RF-30 motor pulley on 7/8" shaft?

[Shotgun]

With a 3 phase motor and VFD, you may not need that pulley position. If you decide you do, I would be inclined to turn the broken part down and press fit a new pulley to the stub.

I'd be inclined to saw that step off and use the rest of the pulley as-is.

 

[RJSakowski]

I'd be inclined to saw that step off and use the rest of the pulley as-is.

On my RF30 clone, that pulley position gives an 18:1 torque multiplication which can be useful in certain instances. Attempting to repair the pulley won't preclude simply removing that section in the future. I would give it a go.

In addition to a press fit, the pulley could be keyed by drilling a hole intersecting both pieces after assembling and driving a dowel pin in.

 

[bulgie]

With a 3 phase motor and VFD, you may not need that pulley position. If you decide you do, I would be inclined to turn the broken part down and press fit a new pulley to the stub.

Both excellent suggestions, thanks. Since the piece that broke is for the slowest speeds, I can definitely make up for the loss of that pulley position by just dialing down the VFD. Plus the option to make a new one and press-fit it is great. That's within my skill-set, less scary to me than welding the aluminum which has a real risk of ruining the whole part.

That plus your earlier suggestion to tap the end of the pulley and use a screw to push it off the shaft, makes 3 great suggestions in a row.

 

[bulgie]

Fixed?

I decided to use the 3/8" thread I tapped in the top to tighten down a big fender washer, that keeps the broken piece of flange in line. Then I gooped it up with Loctite 603, which I have found to be very strong. Clamped it in a vise tightly so almost all the Loctite was squeezed out. The broken-off piece is also glued to the fender washer which hopefully adds some strength. To the eye, from say 3 feet away it looks like new, you have to get in close to see the fracture.




I also bored it to a .001" interference fit on my new spindle and pressed it on.

Anyone want to place bets on whether this kluge will actually work long-term?

As we've discussed, the stakes are not super high, since if it does break again, I can just live without that step on the pulley.

My placement of the VFD is just a little too far away for the piece I have available of 4-conductor 14g cable, so I'm waiting for the longer piece I ordered to arrive. Which is good because I have to wait for the Loctite to cure, and I'd be tempted to fire it up now, if I could. I'm like a kid on Christmas, too eager to get this thing back to making chips.

Hopefully when the new pulley I ordered from Grizzly arrives, they'll let me return it.

 

[OTmachine]

We used Metalset A4 for filler on Helo gearbox mount pads, (an engineering approved repair). And a buddy of mine used it to repair the bore of a Mercury Outboard flywheel that came loose.

 

[bulgie]

Hilariously dumb thing: I hooked up the VFD today and tested it. This VFD (a KBDA-27d from KB Electronics) had already been programmed for a motor to use on a belt-grinder project, that I haven't started yet, it's on the way-back burner. Its LED display was set to read in surface feet per minute, a useful number to know on a belt, but useless on a mill. I figured I'd set that back to reading frequency later, not important for now, so I'll leave it on sfpm. In a hurry to play with my new toy. Not dumb on its own, but it hid from me the fact that I'd also set the max frequency to 120 Hz. Again, a useful number on a belt machine, but all my other VFDs are set to 90 Hz max, and I forgot this one was 120.

The next dumb thing I did, I put the belt on the highest speed position (1-8) and cranked the VFD up to the max, which I figured would be about 3800 spindle RPM. I wasn't going to leave it there for long, just wanted to see if it could do it, what it would sound like. Yes, kinda risky at 3800 rpm, but insane at the 5200 rpm I actually got.

As soon as it reached full speed I heard a loud sharp crack! and I shut it down, assuming I'd broken something important. Took me a while to notice that the little magnet I'd glued to the spindle pulley for the tachometer sensor wasn't there anymore. The crack I heard was when that magnet hit the wall at 120 mph (rough calculation). Good thing it wasn't pointed at my face when the glue let go. I had safety glasses on, under a polycarbonate face shield, but I still wouldn't want to take a tiny metal frisbee to the head at 120.

So lets count all the dumb things I did.

1. Took the belt guard off, cuz you know, it's in the way and what could possibly go wrong? Real Men don't use guards, right?
2. Glued that magnet on without milling a little counterbore for it to nestle into, so it was just surface mounted, no side support.
3. Cranked the spindle up to a much higher rpm than I thought I was getting, because I was in too much of a hurry to change the display.

I've set up 5 VFDs now from factory defaults, but I've never reprogrammed one that was previously set for another machine. Maybe I should learn how to do a Factory Reset, so there aren't weird settings left over from whatever machine it was prgrammed for. Anyone know if that's an option with a KB? Do they have a KnowledgeBase (a "KB KB"?)

I've heard of people getting supposedly new VFDs, then finding there was some setting not at factory defaults. Maybe indicating that what they received was actually one returned to the seller, and repackaged as new. Unethical for a seller to do that, but we know it happens sometimes. Maybe a Factory Reset should be the first step in setting up any VFD, even if you think it's new — but especially if some idiot (like me) has worked on it previously.

Now to find that damn magnet. Maybe I'll find it out in the garden, and a tiny hole in the outside wall of my house?

 

[OTmachine]

Glad that you are Okay. On the cheaper Vevor brand VFDs that I use, I have found it necessary to reset to factory defaults First. Do not know what parameters they use at the factory for if & when they do test them. There is a wide range of possibilities.

 

[bulgie]

On the question of whether my broken pulley is going to work: So far so good. I just used the broken top end of the pulley to make a 2" hole in 1/4" thick steel with a holesaw, probably one of the more high-torque tasks I'll ever do on this mill. I guess an interrupted cut might be a tougher test for it, but it powered that holesaw thru no problem.

 

[bulgie]

The Grizzly replacement arrived and now I have to decide whether to use it or return it.

Pro:
Same height and belt size
More speed range: slightly lower low speed and substantially higher high speed (larger pulley size on the bottom of the stack. I can measure the pulley sizes if anyone's interested. Machining quality looks fine, didn't measure runout but it only has to be good enough for rubber belts.

Con:
It's bored for a 24 mm spindle, and my spindle is 22.2 mm , so I would need to make a precision shim. I can do that, but my existing pulley is working fine, and this Grizz cost $90 and I could use the money.

I think I'll return it. Tho I haven't checked yet to see whether they'll allow it, or whether they charge a restocking fee (which would be fair).

 

[Shotgun]

Unacceptable.
The whole point of this website is for us to help you spend all your money on metal thingies.
You can't go returning things for a refund.
You need to build a machine around that pulley.