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Chuck Backing Plates - Threaded Spindle

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  • Chuck Backing Plates - Threaded Spindle

    What percent of thread engagement should be used on chuck backing plates for threaded spindles?

    I need to make one for the Atlas/Craftsman that is 1.5 - 8.

    Thanks, Ken

  • #2
    Short answer; I don't know. But the alignment is going to key off the counterbore and collar. I've made all mine (so far) so they spin up without too much fuss, class 3 maybe. Soon as it hits the unthreated part of the spindle nose, it takes a tommy bar to coax to the rest of the way to seat. I could be quite wrong about this, advice refunds available upon request.
    I'm here hoping to advancify my smartitude.

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    • #3
      I'm gonna agree, and say that they do not need to be a super fit, as long as the back plate bottoms out against the spindle boss. That will almost guarantee alignment every time.
      Arbo & Thor (The Junkyard Dog)

      Comment


      • #4
        Don't confuse "percent of thread" and "closeness of fit" (i.e. "class of thread"). They aren't the same thing. You could have a 50% thread that is a very close fit.

        Class of thread is, I think, more important in this context than percentage of thread, but like Argo and gizmo2, I don't think you need to worry over-much about it. Get a "good fit" on the threads and good uniform contact between the flat surface of the back of the plate and the spindle shoulder it bears against, and you'll be fine.
        ----------
        Try to make a living, not a killing. -- Utah Phillips
        Don't believe everything you know. -- Bumper sticker
        Everybody is ignorant, only on different subjects. -- Will Rogers
        There are lots of people who mistake their imagination for their memory. - Josh Billings
        Law of Logical Argument - Anything is possible if you don't know what you are talking about.
        Don't own anything you have to feed or paint. - Hood River Blackie

        Comment


        • #5
          back plate threads

          I made an Alu. face plate for a friend who bought a South Bend 10L with out a chuck. My lathe jumped out of gear and messes up the threads. I ended up cutting the sloppest threads of my life but when you tighten the face plate on the lathe everything works out just fine. I got a chuck off Ebay for him without a back plate. I told him he could use the face plate I made him to attach a backplate blank to and machine it to fit his new chuck. The next time I went over to his shop he was using the alu. face plate as a back plate for the chuck. He had attached his chuck the faceplate with four 3/8-16tpi socket head screws. He asked me what I thought and I said I did not think it would hold up but who knows. He said he would make a proper backplate out of steel when he found the time and the right size hunk of steel. Gary P. Hansen
          In memory of Marine Engineer Paul Miller who gave his life for his country 7-19-2010 Helmand Province, Afghanistan. Freedom is not free, it is paid for with blood.

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          • #6
            Thread gauge

            I should have added the best way to turn up a I.D. thread for a backplate is to first turn a O.D. that mathes your spindle and use it as a go-no go gauge when you thread your back plate. Gary P. Hansen
            In memory of Marine Engineer Paul Miller who gave his life for his country 7-19-2010 Helmand Province, Afghanistan. Freedom is not free, it is paid for with blood.

            Comment


            • #7
              Chuck adapter

              Ken:
              POI www.littlemachinshop.com hase 4" and 6" back plates pre machined for $20 and $30 respectfully not the best material and workmanship but not bad. buying the material will likely cost more .

              I just did up a couple with a 1'-16 thread from cast irion and the theads ar a little cleaner than the ones from littlemachineshop.com . I second Gary's suggestion of making a gage first also if your lead screw is an 8 pitch you do not need to wory about a thread dial.
              Ad maiorem dei gloriam - Ad vitam paramus

              Comment


              • #8
                Sorry folks- but I disagree!

                It is the register of the collar( for want of a better word) that matters.
                All the thread does is to mount and screw the chuck and then hold it in position- on the register.

                That's the way it works on my Myfords.

                Regards

                Norman

                Comment


                • #9
                  Here we go again..............................

                  Are you a Shiite, or a Sunni?
                  1601

                  Keep eye on ball.
                  Hashim Khan

                  Comment


                  • #10
                    It may be the way it works on Myfords, but my South Bend lathe doesn't have a registration collar...and it does fine.
                    ----------
                    Try to make a living, not a killing. -- Utah Phillips
                    Don't believe everything you know. -- Bumper sticker
                    Everybody is ignorant, only on different subjects. -- Will Rogers
                    There are lots of people who mistake their imagination for their memory. - Josh Billings
                    Law of Logical Argument - Anything is possible if you don't know what you are talking about.
                    Don't own anything you have to feed or paint. - Hood River Blackie

                    Comment


                    • #11
                      It has been thrashed over here before, and there are as many adherents to the value of the register for alignment as there are who feel it is of no value. Some manufacturers do not use a register at all.

                      There is a theory that the taper of the threads will force the backplate into center. I can neither prove or disprove this, but I am a register guy.

                      Rudy Kouhoupt and Frank McClean both stressed the importance of the register. Scott Logan has said it has no value, yet his website refers to Tony's website for directions in making faceplates. Tony's site stresses the importance of the register fit.

                      At any rate, the best advice I have found is to carefully make a stub spindle that matches the spindle of your lathe, and use that to get the best fit you can when making a backplate.

                      You will have the backplate and lathe for quite a while, and spending a few more minutes in making the best fit possible will not be wasted.

                      BTW, here's a link to Tony's website directions for making a backplate;
                      http://www.lathes.co.uk/latheparts/page7.html

                      And here is a link to FAQ's on the Logan site recommending fitting the register to match a Logan lathe. There appears to be some inconsistancy between Scott's advice here a few years ago and what their website offers;
                      http://www.lathe.com/faq/#_Toc95180275
                      Last edited by JCHannum; 04-25-2006, 10:40 AM.
                      Jim H.

                      Comment


                      • #12
                        Ken, Now look what you have done.

                        Bicker , bicker, bicker.

                        Comment


                        • #13
                          Wolfie!

                          As South Bends are bringing only آ£100 sterling- or two tanks of gas on the UK market, would you like to give an honest price of what these comedians are prattling about.

                          I have followed SGW's edict to the letter.
                          " Don't believe everything you know"

                          JT- do you really mean that instead of having one of my cars in the garage that I could have 300 South Bends instead.

                          Happy me

                          Norm

                          Comment


                          • #14
                            Thanks for all the tips and links. The A/C has a mounting face/flat on the spindle for back plate registration. Even with this registration, the original chuck seems to be a snug fit when installing over the threads. I've got a Bisson 6 1/4" that I want to use so I may just spend the $40-60 and buy one.

                            I'm wondering, other than the galling threat, why Tony prefers cast iron back plates over steel? The cast iron versions are cheaper but I can't see why they're better than a steel back plate. It seems the other way around.

                            Any opinions without kicking up more dust?

                            Comment


                            • #15
                              According to Tony's website; "At all costs avoid steel backplates; they will bruise or damage the spindle nose and, and if they become stuck, will be much more difficult to remove."
                              Jim H.

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