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Pratt and Whitney Model C Cross Slide Nut

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  • Pratt and Whitney Model C Cross Slide Nut

    Is there anyone here who has a Model C to check or have had the nut out on there lathe?

    I am taking the cross slide off and I have everything out of the assembly, screw, front bearing handle support etc. and the rear bearing assembly. Gib is out also.

    The carriage casting is closed front and rear preventing simply sliding it out. The nut has to be removed. It is retained by a large cheese head screw (an inch in diameter at the head). There appeared to be a tapered dowel pin throught the nut and screw perpendicular to the screw but the parts manual shows a dowel in a blind hole in the cross section. Possibly a stop pin? The manual only shows it but has no part number or description.

    I have ordered a large 1/2 inch drive drag link socket to attempt the screw this weekend and I am borrowing an impact driver.


    Has anyone on the forum been into this situation??

  • #2
    [QUOTE=conant;915247]Is there anyone here who has a Model C to check or have had the nut out on there lathe?
    QUOTE]

    Are you talking about the type 3C lathe from the 1940's? http://www.lathes.co.uk/pratt%26whitney/index.html shows the one in question. The construction of the cross slides on these were all similar, but different. If you can post a pix....?

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    • #3
      I am sorry. It is the 16x54 Model C...........1944 manufacture date.
      You can see what I am talking about on page 26 of the manual.
      http://www.rgr8family.com/Manuals/P&W_Mod_C_Parts.pdf

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      • #4
        I think asking about a P&W lathe here is like pissing in the wind.... You question will likely get an answer from another P&W owner on the Antique Machinery formum of Practical Machinist.

        Comment


        • #5
          I have had no luck over their thus far. I have PMed a few with the same machine as well.

          I guess ultimately I will know by hands on. I am just trying to prevent doing the wrong thing. The parts manual creates a lot of questions. I guess I am thankfull I do have the original manuals however. Interesting stepping back into time.

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          • #6
            Originally posted by conant View Post
            The parts manual creates a lot of questions. I guess I am thankfull I do have the original manuals however. Interesting stepping back into time.
            I can see your confusion with respect to what appears to be a pin in a blind hole, but it doesn't appear to have much to do with the retaining screw. I would have guessed it to be an alignment pin from the drawing, but unless there is a line missing in the drawing, it doesn't appear to engage with anything. The drawing does show the big screw to be a right hand thread, which is good to know.
            Let us know how it comes out.

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            • #7
              Thanks for looking at the figure and sharing your thought. Good call on the thread lead. Two heads ARE better than one. I hadn't thought to consider it being anything but a right hand thread. It is good to know as you pointed out.

              I see a great deal of detail on the pin drawn there representing a short dowel in a blind hole. Of course the view doesn't allow the rear pin to be visible.

              I am trying the large drag link socket this weekend.
              Last edited by conant; 04-17-2014, 11:46 PM.

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              • #8
                Originally posted by conant View Post
                I have had no luck over their thus far. I have PMed a few with the same machine as well.
                Did you PM members that had current posts? Like JonOder? Not everyone checks their mailbox. Might be bette to post in a P&W lathe thread, even an old one.

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                • #9
                  JonOder did reply to the best of his knowledge. I should be able to try the drag link socket tommorow afternoon and hopefuly it just un -screws. I have had it soaking with penetrating oil since Monday and it seemed to seep around the screw head so maybe into the threads as well.

                  News tommorow.

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                  • #10
                    You can try to send Froneck a message on the PM board. He got my P&W 16c, and I know he was doing a lot of cleaning and any needed repairs on it. I am not sure if he had any of that section apart or not. I believe it was newer than your since the headstock was more square but that section should be the same.
                    Last edited by oxford; 04-18-2014, 11:26 PM.

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                    • #11
                      Originally posted by conant View Post
                      Is
                      I have ordered a large 1/2 inch drive drag link socket to attempt the screw this weekend and
                      I am borrowing an impact driver.


                      Has anyone on the forum been into this situation??
                      I am borrowing an impact driver>>>>
                      Bad Idea !
                      Never use power on an unknown application.
                      Researching 1st like you're doing.
                      2nd Proding and poking.
                      3rd if needed a Rethink !
                      4th You'll get it.
                      ==========
                      You are talking about fig 22 right?
                      Screw no. 39
                      in nut # 40 ?
                      Last edited by Old Hat; 04-19-2014, 12:35 AM.

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                      • #12
                        Correct. Screw 39 nut 40. Mostly the drag link socket is about the best choice to drive the screw with and I will proceed with caution. I will try by hand first then air impact on low.

                        Most of the problem removing is getting a grip on the screw.

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                        • #13
                          Originally posted by conant View Post
                          .

                          Most of the problem removing is getting a grip on the screw.
                          Perpendicular hold and steady axial downforce come at a premium.
                          Once the slot is deformed it's a chiZel job.
                          Best wishes!

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                          • #14
                            Got the drag link sockets and they worked great. A couple of bumps on the trigger of the air impact set on low and it came right loose. I had to grind the thickness down about .015 and it was a firm tap fit into the slot. The sockets are Proto from Zoro tools. The smaller one was for the cheese head screws in the flat way retainers on the rear of the carriage. Worked great and no grinding to size for fit.

                            The pins are in blind holes and evidently act as stop pins.

                            I hope this helps someone else someday.

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