Turning square shafts
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  1. #1
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    Default Turning square shafts

    Just started learning how to run a lathe. We have an old msc 13/40 3hp lathe at work, that was just sitting. I ordered a Dorian bxa tool post and some carbide inserts to get started. I have been turning some conveyor shafts, but I am having a few issues.
    I am using 1.5” square stock, and turning the ends down to 1.25”. One end has a round section 3” long and the other end is 10” long with a keyway. The total shaft length varies depending on conveyor width. The spindle bore is only 1 3/8”, so I can’t run it through the head stock. I have been using a 4 jaw Chuck and dialing it in a couple of inches from the jaw, indicating off the corners. Then I center drill the end, which was faced off on a mill. Insert a live center and turn down. I start roughing it in with a square insert, .125 doc and .007 feed rate. It goes smooth until I get down to about the 1.4” range and I start getting a lot of vibration, a few inches out. Using about @650 rpms until I get to 1.5” then speed up to @950rpms. At 1.4” I switch over to a tnmg331 and start making .050” passes with a follow rest.
    I am having severe vibration and over 10” I am gaining .010” from thr live center to the shoulder. This is on a 30” total length shaft. After reading quite a few posts on here I understand that running from a Chuck to a center isn’t ideal, so what would my best approach be? Is the heavy vibration from the set up or normal with that diameter and length?

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    I believe you are going to have to use a steady rest on that shaft to keep it stable. Look up "cathead" and make or buy one and use a steady rest.

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    .125 doc seems a lot..can you make a few passes?
    QT; [This is on a 30” total length shaft.] the shaft might be whipping at 950RPM you could try lower RPM.

    A positive top rake will reduce pressure and so might help. A flat-top insert with no positive rake will produce a lot of pressure on the part.

    You might try running the job at 500RPM, play with depth of cut and number of passes. passes with a follow rest.

    File check the part to see it is not work hardening bit/insert.

    Mild steel needs a fingernail shaving sharpness.

    Here an interesting photo of turning Sq stock way out of chuck,
    lathe cat head photos - Bing
    but the time to set up time may be more than just running slower.

    The part will fall away from the follow rest as Od stock is taken.

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    What is this A with a roof over it?? I haven't even seen it on the list of other characters .
    ...lewie...

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    Quote Originally Posted by Lewie View Post
    What is this A with a roof over it?? I haven't even seen it on the list of other characters .
    ...lewie...
    It's a formatting error. Notice how it precedes every " in his post.

    Also, I learned something new today. I was going to suggest making a slug with a round OD and square on the inside to hold the stock for use in the steady rest, now I know that has a name.

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    I guess I forgot to mention another key point. I am working with 304 SS.

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    Quote Originally Posted by DirtyDusty View Post
    I guess I forgot to mention another key point. I am working with 304 SS.
    found this: Hardening: SS 303 cannot be hardened by heat treatment, but can be hardened by cold working. Due to the high P and S content,

    So mere reason for very sharp cutting edge.

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    Since you stated that this is SS then you might want to consider HSS instead of carbide. Carbide does not like interrupted cuts like making a square shaft round and dead sharp might help with maybe a little more back rake then normal.

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    So a couple of questions come up. This probably sounds stupid, but I always thought a center drill would find center, if the end was relatively flat.
    I have a bxn quick change tool post. What would be the best way style of holder for hss, what size stock, and what type, M2 or ?

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    qt: [but I always thought a center drill would find center if the end was relatively flat.]

    The center drill will find and put in a center to the centerline of the spindle not of the part if the part is running out a tad. Also, a poor sharpening on a center drill can start and place the center a bit off the centerline of the spindle.

    Running clunker lathes I would 4 jaw a part and the scalp a tool bit dent at the but end when facing...That practice made a near-dead on center to the part.

    Needing to run a no stock part mostly in grinding an OD I would have to move a center using an abrasive point-mounted wheel.

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    Quote Originally Posted by DirtyDusty View Post
    So a couple of questions come up. This probably sounds stupid, but I always thought a center drill would find center, if the end was relatively flat.
    I have a bxn quick change tool post. What would be the best way style of holder for hss, what size stock, and what type, M2 or ?
    "Best style of holder" for hand-ground HSS-Cobalt (and the Stellites) is probably NOT-even a "QCTP" at all. They are best used with inserted carbides, actually.

    No fear.

    Toolposts are NOT ordinarily welded onto the machine.

    One can have more than one type. One can swap a toolpost. Not just a toolholder.

    I'd want a stout "4-Way" for the least chatter on an interrupted cut in square Stainless. Part of that is a stiffness and shorter hang-out thing. Mass also becomes a resonance/vibration damping contributor of improvement.

    The cutting-tool DOES have to be "right" as to shaping and sharpening, though.
    There is "art" to that. Might be better-off to hang with Carbides if you haven't had the pleasure?

    As to "cat head"?

    You have very, very slender chances that a stock square-bore, round OD part (yes, you can "just buy" such an animal) .. will be a tight fit on your square stock.

    But one not terribly oversized might give you a head-start at making the cathead FROM it ... as can run in a steady rest ... with but a fraction of the effort of pure DIY.

    And with shorter adjusting screws. So it is stiffer, overall.

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    What the heck is "10” with the fancy A. and then a 30.
    I am so confused....
    If I slightly grasp the application. Way negative rake tooling good, positive rake tooling very bad.
    Bob

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    Wow termite, I am not going to repeat the racist shit you wrote under the forum name Monarchist.
    I think whatever dismal support you have left is going to hide in Anal Pucker County Texas!
    You are like a turd in a swimming pool now, Powerful Mentor of the PM forum, as you call yourself!!!!!

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    Quote Originally Posted by CarbideBob View Post
    Way negative rake tooling good, positive rake tooling very bad.
    Bob
    I don't THINK so.

    Neg-rake freakin' bulldozes. Talk about work-hardening?

    Oy!


    It's pos-rake that peels or shaves. Mind it dasn't also pull-in on a sloppy old ride.

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    The donie and mortal enemy thing is getting a bit old.
    "Neg-rake freakin' bulldozes. Talk about work-hardening?"
    No ,no no. Here it about impact and load into the cutting tool. Positive rake bad, very bad. It will not shave and it will break or chip.
    Admit to being surprised that you would make such a mistake in turning square stock to round.
    I thought this was like falling off a log. Negative and T-land. in carbide, cerment or ceramic. Just negative in HSS.
    CBN more neutral top but goodly negative in the edge prep.
    I sort of love these type of applications. Everything is wrong and nothing works as it should.
    Bob

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    Quote Originally Posted by CarbideBob View Post
    "Neg-rake freakin' bulldozes. Talk about work-hardening?"
    No ,no no. Here it about impact and load into the cutting tool. Positive rake bad, very bad. It will not shave and it will break or chip.
    Bob
    THIS is true .. for Carbides, ceramics, etc AKA -"frangible goods".

    And they DO "dominate". It is, after all, a "CNC world" where pennies on a part multiplied by a gadzillion parts made FAST .. is what folks have to deal with.

    Old Skewl HSS-Cobalt are not "immune" either. Subject at ANY time to "nano cracking" failures right at the bleeding edge, even on smooth cuts, NOT interrupted. Nowhere near "perfect" for interrupted. Just enough tougher to make a difference.

    We'd start the DEMANDING jobs..

    - with a tough "T1". "Cobra" my favourite.

    - switch to a Mo-Max moly.

    - finish with a CPM "Rex 95" razor-blade.

    Some other shop? Some other set of cutting tool alloys and makers.

    It was typical as management juggled "overall average" costs that the guy on the shop floor had only a limited selection at the toolroom window. Guy a mile down the road had a whole different set of choices.

    I'm a fan of Tantung-G for instance. Right BITCH to grind it, but NICE to USE it.
    Galis didn't have it in our toolroom AT ALL, though.

    Our Carbides? 100% neg-rake GE Carbolloy. Tear even that thick plain insert to shattered edges before it had gone six inches in corn-cob, bulldoze with the shards, heat the work badly.

    I could beat the time with sharp HSS, hadly EVER even MOUNTED Carbides.
    Time moved on. Carbides became downright BRILLIANT!
    Hard to relate to present-day thousands of option choices.
    Different times.

    But.. THIS tasking?

    It's only an old MANUAL lathe.
    Go figure that interrupted cuts on square stainless.... are still a Royal Bitch Kitty.

    Most here over forty are just not "married" to one type of tooling for all tasking. Obsolete is not the same as "useless".

    If we need a different tool? We just use it.

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    termite, your writing is choppy, can you somehow delete those racist post under your fake ID Monarchist, and you were also banned but can it be done?!
    termite, your style has changed! now you quote someone, and then do your dump.
    Well, yah knowz yuz shouldz of stuck with putuns da WD40 on yer wittle winkey!

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    Quote Originally Posted by CarbideBob View Post
    What the heck is "10” with the fancy A. and then a 30.
    I am so confused....
    If I slightly grasp the application. Way negative rake tooling good, positive rake tooling very bad.
    Bob
    Watch out. I tried playing around with my curlt / alt keys trying to get the A with the mark over it and flipped my computer screen. With the screen off one side and the mouse going the wrong way it was a bugger to get it back to horizontal off the bottom.
    To fix:
    on some computers, you ctrl / alt and then use an arrow key. (likely the way I messed up)
    others you go to appearance and choose landscape or portrait...but with your mouse going the wrong way it is a bugger to click apply.

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    Quote Originally Posted by Lewie View Post
    What is this A with a roof over it?? I haven't even seen it on the list of other characters .
    ...lewie...
    He's posting from Louisiana. Acadian French diacritical marks. Also known as "Cajun".

    Even the French cannot understand it. Or maybe just DARE not?

    Because it is a dialect of French that dates from when they served as fishermen and alligator herdsman ....aboard Noah's Ark.

    Why did you THINK they were so expert at survival in the Bayou?



    PS:

    950 RPM? That square shaft will experience some whip.

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    I haven't tried it on SS but on cr steel I use a 1/2 square HSS . Turn the cutting edge 30 to 40 degrees and go almost full cut , slow spindle speed and very slow feed rate. If the cutting tip is in solid stock it doesn't pound. Leave just enough to finish to size.

    Unless the shaft is longer that the mill table to the floor, you can use a mill to center drill the shaft first.

    I have a big angle plate with a v notch just for this purpose.

    dave


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