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  • #16
    Originally posted by Carld
    If you thread at 150 rpm you better have very fast reflexes and very good hand eye coordination.
    Or a Hardinge

    I love threading on the HLV-H at work. I just wish it cut metric.

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    • #17
      What rpm do you use when you hand tap. Turning the chuck by hand gives you full control all the way to the shoulder.

      Phil

      Originally posted by Deus Machina
      Alright, I know it varies, but I need a general number.

      My 10x22 lathe has a six preset speeds, the minimum is 150 RPM, and I'm wanting to avoid tinkering with the electric bits. I may decide to go that route, but I think if I instead gear it down (using the tensioner as a place for new gears) through two short belts instead of one long one, I could cut it down to, say, 50.

      I can never remember--is it diameter or circumference of a pulley that affects the ratio?

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      • #18
        Originally posted by Mcgyver
        doesn't take that much practice to get good at it; split second timing like a race car driver lol.
        Yea, It really is.. Intresting. Gotta throw the lever at the exact right second or it crashs as it hits the shoulder.

        Of course, Some lathes don't really care about crashs... Like the day I was threading *away* from a shoulder with my tool upside down... Normaly you put the lathe into.. reverse.. Well, I kinda forgot that point... was a 0.3" or so change in diamiter at the shoulder from the runout groove... in aluminum.. I accidently put the lathe into forward and hit the half nut lever... It *displaced* about 4 threads before I managed to stop it and retract the tool. Good thing the back of my threading tool was ground with lots of clearance making a very sharp edge on the bottom. Intrestingly, the vallys of the thread looked pertty good. Especialy for just 1 pass! The crests however.. Where totaly screwed up, nasty gnarly edges.. And where now about 0.1" higher then the origional OD of the metal Total displacement threading, No cutting at all.
        Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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        • #19
          I threaded a 5/8-10 LH acme @ 210 rpm recently, no issues. All my lay-down carbide threading inserts prefer it that way. If I'm a little chicken to thread toward a shoulder, I use an upside down (drophead) toolholder and thread away from the shoulder.

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          • #20
            You can use a normal toolholder to thread upside down with most QCTP, there is enough adjustment range to put an upside down tool on center.

            The issue becomes with the clearance of the bit. A standard threading bit that has most of the clearance on the left, Will have it on the right when upside down. So you need an opposite clearance.
            Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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            • #21
              I used to thread the last bit by hand on my mini, but it's tough to get a good grip on a 6.5" chuck.

              I think I figured out where I can mount the new pulleys, too. I'll have to take some measurements on how much I can cram into the gearbox and what sizes my local tool place has, and go from there.

              The gearbox does have a swinging door to let long stock hang free, and a threaded portion at that part of the spindle... I could mak an adapter and find a nice handwheel, have a friend weld them together.

              Or use is as an excuse to buy a welder.

              Edit: A lot of my threading involved moving up to a shoulder, too. Thankfully, most of the rest involved moving up to an O-ring groove, which turns out to be slightly smaller than the minor diameter. If I have to thread to a shoulder and have the choice, I cut and chamber a small groove just a hair deeper than the minor diameter. Makes things easier and looks neater.
              Last edited by Deus Machina; 03-24-2011, 12:09 AM.

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              • #22
                Originally posted by Black_Moons
                You can use a normal toolholder to thread upside down with most QCTP, there is enough adjustment range to put an upside down tool on center.
                True, but I nailed those holders for under $25 each on Ebay. My QCTP accepts 1" shank holders, so this is all in preparation for a slant bed CNC lathe one day.

                The issue becomes with the clearance of the bit. A standard threading bit that has most of the clearance on the left, Will have it on the right when upside down. So you need an opposite clearance.
                The white boxes in the lower right corner of the photo are the complete set of anvils to cover nearly any helix angle for the threading inserts, including left-hand threads. However, I think you might be mistaken in one respect. When you take a standard tool and flip it upside down, you are effectively reversing the clearance angles along with it. This is OK and the way you want it because the threading being made in the opposite direction needs the clearance angle that way.

                Maybe it's me who can't turn my head around to see it the right way.

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                • #23
                  I can thread an M6x1 thread at 400 RPMs all day long with a geometric die head.
                  There are only 10 types of people in the world: Those who understand binary and those who don't.

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                  • #24
                    Well a VFD 3ph or variable DC drive would be the way to go.
                    But many moons ago before I used variable speed drives on my lathes, I built a automatic half nut disengage system. It was just a simple lever system. A trigger of some sort placed on the ways or bed where you want the carriage to stop. A lever or linkage hooked up to the halfnut lever that contacts the trigger and opens the half nut.
                    My setup was repeatable to about .001-.003" positioning but I never pushed the threading rpm to fast when I used it.
                    I have no pics though.

                    There was also an article in one of the HSM mags quite a while ago on a mechanical system to open the halfnuts for threading.
                    Maybe google automatic half nut opener etc.. if interested in making something like that for your lathe.

                    Steve

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                    • #25
                      I bore upside down, but I'm not sure I'd like to thread upside down, putting lifting forces through my QCTP.

                      Now, mounting the QCTP behind the work, and threading right way up and turning in reverse - I like that idea.

                      One of the reasons the idea of threading away from a shoulder doesn't appeal is that the spindle is still running up to speed when the threading starts. I suppose it should be alright, but the impression is that clearances won't have settled down at the slower speed.
                      Richard - SW London, UK, EU.

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                      • #26
                        Here's a nice looking automatic half nut opening system featured in 1945 Popular science that would not be to difficult to build.-

                        http://books.google.com/books?id=xiA...0lathe&f=false

                        Steve

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                        • #27
                          Originally posted by PixMan
                          True, but I nailed those holders for under $25 each on Ebay. My QCTP accepts 1" shank holders, so this is all in preparation for a slant bed CNC lathe one day.
                          However, I think you might be mistaken in one respect. When you take a standard tool and flip it upside down, you are effectively reversing the clearance angles along with it. This is OK and the way you want it because the threading being made in the opposite direction needs the clearance angle that way.

                          Maybe it's me who can't turn my head around to see it the right way.
                          Ahhh, Nice score!

                          Oh, I did'nt mean the helix clearance angle, I mean the fact that the tool holds the bit on the left or right of the tool body. (or in a custom ground bit, if the thread tip is shifted to the left or right of the blank)
                          With a big enough shoulder, the tool can get in the way once fliped. So you need a tool designed to work to a shoulder on the right, to work on a shoulder on the left, when its upside down. (And the shoulder is large enough to cause problems)
                          I can take a picture of two of my threading tools if you need an example.
                          Last edited by Black_Moons; 03-24-2011, 02:55 AM.
                          Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

                          Comment


                          • #28
                            Originally posted by S_J_H
                            Here's a nice looking automatic half nut opening system featured in 1945 Popular science that would not be to difficult to build.-

                            http://books.google.com/books?id=xiA...0lathe&f=false

                            Steve
                            Neat. But I think I would want something more positive. I have had to really push on a handle a couple time when taking a heavy cut with the leadscrew.

                            I think Rivett had a auto-disengage system. But I am not sure that was for the feed or threading.

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                            • #29
                              Originally posted by Black_Moons
                              Ahhh, Nice score!

                              Oh, I did'nt mean the helix clearance angle, I mean the fact that the tool holds the bit on the left or right of the tool body. (or in a custom ground bit, if the thread tip is shifted to the left or right of the blank)
                              With a big enough shoulder, the tool can get in the way once fliped. So you need a tool designed to work to a shoulder on the right, to work on a shoulder on the left, when its upside down. (And the shoulder is large enough to cause problems)
                              I can take a picture of two of my threading tools if you need an example.
                              No need for photos. I now understand exactly what you mean. That problem is why I slowly added all the seat shims to the collection. With that array of holders you can always get the tool close to the work, you just have to make sure you've got the inclination angle of the insert (for helix) correct.

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                              • #30
                                Originally posted by S_J_H
                                Here's a nice looking automatic half nut opening system featured in 1945 Popular science that would not be to difficult to build.-


                                Steve
                                Logan had a similar system available for the "automatic" apron style.

                                But it only does half the job. You still need to cut a relief, ir retract the tool simultaneously or you will cut a nice stress-raising "charpy notch" all around the part.

                                Not every part CAN have a relief cut, so..........
                                1601 2137 5683 1002 1437

                                Keep eye on ball.
                                Hashim Khan

                                If you look closely at a digital signal, you find out it is really analog......

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