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This may sound silly but....

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  • This may sound silly but....

    If you have access to a mill or a lathe function where you are able to use either the graduations on the machine or an indicator on a tool why would you manually do a only provides a visual reference and usually when I'm machining enough swarf is produced that you can't see your marks anyhow. Not only that but your accuracy is greatly improved (I would think).

    Am I overlooking something?

    I can see it if you're doing relatively loose tolerance work on a drill press but for tight tolerances it doesn't make sense to me (forgive me for I am a relative newbie )
    Allans Rule: Anything worth doing is going to be a pain in the butt.

  • #2
    I do layouts for mill work because it saves me from making silly errors. I don't rely on the layout itself (i.e. machine to the lines) unless the tolerances are wide open. If the part is a casting then there are other more compelling reasons for making a layout. If you never make silly mistakes then perhaps making layouts is a waste of time for you.


    • #3
      Layout lines

      There are times when layout lines can be a good double check to make sure you didn't miss a count on the number of turns of the crank or forgot to add or subtract 1/2 the edge finder or cutter diam. etc.
      I hardly ever do layouts anymore since DROs came on the scene. With the DRO you simply set a zero and work off print dimensions. To me, it removes the need for a layout for the most part.
      Kansas City area


      • #4
        Originally posted by willmac
        I do layouts for mill work because it saves me from making silly errors. I don't rely on the layout itself (i.e. machine to the lines) unless the tolerances are wide open. If the part is a casting then there are other more compelling reasons for making a layout. If you never make silly mistakes then perhaps making layouts is a waste of time for you.

        I "mark out" and centre-punch most of my mill work. It is actually copying the drawing and any errors soon show up before and after it gets on the mill.

        My "marking out" is pretty good. Its easy to "split" a mark-out line with a cutter than it is to work strictly "on the dials". If necessary I finish off "on the dials" and a micrometer.

        Just wipe the swarf off with your hand and the marking out is exposed.

        Its just too easy to be "one turn out" on a lead-screw or even to over-shoot with lathe cross-slide dials.

        CNC work is often just following a (CAD) drawing and a "dry" or "proof" run will soon show up any incorrect tool off-sets etc.

        I'd much rather drill on a drill press than a mill - and a good "mark-out" makes that very easy and often-times just as good and perhaps faster than setting up on a mill. "Spot-drilling" to a centre-punch mark pretty well stops all drill "wander" too.


        • #5
          I do layout work, and I do a fair bit of it, either for cut lines or holes and it's for one reason, speed.

          If tolerances permit and there's a bunch of holes to to do its quicker. So much quicker to layout, punch and go to the drill press. Add in an optical centre punch and transfer punches and the realm of what you can do this way goes way up. as well, milling to a scribed line with zero measuring is fast.

          A DRO would be a nice convenience, but not game can still coordinate layout by counting the turns of the dial....its just that layout this way and drilling in the mill is a lot slower for many jobs, especially those with more than a couple of holes and or multiple parts

          Edit, ok more than one reasons , willmac is right its a good for surveying and planning how to come at a casting
          in Toronto Ontario - where are you?


          • #6
            I never did much layout work in shops, as time was money and CNC pretty much negated the need. Find it’s handy at home though, even if I am using other means to position. I often go for weeks between machining steps and the layout can save a lot of head scratching when I do get back to the shop.

            I did work at one place that went through a phase of requiring a layout on everything that went in the CNC mill. This was in response to the operators making too many keystroke errors when programing at the control. Without the lines, it was hard to tell if the mill’s moves were correct until it was too late.

            One of the operators got tired walking across the shop to do the layout and decided to chuck up a Sharpie marker and program the layout in the mill. He would then make a few changes to the program and use the same locations for his cutting and drilling. Of course, the mill followed the pretty lines every time and management decided that this was the way it would be done from now on. The operator was declared a hero and the rest of us knuckleheads were encouraged to also come up with brilliant ideas like this.

            After months of absolutely no improvement in the scrap rate, it must have occurred to management that perhaps there might be some flaws in this idea. Nothing was ever spoken again of it and the supply of sharpies was not replenished.

            Traverse City, MI


            • #7
              I layout parts for speed mostly. I can then rough out the non-critical areas easily via the "eye ball" method very fast, establish a zero, and make a final pass or two over everything to finish.
              "I am, and ever will be, a white-socks, pocket-protector, nerdy engineer -- born under the second law of thermodynamics, steeped in the steam tables, in love with free-body diagrams, transformed by Laplace, and propelled by compressible flow."


              • #8
                I do a layout for the exact same reasons others have pointed out. I'd think the more experience you have, Then the less need there is for doing one. It's also a dry run for the actual machining. The more complicated the item is, Then the more important a fairly accurate layout for me would be. Forgetting something on a part with multiple locations and then moving the part would be a large PITA. A DRO independant from the feed screws simpifys everything and much less inaccuracys due to the built in ones on comman HSM grade equipment. Other than for a drill press, I don't use center punch marks at all. It's more accurate to drill at the proper coordinates with a center drill and then drill/machine on that location. Ever since I got twisted and perverted from reading the two Moore Tool books, My ideas about what logicly works the best have changed a lot.



                • #9
                  I don't do much layout (using blue, and scribing) but I do use a 1:1 print and spray adhesive it on the part a lot. Mostly for holes (clearance for screws), and for cutting waste off on the bandsaw and such. Saves a lot of time. Also helps to have a 3' plotter handy for those parts larger than 8.5x11 (although you can overlap too).


                  • #10
                    I don't really do a layout per se. I will take a sharpie and put a couple lines on there so I don't do something stupid and put the block in upside down and cut the wrong end or something.

                    I will put VNI (vise not indicated) on my vise when it's not indicated in, just some mental cues that on occasion help prevent me from making mental mistakes.

                    I can't remember the last time I use layout dye and scribed lines on a part. I made a couple levers for the HSM cut knurling tool, and I think I scribed lines on those to cut to those for making the shape.


                    • #11
                      I appreciate the feedback

                      O.K. so it split pretty much along the line of my thinking. My comment was based on a tight tolerance perspective. My understanding is that doing layout work you "normally" are expecting a tolerance in the range of +/- 0.005". I thought that with a DRO working to a thou. should be a reasonable expectation.

                      The point about it being a good reference is a very good point.

                      As for speed, I hadn't really considered it being faster but then again I'm not very coordinated so I expect I'm pretty slow on layout work by comparison.

                      It was an interesting point made about drilling on the drill press. Because I've always used smaller machines I just automatically thought from the perspective of using a mill drill as opposed to a straight mill.
                      Allans Rule: Anything worth doing is going to be a pain in the butt.


                      • #12
                        The question is not silly at all. The reasons for doing a layout have been pretty much answered, but there's another thing to consider. My first thoughts as I began to read this thread were about what method of measuring to use- rely on the handcrank dials or wait until you have a direct readout system in place before doing anything but very loose tolerance work.

                        I'm making the distinction because a- we don't all have dros on our machines, and b- the mechanical dial system can introduce multiple errors. This will be old hat to many here, but for a newcomer it's something that should be thought about and understood.

                        First, and likely the first thing to be thought about is backlash. If you've polished all your marbles, you will have come to realize that the table can be moved around by cutting forces, and the relative positions on the x and y axis will change, even without cranking the dials. If you plan out your cutting procedures, you can keep the 'lash' always to one direction against the lead screws, and in that way you can almost trust your hand-cranked positioning.

                        I say almost because, secondly, you may not know for sure that your axis move in total accordance to the degree of hand crank motion. You may crank the table over say 15 thou, but has it actually moved that much- it could be more, or it could be less. I've seen examples with brand new machines where the error here is horrible. If you have not considered this possibility, and checked to see whether Murphys law is active on your machine, then you could be in for a frustrating experience- parts that don't come out right even when you have carefully done everything right.

                        A dro would show these discrepancies right away, and can show you whether or not to trust the mechanical dial indication, and to what extent you can. But a dro system can't compensate for backlash- it can only show you that for instance the table has suddenly jumped .014 this way or that way- possibly breaking a cutter, and/or ruining a workpiece.

                        You may be able to see a machine error like this on your layout, but of course once you have seen it, it may be too late to save the precision of your work.

                        Anyway, there have been a few relative newbies here lately, so I thought it might be good to raise this issue again.
                        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


                        • #13
                          Absolutely..... dials may be wrong.

                          Dials of the re-settable type can slip. The feed screw can be worn. You KNOW the screw is *wrong* even when the machine is NEW, by *some* amount (nothing is perfect) , and it generally does not improve with age.

                          if you don't think so, then next time you use the mill or lathe, work by the dials, and then compare the theoretical movement to the actual measured metal removal. If it is identical, then you have a very nice machine.

                          Most of these errors don't get to the size that a layout will let you notice, but there are all sorts of reasons for doing the layout anyway.... it makes sure you have "found" the part inside the stock, and don't have any portion of the "part" located out in the air somewhere..... very good for castings, not bad when using "remainders" of material either.
                          Last edited by J Tiers; 03-09-2012, 08:45 AM.
                          CNC machines only go through the motions