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  1. #1
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    Default Spindle Thread Size

    Good Morning,

    Rookie here.

    I have no Mechanical Engineering education, but a little practical skill.

    I have recently acquired an old (1933) Walker-Turner lathe, and need to determine the spindle thread size in order to obtain an adapter to a more standard thread. I am pretty sure the spindle is 1/2-inch diameter. Couple questions:

    1. What is the easiest way to determine the thread size (I tried purchasing 1/2-inch, fine threaded bolt, but no go)?

    2. Research says that 1/2-inch taps are available in TPI's of 24, 27, and 28. Are bolts or nuts also available in these? I would prefer to purchase a bolt or nut to verify the thread before moving on.

    3. I am considering transitioning to a 1"-8 TPI spindle by obtaining a 1"-8TPI Bolt and having the hex head drilled and tapped to match the existing spindle geometry. Thoughts? Is this something that can be done on a drill press, or is a metal lathe required?

    Thanks a lot for pandering to the rookie. I am sure more questions will arise in my journey.

    Thanks and have a great weekend,

    Greg

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    The owner/founder of PM envisioned this site as a resource for industrial woodworking and high end woodworkers.
    So there is no initiative to cater to low end machines or newbies. Most of the posters on this site are machinists first, woodworkers second, though there are a smattering of us. Including the founder of Practical Machinist, who started as a woodworker making high end antiques, then invented some familiar popular tools including the dovetail jig bought and now sold by Porter Cable. Coincidental to the point of your post, he then invented a line of drill & tap machines sold worldwide. Maybe you will be the next to segue into heavy metal work?

    Per initiative, things have gone to heck in a handbasket, few post pictures or post any sort of work let alone "high end" or production, so i'm at least temporarily working with what shows up at the door.

    To answer your Q: 1/2" (If that is the spindle size? Seems ridiculously wimpy? Where are your pics?) is typically threaded either 20TPI or 13 TPI AFA common fasteners go.

    Your plan would work fine, so long as everything is concentric. It is unlikely that you will attain that with a DP. It could be attainable with a metal working engine lathe, a 4 jaw chuck, and a Dial Test Indicator (DTI) to set up the OD running concentrically with the centerline of the part. Then you would center drill, drill undersize, and bore to the minor diameter. Then you would single point thread it using the lathes gearing and half-nut feed.

    You might get close doing all of the above including boring the minor diameter on the higher side tolerance, and then tapping with a tap centered by the tail stock. But chucks mounted on it would probably wobble.

    Once you have access to a metal lathe, the better plan would be to use a short bar of good material such as 4140 prehard. Do all the ops in one set up, never removing the work until it is complete. Turn and thread the OD to a gage. Then drill/bore/thread the ID to your spindle removed from the lathe, or a good proxy or gage.

    Many of us here do this type thing routinely. You can too.

    smt

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    Thanks for the insight.

    Hope I did not step on any toes, or bother too many members.

    Attached are a couple photos of the lathe. Note that the wimpy spindle is solid, unlike a number of others I've seen. Don't have access to a metal lathe to do myself. I'll see about finding a local tool/machinist and see what we can work out. Biggest issue is finding one that will do something this small, or have any interest in a single piece.

    Thanks again for the help,

    Greg
    Attached Thumbnails Attached Thumbnails lathe.jpg   spindle.jpg  

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    The spindle does look small for mounting a chuck, say. But you should be able to do decent work between centers with it. Fine work all over the world has been done with less.

    Most work on lathes like that should be done between centers. The face plate can drive tail dogs.
    It is also useful for turning things like small bowls.
    Large bowls might be less advisable.

    How did you decide it was 1/2"?
    Do you have any vernier/dial/digital calipers?
    If a 1/2" - 20 nut will not start, maybe it is 9/16" - 18 thread? Or even 5/8"? really hard to tell from a photo.

    It certainly looks to be fine thread.

    If a 1/2" -20 nut starts but jams, then it probably is an oddball thread. I think 1/2-24 was sometimes used for woodworking equipment.

    Do you have a drill press?
    Your idea could be made to work, but the concept is fraught with potential for mayhem.

    Figure out what size the thread on the spindle is, and what size you want to make the OD
    & report back. Many of us started out doing bodges to facilitate work on we wanted to do on questionable machines with questionable resources. Just be safe.

    I think there is a guy on OWWM that does such jobs, and there may have been someone on here. If you are clear about your dimensions, and whether there are other features like a shoulder to be included, you might get a quote.

    smt

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    Have you measured the pitch?

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    Thread pitch gages are not expensive

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    I measure the diameter, thread length, and counted the threads and came up with the following:

    Diameter - 0.500 inch
    Thread Length = 0.705 inch
    Threads = 16
    Calculated TPI = 22.7
    Speculated pitch = 24 TPI

    I think I would like to transition to 1"-8. Did a bit of searching online, but no go. There are adapters to go to a 5/8-inch, but that does not help a whole lot. I was considering trying to make one myself, but after buying the 1/2-24 tap, and material, I would hate to have an unmanageable wobble. My thoughts for a base stock has moved to aluminum for easier machining over steel, but I am having some issues finding a 1"-8 bolt or 1"-8 threaded rod. Unless a simple solution rises to the top. I may be left with working between the centers only, or tieing a rope on the whole thing and using it as an anchor .

    Greg

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    If you attained a 1"-8 OD, what do you hope to mount on it?
    Is the current face plate essentially wobble free?
    Do you have a drill press? What size/type?

    If you were not planning to work between centers, what type of work would you like to be able to do on the lathe?

    smt

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    If I were to attain a 1"-8 OD, I would mount a small chuck for bowl work.

    I have not used the face plate yet as the lathe is currently in "clean-up", but will give it a spin and report back.

    I do have a drill press.

    I would appreciate the ability to do both spindle work and a chuck work. I truly do not envision tossing the lathe if the adapter idea does not work out, but would like the flexibility if it does not come at a huge cost.

    Greg

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    A faceplate is superior to a jaw chuck for bowl work, especially on a lathe with a small diameter spindle.
    That spindle is your limiting factor before things bend or break.
    A chuck extends multiples of the thread length increment out from the bearings, and applies that multiple to the bending forces on it, for the same cutting force.

    Another advantage of the faceplate is that you can make the sacrificial wooden (or plastic) pot or plug chuck any size or configuration necessary to the task.

    From the time the lathe was invented until maybe a couple decades ago when some clever operators figured out they could create a whole industry selling complex jewelry to aspirational turners, almost all work was done between centers & on faceplates with quick, purpose made fixturing.

    A lathe with the spindle that small will probably require the TS to be used for all but finishing cuts either way. My (Chemist) dad used to turn goblets for relaxation at times, on a lathe about like yours. Between centers. A stem was left in the bowl of the goblet until it was nearly complete, then snapped out on completion when the goblet was removed.
    To hollow the bottom after cutting it off, the bowl of the goblet was reversed into a quickly turned pot chuck on the face plate (automatically centering it) & the TS brought up to center the foot. Which could then be faced and hollowed to all but a point in the center. Gouged or sanded out after removal.

    There's nothing wrong with "tooling up" your lathe. But a chuck will probably not make it better and might make it worse. With the inherent size of the spindle, it would be advisable to use the TS for all but the lightest finish cuts and sanding. Or small pieces like maybe chess men, e.g. Any work you can imagine inserting into a bought metal scroll chuck can just as easily be held by "older methods". Many things that won't easily work in a scroll chuck can be finessed by those older methods.

    I can think of a way for you to make your adaptor out of a 1" bolt on your DP with some chance of success, but this is enough typing for now.

    smt

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    Afternoon,

    Given you voice of reason, and experience, I am going to move on with what I have. If down the line, I am not satisfied with a face plate and TS, and any other home-crafted fixtures I may find, I may revisit this.

    I appreciate all of your insight, and thought on the subject

    Thanks again,

    Greg


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