How are dovetail tapered gibs made in a production setting?
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    Default How are dovetail tapered gibs made in a production setting?

    Does anyone have pictures or knowledge of how dovetail tapered gibs are made in a production environment? I am assuming they start out with a casting of some kind.

    What is the process? They don't appear to be Blanchard ground. The ones I have seen appear to have been milled on the clearance surfaces (edges). I don't know about the bearing surfaces.

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    The only piece of information I have is rather outdated: at Sheldon they cut their gibs on shapers. From time to time some new engineer would come up with a new idea on how to make them in a more efficient way. Each time, after a few months of testing they were back to the shapers. The trick is that planers and shapers introduce very minimal stress in the part and gibs so produced required only minimal fitting.
    If I were to produce blanks, I would probably start from a plate and a bandsaw with the blade tilted to the dovetail angle.

    Paolo

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    milling is often used. it requires rechucking lightly and multiple light finish cuts. i often mill
    .017 semi finish cut
    .0025 semi finish cut
    .0005 finish cut
    .
    milling can obtain .0003" flatness and waviness tolerance if it is done carefully. it can be .001" out of tolerance easily if not done correctly

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    Quote Originally Posted by DMF_TomB View Post
    milling is often used. it requires rechucking lightly and multiple light finish cuts. i often mill
    .017 semi finish cut
    .0025 semi finish cut
    .0005 finish cut
    .
    milling can obtain .0003" flatness and waviness tolerance if it is done carefully. it can be .001" out of tolerance easily if not done correctly
    Please post a pic of your fixtures
    It would be appreciated
    Thanks

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    A sinemagnet with the pivitpoint on the short side or a magnet clamped in a vise at the right angle
    Then first mill or shape and then grind
    When milling keep the gib touching a shoulder bolted to the side of the sinetable
    To make them fit I make them a fair bit longer
    Then fit them with feelergauges at the end between gib and body
    I adjust feelergauges till the feelergauges are even tight to a accurracy of 0.01mm
    Then I know how much to adjust the magnet If 2 the same feelergauges are even tight I know we are getting somewhere
    Then schrape them
    Richard King can probably scrape them to size faster but not me And I still need the setup for milling

    Peter

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    20170620_233429.jpg20170620_232809.jpg20170620_224404.jpg20170620_233337.jpg20170620_232005.jpg

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    Quote Originally Posted by Iridium77 View Post
    20170620_233429.jpg20170620_232809.jpg20170620_224404.jpg20170620_233337.jpg20170620_232005.jpg
    Beautiful. What book?

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    Quote Originally Posted by Hbjj View Post
    Please post a pic of your fixtures
    It would be appreciated
    Thanks
    .
    i dont currently have a picture of fixture and setup. easier to just use a fixture with all the angles machined into it.

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    I mentioned in another thread about my fixturing alloy jigs. Float the blank on the molten fixturing metal and use the sine calculations to find the angle. Works very well, gib is supported 100% the whole length, and boiling water removes the gib when done.

    I'm soon to make a cross slide gib using one with a 18" long pocket, overall length is 19" and can be set up in two Kurt vises for milling. I'm using continuous cast ductile iron for the gib itself, which seems to have more consistency and finer grain structure than just sawing off a chunk of cast iron.

    Here is one I made a new gib for another 1440 lathe in, note the two set screws so I can duplicate the taper without gage blocks in the vises using a dial indicator;


    A new one for a 17" gib for my current project;

    Same fixture with an old factory gib sitting in it, and a fixturing alloy ingot sitting by it;


    But obviously I'm not doing it to earn a living, just forced by circumstances often over the years. And I'm not trying to teach or brag or somehow put anyone else down, it's just how I do it and there may be better ways.
    If I had a big enough shaper or a planer I'd sure as heck favor that over doing the roughing in the mill, in any case the next step is scraping for a large contact area fit.

    As to how they do it as machine tool manufacturers that would be interesting to know, I assume a dedicated jig with the angle built in. The reason behind the use of fixturing alloy for me was I couldn't find a better way to hold on to a lozenge section, the alloy does that very nicely.

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    This is from American Machinist, 1922, Vol 56 No 6.
    gib-1-.jpggib-2-.jpggib-3-.jpggib-4.jpggib-.jpg
    John

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