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Machining small valve spindles

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  • Machining small valve spindles

    I'm making some valve spindles for some small model globe type valves (PM Research if your familiar with those). The instructions don't mention any particular way to machine the spindle. The material is 303SS and I'm starting from 1/4" in dia rod. The issue is that the work sticks out from the chuck over 1.7" and the obvious deflection is making it difficult to complete the part. I've taken apart a few of these type of valves and I see no obvious center holes for possible holding with the tailstock center. A couple valves will have longer spindles. There is no mention as to whether to do the valve seat first or the handle side first. Obvioulsy trying to do it in a way that allows me to keep everything concentric. I'm looking for suggestions. It's funny, when searching around about making these valves nobody ever seems to mention any issues machining this part LOL... I think some decided to make the spindle from other material other than SS (bronze or brass).


    Looks similar to this guy here:



    Ken-

  • #2
    You can always make it longer, put a center in it and then after its done, just cutoff the excess. And the seating can be cut in the same chucking, just grind a form tool or even better, use the compound to feed in the proper angle. Using a parting tool to make an ending groove first helps.
    Amount of experience is in direct proportion to the value of broken equipment.

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    • #3
      You could use a female center -- chuck a small bit of rod in the tailstock drill chuck and run it into a small center drill held in a collet.

      I assume you know about extending the stock in stages ---- turn down, say, 1/4", then pull a bit more stock out and turn the next 1/4".
      ----------
      Try to make a living, not a killing. -- Utah Phillips
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      • #4
        There is no reason that you can't have a small center hole in the bottom of the disc. What you have there is a stem and disc made in one piece-valves do not have "spindles". In a globe valve the disc is a loose fit on the stem so that it can self align with the seat. How are you addressing this? It would work with an elastomer seat but otherwise the alignment of this part to the seat will be critical.

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        • #5
          I have made a couple of smaller versions of these valves. Jaakko F's procedure is roughly the way I accomplished the task. Sharp tooling and light cuts are the order of the day.

          They more closely resemble plug valves than globe, so TDM's post can be ignored.
          Jim H.

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          • #6
            small stuff like this is doable by two methods i've used (and there may be many more) that don't use a centre. You either keep extending the work out (what a swiss lathe does) and machining a bit OR start with larger stock where 1.7 inches isn't too much overhang. For the first, I like to turn a length down to some dimension then use a collet. The second is very versatile and you do some neat stuff - its one way to turn very small diameters of some length, say 1/16"

            if you can figure out how to use centres that makes it so much easier. if there can't be a centre hole in the finished product, have a sacrificial bit that gets machine off afterword.
            .

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            • #7
              Thanks for all the replies guys. Appreciate it. I tried again tonight and got much better results. Still sort of mystified as to have the disc at the chuck end or out in a center on the tailstock side. Tonight I just faced the stock, drilled small center and then cut the disc/valve angles. Then pulled out about 2" or so and held the end in a center. Was able to get everything done but doing those threads in the center is a bit dicey. Didn't think much about it at the time but I obviously can't get my die holder that far in on a rod that long. Looks like I'll have to single point them.

              Ken

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              • #8
                Originally posted by JCHannum View Post
                I have made a couple of smaller versions of these valves. Jaakko F's procedure is roughly the way I accomplished the task. Sharp tooling and light cuts are the order of the day.

                They more closely resemble plug valves than globe, so TDM's post can be ignored.
                You obviously don't know what a plug valve is.

                http://www.google.com/search?hl=en&s...tm%3B226%3B216

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                • #9
                  Actually I do. There are globe type with plugs rather than discs to provide a throttling function. These are also referred to as plug valves.
                  Jim H.

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                  • #10
                    I have made several PM research valves in both globe and angle style. No problems with seating and/or leaking. One is set up as a throttle for the engine.
                    Jim

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                    • #11
                      Can you make a box tool for it?

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                      • #12
                        LOL. Well I ended up making a jig so I could rechuck the work piece to do the threading. Valve body is 8-32 so is the spindle thread yet they don't actually fit. Is there a trick to taping brass and stainless? I allowed probably .010 under for fit. Tap runs into the brass fine. Die runs over the spindle fine. Spindle does not fit in threaded part of bonnet. Tap does run through die fine. Taped a scrap piece of steel with the die, doesn't fit.

                        Ken-

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                        • #13
                          If you have an adjustable split die it needs to be adjusted smaller.

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                          • #14
                            Originally posted by tdmidget
                            Can't have it both ways. I work on these things. Plug valves are plug valves. Globe valves are globe valves. Why be such an asshole when I only asked a legitimate question?
                            I have worked on a few of these things as well. What you are calling a plug valve is more properly termed a rotary plug valve. It, like a ball valve, is not used in throttling applications. Its primary application is on-off control of flow.

                            When it comes to throttling applications, globe style valves are used. These are loosely referred to as sliding stem valves as the valve stem operates in an up-down motion. There are three basic types: disc, which are used for on-off control and offer coarse control of flow; plug, which offer positive shutoff yet still provide finer control of flow than the disc and needle, which offer very fine control of flow but are not good for positive shutoff conditions.

                            The valve in question is a plug style and in the small size, a floating plug is not needed. The tapered plug, machined concentrically with the stem, will seat in the tapered seat of the valve body if reasonable care is taken in its construction. These are model valves for low pressure applications and are used primarily for flow control to control the speed of the model. There is usually a primary shut off valve on the supply line so there is no real concern that the valve be capable of going to full shutoff condition.
                            Jim H.

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                            • #15
                              Well it turns out there is an issue with, from what I can tell, the die. If I cut an 8-32 thread on a shaft with the die I have and then tap an 8-32 hole, the die cut thread will not enter that hole. If I grab a commercial 8-32 screw it goes fine in the taped hole. Adjusting the adjustable die doesn't make difference in it's ability to size the thread.

                              The hilarious part of this story is that originally I had a marked 8-32 die, "made in USA" that doesn't cut 8-32 threads. I don't know what it cuts but it's not 8-32. I believe it's 6-32. So I bought another 8-32 die and I just confirmed that it won't cut an 8-32 thread either LOL. You gotta love it.

                              Ken-

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