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  1. #21
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    Quote Originally Posted by jhruska View Post
    Meehanite refers to properties of cast iron derived from a specific process rather than weight.

    Never had problems with ballscrews on a Bridgeport. I did change the Biljur oil metering port for both X and Y so a higher volume of oil is delivered to each. Aids in flushing debris. Expect to do a little more housekeeping maintenance to retain accuracy as this is an open system on the Bridgeport.
    John
    J, I always thought the appeal of Meehanite, thanks for the spelling correction, was its similar stiffness for less weight? This is desirable if you are paying by the pound for shipping from China to the US. I also thought this might account for a difference in the weight of the current machines. But you dont think that is correct?

    Charles

  2. #22
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    I all ways marvel that the cost of new is much less than a rebuild. It's kind of sad. But at 8k, that's only 80 hours of work at 100 per hour. 80 hours goes pretty dam fast.

  3. #23
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    Quote Originally Posted by CBlair View Post
    Sam please edit your profile to include your location, look in the upper rt corner of your post and compare it to Richards. You will see were your location is missing. This is a forum requirement, if you do not fix this you will loose your posting privileges.

    Richard that seems cheap for all that , painting included? Not a bad deal, of course it has to meet the customers expectations.

    Charles
    I have my location set I don't know why it isn't showing up sorry

  4. #24
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    Ok Samm, I will see if we can figure it out...

    Charles

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    I got the machine for free the head has already been done the x and z axis are good but the y is really loose in the middle, I am 27 , 3rd generation journeyman tookmaker and just use it to do home projects and side work, planning on upgrading eventually but just need it to function for now

  6. #26
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    Quote Originally Posted by CBlair View Post
    Ok Samm, I will see if we can figure it out...

    Charles
    Could it have something to do with me using the app on my phone that my location is not showing up

  7. #27
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    Quote Originally Posted by samm1929 View Post
    Could it have something to do with me using the app on my phone that my location is not showing up
    I will bet that is it, I have heard of that sort of thing but I dont know the details.

    Charles

  8. #28
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    Quote Originally Posted by RC99 View Post
    That is a BARE machine! Add Servo brand power feeds to all three axis, and a Newall DRO and see where the price goes.

    I was talking "Replacment" cost for the machine equipt identical to what is already in the shop. Not a downgrade of capabilities.

  9. #29
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    Quote Originally Posted by Richard King View Post
    To be honest I have been out of rebuiding Bridgeport's for so long I can't give a honest answer, just a guess. I can check with my rebuiding friends on Monday and see what they have to say. Here is a guess. Ball screws have seals to keep the crud out of the nut so I would bet they last longer. If it is a quality ball screw I would bet it is better because of less back-lash. The lube system is more self contained and also would help to keep it from wearing out faster. Less back-lash, tighter tolerance along with DRO's. Rich
    My concern would be that the ball screw/nut would be too free and easy therefore not giving the required amount of resistance to the cutter, especially during milling. From what other people have said maybe I'm correct.

    Regards Tyrone.

  10. #30
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    I'd be a little concerned about using ball screws for a manual machine. When I do heavy milling on a Bridgeport I always set the table lock and then take up the backlash so the table locks don't have to do all of the work of keeping things in place. You wouldn't get the redundant clamping action with a ball screw.

    Big B

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    Quote Originally Posted by Big B View Post
    I'dWhen I do heavy milling on a Bridgeport
    an oxymoron?

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  13. #32
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    Quote Originally Posted by Tyrone Shoelaces View Post
    My concern would be that the ball screw/nut would be too free and easy therefore not giving the required amount of resistance to the cutter, especially during milling. From what other people have said maybe I'm correct.

    Regards Tyrone.
    If the cross-slide gib in a lathe is loose there is trouble holding size and look out if parting off. The gib is tightened till the resistance is right.
    Proper resistance in a mill is provided by ways in good fit and a properly set gib. A lead screw or ball screw is for accurate positioning, not resistance. The ways take the vibration and the mass of the machine is the damper. I say it is the same for a horizontal bar or a small mill like a Bridgeport. Ball screws are great if and only if the ways are proper and the gibs are set.
    John

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    What ever you do be very wary of using a ball screw on the Z without a brake. I had a manual mill with a ball screw on the Z. The previous owner had fiddled with the sprag brake spring. Most disconcerting to have the table suddenly take off after just raising it a few thou. Of course with a CNC the screws are controlled at all times, not so on a manual.

    Peter

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    Quote Originally Posted by jhruska View Post
    If the cross-slide gib in a lathe is loose there is trouble holding size and look out if parting off. The gib is tightened till the resistance is right.
    Proper resistance in a mill is provided by ways in good fit and a properly set gib. A lead screw or ball screw is for accurate positioning, not resistance. The ways take the vibration and the mass of the machine is the damper. I say it is the same for a horizontal bar or a small mill like a Bridgeport. Ball screws are great if and only if the ways are proper and the gibs are set.
    John
    I agree with you up to a point John. I think we all know that a conventional screw/nut pair will provide more resistance than a ball screw. Certainly this would apply to bigger machines than a " Bridgeport ", the type of machines with a backlash eliminator.

    Regards Tyrone.

  16. #35
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    Compared to a Smithy...

    Quote Originally Posted by Mcgyver View Post
    an oxymoron?

  17. #36
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    Quote Originally Posted by jhruska View Post
    If the cross-slide gib in a lathe is loose there is trouble holding size and look out if parting off. The gib is tightened till the resistance is right.
    Proper resistance in a mill is provided by ways in good fit and a properly set gib. A lead screw or ball screw is for accurate positioning, not resistance.
    I disagree on this. Gib adjustment is to reduce clearance to the oil layer but its wrong to make it friction fit such that its resistance is a factor in counteracting the cutting force to any large degree. This is sometimes done for climb milling, but is tough on the machine leading to rapid wear - think running it with the axis clamp half on. On a lathe for example, the feedscrew and nut are definitely supposed to take the load in the direction of the axis, gibs and ways take the force in all other directions. milling isn't any different. Even if you did tighten gibs up to the point of lots of friction, its still the nut taking the force along the axis in question, else the it would have to be so tight it wouldn't move.

  18. #37
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    Default Ball screws

    Quote Originally Posted by WILLEO6709 View Post
    It would depend on the screw wnd the machine. a place I used to work put a retrofit kit in a 20 year old bridgeport. Noone liked it. You could feel the balls " cogging" like the preload was off, it always jumped 2 thousandths when you needed 4 tenths..... Great for face milling nd such, but it did pull into cut much easier. We went back to acme's.... but on a fresh rescrape it may be a lot better.

    To me it depends on the pitch of the screw, a lot of ball screws are double and triple lead for fast travel
    Hand cranking such a screw will lack the feel of a ten pitch Acme screw.


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