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Project: Building the MLA-18 Filing Machine

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  • #46
    Here's a shot of the finished crank disc:

    Click image for larger version

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    And here's a couple pics of the way the assembly stands for now.
    This will give a rough idea of how the finished machine goes together.
    Notice the felt shield on top, and the "hat" to the left in this pic:

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    Here's a rough idea how it all goes:


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    25 miles north of Buffalo NY, USA

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    • #47
      very cool, you're making great progress! Work holding and order of operations is almost always the hardest part of any project.

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      • #48
        Originally posted by mattthemuppet View Post
        very cool, you're making great progress! Work holding and order of operations is almost always the hardest part of any project.
        Yup..... Far too many times I have found myself standing in the corner with the bucket of proverbial floor paint in one hand, brush in the other and looking longingly at the door on the other side.... I thought it was supposed to get easier with age. 😳
        If it wasn't done the hard way, I didn't do it.

        Lillooet
        British Columbia
        Canada.

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        • #49
          Whew! We are *finally* getting to the heart of the project: creating the shafts and the "scotch yoke" mechanism, that converts the rotary motion into straight-line reciprocating motion.

          The drawings call for the tool holder to be made of drill rod, so a cut off a piece of 1/2" (12mm) type 0-1 round a bit over length and cleaned up the ends. I center drilled and then drilled the ends with a 1/4" (6mm) drill; one end gets about 1" (25mm) deep, the other end gets a bit over 3" (75mm) deep. The end with the 3" deep hole gets a 1/8" (3mm) cross-hole drilled to intersect.

          This is to relieve air pressure and provide an "oil pumping" effect while the unit is working. The end with the 1" deep hole is the part that holds the files, in conjunction with the "hat" made earlier. This requires a 1/2 dia. relief about 3/4" (20mm) long. I did this cut with a die grinder mounted in the tool post. The entire setup was available (new) via eBay, and it did an excellent job. First pic shows the finished assembly, second pic shows the relieving setup:

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          In the photo above, the "hat" is clamping a file into the 1/2 dia holder rod pocket via the set screw.
          The surface area for clamping is considerable relative to the size of the parts: it's a very effective design!

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          It's finally time to start assembling the crank/eccentric. The drawings call for a 3/4" shaft, press-fit and cross-pinned into the crank disc shown earlier. Then I pressed in the crank pin, which is actually a piece of hardened dowel. It needs to be shortened in the pic, which I did later. Specifically I have it 3/8" (10mm) long as measured from the face of the crank disc. I'm proud of the fact that all the dimensions on the crank assembly came within less than .001 of where they should be.

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          Now I am really getting into the heart of the matter: A block of cast iron that will become the scotch yoke, clamped around the tool holder rod shown earlier. This block will be worked up and down by the crank in the above photo. In order to not make a mistake, I decided to mark out the idea of what to do on all the relevant surfaces, basically "copying" the drawing into 3-D with a sharpie marker onto the blank part:

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          Last edited by nickel-city-fab; 06-03-2021, 08:25 PM. Reason: typo
          25 miles north of Buffalo NY, USA

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          • #50
            Thanks for taking the time to post all of this. I know that just taking the pictures and posting them with descriptions becomes something of a project in itself, and I for one appreciate the effort.

            It's always enlightening to see how different people approach the various operations and solve problems.

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            • #51
              Originally posted by alanganes View Post
              Thanks for taking the time to post all of this. I know that just taking the pictures and posting them with descriptions becomes something of a project in itself, and I for one appreciate the effort.

              It's always enlightening to see how different people approach the various operations and solve problems.
              Thanks, Alan -- I actually enjoy doing the documentation as much as the actual machining! The instructions state that my lathe is the minimum requirement to build the kit, but there are parts where a mill would be much easier -- I view it as a personal challenge in creative work-holding. A "tricks and tips" sort of thing.
              25 miles north of Buffalo NY, USA

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              • #52
                Soldiering on, I started work on the heart of hearts: the "scotch yoke" block. Earlier, I had marked out the cuts on the various faces of the block with a sharpie marker, just for a sanity check. I thought about the order of operations and the fact that I completely lack a mill. There are holes drill thru from 2 faces of the block with close clearances and one with a countersink. There is a slot lengthwise which must be a close running fit for the slide block (not shown, already made). Based on the prior experience with trying to part off through a large hole, I decided to make the slot first, since a threaded hole intersects the bottom of the slot.

                After taking cleanup cuts on the two saw-cut faces, I used a digital level to put the part on the same level as the lathe bed.

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                I chucked up a new, carbide 1/4" (6mm) end mill into the die grinder, held in the tool post. I used the combination square to establish the "top" of the slot relative to the top of the part. Just some simple math; the slot is 1/2" (12mm) wide by 3/8" (10mm) deep. The face of the block is 1-1/4 (1.250, say 32mm) by 2" (50mm).

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                Before cutting:

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                Continued next post...
                25 miles north of Buffalo NY, USA

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                • #53
                  I "hogged out" the vast majority of the material with the 1/4" end mills. The cast iron dulled off the mills quickly at 25k RPM, but the job got done with 8 passes. I then switched over to a 1/2" carbide burr and made a cleanup pass or two.

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                  By "bumping" the tool holder with a lead brick while the tool post was still tight, I gained the exact thou or two needed for the slide block to run freely without any play in the slot. Finish is beautiful, no other work needed except to deburr with a fine file.

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                  25 miles north of Buffalo NY, USA

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                  • #54
                    In the last 4 hours since I last posted, I completed the scotch yoke block. I'm very pleased with the way it turned out.
                    I didn't bother to show much of the work because it's so simple: mostly just locating and drilling holes.
                    One hole is tapped (for the shaft clamp) and the other hole is reamed (for the shaft).
                    The hole for the shaft clamp bolt is countersunk with a 1/2" end mill, 1/4" deep to suit the 5/16-18 SHCS.

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                    Yep, a lot of the work was offset.
                    It is possible to locate things very precisely with the 4-jaw, using a dead center in the tail stock to "find" a center-punch mark on the cross-hairs.
                    The following pic shows the moving parts loosely assembled to give a general idea of the machine's operation.
                    Here, you can see the slide-block n the slot, and the saw slot for the shaft clamp.

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                    There is almost no play or looseness between the sliding block and the slot in the yoke block -- but both move perfectly freely.
                    The shaft hole is a reamed fit, .001 oversize to the shaft -- 1/4 of a turn on the clamp screw locks everything rock solid.
                    Everything clears the way it should, and moves the way it should.

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                    Last edited by nickel-city-fab; 06-04-2021, 10:14 PM.
                    25 miles north of Buffalo NY, USA

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                    • #55
                      It's looking good! Seeing your build makes me want to build one, but then I look over at my old Delta scroll like "Well, the old manuals did say I could mount a file in there..." 😄

                      Originally posted by nickel-city-fab View Post
                      Yep, a lot of the work was offset.
                      It is possible to locate things very precisely with the 4-jaw, using a dead center in the tail stock to "find" a center-punch mark on the cross-hairs.
                      Even better than a dead center is a wiggler riding in the punch mark with a dial indicator reading the wiggler. Even a short wiggler works just fine.
                      Location: Northern WI

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                      • #56
                        Originally posted by Galaxie View Post
                        Even better than a dead center is a wiggler riding in the punch mark with a dial indicator reading the wiggler. Even a short wiggler works just fine.
                        Hey thanks for the tip! I gotta remember that one... never would have thought of using a wiggler like that, I always thought they were a "mill only" tool.
                        Fortunately the location tolerances are pretty easy on this. I got away with it on this job.
                        25 miles north of Buffalo NY, USA

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                        • #57
                          OK, time for an update with a crazy setup. I did the unthinkable and read the instructions once again. The next step is to machine the work table casting, and it's an awkward one. It's a lot simpler then the body casting insofar as lack of features, - BUT the sheer size of the part relative to everything else makes work-holding and tool access "interesting".

                          The instructions recommend drilling and tapping a 5/16-18 hole in the center of the casting, which I did with an ordinary handheld drill and tap. Then I took a length of 1/2" threaded rod, and turned down a 5/16-18 threaded stub on one end. Put the rod through the spindle with the face plate on. The rod is held centrally with a bushing near the chuck end. Ran a nut and washer down tight against the outboard end of the spindle. Like a draw-bar right through the spindle, threaded into the part.

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                          Here's where it gets real interesting. I normally want to cut on the front of the part because I have a threaded spindle. I suppose that doesn't matter much in this case due to the draw bar setup, but it still makes me a bit cautious. On the front of the part I couldn't use the normal AXA tool post. It just wouldn't let any of my tooling get near the OD to clean it up. It's too big. So I tried a few things with the Lantern post which gives you all kinds of clearance. I wanted to use a boring bar in the lantern post, but I don't have any LH boring bars. My HSS collection was too short to allow the cut without the part hitting the carriage. So, I reversed my usual CCGT turning and facing holder in the tool block, and took the cut from the backside. I put a jam nut against the part just in case. Work is ongoing, slowly, because it is in back gear at 50 RPM.

                          Looking at the pics, it is obvious that the machine is maxed out.

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                          Last edited by nickel-city-fab; 06-05-2021, 02:45 PM.
                          25 miles north of Buffalo NY, USA

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                          • #58
                            More crazy setup: I finally got the OD cleaned up at some random number (didn't measure, non-critical) and also faced the rim on the underside, all in the same setup.
                            I like to do as much as possible in one setup regardless of where I am in a project. It's easier to guarantee squareness and accuracy that way. The "draw-bar" arrangement works well, rock solid:

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                            In the pic above, you can see how the threaded rod is threaded thru the tool surface, with a jam nut for insurance. Did the whole job with my favorite CCGT holder swapped around in the tool block working from the rear with the spindle running in reverse. Once again power feeds with back gears are my friend here.

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                            This pic shows the general arrangement for facing the surface, again using the draw-bar. I just saw a mistake - I should make the wood blocks longer so the part can seat on the already-machined rim, instead of the raw casting area underneath. I'll fix that tomorrow. I have to get up early and drive 30 miles for a pre-op Covid test in a town don't know. Guaranteed to be grouchy tomorrow.
                            25 miles north of Buffalo NY, USA

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                            • #59
                              Looks like you could use a larger 8.5" faceplate. When you make longer wood pieces, maybe notch the ends so the part's rim prevents them from flying out if something comes loose?
                              Location: Northern WI

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                              • #60
                                Originally posted by Galaxie View Post
                                Looks like you could use a larger 8.5" faceplate. When you make longer wood pieces, maybe notch the ends so the part's rim prevents them from flying out if something comes loose?
                                Nah, I think they'll be OK. The draw bar is pulling the part into the face plate hard enough to crush the wood.
                                25 miles north of Buffalo NY, USA

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