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Old 02-20-2019, 04:40 PM
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Default How to reverse bridgeport spindle

I was using the bridgeport at work yesterday and couldn't figure out how to reverse the spindle. I assume the motor reverses and it is not in a gearbox or something. The only electrical switch I see is a knob that says high and low.
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Old 02-20-2019, 04:47 PM
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High to low, or vice versa.

Most bridgeport type mills reverse rotation when you go from hi to low range in the gearing. Some machines the switch is labelled like yours, the ‘high’ position should be forward in high range, and low would be reverse in high range. Flip the gears, and the switch is now opposite.

Some mills are simply labelled ‘on-off-on’ and as an operator you get to figure out what direction for what range.


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Old 02-20-2019, 05:17 PM
Lew Hartswick Lew Hartswick is offline
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Originally Posted by greywynd View Post
High to low, or vice versa.

Most bridgeport type mills reverse rotation when you go from hi to low range in the gearing. Some machines the switch is labelled like yours, the ‘high’ position should be forward in high range, and low would be reverse in high range. Flip the gears, and the switch is now opposite.

Some mills are simply labelled ‘on-off-on’ and as an operator you get to figure out what direction for what range.


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Yea and some are labeled Forward / Reverse . That is rather disgusting when trying to introduce a newcomer to the milling machine. :-) With the high / low gear change.
...lew...
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Old 02-21-2019, 04:55 AM
threepiece threepiece is offline
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Yea and some are labeled Forward / Reverse . That is rather disgusting when trying to introduce a newcomer to the milling machine. :-) With the high / low gear change.
...lew...
Yes, I train beginners often, I find this is often confusing to them. The important thing is they understand that the electric switch changes the direction of the motor not the speed.
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Last edited by threepiece; 02-23-2019 at 04:33 AM. Reason: More content
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Old 02-21-2019, 06:19 AM
bunkclimber bunkclimber is offline
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Default Bridgeport motor controls

most of the "Bridgeports" I see have a cam switch that changes motor speed and direction.(Never seen one that does it with gears,usually a belt on step pullys)-One side of the rotary cam switch is forward and the opposite is reverse,with the 'up' or 'top' up position being off..of course it could have been molested over the years and may be somewhat differently installed but the basic idea is turn the switch right for forward low,right one more position for forward high..go back to 'top up position' for motor off;-turn the switch handle left for reverse low,one more click left for reverse high.The theory was to have you go thru the low speed first then bump to high if needed.

For my money,i'd strip all that off and control it with a VFD, it gives you infinite speed control,accel/deceleration control over the cutter and 1>3phase conversion in one shot..easily done for under $400 in materials
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Old 02-21-2019, 01:07 PM
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A VFD is not always the correct solution to motor control. The two speed motor can be thought of as two motors with different operating characteristics in one housing. A VFD can be connected to one or the other and set up to do its thing on that motor. The resulting speed/torque curve will not exactly match at both former motor speeds and certainly will not deliver the same cutter speed/torque that will be had with the stock motor /belt set up. At the same time you are seriously compromising the motor's internal cooling fan by running the motor at reduced rpm.
If you are using the machine light duty you will probably be fine. But if you push the machine you may find it will not live as long as the stock set up

If you change the motor to a vfd rated motor capable of meeting or exceeding the spindle torque across the full speed range you will have a trouble free machine but at a much higher cost.
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Old 02-21-2019, 02:01 PM
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I’ve never seen a four position switch like mentioned on a bridgeport style mill. I have seen it on some larger/heavier mills, both on spindle and power feed motors.

A variable speed head bridgeport still has a hi/low range on the side, and is a geared system inside. (Think of back gears on a lathe.)

I’ve just put a VFD on my bridgeport yesterday. Plan is to still run the motor at 60 Hz most of the time, and use the mills variable speed system to adjust speeds.


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Old 02-22-2019, 12:19 AM
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Quote:
Originally Posted by greywynd View Post
I’ve never seen a four position switch like mentioned on a bridgeport style mill. I have seen it on some larger/heavier mills, both on spindle and power feed motors.

A variable speed head bridgeport still has a hi/low range on the side, and is a geared system inside. (Think of back gears on a lathe.)

I’ve just put a VFD on my bridgeport yesterday. Plan is to still run the motor at 60 Hz most of the time, and use the mills variable speed system to adjust speeds.


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So, if I understand, you are primarily using the vfd to get 3 phase power for your mill from the single phase house current in your garage? The next thing I can see biting you is current limitations. How big a breaker do you need to supply the vfd?
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Old 02-22-2019, 01:03 PM
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Originally Posted by camdigger View Post
So, if I understand, you are primarily using the vfd to get 3 phase power for your mill from the single phase house current in your garage? The next thing I can see biting you is current limitations. How big a breaker do you need to supply the vfd?


Actually it’s not bad. It’s a 1.5 hp motor, rated 4.4A at 230 volts 3ph. Feeding with a 15A supply of 240 single phase, the specs of the VFD looked like 15A might be on the limit, and I may have to go 20A.

So far, with no load, and going to a one second startup and shutdown I’ve had no issues.

I still have to wire up a forward/reverse circuit and setup the parameters for that.


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Old 02-22-2019, 06:10 PM
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Quote:
Originally Posted by camdigger View Post
So, if I understand, you are primarily using the vfd to get 3 phase power for your mill from the single phase house current in your garage? The next thing I can see biting you is current limitations. How big a breaker do you need to supply the vfd?
Cam, you can run a 3hp three phase motor all day on a single phase 15 amp breaker.
The killer current is in startup and the VFD takes care of that surge. My mill is very happy sucking off a 15 amp breaker.

My Lagun has the same thing going on, when you go into low range you have to reverse the motor to keep quill rotation correct.
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