Bridgeport Feed Motor Issue
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  1. #1
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    Default Bridgeport Feed Motor Issue

    Last winter I bought a used/refurbished Bridgeport which was built around 1980.
    It came with a power feed, which looks to be original.
    Not sure how you determine the model. I looked and it did not say "Model Number" on the tag.
    It did say......

    R.A. Boehm Co.
    Ser. No. BM-50608
    Spec. No. 4640
    Amps 4.6
    Volts 90 DC-A 100 DC-F


    I finally used the machine and something has happened to the feed.
    The motor runs in both directions and will go faster when you press the "Rapid Traverse" button. The crank turns but the table does not move.
    The table will not move from that end by using the crank handle, but it will move from the other end using the crank.

    I am hoping something has just dropped out like a key-way key or something. Maybe there is a clutch that can be adjusted?
    Anyone got an idea as to what model this is and what the problem could be?
    Thanks
    Greg

    A picture of the face.
    bridgeport2.jpg
    The tag
    bridgeport1.jpg

  2. #2
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    Default

    I had an aftermarket one that would disengage. There was enough axial play in the lead screw that the face gears would disengage.

  3. #3
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    I had a "Servo" on my last knee mill which lasted decades.
    I think if it gets too crazy expensive to fix this one I'll just get one of those.
    I hope it doesn't though. I like the idea of original equipment.

  4. #4
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    Pull the complicate unit off the table ,as I recall those used a pin to drive probables sheered.

  5. #5
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    I did pull it off and there is a sleeve with a keyway that turns the x-axis drive screw. It had a pin through it that transmitted the power from the drive motor to the shaft, but it is gone. 3/16" by 1-5/8".
    Also on the pretty cover that says Bridgeport on it, there was a place for a spring loaded pin to act as a detent to keep the drive out of gear when not in use. Someone has some how broken the spring detent holder and tried to repair it with JB Weld and it didn't work.

    The brass pin shouldn't cost much, but the cover.......?

  6. #6
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    Instead of a brass pin I used a SS 10-32 socket head bolt.
    With a little reaming, it works perfectly.

    It's back on now and works fine.

  7. #7
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    Now if you crash you will tear up something rather than a cheap brass pin. It's called a sheer pin for a good reason.

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  9. #8
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    Default

    Those are typically coupled via a key and keyway, but you already got that straightened out

    Jon

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    There is/was a key/keyway but on the motor end of that coupling was an empty through hole. What got me to thinking about an Allen bolt is that it is counterbored. A 10-32 fit perfectly. It just needed a little clean up with a 0.190 reamer. I guess I could have (and still could) use a cotter key, but it's done now.

  11. #10
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    Default

    Ok so you mean right up against the main gear housing? Ya, that hole is a taper pin that holds the coupler to the main shaft of the powerfeed. That coupler marries to the lead screw via a key.

    If thats the hole you are talking about, then there is not a problem with what you did.

    Jon


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