Repowering SB 9" Lathe

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liveaboard
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Re: Repowering SB 9" Lathe

Post by liveaboard »

So shouldn't rkcarguy use a 3-phase motor and a vfd?

I also have 3-phase at home, but when I put my 3 phase lathe motor on a vfd it's much more versatile.
With VFD's, everyone can have 3-phase at an affordable price.

Or did I miss something?
rkcarguy
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Re: Repowering SB 9" Lathe

Post by rkcarguy »

whateg0 wrote: Thu May 07, 2020 12:18 pm Yes, you are just swapping T5 and T8.

drum.jpg

Dave
My rotary switch wasn't wired right by the previous owner. I followed this diagram and it works great...well I had to swap T5 and T8 because it was backwards to the switch direction but that's easy enough. Just need to button up the wiring and get my T-nut tapped for my QCTP and it'll be time for some test cuts.
rkcarguy
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Re: Repowering SB 9" Lathe

Post by rkcarguy »

liveaboard wrote: Sat May 09, 2020 4:46 pm So shouldn't rkcarguy use a 3-phase motor and a vfd?

I also have 3-phase at home, but when I put my 3 phase lathe motor on a vfd it's much more versatile.
With VFD's, everyone can have 3-phase at an affordable price.

Or did I miss something?
I'm not a fan sorry. The concept looks cool but in my eyes I see $250-$300 worth of made in china junk that can fail instead of $120 made in China motor. It's literally one lever that locks over center, it loosens the belt and you slide it over to the next set of pulleys and lock it again to change speed. It's not going to stop working, throw an error code, require to be turned off and on again to work right, etc.
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Re: Repowering SB 9" Lathe

Post by whateg0 »

I don't necessarily agree that a 3ph motor is undisputably better. However, I have been quite happy with 3ph motors on my lathe and mill. That said, the quality and features, as well as associated price, of VFDs vary greatly. My $100 VFD was not a great fit for the lathe. My 10ee originally came equipped with a BIG DC motor that, along with a backgear provided all spindle speeds through varying motor RPMs. When I bought it, it wasn't functional and rather than try to figure out what was originally wrong, as well as what the PO had done in trying to fix it, I gutted it. The cheap VFD and $10 2hp motor I put in worked alright, but since since the machine relied on near instantaneous stopping for the ELSR, the lack of braking resistor was a real PITA. The DC motor provided that, but the VFD wasn't able to. So, I upgraded to a $300 Fuji Frenic VFD with braking resistor and I'm thrilled with the machine now. On the mill, since a hand brake exists (Waiting on me to tear it apart and put new brake shoes in now) the cheap VFD works fine and provides a range of spindle speeds without having to climb up on the stepstool to change pulleys. I doubt I'll ever upgrade the VFD on the mill, though I could certainly see power tapping benefiting from being able to stop the spindle on a dime, and better yet, just reverse the motor without needing to manually stop the spindle first.

Dave
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Re: Repowering SB 9" Lathe

Post by liveaboard »

I was lucky, I got a US made VFD on ebay for $50. No one else bid on it.
It had some weird setup on it, I'm sure the first owner had failed to make it work. once I got it programmed correctly it works for me flawlessly.
My 3-phase 2HP lathe motor is ancient; it wouldn't look out of place in a museum.
3-phase motors don't lose torque like single phase ones as they're loaded. For machine tools, I find 3-phase totally superior. Even my carpentry tools are 3-phase.

Mr. Tesla invented 3-phase for industrial motors, and it's still the standard today.
No start winding, no capacitor, no internal switching, just lots of torque.
Single phase motors are a workaround to get a motor to work on a power supply made for light bulbs.
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Re: Repowering SB 9" Lathe

Post by rkcarguy »

We lack 3-phase power here except in industrial areas unfortunately. The first machine shop I worked in had a giant inverter because it wasn't even available there.
The lathe is working good and I've done a little test cutting and then chucked up a wheelset and started cutting some tapers. It's certainly a far cry from the 24" x 216" Victor at work as far as power and depth of cut, but it's mine and I can use it whenever I want and I'm liking that. Also, you don't need 2 people, or a hoist, to change the chuck out to a 4-jaw.
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Re: Repowering SB 9" Lathe

Post by liveaboard »

Then all is well!
The lack of 3-phase in much of the US is so odd to me. Europeans think of the US as the land of big power.

I even had 3-phase in my house in a village in India. I have 3-phase on my houseboat in Amsterdam.
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Re: Repowering SB 9" Lathe

Post by rkcarguy »

liveaboard wrote: Wed May 13, 2020 10:50 am Then all is well!
The lack of 3-phase in much of the US is so odd to me. Europeans think of the US as the land of big power.

I even had 3-phase in my house in a village in India. I have 3-phase on my houseboat in Amsterdam.
It's the land of big power IF you spend big money. The utility wanted $40,000 to extend 3-phase power ~1km to the machine shop I mentioned earlier.
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