Recommendation on feed nut replacement
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  1. #1
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    Default Recommendation on feed nut replacement

    I am currently in the process of cleaning up a series 1 BP. I am leaning towards replacing the x and y feedscrews and nuts as they are badly worn in the centers, so even though I can adjust to .005 backlash on the ends there is close to .080 on the x and .025 backlash on the y in the centers. I have a DRO on it but the slop bothers me. My question is what nut to purchase? There is he 2 piece and I also see a one piece which is slotted twice in opposite directions at the center. it seems the double slot design will compress like an accordion allowing greater adjustment then the original single slot design. They are far more expensive than the 2 piece design so I was wondering if there was any advantage to the more expensive nut? my machine currently has 2 piece nuts.

    Thanks

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    If you've got DRO, why are you worried about the nuts? I can't remember the last time I looked at dials. Make some chips and don't worry about it!
    JR

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    Quote Originally Posted by JRIowa View Post
    If you've got DRO, why are you worried about the nuts? I can't remember the last time I looked at dials. Make some chips and don't worry about it!
    JR
    That's a good point. A friend has a Bridgeport with a DRO. He doesn't use it all that much anymore (he has two large CNC machines) but I noticed that it has nearly a full turn on the X axis and a half turn or so on the Y.

    I asked him about it once and he said he never uses the dials when he runs the machine. The DRO tells him what he wants to know.

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    Call me picky, but I find it nicer to use machines that have low (say 1/8 turn) of lash to machines that have a lot (say 5/8 turn) of slop. Maybe it's because I often slightly overshoot then return to a value, but it is something I would spend time to fix. I read off of the DRO for position, but it's still nice to have less lash in the controls.

    I'm also curious about the slotted vs. 2 piece nut as I'll probably end up replacing the one at work eventually. It is well past 1/2 turn lash on center (and about the same at the ends). Last time we had someone looking at it they said it was out of adjustment, so I suspect I'll be pulling it apart at some point.

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    How do you manage to climb mill with that much backlash?

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    I'm not worried about the nuts and I know the DRO makes the dials irrelevant. I just like things to work as designed. It's probably a fools errand to plunk down 500+ for screws and nuts just to tighten up the machine. I'm only considering it because I have the machine apart getting out several pounds of chip embedded grease.

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    Quote Originally Posted by Mark Rand View Post
    How do you manage to climb mill with that much backlash?
    Either you don't or you drag one of the locks. Neither is ideal obviously enough.

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    No brainer 2 piece nut !!

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    Quote Originally Posted by JohnEvans View Post
    No brainer 2 piece nut !!
    If you don't mind, can you explain your reasons?

    Thanks

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    Mutch easier to adjust.

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    Definitely 2pc nut. You can dial it in to exactly the amount of lash that you prefer. If you're crafty you can get the lash low enough to be barely perceptible.

    Have a look:
    https://youtu.be/bvF7WcEh46I

    I'm sure there are other posts here about it, but here's one: http://www.practicalmachinist.com/vb...-happy-185216/

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    Quote Originally Posted by MikeMM View Post
    I'm not worried about the nuts and I know the DRO makes the dials irrelevant. I just like things to work as designed. It's probably a fools errand to plunk down 500+ for screws and nuts just to tighten up the machine. I'm only considering it because I have the machine apart getting out several pounds of chip embedded grease.
    I'd rather have $ 500 of tooling than new screws. I only look at the knee dial 'cause of my two axis DRO...

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    H&W is selling both Y + X two piece nuts for less than 100 bucks, thats what I got. worked great, but I did have chrome plated screws also.

    don't see a real downside to the two piece, thing you don't want is a single slot.

    slop bugs me, DRO or no, but thats why I got decent bits to start out with. got really lucky with the chrome screws, tho, have to admit, as I've got less than 10 thou on both X and Y now.

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    Quote Originally Posted by BDubs View Post
    You can dial it in to exactly the amount of lash that you prefer.
    Not entirely correct. You can only adjust at the ends of the screws otherwize it will be tight. Take a pair of calipers and measure the crest of the thread on your lead screw at both ends and several places in between. This will give you and idea of how much your lead screw is worn. That way you'll have an idea of how much slop you'll have with new nuts.

    If you use your mill, it will never be perfect. Just a fact of life. I'm with Comstock in the fact that I always seem to need some other tooling. Anybody have a 4 or 6 flute, 1 1/8" end mill, with a 3/4 shank that they want to donate.
    JR

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    Quote Originally Posted by JRIowa View Post
    Anybody have a 4 or 6 flute, 1 1/8" end mill, with a 3/4 shank that they want to donate.
    JR
    There's an old timer CNC guy near me on Long Island that I bought a vise from and he has a boatload of larger end mills he picked up from Grumman when they closed their Long Island plant back in the 80's. He wanted a buck a piece for them. Don't remember the shank size. They were too big for my needs but if you want his info, send me a PM


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