# Bridgeport Micrometer dials



## EmilioG (Nov 8, 2014)

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


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## chuckorlando (Nov 8, 2014)

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


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## Holescreek (Nov 8, 2014)

Here's a link to a free manual in PDF format: http://www.truetex.com/bridgeport-manual.pdf


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## Tony Wells (Nov 8, 2014)

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.


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## Holescreek (Nov 8, 2014)

And my favorite, when using back gears the spindle reverses direction from standard.


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## Smithdoor (Nov 8, 2014)

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
> ...


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## Andre (Nov 8, 2014)

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.


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## fastback (Nov 8, 2014)

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


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## EmilioG (Nov 9, 2014)

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


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## fastback (Nov 9, 2014)

The long bed is the X, the in and out is the Y.  The Knee is the Z.

Paul


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## EmilioG (Nov 17, 2014)

Used the mic dials on the BP mill today for the first time.
Worked really well. I used my Starrett 827B edge finder
and was able to locate my holes right on the spot that I
marked off and punched.  I really want an Accurite II.  Working with the mill
would be a breeze!  How much for the complete Accurite set up?
I know theres a lot of hardware to go with the electronics.  Is it a lot of work
to install and what kind of tools would I need?

Thanks


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## chuckorlando (Nov 17, 2014)

Much cheaper versions of dros man. I will get a better unit at some point but right now I got 100 bucks worth of igaging dros. Thats all you need to locate holes.

No they aint hard to put on. Might take a little thinking but just a few holes and bolts and wires to plug in more or less


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## Andre (Nov 17, 2014)

Why not use the dials to locate holes? When you really understand backlash, and how to work around it there are very few things you can not do with dials.


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## chips&more (Nov 17, 2014)

The DRO set-up is one way to go. And there is also Trav-A-Dials that I personally prefer. I don’t like to watch the dancing numbers that the DRO has. I much prefer the analog dial for noting table travel. Some people can say the Trav-A-Dial has limitations but I have not been disappointed…Good Luck, Dave.


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## EmilioG (Nov 19, 2014)

chips&more said:


> The DRO set-up is one way to go. And there is also Trav-A-Dials that I personally prefer. I don’t like to watch the dancing numbers that the DRO has. I much prefer the analog dial for noting table travel. Some people can say the Trav-A-Dial has limitations but I have not been disappointed…Good Luck, Dave.



Curious, what is a Trav a Dial? How does it work.
on a side note, the quill clamp, how is it used and when?
My boss tried to blame me for leaving the quill clamp open, when in reality, I don't remember using it.
Aren;t the operators of mills supposed to check all settings before using it?  The Holex jumped and part got chipped a little.
 Thanks


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## JimDawson (Nov 19, 2014)

A Trav-A-Dial  is a linear measuring device that can be attached to almost any machine tool and is used for position measurement.  It is driven by a small wheel that contacts the table on a mill or the ways in the case of a lathe.





You can see the drive wheel at the top of this picture.





The quill clamp (or quill lock) locks the quill in place so it can't move.

Yes, it is the operators responsibility to check the settings prior to operating the machine.

Quill Clamp:


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## george wilson (Nov 19, 2014)

A Trav a Dial is a dial indicator that has a wheel on it which bears against the table,or against the edge of the front way on a lathe. The device is most often found on a lathe. The wheel tells how many thousandths the unit has moved. It is,of course,mounted usually on the carriage of a lathe.


"Why not use dials instead of a DRO?" I had a DRO at work,but none at home. The reason dials are not as good is they depend upon the accuracy of the lead screw.  The lead screw is subject to wear,just like anything mechanical. Your measurement can be off by quite a large amount if the screw is worn a lot. Years back,Bridgeport tried alternative means of accurately controlling table movement. One method was a special gage block holder mounted on the front of the mill table. Some of these gage blocks were quite long. They were laid in whatever combination needed to set the required distance. Then,the table was moved till it butted against the stack of gage blocks. This was cumbersome and everything had to be very clean between the gage block's surfaces. Then,they invented a glass scale you could read through a magnified window. This was better,but I think it was only usable on the X axis,like the gage blocks. The DRO is the best and most reliable system yet.

There is a cheap one I do not recommend. The "Shooting Star" I think it's called. It uses a small gear rack,like the rack on a dial caliper to measure table movement. It is mechanical,and I would not like to rely on it not breaking down. It is also not as accurate as a good DRO,which can get you down to .0002",or maybe even .0001". I can't recall. The Fagor at work would do .0002" resolution. It is tricky to get the table set to that fine a resolution!! Do anything at all,and the number would shift.

P.S.: I see Jim beat me on the Trav a Dial.


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## 12bolts (Nov 19, 2014)

EmilioG said:


> ...on a side note, the quill clamp, how is it used and when?
> My boss tried to blame me for leaving the quill clamp open, when in reality, I don't remember using it.
> Aren;t the operators of mills supposed to check all settings before using it?


Pretty much answered your own question there. Standard practice (very basic explanation) is to set up the work and tool, position the table, bring the table height up using the knee and then accurately bring the tool down to the work via the quill. If you are drilling holes you wont use the lock, if you were milling with the table travel (x & y) then use the quill lock.
Poor operator blames his tools. Poorer boss blames someone else...........thats why machinists are grumpy and usually work alone. Nobody wants to be around them! 

Cheers Phil


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## EmilioG (Nov 21, 2014)

Thank you Gentlemen, that is a lot of great information.
It is appreciated.


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## Bill C. (Nov 21, 2014)

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
> ...



Would like to add make sure either the set screw or clamping ring nut is tight so the micro-dial doesn't slip.  Try not to over tighten the setscrew, you can strip out the threads.  Trust me I have turn many of those dials only to get half way through the distance I needed to move to the next hole and have the them spin free on me.  I like BP knee mills.  I hope it serves you for many years.


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