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Portable Production Collet Lathe Build Thread

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  • #16
    While I don't have any pictures yet, an improved saddle design has been added to the lathe.
    Last edited by briuz; 02-22-2021, 12:18 AM.

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    • #17
      Awesome job. Looks like a pretty compact but capable machine. Thanks for starting a separate thread.

      I've always wanted to build a similar machine, but based off a Hardinge 2nd op chucker for rigidity. One seems like the perfect blank canvas for such a retrofit. BUT not very portable.

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      • #18
        Wow. I built a CNC lathe for my college masters thesis project,
        but this one is MUCH better than mine. Looks awesome!

        -Doozer
        DZER

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        • #19
          You have certainly taken on an awesome project, congratulations. I take it that you have to keep the temperature fairly constant using aluminium for weight saving.

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          • #20
            Leave enough room behind the spindle for a bar feeder, you will be truly buggered when you begin running production work and find that something is in the way (-:

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            • #21
              way to go and thanks for posting it!
              in Toronto Ontario - where are you?

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              • #22
                Very cool and thanks for sharing. Can I ask how you are closing the collets, and are you able to grab and feed material out using your turret? And what sort of parts are you making (or planning to make) on it?
                Cayuga, Ontario, Canada

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                • #23
                  Thank you for all the positive comments. To answer some questions....

                  I don't anticipate that temperature will be much of a problem as it pertains to using aluminum. Aluminum is used in other small machines such as Sherline without any issues.

                  A bar feeder could be used, of course, but I've been looking into using a bar puller of some sort as it would be more compact. However, I still haven't decided on what would be best for a bar puller here and space is rather limited.

                  This machine is really being built because had this machine been available when we were really busy making a product my company would have purchased a couple of them. At that time there was nothing available that filled a niche for making small turned parts on a small CNC production machine that can easily be moved into a tight basement or back corner then just plugged in like an appliance. Since pocketnc appears to have fulfilled an interesting niche with a table-top 5 axis milling machine it also stands to reason that a table-top 16 position CNC turret lathe also has a market. So high-end features have also been added like the tool setter and parts chute. (The final parts chute will be very similar to the 3rd prototype parts chute seen in the pictures.)

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                  • #24
                    For a bar puller a simple bored bar with tapered lead in, and slotted fingers works great. Pinch it in a bit to grab the bar tight (or bore a bit undersize). I've made a few for the different size bars I run through our lathe, and never had one fail to pull. Might have trouble in say a 2" bar, but I've had no problem with up to 1". On a machine your size it would be perfectly simple. To save space you could incorporate it into the center pivot of your turret if you've got enough x travel to get it on center line. Wouldn't have to give up a turret space for it.

                    That just made me wonder if you could integrate a milling spindle on the turret center line too.....Now that would be a pretty potent compact weapon...

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                    • #25
                      Here is a video of the collet closer working with Prototype 2 and the early geared encoder:

                      https://youtu.be/XgVtzHp_neM

                      The video is so early that a front panel had yet to be added and Version 1 of the turret is visible.

                      The collet closer is the same on Prototype 3 as Prototype 2 as I moved a lot of the working parts from Prototype 2 to Prototype 3. It uses a ball-bearing system with an internal taper that squeezes the ball bearings inwards so as to separate two tapered washers and tighten up the collet. The same type of system was used by SouthBend Lathe once and it appears Sherline now uses something similar. I found the following scanned diagram on another forum and used it to puzzle out how such a collet closer works:

                      Click image for larger version  Name:	collet closer.jpeg Views:	0 Size:	98.0 KB ID:	1930268

                      Originally posted by Tom S View Post
                      Very cool and thanks for sharing. Can I ask how you are closing the collets, and are you able to grab and feed material out using your turret? And what sort of parts are you making (or planning to make) on it?
                      Last edited by briuz; 02-24-2021, 12:42 PM.

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                      • #26
                        I've thought about using such a bar puller. My main objection has been that each stock size would require a custom boring bar. Maybe a mini adjustable bar puller is the answer?

                        Originally, the plan was to build a lathe with live tooling in an 18" x 18" x 36" platform. (Also very portable.) In the interest of time and reducing complexity this machine was built first. If it's successful the plan is to follow up with a machine that has live tooling. Going to an 18" x 18" x 36" platform may also allow for the computer to be integrated as well so as to make a very compact and portable machine. It would probably require 4 people to carry such a machine, though.

                        The current turret is of a ratchet type with a paw that is raised for movement. Some turret designs use a one-way ratchet design but I didn't like that the entire turret had to be rotated just to go back to the previous tool. So a solenoid was added so that the turret can turn either way. Live tooling would require more space and a fully locking turret.

                        Originally posted by Dan Dubeau View Post
                        For a bar puller a simple bored bar with tapered lead in, and slotted fingers works great. Pinch it in a bit to grab the bar tight (or bore a bit undersize). I've made a few for the different size bars I run through our lathe, and never had one fail to pull. Might have trouble in say a 2" bar, but I've had no problem with up to 1". On a machine your size it would be perfectly simple. To save space you could incorporate it into the center pivot of your turret if you've got enough x travel to get it on center line. Wouldn't have to give up a turret space for it.

                        That just made me wonder if you could integrate a milling spindle on the turret center line too.....Now that would be a pretty potent compact weapon...

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                        • #27
                          Originally posted by briuz View Post
                          Here is a video of the collet closer working with Prototype 2 and the early geared encoder:

                          https://youtu.be/XgVtzHp_neM

                          The video is so early that a front panel had yet to be added and Version 1 of the turret is visible.

                          The collet closer is the same on Prototype 3 as Prototype 2 as I moved a lot of the working parts from Prototype 2 to Prototype 3. It uses a ball-bearing system with an internal taper that squeezes the ball bearings inwards so as to separate two tapered washers and tighten up the collet. The same type of system was used by SouthBend Lathe once and it appears Sherline now uses something similar. I found the following scanned diagram on another forum and used it to puzzle out how such a collet closer works:

                          Click image for larger version Name:	collet closer.jpeg Views:	0 Size:	98.0 KB ID:	1930268
                          Very nicely done, and that's a nice drawing so I've saved myself a copy.

                          I was thinking about your project today and wonder if you couldn't develop a version that would allow someone to bolt a turret onto a Hardinge HSL lathe. Very similar to your design and it could be a nice small production machine with a turret bolted on and the motor upgraded to a variable-speed controlled by the CNC controller. Food for thought.
                          Cayuga, Ontario, Canada

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                          • #28
                            Well....now that you mention it.....we are really making another turret for two reasons. One of the reasons is to get the process down to build the lathe and the other is to have the turret as a separate product for the exact scenario you describe. The plan is to initially sell the turret with instructions as to how to integrate it with a lathe then to sell the turret with the electronics so as to allow for more more interfacing options.

                            Originally posted by Tom S View Post

                            Very nicely done, and that's a nice drawing so I've saved myself a copy.

                            I was thinking about your project today and wonder if you couldn't develop a version that would allow someone to bolt a turret onto a Hardinge HSL lathe. Very similar to your design and it could be a nice small production machine with a turret bolted on and the motor upgraded to a variable-speed controlled by the CNC controller. Food for thought.

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                            • #29
                              Here's the forum posting where the South Bend Collet Closer drawing was found: https://www.homemadetools.net/forum/...closer-71284-2

                              Here's a picture in this forum posting that shows some of the internal parts: https://www.practicalmachinist.com/v...7/#post1859229

                              Sherline's parts breakdown: https://sherline.com/wp-content/uplo...9/1150inst.pdf
                              Last edited by briuz; 02-24-2021, 06:58 PM.

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                              • #30
                                Very cool. Interested to see where you go with this.
                                Cayuga, Ontario, Canada

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