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Why so down on lantern toolposts?

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  • #16
    Originally posted by Gary Paine View Post
    This is a very nicely made toolpost, but I have personally avoided using any toolholder with only a round button in the topslide t-slot for fear that a catch would break out the slot. .
    This one is off a unimat, so not an issue there. It's worth considering, but I think you'd have to really work to bust a lathe T slot this way on a larger size.... but if concerned you coud easily make a large rectangle on the bottom instead of the button giving it the same cross section in the T slot as other posts. I more put the pics up to show the structure; modify as you see fit ....its been 10 minutes, you've probably already built one by now
    in Toronto Ontario - where are you?

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    • #17
      My lathe admittedly is a bungie lathe. The compound and cross-slide is more reminiscent of a Inukshuk than a tool. Because the cutter is displaced from the hard point by some distance and in three dimensions it tends to twist under load. Any looseness in the dovetails of the slides compounds the problem and yet they need a certain amount of slop to allow the slides to slide.

      On my system this manifests itself in a bound parting tool, for example, or a deep cut that flexes the parts noticeably. Accuracy and repeatability are dreams unrequited. I've spent some time exploring how to replicate the lantern post on my shaper onto my lathe for certain operations like parting that put so much twist into an overly compliant lathe. McGyver's sample looks like it may solve the problem. I've already purchased a second compound slide from Grizzly to use as a foundation for what ever I come up with so I won't be breaking a working lathe in the process. And I don't see any reason a rocker can't be added to the example to preserve that vertical option although I've used shims for that purpose for years. When I bought the lathe it did not have a QCTP, but a simple four-way tool holder that rested on the compound. Any vertical was done with shims so I got lots. Using rockers and shims should solve any problem of the superior lantern and still eliminate the bungie feature I'm so not fond of.

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      • #18
        Works best on small manual lathes. Used it for forty years. For fast set ups - you just can not beat it.

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        • #19
          The only thing wrong with lantern tool posts is that they do not come with much in the way of bragging rights.

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          • #20
            I assume under the adjusting nut is nothing but free air. The adjusting thread is only seated as well as the clamp bolt is tightened, apply some more load when cutting and the thread may adjust its seating.

            A four way tool post is sitting block of iron on block of iron, with no overhang in the toolpost and absolute minimum overhang of the cutting tool. Apart from a relatively thin adjusting nut the tool in the picture is basically unsupported all the way back to the tool post diameter , and then is only sitting on a thread.

            Phil

            Originally posted by Jim2 View Post
            I've been using a "threaded sleeve" design as described by Mcgyver for the last few years. Somebody posted this idea on "the other" site, and I made a copy for myself. Here's a pic of mine in use.



            I like it much better than the half-moon key and washer that it replaced!

            Jim

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            • #21
              I have a lantern toolpost setup as above, from I believe a schlaubin lathe which used that design ex factory.
              I also had a tripan 111 qctp, and they're so small and elegant I've never had a issue with it that the lantern would solve so have never mounted it.
              But, I've recently sold the tripan and its holders on as I found I wasn't using them either, as I now use a great big hulking beast of a multifix B, but Ive found with a little cunning I can use its rotational indexing to get round clearance issues without pain or readjustment. For a while I kept it and made a holder so I could hold the tripan in the tool holder of the multifix for extra weird setups, but never used that either.

              I'd never go back to a traditional four post though if given the choice. Dont the lanterns have issues with clearance from the corner of the top slide in use as they sit central on the compound slide not hold the tool off towards the edge?
              I think people are down on the lantern type toolposts because with the onset of qctp's the lantern cures a niche itch thats gone away, but if you want to use a lantern for the simplicity and for the best reason in the world (because you can) carry on.

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              • #22
                I just dug it out and snapped a pic of it to contribute to here, no my fingers are not especially giant, its off a small precision schlaubin lathe originally.

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                • #23
                  Originally posted by MrFluffy View Post
                  I just dug it out and snapped a pic of it to contribute to here, no my fingers are not especially giant, its off a small precision schlaubin lathe originally.
                  Perhaps they where the original designers of this....Shlaubin are something aren't they? note the chamfered thread ends. German & Swiss, that's where the quality is

                  A four way tool post is sitting block of iron on block of iron, with no overhang in the toolpost and absolute minimum overhang of the cutting tool.
                  its not either or imo....each would have occasion to shine.
                  in Toronto Ontario - where are you?

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                  • #24
                    Also notice that they used buttress threads to bear the pressure.

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                    • #25
                      Also notice that it is from a watchmakers lathe, used for processes where hand held tools are often rigid enough.

                      It would be interesting to see a photo of the air gap underneath the height adjusting nut when mounted on the slide.

                      Remember the question was "Why does everyone get so down on lantern toolposts?" Not "does a lantern toolholder have a place in the home workshop?" I think the answer to the question is that they provide insufficient rigidity for use as a general purpose holder.

                      Phil

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                      • #26
                        To anyone frustrated with height adjustment on 4-sided tool posts: buy cheap sets of feeler gages and take them apart. Now you have a whole bunch of nicely made shims.

                        metalmagpie

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                        • #27
                          When I was a youngster ,I used a rocker, lantern toolpost for about 10 years full time in a high pressure job shop setting.I swore that some day I would hunt down the guy that invented this abomination and destroy his decendants .These things are an abomination to use and should be thrown in the trash.However I am better and over it. laugh laugh rant over.

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                          • #28
                            Originally posted by philbur View Post
                            Also notice that it is from a watchmakers lathe, used for processes where hand held tools are often rigid enough.

                            It would be interesting to see a photo of the air gap underneath the height adjusting nut when mounted on the slide.

                            Remember the question was "Why does everyone get so down on lantern toolposts?" Not "does a lantern toolholder have a place in the home workshop?" I think the answer to the question is that they provide insufficient rigidity for use as a general purpose holder.

                            Phil
                            No its not, its from a 102 which schaublin denoted a toolmakers lathe, lathes.co.uk has some shots of the range showing the arrangement they had :-
                            http://www.lathes.co.uk/schaublin/page2.html


                            I draw you to my above comment that I dont use this toolholder anymore as I use my multifix b to do everything it can do and more.

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                            • #29
                              Also interesting to note that the 102 in the later photo's on that page has had its lantern replaced by a tripan 111 qtcp

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                              • #30
                                Originally posted by philbur View Post
                                It would be interesting to see a photo of the air gap underneath the height adjusting nut when mounted on the slide.
                                That is true. The design essentially creates a bridge with either end as supports and the holding pressure bearing down directly in the middle. Usually it doesn't matter, but you can deform a 3/8" square shank if you aren't aware. I still use it on occasion with a disproportionately taller shank toolholder:


                                Schaublin later updated the design to eliminate that problem with two hold-down bolts. They then aligned directly above the knurled height-adjustment nut:


                                And parts assembly:




                                FWIW
                                Last edited by Arthur.Marks; 03-22-2013, 11:34 AM.

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