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  1. #21
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    Quote Originally Posted by seaking View Post
    Not like your advice is gonna get him anywhere, either laughed at, big $$$ spent or sitting in his bud's garage for a year. If it's just clearance go at it with a hole saw.
    Blazzle asked about enlarging the stem clearance hole by milling, or using a milling machine. I simply responded with some considerations he would face. Apparently, he has access to a mill.

    My best piece of advice in my first post was that the easiest solution would probably be to change the stem in the lower tree to match the frame.

    Another poster mentioned that he cut out his frame neck with a hole saw, and as long as you could arrange to pilot it effectively, that might indeed be the easiest way to remove the metal.

    Jim

  2. #22
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    Machinists get creative to manipulate much larger and heavier parts like supporting them on forklift tines, adjustable welding stands and slinging them from hoists. I've enjoyed the show many times at my bros shop where he uses a soft sling to hang paper mill and tire company rollers from his small forklift the same way he carries them. (I watch skilled people like a hawk to learn like they did their mentors.)

    There isn't room or rigidity (machine tools flex, EVERYTHING flexes) on a conventional mill table to control the end of an unsupported six or ten foot shaft . End of shaft gets clamped to mill table, far end (ends are levers so gross motion at the end = fine motion at the table end) table is gently adjusted until end to be machined sits where it should, work is clamped, table is fine-adjusted then the part milled. The only rule is do it to spec, not make it purty while you are doing it.

    Pic is a visual aid and there are many ways to do this. Ugly hunk of scrap simulates pretty hunk of steel plate. Ugly scrap can have the surfaces you need squared up if you wish because you have a mill. Only the surfaces you NEED machined need to be machined and the rest can look like my old gray balls. Many shops have a pile of usefully shaped steel for this sort of thing including fixture plates they keep adding features to until they run out of space.

    Drill hole in plate below future neck center location for tool and chip clearance. Mill slots (represented by chalked ovals on plate) if you like for clamp studs. It's easier to get clamping studs into the nuts that way vs a round hole and gives easy gross alignment (vs a single person trying to hold clamps in place) plus you're on a mill so why not? You clamped the plate there for drilling one hole so milling four more is just a tool change away. Or just clamp plate normally. Whatever ya feel so long as it's rigid.)
    Pull machined neck surface (and note how casual the factory were about cutting that because it's not the Space Shuttle- the bearing cups are what hold the most precise parts, the outer bearing races) against plate with whatever is handy like large allthread. Tack weld neck to plate after depainting/derusting neck surface. Neck is now square to plate but of course you VERIFIED that instead of assuming, and can shim the assembly on the mill table to tweak if needed.
    Bolt result to mill table, preferably on short blocks to avoid drilling the table. Mill tables support and control far heavier shit then frames and you/re not taking monster cuts here.
    Since a frame has considerable leverage and everything flexes ( you can observe deflection with your indicator onces it's bolted down if you want to play) you'll want to deload your assembly by supporting the hanging end of the frame. Center quill on work using an indicator. Drill or bore neck center to clear larger fork stem. If you bore the last cut it will be a better reference fo boring cup holes but is certainly not mandatory. You now not only have stem clearance but an internal reference hole for when/if you flip the work when boring for cups. Bore end of neck for big twin cup if you're not using adapter cups.
    Remove from table and grind your tacks (MIGs aren't called "glue guns" for nothing and that's how repair machinists use them) to free the plate.

    Clamp then tack plate to other side if boring for big twin cups, your drilled/bored hole is your centering reference so your cup bores are cut concentric instead of off in space...
    You aren't moving the table more than a little to tram the neck bore to the quill so a cargo strap off your shop cherry picker or fork lift or a jack off a table etc can deload the work. Repair setup isn't a beauty contest.

    Remember you have three ways to changer relationship between part and cutter to cut metal, raising and lowering the table with the quill retracted (most precise), moving the quill with the table fixed, and for holes longer than the quill stroke both in combination but that won't be necessary for a Harley neck unless you're on a really small "toolroom sized" mill.

    If your plate is small enough you can cut it to fit in the mill vise but it will need squared edges for firm squared clamping. Shim if needed.Goal is to make round neck easy to clamp and control. A teeny motorsickle frame isn't shit. Use parallels so you don't drill the (usually expensive especially if it says "Kurt" on the side!) mill vise.

    Fun not-really-trivia: Ever wonder why a knee mill ram rotates beyond the range of the table? That's to machine parts too large to mount on that table. Machine tools are highly refined in many ways not visible at a glance.

    Lest anyone think I'm pulling even a little of this out of my ass, have some pics of the pros making money. Scroll down for pic of shaft in mill:
    https://www.cnccookbook.com/large-part-machining/

    Other notes:
    Manually held tools cannot be held truly square to a workpiece but OP has a mill so no problem.
    Hole saws take fixed cuts so they cannot be used to control fit like a boring bar if boring for bearing cups. Non-carbide toothed hole saws don't make precise cuts and hole saws create discs or rings of scrap requiring periodic removal unless they're of size that their kerf makes the entire cut (reasonably likely here but that much metal removal will likely wear out the teeth before finishing the job unless it's a carbide saw. A Rotabroach on a mandrel could do the crude boring for stem clearance in a mill or serious drill press (they're not for manual use).
    Manually held hones of the brake cylinder style follow the bore. They do not control their own cuts and could easily bellmouth a short or any hole.
    Sunnen hones are more precise than necessary but absurd for this sort of work because they're for finishing and because fixturing a neck to one of them would be a ballbreaker because you have to move the work back and forth over the fixed hone spindle. Hones remove material slowly and hone owners get grumpy when you wear out their stone sets.

    I'm just a noob so someone who does this for a living could knock it out laughing all the way. It's faster than it seems and faster than turning and threading a custom stem.

    If just removing the internal step this is easy because you won't need concentric bearing cup surfaces but I went into detail since many people read these posts. For step removal the tacked plate could be bolted to a (large) drill press table but not snugged, then aligned by tapping gently with a hammer. In that case large holes and washers would substitute for milled slots since the user doesn't have a mill. Many useful things were made before the knee mill was invented.

    Save the plate for future projects.
    Attached Thumbnails Attached Thumbnails exampleneck.jpg  
    Last edited by farmall; 2 Weeks Ago at 4:10 PM.

  3. #23

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    I could have done this with a round file by now.

  4. #24
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    Seems like it wouldn't be that bad with some creative clamping with the frame hanging off the table, could you not just indicate the cup landing on the end of the frame to see if you're level/plumb? the bore for the bearing cup is machined and so are the ends of the neck where the cups sit right?

    Jake

  5. #25
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    The way I described the "creative clamping" does that and also centers the neck bore on the mill quill. Reread the post if not sure.

    >>>> Imagine a pipe tack welded to a plate because that's all it adds up to. <<<<

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