Chatter with 12" Craftsman lathe - Page 2
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  1. #21
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    The threads are not for concentricity. They are there to hold the chuck on. The accuratly bored counterbore on the chuck back plate gives you the concentricity. The same goes for the c-bore, or turned diameter that the chuck mounts to. This chuck c-bore/shoulder should be done on the lathe it will be used on.

    When I have made chuck back plates for friends machines, I cut the threads (generally 1.5x8 tpi)
    and do the c-bore at the same time. I try for a +.0005-.0001 fit on the spindle nose. That way the back plate threads, and c-bore are perfectly concentric. The only better way IMHO is to grind the threads and c-bore.
    Best of luck.
    Doug.

  2. #22
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    I suggest you "level" the machine, this hasn't been mentioned, I think.
    It means to take out the twist in the bed using a very accurate level to get both ends of the bed (and hopefully middle too) horizontal. Horizontal isn't important, getting them "the same" is.

    What can happen is that the carriage can ride on just two corners if the bed is twisted. Obviously, that isn't solid support, and could chatter.

    What is worse, the carriage can wear to fit, and then it won't be right even if you get it level again later.

    Luckily, the square ways on the Atlas are harder to wear out. But the part that rides on the edge can...level it up and tighten gibs and you may have no further problems.


    Oh, yeah on the threads issue....
    I am not going to start a flame war here....I will just say that some accurate machines do not even HAVE that unthreaded portion of the spindle, which is often called the "register". Obviously then, a n accurate counterbore on teh chuck does no good.....
    This point has been hashed out, and I think the consensus is that threads and shoulder are sufficient. The makers of those lathes without "registers" seem to agree.

    It has become a semi-religious issue.

  3. #23
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    Yes J Tiers,

    My other spindle attachments have no counterbore at all and just thread on until seated on the spindle shoulder. It seems a very marginal setup but I guess it works!? I have never leveled the machine and since it is somethig of a wet noodle anyway I did not think it mattered too much. I will try that, thanks.

    Randy

  4. #24
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    ..my 12x36 crftsmn has near .070 lash in the x/feed ,& exhibits no chatter w/ cuts of .125 in . ,mild steel ......getting tired of accomodating it ,but think u need to look elsewhere for the problem .....

    chucks can cause some strange happenings ..bell mouthed ancient 6 in 3 jaw on my 1895 antique 14 in, caused horizontal planing cuts rather than taking the diameter down ..had to be told that cut was only occuring when bar was pushed to limit of wobble in jaw & then only cut again as it came around & was pushed away again .....stomach got a lot better after i ground the jaws & took a cut ......

    best wishes
    docn8as

  5. #25
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    Randy, I quickly read the other posts and saw no mention of this. You mention Kennametal carbide inserts and holders. If they are negative rake, it can be a significant cause of chatter on some lighter machines. They need serious horsepower and are for serious metal removal (not for fine finishes).

    If you start out with a few HSS tools with nose radius down around 1/16" or less and proper angles for the material you are turning, you may see a major difference in performance ... like mirror finishes on AL, etc.

    If that works, you could move up to carbide inserts such as CCMT, TCMT, DCMT with positive rake and appropriate tool holders for them. Choose the nose radius based on the finish you want AND your available feed rates on that lathe. www.carbidedepot.com has a number of handy calculators including a surface finish one.

    Lastly, be sure that you have adequate preload on the spindle bearings (although I would think your between center tests would have masked that if it were the problem).

    My $0.02 on the threads/register/shoulder ... on my smaller Emco Maximat 7, a new Bison 3 jaw threads on, hits the shoulder and runs 0.0005" TIR out of the box (direct mount, 1-1/2x8).

    Den

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    Post Chatter on Craftsman 12" lathe

    I was given a craftsman 12" lathe and it chattered as well. Having been a machinist my entire life I found this frustrating. I believe it is caused by a small spindle diameter. It is also not a hardened spindle. I obtained a large spindle from a South Bend lathe and am installing it in the Craftsman head stock. It is 2 1/4 dia. with a 1 3/8 thru hole. It will also get a 5C collet closer. This has been a lot of work and think it would have been better to purchase a heavier lathe. However, I am retired and have the tools and ability to do this. I also changed the belt drive to serpentine 8 row belt. I will eliminate all the pulleys and go to a VFD drive. Next will be a total tear down and rebuild, and new paint. Hopefully this will be a sweet little lathe when complete.

    Hacksaw

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    Quote Originally Posted by Hacksaw Williams View Post
    I was given a craftsman 12" lathe and it chattered as well. Having been a machinist my entire life I found this frustrating. I believe it is caused by a small spindle diameter. It is also not a hardened spindle. I obtained a large spindle from a South Bend lathe and am installing it in the Craftsman head stock. It is 2 1/4 dia. with a 1 3/8 thru hole. It will also get a 5C collet closer. This has been a lot of work and think it would have been better to purchase a heavier lathe. However, I am retired and have the tools and ability to do this. I also changed the belt drive to serpentine 8 row belt. I will eliminate all the pulleys and go to a VFD drive. Next will be a total tear down and rebuild, and new paint. Hopefully this will be a sweet little lathe when complete.

    Hacksaw
    The rest of that lso (lathe shaped object) is just as wimpy as the spindle. There are so many good lathes available I can't understand why anyone would waste time money and effort on that POS. By the way, check the rules, no discussion of crapsman, smithy, and other equivalent junk.

  8. #28
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    Surprised this thread hasn’t been locked in 14 years.

  9. #29
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    Quote Originally Posted by SteveBausch View Post
    Surprised this thread hasn’t been locked in 14 years.
    14 years ago the subject was ok.

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  11. #30
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    Chatter with a 12 inch Craftsman.......sounds like the little people to me.....be sure not to blink ,and at sunup a bag of gold will be yours.

  12. #31
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    I didn't know I was up against all these experts. I also didn't join to be made sport of. If this is what you guys do, then I don't need to be here. People who are serious about this trade don't act like this. I will post a picture of my head stock mods for you to laugh at if you like.

  13. #32
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    This place can be harsh, but it’s pretty simple.
    There are rules, and new folks don’t read them(or ignore them) and post forbidden topics.
    It’s a forum for professional machinists with professional problems, not for home-shop conversions and “ how can I do this cheapest possible way” topics



    Sent from my iPhone using Tapatalk Pro

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  15. #33
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    There are other forums that specialize in hobby shop activity. Home Shop Machinist is one and in my opinion a great one for what you want to do. I was a member from the start of the magazine but dropped my subscription when I moved from strictly hobby to a mix of hobby and professionalism.

    One reason for the banning of Atlas, Craftsman a other machines of this ilk is that these machines were never designed for professional use. An example is the die cast zinc gears and handles. After a few years zinc disease with turn these into powder, plus zinc under stress will cold flow, crack and fail. The fit and finish of these machines is nowhere like even the next class of machines, the South Bend, Clausings, Sheldons and Logans.

    Can you do good work with a Craftman? Yes, you can if your expected tolerance is +-.005 inch. You can get +-.001 if you baby it. This when the machine is new. Used, well.... The next group up, the SB's and such when new can easily hold .001 to perhaps .0005.

    The list goes on.

    We are not attacking you. Its just that people with good intentions come here be schooled in and celebrated for what they can do with one of these machines. If you wish to stay and listen you will find a wealth of information on machining. You can discuss problems, just don't mention the names and you will be ok.

    Tom

  16. #34
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    Well folks, I guess my 60 plus years in this industry doesn't account for much. I also retired from owning my own manufacturing machine shop for the last 28 years. I was not the type to sit in the office all day but worked side by side with my crew. You guys act like a bunch of know it all bench racers. If you are all upset about a 14 year old post, why are you responding to it.

    I am a very serious machinist and at 76 years old I still enjoy a challenge. The 12" Craftsman being one of them. What I would like to do is do a Rodney King, can't we all just get along?

    This is a great trade that few people actually know about or understand. We do incredible things with all types of materials. I have had my products go into space, deep sea oil exploration, as well as well as medical device manufacturing.

    So lighten up no clothes boy.

  17. #35
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    So did the chatter problem get solved . I see this is a 2004 thread...the changes made in your tools or process better?.
    guess I would say speed(RPM) depth of cut perhaps .080 or more too so much for a small lathe, wrong tool rake attitude. Tool bot sharp enough (fingernail harp, perhaps a bell-mouth chuck,and lathe spindle bearing, too much part hanging out....

  18. #36
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    Here is the spindle upgrade, if I did it right.
    Attached Thumbnails Attached Thumbnails 20190215_130943.jpg  

  19. #37
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    Looks pretty good to me, you went a long way to prove your point. I would like to see the completed lathe. Don't give a damn of all all the negative comments. This doesn't appear to be a Craftsman lathe anymore.

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    Quote Originally Posted by Bruce Nelson View Post
    Looks pretty good to me, you went a long way to prove your point. I would like to see the completed lathe. Don't give a damn of all all the negative comments. This doesn't appear to be a Craftsman lathe anymore.
    Thank you, lots to do yet and I will post pictures as well as results.


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