Boring Bar Push Off? - Page 2
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  1. #21
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    Quote Originally Posted by Mot3s View Post
    7075 Aluminum

    In Al I would initially suspect chip weld but usually you see this when pulling the tool.

    Chip wrap or plugging can be a bigger problem if it gets between the bar/insert and the finished section of the bore.
    Once this wrap or wedging occurs it's all over. The cut material becomes a guide pad and the bar will bend.
    Normally you can see this as scarring on the part and bar. Sometimes a good continuous air blow into the hole during the cut can persuade those chips to leave.
    Any sign of contact behind the cutting edge past one feed per rev is bad.

    The DRO moving is a bad sign but something increased the pressure to make it do that.
    Are you using aluminum cutting insets?
    What do the chips look like and is there a sign of rubbing behind the cutting edge on the insert or on the bar itself?

    Cutting from the inside out does not work well or at all on some boring bars but will indeed work in some cases and light cuts. Everything changes when you do this.
    Bob

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  3. #22
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    Quote Originally Posted by litlerob1 View Post
    What type/brand Lathe are we talking about here?

    If there is something wrong with the actual cutting action, then logic dictates that it will not get better as you keep going (with exceptions). So if the Bore diameter is getting smaller, then you have to take the opposing action to counteract it.

    R
    Assuming there's cross slide backlash, I was talking about which direction I should feed the cross slide before stopping to feed in Z to eliminate its backlash and potential to move away from me caused by cutting forces.

    For instance, I touch and set DRO to 0.625 and I want to take 0.030 DOC to increase hole diameter to 0.655:

    1) To reduce backlash in cross slide, shouldn't I move toward me say 0.100 (DRO reads 0.725) then move away 0.070 (DRO reads 0.655), stop, and then feed in Z?

    OR

    2) Set to 0.625, move slide toward me to 0.655, stop, feed in Z.

    Which process, 1) or 2), would better eliminate cross slide backlash and its tendency to move away from me causing the DRO to read a smaller DIA than I wanted to cut? Perhaps I'm thinking of backlash all wrong here

  4. #23
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    Scenario is; You have a .625" hole. You touch the Bar off by taking a cut on the Bore, ( to take the cut you're last X axis feed motion would be toward you). Measure the cut, move the cross slide the SAME direction-toward you.

    Think of it like a screw and nut, if it's loose the nut can wiggle around on the screw. If it's tight it won't (theoretically).

    R

    Still a no name Machine?

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  6. #24
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    Quote Originally Posted by CarbideBob View Post
    In Al I would initially suspect chip weld but usually you see this when pulling the tool.

    Chip wrap or plugging can be a bigger problem if it gets between the bar/insert and the finished section of the bore.
    Once this wrap or wedging occurs it's all over. The cut material becomes a guide pad and the bar will bend.
    Normally you can see this as scarring on the part and bar. Sometimes a good continuous air blow into the hole during the cut can persuade those chips to leave.
    Any sign of contact behind the cutting edge past one feed per rev is bad.

    The DRO moving is a bad sign but something increased the pressure to make it do that.
    Are you using aluminum cutting insets?
    What do the chips look like and is there a sign of rubbing behind the cutting edge on the insert or on the bar itself?

    Cutting from the inside out does not work well or at all on some boring bars but will indeed work in some cases and light cuts. Everything changes when you do this.
    Bob
    Good info. Dang, that could have very well happened. I don't have a way to blow air like that continuously. What if I just clean it out good after every pass? No this boring bar did not accept inserts. Came in a little set with round shanks, pretty sure it was HSS. Yeah I could push the cross slide and see the DRO move. It took some strength to do it, but I don't know how easy it should do that. Now that you mention it, the insert for the new bar coming says it's recommended for steel. Is this going to be a major issue if I use it on aluminum, or is completely necessary that I buy separate aluminum inserts?

  7. #25
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    This sounds like the same problem my neighbor is having with his new Precision Mathews lathe, is this Russell?

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    Quote Originally Posted by litlerob1 View Post
    Scenario is; You have a .625" hole. You touch the Bar off by taking a cut on the Bore, ( to take the cut you're last X axis feed motion would be toward you). Measure the cut, move the cross slide the SAME direction-toward you.

    Think of it like a screw and nut, if it's loose the nut can wiggle around on the screw. If it's tight it won't (theoretically).

    R

    Still a no name Machine?
    I don't know the model, do not have access to the shop today.

    I understand now. In order for the cross slide to move towards the user, a force is pushing it that way(I'm assuming a screw rotates and pushes a nut when you rotate the wheel?). You want that force directed toward the user before stopping the slide and feeding so that the slide doesn't move away from the user, at least the backlash length.

    If I'm wrong with that explanation then I give up. I'm done

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    Quote Originally Posted by dalmatiangirl61 View Post
    This sounds like the same problem my neighbor is having with his new Precision Mathews lathe, is this Russell?
    This is most definitely not Russell

  10. #28
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    Quote Originally Posted by Mot3s View Post
    Good info. Dang, that could have very well happened. I don't have a way to blow air like that continuously. ....
    Think, Think, think.
    An air nozzle from a small compressor plastic cable tied to your holder post works.
    Crude but effective
    Bob

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  12. #29
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    Quote Originally Posted by CarbideBob View Post
    Think, Think, think.
    An air nozzle from a small compressor plastic cable tied to your holder post works.
    Crude but effective
    Bob
    I'd be on board if this wasn't for my mechanical engineering design project at a state run school. I'm about 99% sure a rigged air compressor would not be allowed. We're not even supposed to use our bare hands on the metal chips. We might get a boo boo.

    Anyways, I think all this gives me enough information to diagnose a future boring problem.

    Thank you

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    Quote Originally Posted by Mot3s View Post
    I'd be on board if this wasn't for my mechanical engineering design project at a state run school. I'm about 99% sure a rigged air compressor would not be allowed. We're not even supposed to use our bare hands on the metal chips. We might get a boo boo.

    Anyways, I think all this gives me enough information to diagnose a future boring problem.

    Thank you
    You’ll get it. In the meantime attached below is lost motion in a machine tool from Caterpillar U.

    Although CNC doesn’t have exactly the same problem as the old screws, most WILL yeild more easily in one “axis” direction vs the other or whether the ballscrew is pushing or pulling the recirculating nut (and how far nut is from the fixed end).

    We don’t know if that’s exactly what you have though...

    Good luck,
    Matt
    Attached Thumbnails Attached Thumbnails lost_motion.jpg  

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    Quote Originally Posted by Mot3s View Post
    I'm away from the setup and have a new bar coming in. I'll take a pic next go-round just in case I fail again. I never know how much info you all need given that I have no idea whether these problems are simple or not. For those of you on these forums that request diagrams and every detail possible, I think most people don't have that much time on their hands. I'm just in search of possible problems when push off occurs. But I think what most of you have told me gives me enough ideas as to what it could be. I think the tool is crap and there was too much play in the x direction.
    A pix is worth thousand of bytes.....don't forget that.

    I may be accused of having too much time, but I can't see thru the screen, at your set-up, we can only help with what you give us.

    And contrary to the peanut gallery here, I am trying to help you.

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  17. #32
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    Your young your new to lathe work so you need a book on How to run a lathe not expensive it will show you how to grind your boring bar and the does and dont,s on boring hole.So spend a few bob and get a book that you can refrence off.Doesnt sound like your getting much training or help so you will have to learn to help yourself much easier these days with help of the internet than it was years ago.Even a DRO is a great help when you can see the crosslide "creeping" when your cutting thats normally a sign you arnt taking your backlash off.And you want to learn to tighten things up.Theres screws on the compound that should be locked and when your put cut on you should lock the crosslide take you cut check loosen the crosslide then put your next cut on and lock the crosslde again.Sound complicated but its not so that why you need a book to refrence these things.Obviously you tool need to be set right and be sharp hence a book and tool grinding.Remember theres such things as libraries where you can get refrence books out on loan

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    W

    T

    F

    ??

    I can't understand any of this.

  19. #34
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    Quote Originally Posted by onecut View Post
    Your young your new to lathe work so you need a book on How to run a lathe not expensive it will show you how to grind your boring bar and the does and dont,s on boring hole.So spend a few bob and get a book that you can refrence off.Doesnt sound like your getting much training or help so you will have to learn to help yourself much easier these days with help of the internet than it was years ago.Even a DRO is a great help when you can see the crosslide "creeping" when your cutting thats normally a sign you arnt taking your backlash off.And you want to learn to tighten things up.Theres screws on the compound that should be locked and when your put cut on you should lock the crosslide take you cut check loosen the crosslide then put your next cut on and lock the crosslde again.Sound complicated but its not so that why you need a book to refrence these things.
    Obviously you tool need to be set right and be sharp hence a book and tool grinding.

    Remember theres such things as libraries where you can get refrence books out on loan
    Dollars to Donuts, the OP is running "inserted tooling"

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    Didn,t notice he mentioned he was using inserts,Must have been when he said "No this boring bar did not accept inserts"Still handy for the lad to get himself a refrence book as you will know understanding how to grind his own tools will help him understand clearance angles etc-Good luck to the kid he will get there

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  22. #36
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    Quote Originally Posted by onecut View Post
    Didn,t notice he mentioned he was using inserts,Must have been when he said "No this boring bar did not accept inserts"Still handy for the lad to get himself a refrence book as you will know understanding how to grind his own tools will help him understand clearance angles etc-Good luck to the kid he will get there
    I agree 100%, and I didn't see any reference to inserted tooling, just my "hunch".


    Even so, let's see the set up, and the tool angles.

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  24. #37
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    Quote Originally Posted by digger doug View Post
    Dollars to Donuts, the OP is running "inserted tooling"
    It was 100% not inserted tooling, not the boring bar. One solid HSS piece that came in a set much like this one, except way crappier:

    Boring Bar Set, 1/2" Shank, HSS 2682 - LittleMachineShop.com

    I chose the size that allowed for tightest fit and least amount of tool overhang to reach where I needed to go

  25. #38
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    Quote Originally Posted by Mot3s View Post
    It was 100% not inserted tooling, not the boring bar. One solid HSS piece that came in a set much like this one, except way crappier:

    Boring Bar Set, 1/2" Shank, HSS 2682 - LittleMachineShop.com

    I chose the size that allowed for tightest fit and least amount of tool overhang to reach where I needed to go
    Looks like your feeding the leading edge (of the tool) into the un-cut shoulder (of the piece)

    Hand grind some clearance there ?

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  27. #39
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    A few pictures of the business end of the boring bar after use please.

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    This boring bar worked just fine for me:

    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    I got 3/8 because I also needed it for a shoulder bore. It squeaked some before I lowered rpm.

    I found that if I took 0.020 to 0.030 cuts at 900 rpm with a decent speed that it worked well with 7075.

    I'm pretty sure what helped was choking up more and the bigger shank size. I left stock that didn't need to be tapped all the way, so I only bored the portion I needed, tapped some of it, flipped it and faced, flipped back to finish the tap. I didn't think of that the first go around and could have actually shortened the last setup. But not only that, I'm fairly certain it wasn't a proper boring bar, at least wasn't ground to a proper cutting angle.

    Anyways, thank you all for your help and useful insight


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