Bridgeport Micrometer dials

EmilioG

EmilioG

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I just started working with an old Bridgeport milling machine and
at first it was a little daunting, but gaining more knowledge and getting more comfortable.

I don't have a manual and I'd like to know how to change
the speeds, it has belts but no speed dial. It shows a high and low speed setting
along with other RPM speeds. The BP has a break on top to keep the spindle from
moving so that you can change collets. I'll take a photo and post it but I'm sure
the vets here know what type and model this is.

I did find this> https://www.youtube.com/watch?v=xqWwDi93Esw

but it's not entirely clear and not the same machine that we have.

So I have two questions, how do I change the speeds and how do the micrometer dials work?
Are there any downloads for BP mills? pdf manuals on various models?
Thanks
 
machinery parts depot is where most us get manuals.

On the back right side of the head, above the pulleys but under the motor, you will find a lever. Pull it towards the front to loosen the motor. Slide the motor forward and put the belt where ever you want. Slide the motor back and lock it. Top pulleys are the slowest and consecutively increase speed as you go lower.

Next to the brake is a lever pointing to the front. Slide that over to the right. Then behind the big oil cup on the right side of the head, under the pulleys, you will find another knob. Pull the ball and rotate it to the next hole. Now your in back gears or low gear. In low you run in reverse for forward. And you run in forward for reverse.

The handles are just standard micrometer handles. Every tick is .001 on the table. One full rotation of the handle will move the table .200. On the knee one rotation will move the knee .100.

Touch off the part, rotate the mic wheel to 0. If you need to move over .005 then you count 5 lines from 0. If you need to go .010 then move 10 lines or to the number 10 from 0. Every .010 is marked 0-10-20-30 ect. The big lines between each number is always .005 so between 10 and 20 the big line =15 or .015. If you move to the 6th line between the 10 and 20 you got 16 or .016
 
I'll add that when you shift gears, make sure things are engaged properly. It will sound like the end of the world if you power up and the back gears have not "dropped" in. I typically hold the spindle in my left hand and turn the motor pulley with my right fingers until it drops, if it doesn't when I shift into "back gears", or low range. The ring on top of the spindle that has the inclined slot and lever handle is what "drops" the gear in. If you are lifting it out of low, you don't have to worry so much about the gear engagement, but when you turn that ring to drop the gears, you will sense whether it falls into engagement or not.
 
And my favorite, when using back gears the spindle reverses direction from standard.
 
Yes there are places that you down load for free
It take time find and they from 1960's on bad news I lost the sit
The Bridgeport mill use a back gear with belt so have use Reverse for slow speeds

Dave

EmilioG said:
I just started working with an old Bridgeport milling machine and
at first it was a little daunting, but gaining more knowledge and getting more comfortable.

I don't have a manual and I'd like to know how to change
the speeds, it has belts but no speed dial. It shows a high and low speed setting
along with other RPM speeds. The BP has a break on top to keep the spindle from
moving so that you can change collets. I'll take a photo and post it but I'm sure
the vets here know what type and model this is.

I did find this> https://www.youtube.com/watch?v=xqWwDi93Esw

but it's not entirely clear and not the same machine that we have.

So I have two questions, how do I change the speeds and how do the micrometer dials work?
Are there any downloads for BP mills? pdf manuals on various models?
Thanks
Click to expand...
 
You didn't mention if your machine was a step pulley J head or 2j with the crank adjustable pulleys.

On both machines, the hi/low selector is on the right side of the head. I forget how it moves, I think you pull it out and turn if I'm not mistaken.

2J: start the motor and turn the crank in front of the head. That will change speeds from 50-500 in backgear and 500-3200 (I think) in high gear.

J: On the right side of the motor, under the bolt mount is a handle. Loosen it and slide the motor forward to change the belt position on the pulleys.
 
Something else, use the brake once you shut the machine down that way you won't have to wait for it to coast to a stop. Also, use the break when changing collets. Place your 3/4-inch wrench on the spindle nut and hold the break while you tighten or loosen the nut. Don't try to over tighten you'll be asking for trouble. You will note on the front of the housing the speeds in both direct drive and back gear. Reverse is used mostly in back gear because when engaged the spindle will turn in reverse. They also make end mills that cut in reverse or when using a fly cutter, if you wish, depending on which way you have it set for. There are a few other things you will need to learn like how to engage and disengage the power feed and feed speeds, as well as, tilting and traming the head etc.

Paul
 
Wow, thank you all so much. Very informative. I will post pics of the machine I am using at work. Thank you all!
Why are the dials different on the knee? Is the knee the front? is this the x axis? The side to side or left right move,
is that the Y axis? Why are the dials different making full rotations .100 and .200? Should I fix the backlash screws?
I see that the manual has information for this. Thanks
 
Last edited:
The long bed is the X, the in and out is the Y. The Knee is the Z.

Paul
 
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