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Why are lathe ways shaped the way they are?

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  • Why are lathe ways shaped the way they are?

    This is the shape of my lathe ways:

    Seems to be a pretty common shape.
    Seems pretty complicated.
    Why so many surfaces? Why is one side higher than the other? Why is one side larger than the other. Why is there 2 seperate sides at all, Why not just have one flat top and 2 perpendicular sides?
    I'm an abstract poet and I didn't even think I was.

  • #2
    Wow, what a can of worms you've opened.

    *makes some popcorn and gets comfortable*


    • #3
      Its like bring up comparisons in boat hulls


      • #4
        There are many way configurations. Flat, inverted vee or a combination of both and don't forget the round bed ways or the bar beds like the Barker, Unimat and the triangular bed lathes.

        People have been arguing the merits of bed configuration for at least 150 years, each type has its advantages and disadvantages. Inverted vee type tolerate wear better, holding there accuracy but some people think flat beds are more sturdy and less prone to having the saddles lift under heavy loading. Bar beds like the Drummond Round bed were used to make lathes cheaper so amateurs like us could afford a lathe but they had trade offs in use.

        It's apples and oranges.

        Check out books like "Lathe Design and Construction and Operation", Lindsay Press sells it but you mite be able to download it off of the Internet archive or google books for free. It's old but still relevant on this subject.
        The shortest distance between two points is a circle of infinite diameter.

        Bluewater Model Engineering Society at

        Southwestern Ontario. Canada


        • #5
          A lot of it has to do with hereditary design, the country of origin and the price of kippers.....


          Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.


          • #6
            On the shape that I have shown, how many of the surfaces are actually in contact with the carrage? They can't all be... can they?
            I'm an abstract poet and I didn't even think I was.


            • #7
              One inverted v is for the carriage the other is for the tailstock.

              They are great until they wear ...then you have to be a master craftsman to get them right again ..

              The all flat ways Machines are much simpler and could be put right with the minimum of specialised tooling when they wear out.

              all the best.markj


              • #8
                Usually on the style in your picture, the carriage uses one vee and one flat and the tailstock uses the others.
                Jon Bohlander
                My PM Blog


                • #9
                  And the machined underside towards the center is where the carriage lock rides against.
                  Brian Rupnow


                  • #10
                    Originally posted by aboard_epsilon
                    The all flat ways Machines are much simpler and could be put right with the minimum of specialised tooling when they wear out.
                    Oh, I thought it was because British engineers hadn't discovered prismatic ways yet?
                    "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."


                    • #11
                      They're lips to stop your files, screwdrivers, and hammers falling off the edge, which happens on flat slideways.



                      • #12
                        One option I really like in the later LeBlonds was the replacable front way. Either the whole way could be replaced or it could be taken off and reground. Of course either way you are looking at scaping the saddle . One thing to consider is that for the most part the tailstock ways will wear fairly evenly as when not in use the TS tends to get pushed to the far end of the ways while the wear on the saddle ways tends to be concentrated towards the headstock
                        Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.


                        • #13
                          You left out the bottom ways for the carriage. Your diagram shows distinct ways for the carriage and another for the tail stock. The shape solves the requirements for good four point surface contact, good surface area without being excessively wide (pyramid shape), side force resistance, and are self-aligning for the carriage. The structure between the rails provides rigidity for torsional forces. It is also easily reproducible by casting, and is maintainable through resurfacing.

                          It's but one of many designs, of course, but they all have similar objectives.


                          • #14
                            To me it seems like an angle way and a flat way would be good, not a vee way and a flat way.


                            • #15
                              As mentioned, the front V is for the carriage and the flat on the opposite side also guides the carriage. The flat way on the front guides the tailstock and the v on the back side also guides the tailstock. The "v"'s keep things aligned and straight, the flats allow for glide and pressure. The carriage glides on its own set of V and flat and the tailstock the same to minimize the wear that would occur if they rode on the same way V's and flats.

                              Just what I learned......
                              CCBW, MAH