I Want A New Grinder

[Ken H>]

Oh, you are correct on the "inverter" rated motor - it's general purpose. Do you happen to know the difference in "general purpose" vs "inverter rated motors? A bit more insulation on the windings. In industry the motor manuf ALWAYS recommends changing a perfectly good general purpose motor to an inverter rated motor when changing a system to VFD drive. We never did - just continued using general purpose motor with VFD saying "we'll change when it fails" - never did, or at least lasted as long as expected.

The purpose of the inverter rated motor extra winding insulation is to allow better handling any voltage spikes that might happen due to standing waves on the electrical line. The longer distance from MCC where the VFD is located to motor, the higher these standing waves can be. In our case, the electrical line is very short, just from VFD to motor might only be 3 ft, NOT the 300+ feet it can be in industry.

I've been trying to correct my previous post about 4/C cable - only 3/C is required for extension cord to VFD, 4/C is required from VFD to motor.

 

[Drew Riley]

Oh, you are correct on the "inverter" rated motor - it's general purpose. Do you happen to know the difference in "general purpose" vs "inverter rated motors? A bit more insulation on the windings. In industry the motor manuf ALWAYS recommends changing a perfectly good general purpose motor to an inverter rated motor when changing a system to VFD drive. We never did - just continued using general purpose motor with VFD saying "we'll change when it fails" - never did, or at least lasted as long as expected.

The purpose of the inverter rated motor extra winding insulation is to allow better handling any voltage spikes that might happen due to standing waves on the electrical line. The longer distance from MCC where the VFD is located to motor, the higher these standing waves can be. In our case, the electrical line is very short, just from VFD to motor might only be 3 ft, NOT the 300+ feet it can be in industry.

I've been trying to correct my previous post about 4/C cable - only 3/C is required for extension cord to VFD, 4/C is required from VFD to motor.

The inverter rated motors basically handle more heat. That said, long cable runs aren't the only consideration. Running at slower speeds can also heat up a motor pretty good. Whether the "slower" speeds that an average knife maker uses are enough to heat the motor to premature failure, or how long it would take, I have no idea. Certainly something to be mindful of, but not necessarily a "don't ever do this" kind of thing.

 

[HSC ///]

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I see, thank you
so the MTCP class of Ironhorse has different torque ratings than the Ironhorse I bought , but I still don't think the MTCP is a full inverter class model.
The MTCP seems to be a premium efficiency vs the general purpose.
Also this MTCP has a 7/8" shaft and I believe a 5/8" shaft is more desirable for knifemaking accessories, discs, drive wheels. etc.

 

[colu41]

Im definitely learning a lot from this thread. And for the inverter motor. I will obviously use it at low speeds, but literally for only seconds at a time. I use my 1x30 now at whatever fast rpm it is and works for what I need so, I dont think it will be a problem for me.

 

[Ken H>]

The man's right - "IF" you run a motor at a crawl for hours on end, you could well over heat the motor because the fan isn't blowing enough air for cooling. On lathes many folks have added an external fan to help cool motor because a lathe can be used a lot at slow speeds. I seldom run my lathe are more than 50% speed. For hobby grinding operations I doubt there are many times the grinder will be running over a few minutes constant at low speed, or any speed. Some of these folks who are running a professional operation I'm sure may set to grinding and grinder runs a long time without stopping.

The specs for the MTCP motor does state: • Service Factor: 1.15 (1.0 with AC drive), with 4:1 (constant torque) which tends to indicate rated for VFD drives. the cheaper motor I linked to is also inverter rated from spec sheet. BUT - it is a lighter duty motor with only a 2:1 (constant torque) rating. The service factor and insulation class F are the same on both motors.

I'm going by the spec sheets for the above. Is the MTCP motor worth the extra $60 AND the extra 20lb of weight of motor? Not to me - the 20lb weight is a lot more than I'd wish to deal with since I move my grinder around from time to time, and also flip grinder horizontal.

Ken H>

 

[Ken H>]

I've been trying to post this correction to my post about use of 4/C cable but have not been successful to get posted. I'm wondering if it's because I pasted in all the text before. OK, try this link for a selection of SOOW cable, use the 3/C #14 for extension cord and 4/C #14 from VFD to motor.

http://www.wireandcabletogo.com/14-AWG-SOOW/

Up to 1-1/2hp works just fine with 120vac - once you get over 1.5hp you'll need 240vac. #14 cable is all you really need for the extension cord. How many feet do you need? 50 ft?

Ken H>

 

[colu41]

I've been trying to post this correction to my post about use of 4/C cable but have not been successful to get posted. I'm wondering if it's because I pasted in all the text before. OK, try this link for a selection of SOOW cable, use the 3/C #14 for extension cord and 4/C #14 from VFD to motor.

http://www.wireandcabletogo.com/14-AWG-SOOW/

Up to 1-1/2hp works just fine with 120vac - once you get over 1.5hp you'll need 240vac. #14 cable is all you really need for the extension cord. How many feet do you need? 50 ft?

Ken H>

Thanks. I'll keep looking into it.

Anyone know of any grinder plans out there for that simple design I showed earlier in the thread? All the plans I found either for free, or the pay for ones, were for the extravagant grinders with the extra tension arm that end up costing $1200+. I want a plan for a $500 grinder

 

[Ken H>]

I can't imagine spending $1200 to build a nice grinder. Check the thread I linked to before, it's a KMG clone (sorta) and I do think you can purchased everything, wheels and all for $500 or so. Takes a bit of work, but it's sure a nice grinder that runs smooth 'n quiet.

 

[colu41]

Thanks. I'll keep looking into it.

Anyone know of any grinder plans out there for that simple design I showed earlier in the thread? All the plans I found either for free, or the pay for ones, were for the extravagant grinders with the extra tension arm that end up costing $1200+. I want a plan for a $500 grinder

Just talked with my brother, and he is going to help me with all of the electrical stuff. (I am in no means an electrician)=D, I'm sure I could slowly figure it out but, I'd rather let him who actually went to college for it do it for me. I'm deciding I'm going with a 110/120vac motor. And he found a cheap alternative for a variable speed. It may not be as refined as the bigger VFDs, but will be completely ok for what I want.

Now my problem is, is finding the right motor (in 110v). I'm on a motor wholesale site, and there is literally 20 different styles/types of motors.
Am I looking for general purpose, farm duty, compressor duty? I'm not quite sure.

 

[Drew Riley]

Thanks. I'll keep looking into it.

Anyone know of any grinder plans out there for that simple design I showed earlier in the thread? All the plans I found either for free, or the pay for ones, were for the extravagant grinders with the extra tension arm that end up costing $1200+. I want a plan for a $500 grinder

It's not really an 'extra' tension arm, so much as it's just put on a pivot instead, although, yes the NWGS was have one additional upright than the grinder you linked to, as well as a "base tube".
At any rate, it really shouldn't amount to more than $20 worth of extra scrap metal and a pivot bolt.

I'm guessing that the $1200 you see for most grinders is usually factoring in a few hundred bucks for wheels and then $600+ for a VFD set up. As has been stated, wheels and motors and drives can be found much cheaper. The actual frame of the grinder will be the cheapest part.

 

[colu41]

It's not really an 'extra' tension arm, so much as it's just put on a pivot instead, although, yes the NWGS was have one additional upright than the grinder you linked to, as well as a "base tube".
At any rate, it really shouldn't amount to more than $20 worth of extra scrap metal and a pivot bolt.

I'm guessing that the $1200 you see for most grinders is usually factoring in a few hundred bucks for wheels and then $600+ for a VFD set up. As has been stated, wheels and motors and drives can be found much cheaper. The actual frame of the grinder will be the cheapest part.

You're probably right. I never thought of that really. Most of the framing itself I may get for free, as my brother has access to unlimited scrap steel lol. (His work literally gives it away).

So if I were get a set of these plans, I could still make this in my price range? In this case, any plans anyone know of that you recommend? Remind you, I do not have access to a mill or lathe, so anything needing special equipment I would rather stay away from. I do have access to a welder so thats not a problem.

 

[colu41]

I can't imagine spending $1200 to build a nice grinder. Check the thread I linked to before, it's a KMG clone (sorta) and I do think you can purchased everything, wheels and all for $500 or so. Takes a bit of work, but it's sure a nice grinder that runs smooth 'n quiet.

Thanks Ken. I have the link still open on my laptop. Lol. Ill scope it out again. I just thought they were more expensive because of the "extra" parts it looked like it had.

 

[colu41]

Thanks Ken. I have the link still open on my laptop. Lol. Ill scope it out again. I just thought they were more expensive because of the "extra" parts it looked like it had.

I'm not sure what to call it but I'm looking for plans for a WELDED grinder. They all come up no weld. I'll be using steel as that's what I'll have and it would be way more convenient to weld everything.

 

[Brian Ayres]

Weld the no-weld grinder together..

 

[colu41]

Weld the no-weld grinder together..

Haha. I suppose. But the no welds usually have multiple aluminum bar stacked all over and drilled and tapped. Where I can just use steel tubing in one piece. I'll figure it out. I'm looking into measurements now. I hope to order a motor by the end of this week or next week.

 

[Ken H>]

Well, if you can find the 1-1/2" ID square metal tubing with good thick walls, then no problem. I couldn't find any locally that was "cheap" so the aluminum I bolted together was the least expensive option I had at the time.

Get the steel 1-1/2" ID tubing, get some 1/4" or 3/8" steel plate. Since you've got access to a welder, I'd guess you've got access to a cutting torch? Band saw (or Portaband) to cut metal? Just whack the plates up into shapes you need, weld it all together. When welding, be darn sure to keep things lined up. I was more comfortable with the idea of welding at the start myself, but after working with the aluminum plate that turned out pretty good. All the aluminum to build the grinder was well less than $150 shipped.

Ken H>

 

[colu41]

Well, if you can find the 1-1/2" ID square metal tubing with good thick walls, then no problem. I couldn't find any locally that was "cheap" so the aluminum I bolted together was the least expensive option I had at the time.

Get the steel 1-1/2" ID tubing, get some 1/4" or 3/8" steel plate. Since you've got access to a welder, I'd guess you've got access to a cutting torch? Band saw (or Portaband) to cut metal? Just whack the plates up into shapes you need, weld it all together. When welding, be darn sure to keep things lined up. I was more comfortable with the idea of welding at the start myself, but after working with the aluminum plate that turned out pretty good. All the aluminum to build the grinder was well less than $150 shipped.

Ken H>

Thanks. I will be squaring up and clamping the crap out of anything I will weld.

I actually found a grinder plan the I was looking for. Calls for 2" square tubing for the main frame and 1 1/2" square tubing. For the tracking/tension pillar & the attachment arms. I decided Im going to purchase steel as if I used the free stuff I could possibly get, it would be more of a headache welding it all together than just getting the right tubing size.
I found a webpage with all the steel tubing I would need plus plenty more for $70 shipped. Oh man am I ready to do this!

 

[Fortydegnorth]

Check local recycling center or steel suppliers that have a drop section or used. I bought all the tubing and plate for my project for $13 at the steel yard. I can walk around and find whatever sizes I need and it's priced by the pound usually.

 

[colu41]

If I were to get a single phase motor, could anyone tell me why something like this wouldn't work? I know VFD is the proper way to go, but honestly, I don't need such fine tuning as the vfd would offer.

 

[colu41]

Check local recycling center or steel suppliers that have a drop section or used. I bought all the tubing and plate for my project for $13 at the steel yard. I can walk around and find whatever sizes I need and it's priced by the pound usually.

I definitely will before I decide to order anything. Thanks!