 rpm motor, and double the HTZ with the jumper in the Kbac, you will top out at over 6000 SFPM with a 4 inch wheel, That is plenty of speed, with an easy to get contact wheel.
 
You can set the KBACs to "2x" with the speed jumper. It's very simple. Concerning starting with a faster motor vs. a larger drive wheel, I'd pick the largest drive wheel before I started with a 3600RPM motor. The 1800 rpm will give better torque on the lower speeds than the 3600.

Personally, I have the motor I linked to above, set to "2x" with a 5" drive wheel from VWJackStraw (ebay seller), and it works well for what I do. Sure, a little more speed might lend a little more efficiency to my ceramics, but I rarely grind at full bore anyway, unless I'm hogging steel.

Now, I will add that the KBAC switches can probably be found for a few dollars cheaper if you already have some female spade connectors and a roll of hook up wire. They're just basic switches with dust covers on them, and they're very simple to hook up. If you DON'T already have some odds and ends lying around, you're probably better off to just add them when you buy the KBAC, and be done. Depending on where you buy the drive, they'll probably ship it with everything connected already, but if not, it's a simple matter of plugging in a couple of wires.
 
I'm running a KBAC 29 1P with an IronHorse 3HP 3600 motor. With the 2X jumper on you can get 7200 SFPM with a 4" drive wheel and still have plenty of torque on the low end. The only time I crank mine wide open is hogging in the profile and have never needed more running a good belt. A new 36 grit ceramic belt cuts like butter. I'd recommend spending the extra few dollars for their plug and play switches. Worth the money not to have to make your own.
 
how far from 240 is you shop? run an extension cord for time being. many more VFD to choose from with 240 input. these folks are a good source, fast service http://dealerselectric.com/230V-sin...23456808&pgID=1&SortBy=PriceAsc&GdPageSize=20 if you can only afford one drive wheel, get a 4". if more than one, get a 3" and a 5" or 6", going from 3" to 6" will double belt speed. the auction site that starts with E is a good place to find short lengths of 4 conductor cable, plugs and receptacles for connecting VFD to motor.
 
knife to a gunfight said:
You can set the KBACs to "2x" with the speed jumper. It's very simple. Concerning starting with a faster motor vs. a larger drive wheel, I'd pick the largest drive wheel before I started with a 3600RPM motor. The 1800 rpm will give better torque on the lower speeds than the 3600.

Personally, I have the motor I linked to above, set to "2x" with a 5" drive wheel from VWJackStraw (ebay seller), and it works well for what I do. Sure, a little more speed might lend a little more efficiency to my ceramics, but I rarely grind at full bore anyway, unless I'm hogging steel.

Now, I will add that the KBAC switches can probably be found for a few dollars cheaper if you already have some female spade connectors and a roll of hook up wire. They're just basic switches with dust covers on them, and they're very simple to hook up. If you DON'T already have some odds and ends lying around, you're probably better off to just add them when you buy the KBAC, and be done. Depending on where you buy the drive, they'll probably ship it with everything connected already, but if not, it's a simple matter of plugging in a couple of wires.
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low end torque on a belt grinder isn't really that important.
 
KnuckleDownKnives said:
For me it kinda is. I grind my bevels at a slower speed because I screw up less. I'm getting better though.
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but since a grinder has very little starting resistance, even with a flat platen, it really shouldn't matter. Unless you are saying you are hogging at under 2k SFPM. Most people aren't pressing hard when the belt is moving slowly, and once up to speed, torque matters little. I've had both 1750 and 3600 motors on 2x72 grinders and really see no difference in regards to performance related to torque.
 
From the sounds of it a slightly slower SFPM would lend a bit more forgiveness even if it means shortening the life/losing efficiency on my ceramic belts. I think I would benefit from this as I am still a novice.
 
I agree with Kevin, low end torque isn't important. Starting with a 4 " drive isn't a bad thing. I wouldnt want to run a motor at 7k rpm though. Jmho. I grind much quicker than most makers so the advice about belt speed is a personal preference. You will have to figure out your own process and comfort level with speed. Though it is a fact that ceramics are designed to run fast and hard. I wouldn't drop the extra coin on them if you can't hit at least 5k sfpm. I grind post ht with a wet belt and can cut clean bevels on a 4" blade in under two minutes without a jig. I forced myself to learn this way because I hate masks. You won't want to try this without the muscle memory gained from experience. But it's nice to have capability to try it later.
 
I have a similar setup and love it. stock Oregon grinder, iron horse 1.5hp 3phase motor, kabc-27 vfd. I run off of 220v as I do have that in my garage, use a 30' cord to a wall socket for that. Also use a 20amp breaker. Runs great, never bogged it down myself, plenty fast too. my only regret is I mounted it a bit higher than I would like. One day I will get a 6" wheel and arm for it, but have gotten by without it for last year.

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I recently bought a new 1.5 hp single phase motor for my new 2x72 setup. I was told on reddit that I needed a thermal overload protector and I was wondering if that is necessary or if I can just wire it to an on off switch?
 
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