Basic Lathe Procedures

Discussion in 'Clock Repair' started by Jerry Kieffer, May 12, 2019.

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  1. Jerry Kieffer

    Jerry Kieffer Registered User
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    This week a beginning repair person stopped by inquiring if I would make a matching replacement screw for a platform escapement on a Carriage clock. In addition she also needed a seconds hand bushing with a long pipe. Since both of these items are basic Lathe projects, I machined them while she waited and watched and photos were taken for her future reference. Since I had the photos and beginners often inquire about work holding and machining, I thought I would share the procedures used for any beginners who may have a interest.

    I should first mention that years ago when purchasing a Lathe, it came with a factory tool post designed to hold a center cutting 3/8" shank boring bar left side in the first photo. At first glance, one can see that this size boring bar is to large for general boring work in Horology. My preferred commercial boring bars for Horology have 3/16" and 1/8" shanks and can bore down to .015" (.375mm) right side front in the first Photo.
    To resolve this issue, I simply spot drilled/drilled a 3/16" and 1/8" hole centerline to the spindle in another standard tool post again right side first photo. Little did I realize how useful these two holes would become over the years for many uses other than boring bars.

    Machining the Screw

    (1) For myself personally, the most dreaded thing about making screws when I started out, was the slot. I preferred a centered slot with parallel side walls that included a flat bottom and square corners. With proper setup and a more versatile Lathe, it is now a snap.
    In this specific case, the screw head was well under 4mm, so a piece of 3/16" stock was mounted in the 3/16" boring bar hole. Since the hole is dead center to the spindle rotation, the slot can be machined with a Endmill assuring it will be centered with parallel side walls and flat square bottom. (second attached Photo)
    In the Photo, a .015" four flute stub solid carbide endmill is being used. Depth is controlled by Carriage hand wheel settings. Because of the size of the endmill, three passes were taken at about .005" deep per pass. Each pass took about 15 seconds. What seemed to take forever in the early days, is now assured perfection in less than a couple of minutes.

    (2) From this point, the screw stock was mounted in the lathe headstock and the body of the screw was machined. For this and other small work, I sometimes use a insert tool designed for grooving when there is an advantage to do so. It is solid carbide, about .200" long and has a tip that is .019" wide. while it is only designed for grooving, it also works well for parting and machining right and left per the third attached photo.
    The insert holder shown is one that I machined, but commercial holders of all sizes are readily available.
    Once the body was machined to size, it was then parted off to length using the same tool.

    (3) Once the screw was parted off it was then threaded. While there are many methods of threading including single point for odd balls, I prefer dies when I have them as was the case for this project
    The head of the screw was then mounted in a collet in the headstock. The screw was inserted into the die and the Tailstock chuck brought up against the die to hold it square per fourth photo. At this point, one thread was cut on the screw to get the thread started by turning the spindle by hand. The thread can then be cut by hand or by powering the spindle. If by power, its best done under 25 RPM. When starting the Lathe, the screw and die rotate. With my left two fingers I hold the die and use my right hand to slide the tailstock/chuck face against the die and hold it square too the screw. when depth is reached, I remove my fingers and allow the die to spin free. The lathe is then shut down and the die spun off the screw. Again as mentioned, there are many ways of doing this. For small screws, I personally prefer this method where possible, because I can feel what is happening.

    (4) Once threading was complete, the screw head was machined to diameter, then shaped and polished
    as required per fifth photo.

    Second hand Bushing

    (1) First the pipe on the bushing was machined to length and a .029" center hole was spot drilled/drilled.

    (2) The stock was again mounted in a boring bar hole and slitted with a .008" slitting saw per sixth photo.
    While the slitting saw can be centered to perfection using carriage hand wheel calibration, positioning with a loupe is much faster
    Again, the lathe setup assures success with a quality appearance and proper function in a timely fashion.
    (3) After slitting, the remaining machining was completed.

    Both projects were completed in about 15 minutes.

    Jerry Kieffer

    fullsizeoutput_3b4.jpeg fullsizeoutput_3af.jpeg fullsizeoutput_3c0.jpeg fullsizeoutput_3b2.jpeg fullsizeoutput_3bc.jpeg fullsizeoutput_3ac.jpeg
     
  2. shutterbug

    shutterbug Moderator
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    Thank you for your willing to share spirit, Jerry! Always educational. :thumb:
     
  3. Willie X

    Willie X Registered User

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    She must've had 'tea and cookies' ...
    Willie X
     
    Kevin W. likes this.
  4. Jerry Kieffer

    Jerry Kieffer Registered User
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    Willie
    No tea, but they were home made Chocolate Chip.

    Jerry Kieffer
     
  5. Jerry Kieffer

    Jerry Kieffer Registered User
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    Shutterbug
    Thanks for the kind words and your welcome, but some days you just need to get out of the shop.

    Jerry Kieffer
     
  6. bangster

    bangster Moderator
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    Good job, Jerry. :thumb::thumb:
     
  7. Willie X

    Willie X Registered User

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    Sometimes, you just gotta leave. Like when they start bringing in stuff like this! Willie X

    20190511_093222.jpg
     
  8. wow

    wow Registered User
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    Jerry, thanks for the great tutorial. I am building a new shop and planning to get set up so I can learn how to do more of these type jobs. I wish I lived closer to you.
    Will
     
  9. Jerry Kieffer

    Jerry Kieffer Registered User
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    Will
    On the other hand, you could come to Lathe class and we will get you up to speed in no time.

    Jerry Kieffer
     
  10. Rockin Ronnie

    Rockin Ronnie Registered User
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    This is helpful. I have a smaller lathe and only now beginning to explore its potential.

    Ron
     
  11. Jeff T

    Jeff T Registered User

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    Thanks for the info! The pics really help too
     
  12. RJSoftware

    RJSoftware Registered User

    Apr 15, 2005
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    Let me guess, 3 per each 5 minute section = 12 x 3 = 36-1(existing) = 35 missing star burst pointy things.
     
  13. Willie X

    Willie X Registered User

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    The only reason they left that one bottom 'ray' was that the 'D' cell had dripped acid into the wing nut at the bottom 'ray' and the wings broke off. I will repair that too and reuse the original hands.

    It's from a good customer that does not mind the cost. I usually give her a call anyway though. :) Willie X
     
  14. Kim Miller

    Kim Miller Registered User
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    Thanks for sharing Jerry. I always enjoy reading your informative posts.
     
  15. Allan Wolff

    Allan Wolff Moderator
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    Jerry,
    Thank you for sharing this process. Many great tips. I especially like the modified tool holder with boring bar holes.
    I found it interesting that you use a .015" end mill to cut the screw head slot since I can snap one of those tiny end mills just by looking at it. Is that your preferred method vs. a slitting saw like you used for the hand bushing or just more convenient for the setup at hand? The slitting saw would provide the same straight sides and flat bottom so I am curious to hear pros and cons of each method.
    Thanks again for the helpful information,
    Allan
     
  16. Jerry Kieffer

    Jerry Kieffer Registered User
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    Allen
    Great questions.

    While technically both methods produce the same result, real life tends to screw up everything.

    Using the Endmill to machine a screw slot.
    I really like this method where it is possible to use. It is very quick, accurate and assures perfection. All that is required is to mount stock in the tool holder, a endmill in the spindle and immediately turn hand wheels. The endmill assures the quality of the slot while the lathe is made responsible for centering the slot requiring no setup and virtually no skill other than not breaking the endmill. (The real life thing)
    When using a endmill, one must select what is required for the job while placing yourself at the greatest advantage. Endmills generally come in long, standard and stub length.
    In this case, for reasons of strength, I use stub length four flute endmills. The short stub flute greatly increases strength while the four flute adds additional material in flute area over two flute, again increasing strength. When purchasing endmills, it is important to closely observe specifications. The following is link to a .015" endmill showing specifications.

    TC54015 0.015" Micro End Mill 1.5xD Square End 4 Flute Uncoated

    One can see that this endmill only has a flute length of .023" that is ideal when a slot depth is in the .015"-.020" range as was the one shown in the original photo. It also helps when the Lathe used has Micro tool feed back that is a whole other issue by itself.

    Cutting screw slots with a slitting saw
    While cutting screw slots with a slitting saw can be done on the Lathe, it is a time consuming complicated setup. A more practical method is to mount the screw in a indexer in a milling machine. In this case I would machine and thread the screw in the Lathe and then transfer it to the indexer on the Mill. from there, the saw blade must be centered on the screw head and a cut taken. To assure centering, the indexer is rotated 180 degrees and another cut is taken. Slot width can be adjusted by adjusting the"Z" axis slightly on the Mill and retaking the two initial cuts This is where real life rears its head again. When thin slitting saws are mounted on arbors, they often warp slightly and do not run true. In this case, as the blade wobbles as it enters the screw head, it produces slightly wider slot on the ends than in the middle where it is stabilized by the metal it is cutting. The slot then sort of looks like my Mother in laws physique.
    However, this issue is easily corrected by machining a arbor that supports the blade minus the amount required to do whatever job is required. An example used for slotting screws can seen in the attached photo.

    While each method can produce identical results, I personally find the slitting saw less efficient but required in some cases.

    Jerry Kieffer

    DSCN2097.jpg
     
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  17. Kevin W.

    Kevin W. Registered User
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    I work at the Veritas Tools machine shop.
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    If only i had a shop and the time that same do, i am very envious of many here with the really nice shops and the machines they have. I work in a machine with some pretty cool machines, but sadly i dont get to operate many of them.
     
  18. Jerry Kieffer

    Jerry Kieffer Registered User
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    Kevin
    If you come to NAWCC class, we will let you operate machines all day long. Nothing is required, you just walk in, sit down and start to work.

    Jerry kieffer
     
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  19. Steve Gunsel

    Steve Gunsel Registered User
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    Kevin, sign up for one of Jerry's classes at NAWCC if you can. I did and really learned a lot and had a lot of fun. You will go home with confidence and the ability to operate a Sherline lathe and/or mill with surprising precision.
     
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