# Planning To Power Up Bridgeport Milling Machine



## toolman_ar (May 19, 2015)

I have a 1964 Bridgeport mill with a US Motors, 1.5 horse Power, wired for 230v 3 phase. 4.2 amps @ 220v.

The Previous Owner had the supply line fed from a breaker to the drum switch.

Now that I have my RPC working, 2 hp max motor. I would like to power up my mill. 

Looking at a motor starter, with heaters and a two button, 3 wire switch. 

I have to finish my bansaw first, but wanted to start planning what I need to get the mill going next.

My question is do I need a reversing motor starter? Or will the drum switch work just fine with a properly sized motor starter?

toolman_ar


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## gr8legs (May 19, 2015)

That's an interesting question.

The motor starter doesn't care what direction the motor is turning but putting the drum switch ahead of the starter will cause the starter to drop out each time you reverse the switch.

If it was me I'd immediately install a VFD and get rid of the RPC and the drum switch, but you're not me and I don't know what your constraints are. 

Using the parts you've described I'd put the starter in line first from the RPC, then go from the starter to the drum switch and then to the motor. You may pop the thermal overloads if you do a lot of short runs with frequent reversing at full load - otherwise it should last forever less three days. 

Stu


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## toolman_ar (May 19, 2015)

Stu,
I may end up with a VFD. But since I have the RPC, may as well use it.

Need to scrounge a motor starter.

Toolman_ar


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## gr8legs (May 20, 2015)

I misunderstood your question - If you don't already have a motor starter, don't bother buying one. 

Your motor will work just fine using the drum switch for forward - off - reverse without adding a motor starter. The starter for this small a motor isn't anything more than a relay with the thermal overloads interrupting the relay coil circuit if motor current gets too high, but that's unlikely in your situation.

Your rpc will probably current limit itself and protect both itself and your motor. For a 'belt and suspenders' approach, put a fused disconnect or circuit breaker in the rpc output before it goes to the mill.

My experience with motor starters is big motors (25 HP and up) running high-inertia loads (think 20 foot diameter squirrel cage ventilating fans) and it takes so long for the motor to bring the load up to speed that the current has to be limited during startup to avoid popping the fuses. Your mill motor has neither of these characteristics and it is probably better to have rapid reverse available - which is what the rpc / drum switch combo will give you.

Stu


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## toolman_ar (May 20, 2015)

Stu,
Thank you for the advice.

I have a 00 size starter that I plan to use. That way I will have proper overloads and a start/stop switch, at the tool.

Eventually I will plumb the RPC through a distribution Pannel with breakers for each leg.

toolman_ar


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## Karl_T (May 20, 2015)

toolman_ar said:


> Stu,
> Thank you for the advice.
> 
> I have a 00 size starter that I plan to use. That way I will have proper overloads and a start/stop switch, at the tool.
> ...



Good ideas here. Just put your starter ahead of your drum switch. For something like power tapping, it doesn't hurt a bridgy to go right from forward to reverse.

I got a 3 phase load center off eBay for peanuts. Works extremely well to give each machine its own circuit breaker this way.


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