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Clausing compound screw threads.

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  • #16
    The compound on my 5914 advances .100 per revolution. The dial has 200 increments.

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    • #17
      Ideally one should have a gear tooth vernier caliper handy but there's a simple (and a whole lot less exensive) way to check the wear of your Acme lead screws.

      Most wear occurs in the part of the screw that sees the most use (duh!) and the very ends see little. There's a way of checking Acme screws by the "best rire size" where a gage wire (straight shank of a drill, dowel pin etc) is selected to fiit in the thread space so it's flush with the thread OD. Rummage in your drill set for a best wire size at the un-worn portion of the thread and again at the worn portion. Work the math if you wish but you don't need to.

      Use the un-worn best wire size as a gage to chase the thread of the new screw. Make the thread of the new screw to to comply with the tooth space of the unworn part of the screw. Cut the thread with 2" of extra length. Part it off for use as a gage when boring the threads of the nut.

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      • #18
        Both dials on my 5913 read .200. The threads on the original screws are ground. When I replaced the cross slide screw the first thing I noticed was the threads were turned......... cheaper version I guess. I find it hard to believe that the compound screw is worn unless the slide was over tightened and used a lot. I don't believe that either screw are standard ACME thread pitches. I would double check the thrust bearing behind the dial and the associated parts.

        JL.....................

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        • #19
          Realistically, the direction and pitch of the thread make little difference in the grand scheme of things here. If you want to be picky and have it like new again, cut yourself a nut and a screw to match. You could always just convert it from whatever it is now to direct reading on the dial and a standard acme thread.

          As others have said, be sure to confirm both the thrust bearing and gibs are adjusted properly.
          Last edited by justanengineer; 10-25-2012, 11:31 AM.
          "I am, and ever will be, a white-socks, pocket-protector, nerdy engineer -- born under the second law of thermodynamics, steeped in the steam tables, in love with free-body diagrams, transformed by Laplace, and propelled by compressible flow."

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          • #20
            Hmmm, The Top-slide usually has a right-hand thread (the nut stays still while the handle and screw move) . Cross-slides and tail-stocks are usually LH (the nut moves)

            If the TS dial has .200" marking it would suggest the original screw had a .200" lead so was either a single start .2" pitch or a two start .1" -

            I wonder if, as speculated above, someone has replaced a two start screw thinking it was a 0.1" single start? If not perhaps the screw is not ACME , i.e. could it be a square thread or, if metric, trapezoidal ?

            Bill
            Last edited by BillTodd; 10-25-2012, 09:57 AM.

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            • #21
              Is there any possibility that this is a STUB ACME thread? The pitch will be the same, but it sure wont fit the nut!
              Duffy, Gatineau, Quebec

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              • #22
                Duffy: that is what I was beginning to wonder too...

                "jayhawkman" on PM at one time sold a repair kit, with a 4" chunk of 4140 round and a 4" length of 3/8" - 10 precision acme" for this model of lathe, so I assume those are correct sizes (thread and diameter, no mention of number of starts))

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                • #23
                  Colchesters have a dial that reads diameter. So a 3/8x10 compound screw will advance 0.100 per revolution but take 0.200 off the diameter. You must ignore the dial when you measure the pitch of the screw. Put a gauge on the compound, and rotate the dial until you have a handle on what's going on.

                  Colchester Bantams, as JS observed above, also use a two-start on the compound. This would mean that the profile of the thread would conform to a 5 tpi thread.
                  Richard - SW London, UK, EU.

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                  • #24
                    For now don`t worry about the dial . Lay the screw on a bench next to a steel rule and count the threads on the original screw are use a regular thread pitch gage . Try 10 threads per inch first . I bet it is 5 threads per inch with 200 on the dial.also mike the diameter in a few of the unworn places. The neet think about a acme thread is they are NOT necessarily a specif fractional size . The screw on my lathe is a 5 pitch screw but is .540 diameter not .500 as you would think. Try the measurement thing and check back.
                    Every Mans Work Is A Portrait of Him Self
                    http://sites.google.com/site/machinistsite/TWO-BUDDIES
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                    • #25
                      Thanks for the replies. It a 10tpi screw. The dial also has .200" for one rev. At least someone confirmed that there slide only moves .100" for every rev and there dial also has .200" on it. That clears up one thing, that it is the correct thread pitch and a single start screw, although I still find it odd that the compound has this. I am also wondering now if the threaded rod that was sent from McMaster is a stub acme thread, that would make some sense. Here is a pic of the old screw next to the new rod.



                      As far as making a acetel nut using Evans method, how would you go about making a nut like this. I was thinking of making a nut out of some crs but instead of threading just make a straight bore then doing a slight press of the molded acetel nut into it then putting a roll pin through to hold it in place. Any other ideas.

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                      • #26
                        Originally posted by oxford View Post

                        As far as making a acetel nut using Evans method, how would you go about making a nut like this. I was thinking of making a nut out of some crs but instead of threading just make a straight bore then doing a slight press of the molded acetel nut into it then putting a roll pin through to hold it in place. Any other ideas.

                        Don't know if parts for your Clausing are interchangeable with an Atlas 12"... if this one is:



                        ...you can get it at Tools4Cheap here: http://www.tools4cheap.net/proddetai...nutatlas12comp

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                        • #27
                          Originally posted by oxford View Post
                          Thanks for the replies. It a 10tpi screw. The dial also has .200" for one rev. At least someone confirmed that there slide only moves .100" for every rev and there dial also has .200" on it. That clears up one thing, that it is the correct thread pitch and a single start screw, although I still find it odd that the compound has this. I am also wondering now if the threaded rod that was sent from McMaster is a stub acme thread, that would make some sense. Here is a pic of the old screw next to the new rod.
                          well its not a two start and its going the right direction.....

                          maybe Duffy nailed it....that bottom one doesn't look deep enough. Have you measured it? The depth of the acme should be half the pitch, much less for the stub, ie minor diameter should be P (pitch) smaller than major

                          If they sent you the wrong one, get it replaced.

                          if measurement shows its not a stub, measure with thread wires and check machinery's handbook.....if its within tolerance it'll fit. Do the same at the end (unworn section) of the original.....there's only so many things that could be wrong and they are easily checked.

                          The nut basically doesn't matter for accuracy or anything else....might be easiest just to use the original if you can get the right screw
                          Last edited by Mcgyver; 10-26-2012, 08:55 AM.
                          in Toronto Ontario - where are you?

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                          • #28
                            I wouldn't make the nut out of any plastic type material, simple reason being it's too soft and will give too much under a load.
                            Especially since that nut extends about an inch below the bottom of the slide. You know it's going to give.

                            If I was dead set on making one I would use bronze or brass. You could try making a tap out of the ACME rod by turning a taper on it and then slotting the taper and relieving one side of it a bit. In other words you would almost be making a self tapping screw out of the ACME rod. That may do some cutting in soft material.

                            JL................

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                            • #29
                              Originally posted by JoeLee View Post

                              If I was dead set on making one I would use bronze or brass. You could try making a tap out of the ACME rod by turning a taper on it and then slotting the taper and relieving one side of it a bit. In other words you would almost be making a self tapping screw out of the ACME rod. That may do some cutting in soft material.

                              JL................
                              That was my original plan. I figured that the original screw must have a little but of wear and using a piece of new rod to make a tap would cut the threads with a little interference so it would work good on the old screw. Then when the rod showed up and was different from the old one is where things went down hill. I will have to try and measure the new screw and find out if it is speced for regular 3/8-10 acme threads.

                              I could always make a new nut with the new rod and then put a piece or the rod onto the old screw, but for that much work I think I would be better off finding some 2 start acme so I can get the slide movement to equal what the dial reads. Anyone have a short piece of 3/8-10 RH 2 start acme rod they want to part with.

                              I am seeing this going back together with the old nut and screw for a while untill I can get things sorted out.

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                              • #30
                                Looking carefully at the compound screw and the screw beneath, it appears they are not the same pitch. There's almost a half pitch difference in 29 threads. Doesn't that suggest the compound thread pitch is 2.5mm?

                                (2.54 -2.5)X29 = 1.16mm = .046", roughly 1/2 pitch.

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