Lubrication of Knee Screw
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    Default Lubrication of Knee Screw

    I recently purchased a used Bridgeport that has one shot lubrication. I noticed the other day that the knee will start to "sing" when lowering it. At first I thought the vertical ways weren't getting any way oil from the one shot system. But after removing the ends of the lines feeding each of the vertical ways and giving the one shot a pump, way oil is definitely coming out of both lines (I did this one at a time on each side of the knee). Also there is a thin coat of way oil on the vertical ways as well.

    After doing some searching on here, I found a couple of threads indicating that the "singing" could be coming from the screw and not the ways. In one post someone mentioned putting some way oil on the screw. So I raised the knee all the way up and noticed there is a zerk fitting at the base of the screw. I can't find anything in the manual for this fitting. I am assuming this would be a way oil zerk fitting instead of grease similar to what would have been on the ways prior to the one shot system?

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    First of all welcome to the forum.

    The singing comes from a dry screw. I've got a bunch of manuals and have never seen a knee nut with a zerk.

    I'm thinking that what might have happened is that the line that lubricates the nuts and the knee screw is not working. The line could have been pinched or plugged. Then, somebody decided to add a zerk instead of fixing the problem.

    Inspect your one-shot oiler carefully. If there is any dirt or debris in the tank, tank the unit appart and clean throughly. Then start with the lube lines, make sure that all of them work.

    BTW, be careful when desassembling the lube system. The Bijour orifices have numbers on then an go in specific locations.
    JR

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    Thanks JR, I will take a look to see if I can trace out the lines from the manifold to see if there is something pinched or plugged.

    -Mike

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    There are no lubrication provisions in the system to lube the knee screw, just put some oil on it by hand, also the zerk is somthing someone added, we have plenty of machines that sing with well lubricated screws, it's nothing to worry about, you may try udjusting the gib screw to change the load on the screw, I don't recall that helping but it's worth a shot.

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    Quote Originally Posted by Downwash77 View Post
    There are no lubrication provisions in the system to lube the knee screw, just put some oil on it by hand, also the zerk is somthing someone added, we have plenty of machines that sing with well lubricated screws, it's nothing to worry about, you may try udjusting the gib screw to change the load on the screw, I don't recall that helping but it's worth a shot.
    My limited understanding is that the oil going to the Y-screw is intended to drip down and lubricate the Z-screw. Or something like that. Which means that, if the Z is dry, so may be the Y.

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    Quote Originally Posted by Downwash77 View Post
    There are no lubrication provisions in the system to lube the knee screw
    The knee screw is lubricate by the same line that lubes the other screws. This was done the same way before one-shot systems. Then, you had to line up the table marks and remove the set screw in the table.

    If your knee screw is singing, it is not getting enough oil. That is caused by one of the 2 reasons I mentioned above. All BPs are total loss systems, the oil goes in and runs out. If you don't have oil on the table or vise, you aren't putting enough in the oil cups. If you don't have oil on the machine base, you aren't using the oiler enough. Way oil and hydraulic oil are much cheaper than a rebuild or a new mill.
    JR

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    Many times when I have the Z axis screw and nut out I drill and tape a 1/8" pipe thread into the larger diameter of the nut. Just drill down with the tap drill so you can screw in a zerk and drill the rest of the way with a 1/8" drill so you don't bugger up the tread. You may have to file off any burrs in there, but it works good. Then you don't have to depend on drip of oil running through the chips to reach the nut. one squirt of grease there will last for years on average.

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    Rich, I see your point, but if they aren't getting enough oil to lube the knee screw, how about the other 2?

    One of my mottos ~ never seen a BP die from too much oil!
    JR

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    Thanks everyone for the info. I will take a look this weekend and check the X and Y screws as well. I can say that the X and Y ways are getting plenty of way oil as it constantly leaks out and down the sides of the knee. But I have not checked the actual screws for the X and Y.

    -Mike


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