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New to me Bridgeport Mill

Maybe the joke is on me. I thought they were 'metricating' a common 1/2" thread, hence my attempt at ha-ha.
 
It was definitely funny as heck to me. But I can laugh easily at all the dumb things I do myself so I feel like that entitles me to laugh at everyone else too!

In my minds eye, I see this Chinese web guy posting the add on the Ali website, sees the 1/2 for the stud size, and says to himself, "Wow those engineers can be dumb sometimes - they forgot the M in front of the stud size. No biggie, I'll fix it for them."

Nonetheless, I'd like some locks like that for my mills and the price is right.

Do you think it's actually an imperial half inch lock stud that they figured needed an M in front of it or do you think it really is a metric version of a 1/2" lock with oddball pitch and diameter?
 
Sometimes they are receptive to answering questions , might save you a desk ornament if it's truly metric and only 'close to' 1/2".
And actually - is a real Bridgeport fine or coarse threads 1/2"?

This picture kind of appears making a distinction to 'British'?, OD = 12.78mm = 0.491"
 

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PeterT said:
Sometimes they are receptive to answering questions , might save you a desk ornament if it's truly metric and only 'close to' 1/2".
And actually - is a real Bridgeport fine or coarse threads 1/2"?

This picture kind of appears making a distinction to 'British'?, OD = 12.78mm = 0.491"
Click to expand...

Good point. I'll check my BP and then see if they can help.
 
I know from experience that you can run at 1/2" - 13 tap through what I assume was a M12 x 1.75 nut and end up with a nut that works quite well on either 1/2" or 12mm. Don't ask. (It was late at night and cold in the garage)
 
RobinHood said:
430V is a good thing: take a VFD connect it to 220V and a 3 phase 1:2 step-up transformer to the motor - done.
Click to expand...

Jesus, that appears to be a very elegant solution.

Sometimes you just don't connect the dots... Just like the commutator in a DC motor chops DC current into AC current, the 3 phase pwm output of the VFD does as well.

So I have a few issues... what would be the best carrier frequency to program our VFD for if we wanted to use a step up transformer? Also am I correct in assuming that as the magnetic flux travels thru the iron core of the transformer that it may alter the choppy pwm waveform, and if so might that create issues with the output voltage? I'd think potentially the digital signal just may become more sinusoidal and not affect the output voltage... IDK.

Finally would you know where to get a transformer of an appropriate size for less than a new motor cost?
 
TorontoBuilder said:
Jesus, that appears to be a very elegant solution.

Sometimes you just don't connect the dots... Just like the commutator in a DC motor chops DC current into AC current, the 3 phase pwm output of the VFD does as well.

So I have a few issues... what would be the best carrier frequency to program our VFD for if we wanted to use a step up transformer? Also am I correct in assuming that as the magnetic flux travels thru the iron core of the transformer that it may alter the choppy pwm waveform, and if so might that create issues with the output voltage? I'd think potentially the digital signal just may become more sinusoidal and not affect the output voltage... IDK.

Finally would you know where to get a transformer of an appropriate size for less than a new motor cost?
Click to expand...

Those are good questions.

I'd call the VFD manufacturer tech support line to ask that question.

FWIW, I would reverse the process and feed a higher voltage VFD with the transformer rather than feeding the transformer from the VFD. It all gets a lot easier that way and you won't lose so much of the variable speed benefits of the VFD. Just my opinion.
 
Susquatch said:
Those are good questions.

I'd call the VFD manufacturer tech support line to ask that question.

FWIW, I would reverse the process and feed a higher voltage VFD with the transformer rather than feeding the transformer from the VFD. It all gets a lot easier that way and you won't lose so much of the variable speed benefits of the VFD. Just my opinion.
Click to expand...

Apparently putting a transformer between the VFD and motor will not work. The VFD won't see the voltage/current feed back it needs.
 
Susquatch said:
Those are good questions.

I'd call the VFD manufacturer tech support line to ask that question.

FWIW, I would reverse the process and feed a higher voltage VFD with the transformer rather than feeding the transformer from the VFD. It all gets a lot easier that way and you won't lose so much of the variable speed benefits of the VFD. Just my opinion.
Click to expand...

wont work when I dont have 3 phase power... have to create the 3 phase signal to step up in my case
 
YYCHM said:
Apparently putting a transformer between the VFD and motor will not work. The VFD won't see the voltage/current feed back it needs.
Click to expand...

Thanks for the answer craig. I had never heard that was a possibility so had never looked into such a thing
 
A transformer after the VFD does 2 things that are unforgivable: it changes the inductance of the system, and it changes the apparent inrush current - it is the effective inductance and the inrush current that the vfd uses to produce proper motor response when running at low speeds. At higher speeds, say 30 Hz to 100Hz, your solution would work, but not at peak efficiency.

At alberta prices, it is cheaper to find a 1.5 or 3HP 3ph 220V motor to replace the 575 one instead of the transformer.

[edit] once again - we posted at the same time! oops.
 
a
YYCHM said:
Step up the single phase then feed the VFD at the target voltage.
Click to expand...

thats the preferred way, and besides, 600v vfd's are way cheaper on the used market...nobody wants em.

every vfd will accept single phase input, its whether they will trip on phase loss thats the issue. read the manual, see if phase loss can be ignored. That said, theres ways around that usually.
 
Dabbler said:
once again - we posted at the same time! oops.
Click to expand...

So many posted at the same time I got lost! LMAO!

I even deleted a post because it somehow got pieces that I didn't put there!

Oh well, looks like all the right answers are there now.
 
Dabbler said:
A transformer after the VFD does 2 things that are unforgivable: it changes the inductance of the system, and it changes the apparent inrush current - it is the effective inductance and the inrush current that the vfd uses to produce proper motor response when running at low speeds. At higher speeds, say 30 Hz to 100Hz, your solution would work, but not at peak efficiency.

At alberta prices, it is cheaper to find a 1.5 or 3HP 3ph 220V motor to replace the 575 one instead of the transformer.

[edit] once again - we posted at the same time! oops.
Click to expand...
got it.
 
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