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  1. #1
    Ox's Avatar
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    Default Box Roller Tool Leaves Bowed Parts W/ a Swiss Twist

    I have some parts that were ran on a box roller box tool on my CNC lathe.

    Taken from 5/8D 303 and turned to .250 +/-.0005 x (?) 6" long. (1 pass)

    Parts come out looking and measuring fine, but the rod tends to have a bow to it. Some strait, some real bad, others in between. I have ran these and others like them several times in the past - and this is always an issue.

    I don't know if it is something that I am dooing wrong, or if it possibly is the bar it'self? I am wondering if this is stress left from the straitening process of the original bar?

    Also - other than tossing between two V blocks and tapping it - anyone know of a better method to tweak them? (There's only 75 pcs.)



    Swiss

    I have not ran these in my Swiss yet. (Actually - I'm concerned with push-back in the collet with this much thrust.) I have ran some REALLY long rods in there with this much L/D and they look strait as an arrow, but those weren't peeled down nearly as drastically as this one, and also made from med carb steel as well. Has anyone seen similar effect in the Swiss machine on this kind of L/D/peel depth?


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    Think Snow Eh!
    Ox

  2. #2
    J.R. Williams is offline Hot Rolled
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    Default Bow

    I sounds to me the part should be re-designed and made in two pieces.

    JRW

  3. #3
    chip_maker's Avatar
    chip_maker is offline Stainless
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    Default

    I don't know if this applies to 303 round but...... I've done quite a bit of milling on 303 flat stock and that stuff seems to have more stress in it than 1018 . I mean major warpage and distortion issues. Maybe that is what you are seeing? you are peeling of some material there.

  4. #4
    PixMan's Avatar
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    I used to make some very thin-walled parts on a Swiss machine. We'd drill a 3-1/2" deep hole of .197" into some 1/2" O.D. stock, then turn the OD over most of it to .218".

    When we first started making those parts (light guides for surgical fiberoptic lighting devices), we got quite a bow in them. We changed to (what is now) Schmolz + Bickenbach Ugima SMQ 303XL material and it got 90% of the bow out. Then changing to the cutting insert to a particular Kennametal CCGT32.51 grade KC730 (can't recall the chipbreaker) got the part coming out perfectly straight.

  5. #5
    WILLEO6709's Avatar
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    I have made parts from 4140 prehard with almost that reduction on long length. If there are any steps in the diameter you could segment it.... but as long as your tool is clamped good and tight, with a tool to stand that doc....it should work. You can also spot drill it and time the main and sub and hold a center in it while making a finish pass I think.... never have done that yet but it is possible.

    where is swisspro when ya need him????? I am sure he'll swing by shortly for the swiss turn lesson of the month...

  6. #6
    Limy Sami is online now Diamond
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    My gut instinct says it's locked up stresses being relieved.

    However a high positive, sharp, low cutting force insert with a (theoreticly ) lower cut temperature might help,.......... high very localised heat at the cut can't do much to help you.

  7. #7
    Ox's Avatar
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    Default Heat

    However a high positive, sharp, low cutting force insert with a (theoreticly ) lower cut temperature might help,.......... high very localised heat at the cut can't do much to help you.

    I mount this tool in a block that will introduce coolant through the shank. Not HP by eny means, but decent flood. [Other than the DOC part] I am not pushing the S/F too hard. I think the coolant should be able to reasonably keep up. ????

    edit in - This does use a positive insert w/breaker.


    If there are any steps in the diameter you could segment it
    No steps.


    but as long as your tool is clamped good and tight, with a tool to stand that doc....it should work. You can also spot drill it and time the main and sub and hold a center in it while making a finish pass I think.... never have done that yet but it is possible.
    Not quite following along with your train of thought there. ???
    1/4" D by 6" long - finish cut?

    This gets a tiny 1/8 stem put on the end. So that rules out a center, but along that same line of thought - a guy COULD just use a bushing to hold the tip on C/L while turning it I guess. But I'm not convinced that this is "whipping" related. I don't recall the speed I twist it - but it is relatively slow. ??? (<1000 for sure)


    we got quite a bow in them. We changed to Schmolz + Bickenbach Ugima SMQ 303XL material and it got 90% of the bow out.

    My gut instinct says it's locked up stresses being relieved.

    I always fealt that it was in the material, but figgered if it was - then someone else has fought this battle before too. At least to confirm whether it is ME or the stock.

    I couldn't think of ever hearing of stress relieved 303 before, but apparently high grade stock is a BIG part of this equassion.


    (what is now) Schmolz + Bickenbach Ugima SMQ 303XL material
    Ugine got bought out?

    (Did you edit that into your post?)


    I wonder if anyone can compare this aspect to Project 70? (Copper and Brass Sales stocks that...)


    --


    The next question then begs:

    This shouldn't be a chemistry thing, and should (IMO) be soley be a physical processing issue. Does the "good stuff" go through an extra step in the cold werking prep than the std stuff? (Stress-Proof/Fatigue-Proof)



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    Think Snow Eh!
    Ox
    Last edited by Ox; 08-27-2010 at 03:51 PM. Reason: edit

  8. #8
    Gerrythewelshman is offline Cast Iron
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    Default rollerboxing

    Hi Ox,
    Pressure.
    Over feeding has this effect when boxing.
    put the tool 0.008".to 012" in front of thee tool and use half the feed.
    make sure the front rake is good.
    Setting.
    turn a piece to size +0.004" above finnished dia
    set the tool to touch ,then bring in the rollers so they
    roll and do not stop when finger touched.finally set when you put on a full cut.
    Pressure may make the tool dip so I normally set 0.004 above center this will
    rise above center when the cut finishes and you will have no return marks.
    (I do this even when using a tangi flow type of box)

    hope this helps.

    Gerry

  9. #9
    WILLEO6709's Avatar
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    Default

    Quote Originally Posted by Ox View Post
    Not quite following along with your train of thought there. ???
    1/4" D by 6" long - finish cut?

    This gets a tiny 1/8 stem put on the end. So that rules out a center, but along that same line of thought - a guy COULD just use a bushing to hold the tip on C/L while turning it I guess. But I'm not convinced that this is "whipping" related. I don't recall the speed I twist it - but it is relatively slow. ??? (<1000 for sure)
    On my ksi sqc32 - if I am pushing the main turning tool - a d shaped insert 1/2 ic I can make that cut for that length - but if I don't clamp the holy bejeesus out of the tool or I slide it out of the clamp - pushes the tip right along the axis and messes up lengths.

    on my ksi - I have 3 tool station on the fron of the sub spindle housing - one is a 3/4 boring bar pocket - can also hold a straight shank live or dead center - I can bring it onto the part, enter the right syc code and sub and main traverses identically in z1 - as like a regular lathe, but not sure about your tornos.
    You might try a reverse center on your 1/8 tit to center it for a finish pass.

    I'd be going for doing it in your swiss....

  10. #10
    Belding's Avatar
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    Default

    Quote Originally Posted by PixMan View Post
    perfectly straight.
    That's a dangerous word.

    If only we could all make perfect parts...

    Perfect for the application maybe, not perfectly straight.

  11. #11
    Ox's Avatar
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    Default

    Oh - I got it!

    It's not that your INSERT is shifting in the pocket - but rather your pushing the whole stick tool out of location! I GOT IT!

    I have had issues with holding that tight of tol on the Swiss when pinch turning. I don't know why? My #1 turret is mounted on the same casting that the bushing is on. But when I rough with the back turret ahead of my finish tool - it (finish tool on #1) cuts maybe .002 under, untill the last .025 when the rougher pulls out - and then it goes back the other way.

    It must simply be flex in the piller to the bushing of .001 is all I can figger. ??? I'm guessing the best way to accommidate this is to just go back and clean up that last little bit .002 "undersize" and then go about with business.

    Is this an issue on other machines? New? Used?

    Have they gotten away from puting the bushing on a seperate casting and mounting it more perminent?

    If I was to try to peel all of that with one tool on the Swiss my finish would be fer sheet. I have tried it on other parts. But with the box - I git the finish burnished for free.

    I have also considered the option of even puting the box in the Swiss and roughing and then finishing it. Seems awfully far "out there" and counter productive tho.


    Either way - I'm thinking that if I am releasing pent up stresses in the stock, no-matter how I skin the cat, there will still be a bow in it. ???

    There is no way to finish turn 24X between centers [successfully] that I am aware of.
    But it would theoretically cut the bow out if it were possible I guess...
    Are we on the same page here?


    I had very good success turing 11.5" long peel just recently tho.

    I was loking at the print at my desk a few weeks ago and my boy sneaks a peak of it and says "that looks like an awfully basic part." Untill I explained the L/D issue. (Especially the L!) How long can you peel on that 32?


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    Think Snow Eh!
    Ox

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