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Making Acetal leadscrew nuts the easy way

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  • Evan or anybody else...

    I see that you need to turn these to be round after they are formed, but how you do mount them? The couple I am thinking of fixing all are round on the top and flat on the bottom with enough material for a screw into the bottom. Cant achieve that with a round nut...

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    • Make them round so you have a concentric diameter to work with and then mill flats. There is no rule that prevents starting a with a larger diameter chunk of acetal than I did.
      Free software for calculating bolt circles and similar: Click Here

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      • I think I want to attempt this to fix my super awesome chinese project which may indeed someday become a lathe...

        Where are ya'll getting the leadscrews to grind down to make a "tap" Ive been looking for a tap and I havent had much luck finding spare rod, or a tap in my size 5/8-10 acme. Roton has the screw, but you have to buy 60 bucks minimum from them.

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        • Originally posted by Socko124
          I think I want to attempt this to fix my super awesome chinese project which may indeed someday become a lathe...

          Where are ya'll getting the leadscrews to grind down to make a "tap" Ive been looking for a tap and I havent had much luck finding spare rod, or a tap in my size 5/8-10 acme. Roton has the screw, but you have to buy 60 bucks minimum from them.
          McMaster-Carr has 1018 carbon steel Left Handed 5/8"-10 precision acme screws for just over $45 for a 3' piece. http://www.mcmaster.com/#catalog/117/1093/=b8n97s (just over $66 if you need 4140 steel)

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          • Originally posted by Socko124
            I think I want to attempt this to fix my super awesome chinese project which may indeed someday become a lathe...

            Where are ya'll getting the leadscrews to grind down to make a "tap" Ive been looking for a tap and I havent had much luck finding spare rod, or a tap in my size 5/8-10 acme. Roton has the screw, but you have to buy 60 bucks minimum from them.
            Use the lead screw you got.....Custom fit

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            • What are the chances that I could do the half nuts on half at a time. I know I would have to clean it up with a mill, but my leadscrew is an older one with a slot for keyed feed.

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              • Just guessing here but you may be able to fill in the slot with something solder, JBweld, Bondo, Bisquick... and use a nut (or half nut) you have as a mold to help form the full thread and use the filled in section to make the Acetal nut.
                maybe the biggest worry would be uneven heat flow if you used something non metallic for the filler.
                using something you could dig/melt out of the slot later would be good too
                --
                Tom C
                ... nice weather eh?

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                • Half nuts one at a time- why not? Drill a hole the diameter of the leadscrew in some scrap, then saw that piece in half. Now you have two half nuts with no threads, basically. Use one to press the heated leadscrew into the acetal, which could be held within a frame with cutouts for the leadscrew to nest into for alignment purposes. After you've made two pieces, put them together around the leadscrew to align them for trimming.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                  • lead screw nuts in 30 seconds



                    Hi
                    Thanks to Evan I finally got around to making a lead screw and nut for an ageing Union T & C Grinder and thought I should share the method used.

                    Cut the lead screw with ACME half inch by 10 RH thread from FCMS but with an additional 2 inches length on the thread which was parted off and drilled to take a heater glow plug to make a “Hot Tap”. A nose of hole dia. is formed on the hot tap. Glow plugs are used to aid starting of diesel engines.

                    Two flats were milled on the hot tap to take a small spanner which is held by hand and used to “feel” how soft the synthetic material is as hot tap is being screwed in.

                    The set up on a lathe is: 4 jaw chuck, nut drilled to lead screw dia. less one thread thickness, "hot tap" with glow plug inserted and connected to a basic 12Volt battery charger, push piece with hole mounted on lathe tool post and on lathe centreline.

                    Procedure is: Setup 10 TPI on lathe and very slow spindle speed, switch on Battery charger and wait (seconds) until "hot tap" is hot, engage thread lead screw on lathe and insert "hot tap in prepared hole(approx 10 turns in my case), switch off battery charger and allow to cool.

                    There is no attempt at precision before or during the nut thread forming process. Precision is achieved after a satisfactory nut is threaded by inserting the lead screw and aligning screw/nut combination on lathe or mill and machining as necessary.

                    I did plenty of practice runs on scrap pieces on synthetic materials (don't know what they are because origin is scrap yards). With practice, this procedure takes less than 30 seconds any longer and the hot tap overheats. I believe the final nut selected to be toughnol.

                    Battery charger shows 4 amps with this glow plug. Plug goes red literally in seconds. This is much too hot for synthetic material but with hot tap outer sheath and limited time some temperature control can be affected.

                    Others have mentioned that nuts are tight and this was my experience. I used a hand held drill to “run in” the practice and final nut.

                    Failures were due in one case to overheating the hot tap and in one case to overheating during the “running in” process.

                    I intend to make a cross feed lead screw and nut for my lathe will use this method. May use a slice of the nut material set on the hot tap to give an indication (it melts) of when to insert the hot tap.

                    Photos are attached and questions welcome. Trust this explanation is sufficient.

                    The T&C Grinder is now a delight to use.

                    Cheers
                    Paul

                    Comment


                    • Nut static strength:

                      If I may repost what Evan had posted for the strength for these nuts, he states that for a half inch it is 650 lbs and I went 5/8 so im pretty sure they will be good for my small mill.
                      Just wanted to bring this back up as every time i reread this subject i pick up something new and this point is one to really consider when deciding to or not to use this material.

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                      • lead screw nut in 30 seconds!!

                        Apologies for earlier post. Photos were not properly attached



                        Hi
                        Thanks to Evan I finally got around to making a lead screw and nut for an ageing Union T & C Grinder and thought I should share the method used.

                        Cut the lead screw with ACME half inch by 10 RH thread from FCMS but with an additional 2 inches length on the thread which was parted off and drilled to take a heater glow plug to make a “Hot Tap”. A nose of hole dia. is formed on the hot tap. Glow plugs are used to aid starting of diesel engines.

                        Two flats were milled on the hot tap to take a small spanner which is held by hand and used to “feel” how soft the synthetic material is as hot tap is being screwed in.

                        The set up on a lathe is: 4 jaw chuck, nut drilled to lead screw dia. less one thread thickness, "hot tap" with glow plug inserted and connected to a basic 12Volt battery charger, push piece with hole mounted on lathe tool post and on lathe centreline.

                        Procedure is: Setup 10 TPI on lathe and very slow spindle speed, switch on Battery charger and wait (seconds) until "hot tap" is hot, engage thread lead screw on lathe and insert "hot tap in prepared hole(approx 10 turns in my case), switch off battery charger and allow to cool.

                        There is no attempt at precision before or during the nut thread forming process. Precision is achieved after a satisfactory nut is threaded by inserting the lead screw and aligning screw/nut combination on lathe or mill and machining as necessary.

                        I did plenty of practice runs on scrap pieces on synthetic materials (don't know what they are because origin is scrap yards). With practice, this procedure takes less than 30 seconds any longer and the hot tap overheats. I believe the final nut selected to be toughnol.

                        Battery charger shows 4 amps with this glow plug. Plug goes red literally in seconds. This is much too hot for synthetic material but with hot tap outer sheath and limited time some temperature control can be affected.

                        Others have mentioned that nuts are tight and this was my experience. I used a hand held drill to “run in” the practice and final nut.

                        Failures were due in one case to overheating the hot tap and in one case to overheating during the “running in” process.

                        I intend to make a cross feed lead screw and nut for my lathe will use this method. May use a slice of the nut material set on the hot tap to give an indication (it melts) of when to insert the hot tap.

                        Photos are attached and questions welcome. Trust this explanation is sufficient.

                        The T&C Grinder is now a delight to use.

                        Cheers
                        Paul

                        Comment


                        • That is an excellent idea. The same thing could be accomplished using a soldering iron element. However, using only 12 volts is a lot safer.
                          Free software for calculating bolt circles and similar: Click Here

                          Comment


                          • Firstly, many thanks to Evan and crew for developing and documenting this slick way to make acetal nuts. I'm doing a CNC retrofit on a Clausing 5914 lathe and this looks like a great way to make zero lash nuts for it.

                            I'm working on the cross-slide nut first and room for it is tight so I'm going to try a slightly different approach where I machine a split housing that will be filled with acetal "blanks" with the whole assembly molded around the nut.

                            Here's what the stock nut looks like:



                            It mounts by a set screw that clamps the round stud. Its a flexible design as it can rotate to set the x-y plane right and also be moved up or down get its Z plane setting right. This flexibility in the mounting method should make it easier to get the acetal version aligned.

                            Here's the top half of the housing, I'm planning to machine it out of brass. There will be a bottom shell that is the same as this part minus the mounting stud. Four 6-32 screws in the corners clamp the two shells together.



                            I plan to fill the halves with 2 acetal blanks, with the correctly undersized clearance half-round grooves machined in to them, then use the 6-32 screws to clamp the halves together as the screw is heated.

                            Does anyone see any problems with this or have any tips on making it work out?

                            Did any of the efforts to coat the screw with graphite or moly or any other substance work out for anyone?

                            Thanks,

                            Paul T.
                            Last edited by PaulT; 05-17-2012, 05:29 PM.

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                            • Seems to me the easy way would be to drill and tap it. This is the cheap way.

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                              • Forrest, thanks for the suggestion but keep in mind I need to make a zero backlash nut.

                                Drilling and tapping a new nut will take me around in a circle, I already have a standard nut for the cross slide, it works fine but has around 0.010" of backlash, probably about what I would get with a tapped nut.

                                Also Acme thread taps aren't cheap. Your looking at over $150. for a left hand thread 5/8"-10 Acme tap.

                                The acetal method takes some labor but its way cheaper in hard costs than that tap.

                                Paul T.

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