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Setting up Bridgeport Mill with VFD

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Registered Member
Jul 24, 2017
Hello everyone,

I am working on this project for my father he is a machinist by trade. I on the other hand am a Automotive Technician with a background on European vehicles. I do have some experience in using both the Mill and the Lathe because I took machine shop in high school. My dad picked up a Bridgeport Mill from his work and I have been tasked with getting it operational in his garage.

I will be using this tread to ask questions and to show my progress on this project.

First off I am planning on using a VFD from automation direct. My dad's house electrical set up is as follows. 200amp service into the main with a 60amp feeding the garage subpanel on 8awg wires. From the subpanel I wanted to run a dedicated circuit to the VFD that will receive 1phase 220v in with 220v 3 phase output to the mill. The original harness that is attached to the mill currently tagged as 14/4 (4 wires/ 14awg).

My first question is can anyone help me understand the voltage and amperage requirement plate?

From what I am understanding is the mill is rated at 2hp with 3hp intermediate duty. Should I go with the 2hp VFD in the image or should I get a 3hp rated one?

Also I will be building a VFD enclosure, what gauge wire do you recommend running from the sub panel to the VFD?

Also if this is the only load on the circuit what amperage rating do you recommend? By looking at the full load amps sticker it appears that the most this machine will draw would be about 7.1amp.

Thank you in advance for your help. I will keep updating as the project progresses 20170711_184923.jpg 20170711_184943.jpg VFD for mill.PNG


Active User
Active Member
Oct 13, 2014
I would go with a 3 hp VFD. So far, I have had good results with these :http://dealerselectric.com/L510-203-H1-N.asp

12 gage wire between panel and VFD, you can reuse the 14 ga harness between the VFD and the motor but you have to bypass the switch on the mill, The Motor must be wired directly to the power output on the VFD and the switch wired to the control inputs of the VFD.

You need to size the breaker according to the VFD input rating not the motor since the VFD will draw more power as it is using a single phase to power 3. probably a 15 or 20 amp 2 pole breaker.


Active Member
Active Member
Apr 25, 2017
You can get a guaranteed used VFD from Radwell Intl. for around $100. I use 20 amp breakers with 12 ga. wire. If you want to use the original Bridgeport switch there is a connection on the VFD for it, and you can program it to work. All my 3 PH machines have Lenze AC Tech VFD's and their customer service in helping to program and set up is 2nd to none.


Active User
H-M Supporter-Premium Member
Jun 12, 2014
The VFD manual will specify both the wiring and breaker/fusing. I would use a 3Hp VFD, single phase input. Per Eddyde, the Teco L510 is reasonable, the Automation Direct GS3 are also very good but a bit more. Usually there is a nominal price difference between 2 and 3 Hp single phase VFDs.
As mentioned fusing/breaker is based on 125% of the VFD rating. The GS3 specifies a 40A breaker for the GS3-23P0, if using fusing I would go with a 30A. This is what I use in my 3Hp mill with a VFD. Usually fuse or J class or CC class. Usually recommendation is to use a fast blow high speed fuse, but some VFDs recommend a dual element Low Peak. If you have a 30 or 40A panel breaker you may want to use 10G wire to the VFD, 12 G to the motor. In reality, you could probably go a gauge smaller with no worries but I would follow code.

Probably want a braking resistor with either VFD, something like 70-100 ohms, 300W or more, nothing special, these can be had for $30-50.

Most people use 3 wire control for the mill, momentary start and stop buttons along with a Forward/Reverse switch. Simple, although the VFD needs to be programmed as such. Although many people may use the previous motor switch to control direction via the VFD inputs, the contacts are usually burned and do not work well with low level VFD signals. By a small enclosure and buy new switch gear.
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