1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  2. PLEASE: Read the FORUM RULES BEFORE registering!

    Dismiss Notice

Getting the workpiece straight in the chuck.

Discussion in 'A BEGINNER'S FORUM (Learn How To Machine Here!)' started by Tailormade, May 2, 2017.

  1. Tailormade

    Tailormade United States Iron Registered Member

    Likes Received:
    5
    Trophy Points:
    3
    City:
    Idaho Falls
    State:
    Idaho

    -Return to Top-

    So, I've got a question so basic it seems no one else has even had to ask it. (Or if they did, I didn't know the right terms to search on)

    In my 3 jaw chuck, I have yet to figure out a way to get the work piece even close to straight in the chuck.

    I feel like there has to be some better way than what I'm doing. If there is some method that is well accepted for getting things aligned in the 3 jaw chuck, I am all ears.

    What I *thought* would be the way would be to use a center finder, scribe some lines, and then center drill at the intersection. However, with the longer shafts I cant even drill there, the chuck is so far off. Longer as in, 15-20 inches.

    I also have a four jaw chuck, but haven't tried switching the chucks just yet. I anticipate the same problem with this though, as I seem to be missing something basic about getting the shaft at least close to parallel to the ways perpendicular to the chuck face.
     
  2. Wreck™Wreck

    Wreck™Wreck United States Active User H-M Supporter-Premium

    Likes Received:
    1,114
    Trophy Points:
    113
    City:
    Riverton
    State:
    New Jersey

    -Return to Top-

    If I read your description properly you are trying to center drill 15-20 inches out. Is this correct?
     
  3. Frank Ford

    Frank Ford United States Active User Active Member

    Likes Received:
    117
    Trophy Points:
    43
    City:
    Palo Alto
    State:
    California

    -Return to Top-

    Franko, 428Bird, TTD and 2 others like this.
  4. markba633csi

    markba633csi United States Active Member Active Member

    Likes Received:
    234
    Trophy Points:
    43
    City:
    Mountain View
    State:
    California

    -Return to Top-

    Well first off, 3 jaw chucks (especially cheap ones) don't have great repeatability. If they did we wouldn't need collets and 4 jaw chucks.
    What I do with mine is try inserting the piece in several times and see what happens. Sometimes it's right on the money. Other times it's all over the map. Another trick is "tapping" on the workpiece to help center it. Some people can do this with remarkable accuracy. But when it absolutely has to be perfect, use a collet or a 4-jaw.
    Also for long pieces you must use a steady rest. I don't own one, but I suspect the day is coming soon when I'll have to break down and buy or make one.
    Mark S.
     
    scwhite likes this.
  5. Tailormade

    Tailormade United States Iron Registered Member

    Likes Received:
    5
    Trophy Points:
    3
    City:
    Idaho Falls
    State:
    Idaho

    -Return to Top-

    Wreck">
    Yes, it seems like a bad idea to me to, but the piece won't fit through the head stock, so I didn't see another option.

    Sent from my SM-G900P using Tapatalk
     
  6. scwhite

    scwhite United States Active Member Active Member

    Likes Received:
    99
    Trophy Points:
    28
    City:
    Shreveport
    State:
    Louisiana

    -Return to Top-

    If you have a steady rest set it up for anything long .
    I don't know what size lathe you have but it is most
    Likely a small lathe like my 10" swing Clausing 4900
    It can run about 2-7/8 dia. In the steady rest . And to set the steady rest on center and the right dia. You
    Put a short piece os stock in the chuck turn it down to the size of you 15" shaft . Put you steady rest right up close to the chuck where you just turned the location to the size of the 15" shaft . Set your steady ready up on that short piece . Open it up do not move any of the jaws on the steady rest . Open the three jaw chuck and take out that short test piece you just set your steady rest to . Now in clamp the steady rest and move close to the other end of the shaft about 13" form your chuck . Put your shaft in the chuck
    Snug it and best it on the bottom two jaws of your steady rest . Now you have to make sure you have you carriage on the side of the steady rest you plan on working . Close the top jaw on the steady rest . And clamp the bed clamp and the steady rest clamp .
    Don't run any work in a steady rest very fast no faster than your back gear will run .
    Check all of the jaws make sure you have them all
    In the right slots . Each slot is numbered and each jaw is numbered and must go in the proper slot .
    If you have two peace jaws the also should be a match with its number and should have the same number on it as the jaw slot.
    You will have to take the all out a start number one first in the slot and the scroll must catch the number one jaw first then don't turn the scroll past number two slot make sure you catch number two the same thing on number three . Now you can screw them on in . Your chuck should be right now .
    And just like markba633csi said I will tap on the face with the lathe in motion with a brass mallet
    Don't run it to fast or to slow it should be about
    250 to 350 rpms
     
    Last edited: May 2, 2017
  7. Tailormade

    Tailormade United States Iron Registered Member

    Likes Received:
    5
    Trophy Points:
    3
    City:
    Idaho Falls
    State:
    Idaho

    -Return to Top-

  8. scwhite

    scwhite United States Active Member Active Member

    Likes Received:
    99
    Trophy Points:
    28
    City:
    Shreveport
    State:
    Louisiana

    -Return to Top-

    I like that tool you made I will put it on my list
    I had one years ago but I used mine for rolling
    Metal into a bore that might be one or two thousands
    To big . Or rolling metal on a shoulder the same way that might be turned to small a few thousands.
    Mine was heavy duty a 1" cam lock roller .
     
  9. kd4gij

    kd4gij United States Active User Active Member

    Likes Received:
    913
    Trophy Points:
    113
    City:
    St. Petersburg
    State:
    Florida

    -Return to Top-

    I use a dial indicator and a soft mallet ton get the part running true. For a longer bar indicate out near the end first then check up near the chuck.
    The roller posted me Frank works great on shorter parts.
     
    scwhite likes this.
  10. Glenn Brooks

    Glenn Brooks H-M Supporter - Premium Content H-M Supporter-Premium

    Likes Received:
    287
    Trophy Points:
    63
    City:
    Woodinville
    State:
    Washington

    -Return to Top-

    Here's a method I adopted from my master machinist friend, who learned this from from old time master machinists 35 yrs ago when he was starting out in the trade.

    Loosely Chuck up your part in the three jaw, and turn on your machine at slow speed (50-100 rpm or thereabouts).

    Lightly tap the high part with a light hammer 2 or 3 times as it spins around.

    After you get the hang of it, this will true up the part 9 times out of 10. If not, loosen and repeat.

    Tighten up the chuck enuf to hold the work.

    I hardly ever use a dial indicator with my three jaw now, after I learned how to do this.

    Glenn
     
    Ulma Doctor, scwhite and T Bredehoft like this.
  11. kd4gij

    kd4gij United States Active User Active Member

    Likes Received:
    913
    Trophy Points:
    113
    City:
    St. Petersburg
    State:
    Florida

    -Return to Top-

    A few years ago I saw franks tool on his web site. So I found a good use for those useless single wheel knurling tools that come in tool sets. Replaced the knurl with a bearing.
    upload_2017-5-2_22-38-5.png
     
    Ulma Doctor, Franko, scwhite and 3 others like this.
  12. DAT510

    DAT510 United States H-M Supporter - Premium Content H-M Supporter-Premium

    Likes Received:
    60
    Trophy Points:
    28
    City:
    San Mateo
    State:
    California

    -Return to Top-

    What part of the work piece are you trying to machine? If it's the end, then as others have suggested a steadyrest would be a way to go, since it sounds like piece is too big to fit through the bore. If it's the "side" of the work piece, what about mounting it between centers and using a dog drive?
     
    WoodBee, scwhite and brino like this.
  13. Tailormade

    Tailormade United States Iron Registered Member

    Likes Received:
    5
    Trophy Points:
    3
    City:
    Idaho Falls
    State:
    Idaho

    -Return to Top-

    It's a 12X36, but its headstock has a pretty narrow openning, so I assume I'll be getting to know that steady rest pretty well.
    I'm pretty sure the prior owner didn't listen to that advice, the arms on the steady ready rest are.. a bit rough at the ends. I don't see any indexing on the arms, can I just dress up the ends of the arms or must they be replaced? On that same topic, are those steady rest arms with bearings on the ends worth having?

    I'm going to give that a try with a wooden mallet tonight, thanks.

    I haven't seen a tool set with a single knurl, what makes them useless? Of course with the existence of google and ebay now I've seen many of them. Still not sure why useless.

    Thanks for mentioning the lathe dog. I'd heard the term turning between centers but not understood how it would be done.
     
    scwhite and brino like this.
  14. Frank Ford

    Frank Ford United States Active User Active Member

    Likes Received:
    117
    Trophy Points:
    43
    City:
    Palo Alto
    State:
    California

    -Return to Top-

    NOT useless, but quite useful! Great for straight knurls on the lathe to avoid double-tracking, among other regular uses.

    Here's an irregular use, renewing the knurling on a bar clamp:

    [​IMG]

    [​IMG]
     
  15. dontrinko

    dontrinko United States Active Member Active Member

    Likes Received:
    25
    Trophy Points:
    28

    -Return to Top-

    I use the tail stock to put a little pressure on the work as I tighten it. This helps but I still end up trying several times until I get it close.
    If you are not using the part that is in the chuck you can turn the extended part and it will end up round even if you do not have it perfect in the chuck. I have done this on long pieces: turn one end then turn it around and turn the other. This helps if the work is not perfectly round to start with. Don
     
  16. jlsmithseven

    jlsmithseven United States Active Member Active Member

    Likes Received:
    146
    Trophy Points:
    43
    City:
    Ephrata
    State:
    Pennsylvania

    -Return to Top-

    Sorry for asking, but what exactly does this little wheel do that touches the piece. Is it meant for tool height or runout of the piece? I am just a little confused on how this little tool works, but it looks like a good tool to have?
     
  17. 428Bird

    428Bird United States Steel Registered Member

    Likes Received:
    30
    Trophy Points:
    13
    City:
    Deer Park
    State:
    Texas

    -Return to Top-

  18. mikey

    mikey Active User H-M Supporter-Premium

    Likes Received:
    1,745
    Trophy Points:
    113
    City:
    Honolulu
    State:
    Hawaii

    -Return to Top-

    It's just a bearing mounted on a piece of square stock. In use, the work piece is mounted in the 3JC and lightly snugged. Then the lathe is run at low speed and the bearing is gently brought into contact with the work. Initially, only the high spot contacts but as you slowly feed the tool in, the work is brought into relative concentricity with the spindle and you will see the work start to run true(r). At that point, you stop the lathe and tighten the chuck firmly and you're set.

    This works for shorter pieces or even thinner work like a washer that you're trying to get to run true in a 3JC (you bring the tool into the face of the washer). It is not a precise method but it is better than nothing. Its actually a good tool; I've had one for years but I cannot recall who came up with the idea to use a bearing. An old machinist friend of mine used a piece of maple with a rounded end that worked just as well.

    In the case of the OP, this tool would not be useful due to the length of his work piece. A steady rest and a dial indicator would allow him to center drill for live center support but that has been discussed already.
     
  19. jlsmithseven

    jlsmithseven United States Active Member Active Member

    Likes Received:
    146
    Trophy Points:
    43
    City:
    Ephrata
    State:
    Pennsylvania

    -Return to Top-

    Oh so you're saying loosen the chuck jaw a little bit, run it at like 35 rpm or something and it will true it up and then just tighten the screws. Sounds simple and awesome, not sure if I will be able to do that though.
     
  20. benmychree

    benmychree United States Active User H-M Supporter-Premium

    Likes Received:
    164
    Trophy Points:
    43
    City:
    Saint Helena
    State:
    California

    -Return to Top-

    Not always necessary to turn a blank piece to line up the steady rest; I just get it close, then put a center drill against the shaft end lightly and see what trace it leaves on the shaft end if not on center, then adjust the SR jaws until the center drill hits the shaft dead center and drill the center hole, With a bit of practice it is easy and quite accurate. There is nothing wrong with running things fast speed in the steady rest as long as the jaws are not overly tightened and a lubricant is used; way oil, center lubricant, white lead or whatever is at hand. If the jaws are roughed up, they can be re machined. I have thought of using a hand reamer in the spindle and carefully adjusting the jaws, one at a time against the rotating reamer, but have never tried it; same could be done using an end mill, the more flutes the better.
     
    Bob Korves, rdean and scwhite like this.
  21. brino

    brino Active User H-M Supporter-Premium

    Likes Received:
    2,020
    Trophy Points:
    113
    City:
    Almonte
    State:
    Ontario

    -Return to Top-

    Never be!
    Ask away!

    -brino
     
  22. mikey

    mikey Active User H-M Supporter-Premium

    Likes Received:
    1,745
    Trophy Points:
    113
    City:
    Honolulu
    State:
    Hawaii

    -Return to Top-

    Just run it at the lowest speed you have. It works well but don't expect to be dead on concentric this way. It will get you close enough, though, and the tool is worth making and using.
     
  23. benmychree

    benmychree United States Active User H-M Supporter-Premium

    Likes Received:
    164
    Trophy Points:
    43
    City:
    Saint Helena
    State:
    California

    -Return to Top-

    What are you saying????
     
  24. brino

    brino Active User H-M Supporter-Premium

    Likes Received:
    2,020
    Trophy Points:
    113
    City:
    Almonte
    State:
    Ontario

    -Return to Top-

    I had quoted jlsmithseven who apologized for asking a question.
    I want him to know that asking any question is fully encouraged here!

    -brino
     
    Franko likes this.
  25. benmychree

    benmychree United States Active User H-M Supporter-Premium

    Likes Received:
    164
    Trophy Points:
    43
    City:
    Saint Helena
    State:
    California

    -Return to Top-

    Yes, there should be no need to apologize for asking any question, no matter how basic it may be; that is what this forum is for.
     
    scwhite likes this.
  26. dlane

    dlane Active User H-M Supporter-Premium

    Likes Received:
    588
    Trophy Points:
    113
    Location:
    Lake oroville
    City:
    Oroville
    State:
    California

    -Return to Top-

    3jc it forces the stock to conform a little.
     
  27. scwhite

    scwhite United States Active Member Active Member

    Likes Received:
    99
    Trophy Points:
    28
    City:
    Shreveport
    State:
    Louisiana

    -Return to Top-

    The best way to dress the end of the steadyrest
    Jaws is to make a leaping mandral and run the mandral with a live center in the tail stock
    The bring in the jaws on the mandral with the laping
    Compound on your mandral
     
  28. Chipper5783

    Chipper5783 Active User H-M Supporter-Premium

    Likes Received:
    319
    Trophy Points:
    63
    City:
    Red Deer
    State:
    Alberta

    -Return to Top-

    The above responses are all good and will likely give a better result than simply putting that piece of bar into the chuck and cranking down on it. Of course, a 3 jaw chuck does not hold perfectly, either on center or aligned to the axis of the bed. If you pay lots of money and get a new top end chuck and then mount it correctly - it will be closer to "perfect" - but it will not be zero runout up close to the chuck and well out along the bed (assuming you have an accurate test bar).

    However, very few people here would actually spend that kind of $$. It really is not necessary. Using techniques like the ones described above will get a pretty good result, with a pretty ordinary chuck (cheap or well used). Don't sweat it. I actually don't do any of the tap/bump/rolling techniques. I have been through the whole chuck mounting/tuning - and for 3 jaw work, I simply snug the stock - and go. The run out is 0.003 close to the chuck and twice that 6" out. The reason it is no big deal is because after the first couple passes it will be running as true as the machine is capable of!

    I have never checked using an unsupported bar, 15-20 inches out from the chuck. I can't imagine very many situations where it would be relevant (center drilling something too big for the spindle hole, even then there are other ways to get'er done)?

    Another excellent solution (not mentioned above) is to set yourself up with soft jaws: load the jaws, skim them and then the work will run very close to true.

    You said that it is running way off? Take some measurements (make sure it is an accurate piece of material), and check the run out at several locations out from the chuck. Maybe there is an issue with how the machine or the chuck are set up?

    Let us know how you make out. Regards, David
     
    scwhite likes this.
  29. Glenn Brooks

    Glenn Brooks H-M Supporter - Premium Content H-M Supporter-Premium

    Likes Received:
    287
    Trophy Points:
    63
    City:
    Woodinville
    State:
    Washington

    -Return to Top-

    One essential use for the tap/bump roll techniques in a three jaw is to true up a part that has been previously turned.

    Glenn.
     
    scwhite likes this.
  30. kd4gij

    kd4gij United States Active User Active Member

    Likes Received:
    913
    Trophy Points:
    113
    City:
    St. Petersburg
    State:
    Florida

    -Return to Top-

Share This Page