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Fino's D27 Knuckle Stud Project

Discussion in 'Builds and Fabricators Forum' started by FinoCJ, Aug 19, 2021.

  1. Aug 21, 2021
    colojeepguy

    colojeepguy Colorado Springs

    At the foot of...
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    IIRC the boring tool I used was 5/8 and I ground the bolt heads down enough to just fit in that hole.
     
  2. Aug 21, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

    Denver, CO
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    I got the 5/8 (think its actually 19/32) milling diameter, but its the pilot tip that won't fit down into the threaded section....I looked into a flat boring tool without a pilot tip, but wasn't sure if that would work...posted here: Spot Facing/counterbore Bit
    the best info i could find was from Don Butler in an old post thread with Wheelie, and I tried to order the same tool, but it seems that maybe he was using the press-in studs that require the threads to be drilled out, and that allowed the pilot tip to fit? Not sure....
     
  3. Sep 4, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

    Denver, CO
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    So, one of the biggest challenges i am finding with this project is getting the proper tool for the spot facing of the knuckles...The absolutely right tool is from Mcruff that I think he made and is probably not an everyday available item. Thought I'd post up the differences and maybe it would help others avoid some of the pitfalls.

    Here is a pic of Mike's tool (top) and two other counterboring bits commonly found online that do NOT work:
    [​IMG]

    Mikes tool looks to be just under 11/32 on the pilot tip, and 21/32 on the counterboring portion...And I think its key that the pilot tip is just UNDER 11/32 (although 5/16 would also work I think) so that it can center in the threaded holes without causing damage to the existing threads.
    The next tool down is a commonly found 3/8" pilot according to its stamping (but I measured closer to 13/32) with 5/8 (maybe 19/32) counterboring face. The counterboring face would work if the buttonheads are ground down a bit, but the 3/8 pilot tip is too large to fit into the existing 3/8 threaded bolt hole. This tool may very well work if press in studs are used instead of threaded buttonhead bolts, although I cannot verify that.
    The last tool is a commonly found 5/16 pilot tip (as stamped, but I measured more like 11/32) with a counterbore of 1/2 (maybe 15/32), that I figured would have a small enough pilot tip to fit into the threaded hole, but I didn't try it as it seems it would have to be forced in using the drill press and I figured it would damage the threads - in other words, it doesn't slip into the hole by hand. Additionally, this tool would not provide a large enough diameter counter bore needed for the just over 5/8 diameter head on the buttonhead.

    So in summary, it seems the standard counterboring tools that I found do not work for this application, unless you get a set of counterboring bits with interchangeable pilot tips (expensive). I don't know if other people used different tools, or just straight flat boring bits without the pilot tip, or ground as flat as possible by hand, but without Mike's special tool, I don't know how this gets done.
     
    Last edited: Sep 4, 2021
  4. Sep 6, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

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    Okay...so with the help of a number of members, making a little bit of progress...
    Doing a bit of test fitting for clearance with the buttonheads against the axle housing sphere - its the 3 and 9 oclock heads that hit the sphere. Working on the right side, here is 3 oclock:
    [​IMG]

    and 9 oclock:
    [​IMG]

    And here is the axle mounted stop screw still in its original location:
    [​IMG]

    That stop screw has quite a big gap between it and the knuckle, although some of that space will be taken up by the felt seal/plate and mostly the hex head that hold the felt top plates on. But I decided to make a bit more clearance...it may not really have been necessary. But I ground the buttonheads down a bit. From the backside of the knuckle, the one on the left is 3 oclock in its finished state, and the one on the right is 9 oclock and only partially finished. Its hard to test if the 9oclock one is okay as there is no stop screw on the backside - the only proper way to test would be to jack up the entire front, re-connect the steering linkage and turn the steering wheel to see what hits first, the 9 oclock head, or the stop screw on the opposite side wheel. Anyway, I just kind of eyeballed it - it reality, all this tedious fit testing and re-testing probably doesn't truly affect the turning radius much.
    [​IMG]

    and also ground some notches in the sphere:
    [​IMG]

    With all that done, the fit looks good....the knuckle now with seals installed contacts the stop screw still in its original location.
    [​IMG]
     
    Steamboat Willys, Twin2, Jw60 and 3 others like this.
  5. Sep 6, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

    Denver, CO
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    With all that done, new kingpin bearing and races went in packed with grease:
    [​IMG]

    And the knuckle in its final state - I actually had some trouble getting the knuckle seal to fit - seemed like it wouldn't stay in place and I had to sort of keep working it into place as it was clamped down by the seal plates and crushed felt....I tried to add a bit of RTV to the outer edge of the seal that contacts the outer knuckle, and basically it just made a mess. The inner lip that slides over the sphere gets a bit of grease...I also added a bit of thread sealant to the bearing cap bolts and torqued to spec.
    [​IMG]

    Think everything is now ready to slide the axle shaft back in - the axle ujoint seems perfect so leaving it alone. Spindle will slide on, and then brake backing plate and tighten down nuts on the newly installed buttonhead bolts/studs.

    Also, I should give a shout out to TomTom who sent along a set of knuckles with the buttonheads already installed! I was really struggling with the spot facing aspect, so that has really helped keep my progress moving forward on the cj so it will be ready for Moab. I am working on a 2nd set of knuckles (thanks to Wheelie!) that is getting the full spot facing treatment now that I have the right tool (thanks to Mike) and possibly know what I am doing (eh, probably not) so I can finish the same project on the 58. So far, no highly desired 2 hole knuckles have been destroyed in this process...
     
    Last edited: Sep 6, 2021
  6. Sep 6, 2021
    tripilio

    tripilio Proud American! 2020 Sponsor

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    I had some serious protrusion of the button heads on my studs conversion. Easier for me than setting up the knuckles on the milling machine ( level, centered, etc) I mounted the bolts in the lathe and on those two, I think at 3 and 9 o'clock and turned the heads down to remove enough material to eliminate the interference. Just my 20 cents. As someone said a while ago, it is 20 cents to compensate for inflation. :D
     
  7. Sep 6, 2021
    Jw60

    Jw60 Member: Club Foot Dad Club. 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    James have you turned the button heads down for the 58 yet?
     
  8. Sep 6, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

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    Everything back together with nuts on the outside
    [​IMG]
     
  9. Sep 16, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

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    So, back to trying to learn how to spot face the backside of the knuckle...I was able to initially skip this step on the cj repair, but figuring it out now for the next set of knuckles. Using Mike's tool - which really makes this easy even in a drill press - I am trying to figure out how far down to machine the knuckle surface. I did two of them (4 and 8 o'clock) just enough to machine the raised surface of the knuckle flat (remove casting irregularities), but did not remove all of the raised section thickness.
    [​IMG]

    In this scenario, the outer rim of bolt head will overhang or extend beyond the machined surface, but because its raised it will not be in contact with the surrounding rough casting. This limits how much surface area the head bolt sits on the knuckle, but it keeps a bit thicker material around the hole. I could machine down until the entire raised section is flat with the surrounding casting, and then the bolt head will seat essentially sit entirely supported on the knuckle surface, but it also makes the area around the hole a bit thinner....does this difference really matter, and if so, which method do people think is best? thanks...
     
    Last edited: Sep 16, 2021
    Rich M. likes this.
  10. Sep 16, 2021
    jeeper50

    jeeper50 jeeps 'till I die

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    I would leave as much meat on the inside of the knuckle as possible for strength, except for 3 and 9 position then just enough to clear the axle sphere.
    What a great thread showing your progress!
     
    colojeepguy likes this.
  11. Sep 16, 2021
    dnb5853

    dnb5853 Member 2021 Sponsor

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    For what it's worth, here is a picture of the inside of a Dana 30 knuckle (Narrow Track mid-80's version). All six studs have the heads shaved on one side so as not to interfere with the outer casting diameter.
    The thickness of the main flange is .400".
    [​IMG]
    I will agree with jeeper50; leave as much flange thickness and don't worry about some bolt head overhang.
     
    Last edited: Sep 16, 2021
  12. Sep 18, 2021
    wheelie

    wheelie beeg dummy 2021 Sponsor

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    Mine were machined just enough to create a flat surface for the buttonhead with the intent of leavings much of the knuckle meat intact as possible, just as you suggest. I did have to chamfer the inside of the threaded hole just a bit as the buttonhead screws have a slight taper at the base of the threads where they meat the flat surface of the underside of the head.
     
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  13. Sep 26, 2021
    Warloch

    Warloch Did you say Flattie??? Staff Member

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    James - the 'strength' will be dictated by the thickness of any given point where the metal can flex. This can be at the shoulder of the casting or the mating surface of the bolt/stud inserted. Thickness will only truly matter around the whole for the thread engagement. More threads engaged - stronger bonding for lock tight. This will NOT impact the inflection points (shoulder points) of the mating surfaces.

    Summary - you could take them down to the surface of the ring and not impact the overall strength. I would take them to the point where the shoulder of the bolt/stud has either a step to increase inflection strength or meets the most surface area.
     
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