# Mystery Lines On Bridgeport



## vortechys (Mar 25, 2017)

Hi All,
I just picked up a circa 1980 Series I Bridgeport Mill.  Upon closer examination I noticed two , what appear to be, hydraulic lines that attach to the z -axis base.  Also, the knee pedestal looks different than other bridgeports I've seen.
Does anybody know what these lines were used for?
I'm thinking they were possibly used to raise the z-axis.
Any input would be appreciated.


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## Kroll (Mar 25, 2017)

I say clean the paint off that tag and see if maybe its a hydraulic cylinder,maybe a supply line and a return line???


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## darkzero (Mar 25, 2017)

Does it still have a leadscrew & crank to raise & lower the knee?


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## Silverbullet (Mar 25, 2017)

Sure looks like it is, the large bottom piece looks like it may have a tag in front . You may be able to tell by adding some lines and put some air pressure to one side then the other. Hold the end with a valve in a bucket to Ck for movement , by putting maybe fifty psi on one line with valve shut. If no movement reverse the process. It should move some one way or the other. Unlock the knee don't try with it locked. 
If it is and you want to hook it up , you'll need a pump , reservoir, two way valve ,,, log splitter,,, , SAFTEY valve too or unloader in the pump to tank and motor to run pump. Be easier to buy it made up like an above ground lift. 
It was probably an older CNC type or tracer mill ,,, my bet


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## Rustrp (Mar 25, 2017)

It does look like hydraulic or air over hydraulic and this begs the question of what operation was performed and why. If it's hydraulic you could always hook up something like a hand operated port-a-power. I'm wondering how much accuracy you would have. Just remember hydraulic fluid doesn't compress and air does so things can go squirrely real fast.


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## JimDawson (Mar 25, 2017)

Never seen that before.  But it does look like a hydraulic cylinder.


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## fast freddie (Mar 25, 2017)

Some machines had tracers on them, i had one in 1980 that had a truetrace 180 degree tracer (up and down) tracer for die sinking and it used that cyl on the knee and it still had a conventional lead screw for up and down, also a old 3d truetrace tracer used that cyl on the knee too


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## markba633csi (Mar 26, 2017)

Isn't that a hydraulic motor of some kind?  I assume there's a leadscrew in there somewhere..
Mark S.


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## vortechys (Mar 26, 2017)

Update... I removed the tag plate and it exposed a hydraulic ram in the base.
This must have been used to raise and lower the knee, possibly when something very heavy needed to be lifted on the table.  At least, that's my guess.
I don't think I'll hook it up to use.  The tracer theory seems logical.
The knee raises and lowers with the lead screw, so there is no loss in function of the knee.
Thank you all for your responses.
Dave


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## fast freddie (Mar 26, 2017)

That is from a true trace tracer, google bridgeport with true trace tracer. The knee worked both ways crank it up or with tracer. I had those mills for years but i can't explain it good enough for you to understand


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## fast freddie (Mar 26, 2017)

its not a theory, I ran a dozen bridgports with that kind of hydraulic knee, they had true trace tracers like the one in picture


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## vortechys (Mar 27, 2017)

Thank you for information FF.   That explains why its there.


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## Billh50 (Mar 27, 2017)

That may have been a tracer mill at one time. They may have removed all of the tracer parts and made it a regular Bridgeport. The tracers had both hydraulic and screw to raise the table.


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## fast freddie (Mar 27, 2017)

Billh50 said:


> That may have been a tracer mill at one time. They may have removed all of the tracer parts and made it a regular Bridgeport. The tracers had both hydraulic and screw to raise the table.


I reckon ur rite


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## lawlessman (Apr 1, 2017)

I have something similar on my 80's BOSS 6 Series II. It used to function as an air-assist to the crank mechanism for raising the table. . On my machine, there is a valve and gage just for the pressure to the air-assist, on the left side near the mist coolant unit. Originally, with enough pressure, the table would almost lift itself as you cranked the handle. At some point, an internal seal blew and I no longer have the air assist. Maybe increasing the pressure wasn't a good idea. There is a small tapped hole in the front of the lower portion of the column that I had to plug to keep the air from just blowing out all day. It didn't improve the lift action by plugging it, however. That table is a beast to raise but I'm not going to tear the whole machine apart to fix the seal. To test if that is what you have, try putting air to the system and attempting to raise the table, then turn it off and try again.


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