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parting tool for brass

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  • #31
    Originally posted by Mcgyver View Post
    that goes without saying, but why would alignment with the loupe precludes this? What I described (visual alignment with a loupe) is SOP for lots of the machining of small stuff among clock and watch makers, who have a lot of neat ways of making small parts. Simple fast and it works. Don't overthink think it gents.
    Someone is going to have to explain how this is so much better. Unless I am missing a big point somewhere, it seems very slow, fussy, and potentially inaccurate, the exact opposite of "simple, fast, and it works"

    I very much suspect that entirely different things are being done... the watchmakers are likely NOT doing the same thing, so for their purposes the front edge IS important.

    My question is VERY MUCH about "NOT overthinking"... Trying to set the perpendicularity of the tool by carefully aligning the very smallest feature on the entire tool seems to be the "overthinking" here..... It seems to involve a number of assumptions, as well as introducing very possible errors, yet it is apparently being touted as the "best and most accurate" method.

    1) A slight error of seeing the lineup of the short side leads to a much larger error on the longer portion that corresponds to the depth of the fins. Seems the exact opposite to what you want.

    2) There is an assumption that the short edge is correctly at a 90 degree angle to the axis of the cutter. Who says it is?

    3) There is an assumption that you can in some way more effectively align a short side than a long side. This seems exactly backwards

    4) There is an assumption that it is somehow faster to get out the loupe, with paper and a strong light, proceeding to minutely examine a tiny edge while adjusting the angle, rather than to quickly set the holder against the flat of the chuck and move on. This also seems exactly backwards. I certainly would not find it faster, I would find it quite a but slower. Even using a square seems faster and more effective

    Now, the comment is going to be made that the "blade" is dovetailed, and consequently cannot be measured against. But the side of the tool blank can be measured against, so if you take care up front to grind the tool square, you never need to concern yourself about that, if the tool side is square to the work, so is the blade.

    Honestly, unless someone can explain this to us as to how it is better, it really seems to be going the long way around the barn, blindfolded and walking backwards. I'm not arguing, I'm just puzzled. Flabbergasted, maybe...
    4357 2773 5647 3671 3645 0087 1276

    CNC machines only go through the motions

    "There's no pleasing these serpents"......Lewis Carroll

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    • #32
      What this comes down to is clearence angles. Just like how a parting blade is tapered down creating a v shape to eliminate rubbing; my small parting tools are tapered back from the cutting edge. This eliminates rubbing and also allows for chip evacuation. Since the cutting edge is what is doing the actual cutting, doesn't it make sense to setup off of it and the work? Would it work setting off of the tool side? Sure. But, since I tend to use collets, and the parts are very small, the loupe gets the job done. The loupe is easier and faster then setting up an indicator and indicating the tool.

      When you thread, do you set off the side of the tool and the chuck? Or, do you use a center gauge and set off of the work and the cutting edges? Of course you can set the gage on the chuck and set the tool. But in any case, the cutting edges are used to set the tool when using the gauge.

      Side Note: The right click, copy and paste doesn't work for me Paul. Also, they show in this thread on my pc but not my Ipad.

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      • #33
        If it's "I don't care" parting, I align the tool with the chuck face by feel/look.

        If I care, I pop my magnetic base dial indicator on the ways or carriage and adjust the TOOL side (not the holder) for zero angle while winding the carriage in/out. Easy... almost as easy as pushing it against the chuck.

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        • #34
          Originally posted by lakeside53 View Post
          If it's "I don't care" parting, I align the tool with the chuck face by feel/look.

          If I care, I pop my magnetic base dial indicator on the ways or carriage and adjust the TOOL side (not the holder) for zero angle while winding the carriage in/out. Easy... almost as easy as pushing it against the chuck.
          THAT makes perfect sense to me......

          The holder deal I mentioned is because the "tool" does not stick out, but the indicator can reach in. Also the tool tip may have a dovetail which means it has no perpendicular surface there.

          If you are working in a collet, then no chuck so you have to align a different way and indicator is sensible.
          4357 2773 5647 3671 3645 0087 1276

          CNC machines only go through the motions

          "There's no pleasing these serpents"......Lewis Carroll

          Comment


          • #35
            Do you have you spindle correctly tensioned?, do you lock the carrige up?
            Because it sounds like somethings on the move.
            I like the slitting saw suggestion a 1mm is already cleared.
            Mark

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            • #36
              I guess no one here has used radius gages, optical comparators, squares, protractors, templates, etc. where a part feature is compared against the gage's surface/line. It's the same simple principle.

              I guess it is from too many years in QA/QC on my part.

              -Bob

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              • #37
                Originally posted by 90LX_Notch View Post
                I guess no one here has used radius gages, optical comparators, squares, protractors, templates, etc. where a part feature is compared against the gage's surface/line. It's the same simple principle.

                I guess it is from too many years in QA/QC on my part.

                -Bob
                Pretty much everyone IS talking about exactly that.

                The question is what surface or edge to compare against.... essentially what surface to "believe in", as well as which one gives the simplest procedure and most accurate result within the needs of the situation.
                4357 2773 5647 3671 3645 0087 1276

                CNC machines only go through the motions

                "There's no pleasing these serpents"......Lewis Carroll

                Comment


                • #38
                  Unless I'm missing something, this should be a pretty simple thing- a shallow groove in brass, cleanly.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                  • #39
                    Every technique mentioned in this thread I have atleast used (off the chuck, indicating, loupe). People who apparently have not, have determined that the loupe is an invalid method. That's fine. I seem to not be capable of articulating it's merits.

                    This thread has become a stillbirth. To each there own.

                    -Bob

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                    • #40
                      Invalid? Not nevessarily.

                      I don't have to have used it to understand it. But lining up a half or 3/4 inch of cutter by looking at the tiny .025" end of it seems odd. I don't doubt that when the stars align correctly that it could work. But it seems so easy to have it turn out wrong, and so easy to use other methods of proven accuracy, I wonder why it is so stoutly defended.

                      I have asked for the explanation, in case I have missed something.....I would be happy to learn a new technique that is better. I admit that I might take some convincing. But nobody has compared and contrasted the methods and shown WHY the loupe is so far superior.

                      Care to give it a shot?

                      Originally posted by darryl View Post
                      Unless I'm missing something, this should be a pretty simple thing- a shallow groove in brass, cleanly.
                      I think so.... less fussy than parting, although the interrupted cut could be an issue until the cut gets past the corners.

                      Maybe the OP has a problem related to the interrupted cut knocking the tool askew. Should not happen if the carriage is locked.

                      But, I have seen cases where the crossfeed screw or compound screw will back out or even run in farther due to the vibration from an interrupted cut. That could be part of the problem also.
                      Last edited by J Tiers; 02-04-2017, 06:07 PM.
                      4357 2773 5647 3671 3645 0087 1276

                      CNC machines only go through the motions

                      "There's no pleasing these serpents"......Lewis Carroll

                      Comment


                      • #41
                        Ah, yes. I've had the problem of the tool getting sucked in during an intermittent cut. Comes to mind that I've solved, or at least reduced, problems by not using the compound. I made a rigid mount for the tool post that takes away the play that the compound gives, and also the flex. I seldom use the compound anymore. What I'm left with is only the play from the cross slide, so things are much more rigid now. My cross slide has T slots, so the mount I made can be adjusted for position independently of the slide position.

                        Comes to mind that many carriages are equipped with threaded holes on the left side with which to mount a steady. This could be used to mount an independent tool holder that would have its own slide to mount a cutting tool into. It would probably be useful for cutoff and grooving tools. I have something like this, though it doesn't mount to the carriage, it mounts directly to the ways- thus you have to loosen a nut and slide it to position, then tighten the nut. It's about the most rigid way of transferring cutting forces directly to the lathe bed, while minimizing side to side motion during a cut.

                        The best interrupted cutting I've done coincides with minimum noise levels from the operation. If there's hammering and vibrations being set up, then determine what can be done to minimize that.
                        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

                        Comment


                        • #42
                          How far does the parting/grooving tool stick out from the holder?

                          If the tool or blade is flexing causing chatter or worse try reducing the stick out to an absolute minimum.

                          I have cut 0.125 deep grooves in 316 stainless over a 2 inch length , the first one snapped an insert because the holder could flex, ass soon as the setup was made more rigid , no more problems.

                          Brass can be a pain as if there is any slight miscalculation with set up it will and does GRAB , often with costly results. Check all angles and make sure parting blade/ tip is sharpened for the material being machined.

                          EG part almost completed and it grabs while putting in an "o" ring groove after an hours work on the bulk of the machining, ruining the part.

                          Michael

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                          • #43
                            Seems a mill and rotary table would probably be better for you if you have the kit, slitting saw in arbour, wind in for full cut and rotate the table, should work ok, there appears to be a consensus that the intermittent cut is taking the front load off the crosslide and it's moving by however much the backlash is, a fairly common problem that destroys inserts too I've found ( I have a large amount of backlash myself, worn screw and nut, I need to replace them but haven't got round to it, it does affect parting making it a very unpredictable affair)
                            I suppose finning on the vertical you could fin the whole thing by ganging cutters, I've done that cutting combs in the past, the spacer being equal to the fin thickness, small slitting saws are fairly cheap last time I bought some, fortunately as they do break in hard stuff easy, some say keep new for brass and used for steel as per files, I haven't seen a lot of difference myself.
                            A toolmaker friend of mine had a neat little trick, he had a holder for hacksaw blades, it took a 2" peice of all hard hacksaw blade, teeth pointing up, he made it to cut clip grooves, there was a long tee shaped tool and the stubs of hacksaw blade were clamped in a groove in the end of the tool, a couple of Allen cap screws closed the slit.
                            You could fit several bits in for thicker grooves, I don't have the tool anymore to take a photo, but imagine a grout cleaning thing.
                            Mark

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                            • #44
                              If you DO cut them in the lathe, I suggest starting with the MIDDLE ones. Work outward to the ends, so that you do not have such a flexible workpiece.

                              Workpiece flex can cause a lot of trouble similar to the tool catching, as instead of the tool flexing or moving, the workpiece does.

                              Or, perhaps better, use the 4 jaw, stick out a bit of the part, groove it, then move the part out again, using a center to stabilize the cut part, and cut the next bit. go like that down the length. start with longer stock than needed so you retain something to hold.

                              There must be a center hole, that drill FIRST.
                              4357 2773 5647 3671 3645 0087 1276

                              CNC machines only go through the motions

                              "There's no pleasing these serpents"......Lewis Carroll

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