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Spot face

Discussion in 'Early CJ5 and CJ6 Tech' started by BlueComet, Aug 22, 2011.

  1. Aug 22, 2011
    BlueComet

    BlueComet 1962 JEEP CJ-5

    Montrose, Colorado
    Joined:
    Mar 17, 2006
    Messages:
    204
    Hello all. I'm getting ready to do a knuckle stud conversion on my Spicer 25 axle as per the instructions in the tech area of this site. In that write-up it specifies the source and part number for the correct fasteners - button head bolts. (McMaster Carr part number is 91255A647 for the 3/8-24 NF x 1 1/4” hex socket, button head cap bolt.)

    So, my question is this: does anyone have a recommendation for a spot face "bit" that I could chuck up into my drill press that would make the proper sized spot face? Do I need an arbor or guide of any kind too? I'm not very knowledgeable about these matters, and I'm sure this will be an obvious question to many of you. Anyway, I do have a basic drill press, and would enjoy trying this. Thanks for your help! :)
     
    Last edited: Aug 22, 2011
  2. Aug 22, 2011
    n6ifp

    n6ifp Member

    San Bruno/...
    Joined:
    Sep 15, 2004
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    206
    I got mine from McMaster-Karr. The toll and pilot are from them. I don't have their website in front of me ,but they are easy to find. I used the tool with a cordless drill. It was very easy to control that way. The other option is to find a local machinist. Larry
     
  3. Aug 22, 2011
    duffer

    duffer Rodent Power

    Bozeman, MT
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    Sep 17, 2009
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  4. Aug 22, 2011
    BlueComet

    BlueComet 1962 JEEP CJ-5

    Montrose, Colorado
    Joined:
    Mar 17, 2006
    Messages:
    204
    Thanks for the link - those prices aren't bad. So it looks like I would have to buy both a pilot and a counterbore. The big question is then which ones - meaning sizes? I would assume that the spot face should be just a little bigger than the head of the bolt, but does anyone have any recommendations for the bolt size listed above? Not sure about the pilot either, but the counterbore size probably dictates that, right? I know these are dumb questions, so thanks for your patience!
     
  5. Aug 22, 2011
    Billywam

    Billywam Billywam

    Lyons, Colorado
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    Nov 9, 2005
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    139
  6. Aug 22, 2011
    BlueComet

    BlueComet 1962 JEEP CJ-5

    Montrose, Colorado
    Joined:
    Mar 17, 2006
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    204
    Hey, thanks for the link Billywam, that answered my questions. Just for reference, Vern says:

    "A drill press and counterbore will make quick work of the machining. Select a counterbore with an outside diameter of 5/8" to match the heads of the studs. If you go larger than that, the edges of the cutter will hit the inner wall of the knuckle. The only 5/8" counterbore I owned had a 5/16" pilot, which was too small for the 3/8" finished hole. While scratching my head, I noticed the 5/16" pilot fit perfectly inside the existing 3/8" threads. So should you need to use a 5/16" pilot like I did, do the counterbore operation first."
     
  7. Aug 23, 2011
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    Aug 10, 2003
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    23,596
    Good excuse to buy a drill press, if you don't have one. Check your local Craig's list.
     
  8. Aug 23, 2011
    djbutler

    djbutler Sponsor

    Rio Linda CA
    Joined:
    Nov 5, 2007
    Messages:
    727
    Hi Blue,
    Yes, a 5/8 counterbore and the 5/16 pilot is what I used. Check the diameter of the head of the button head cap screws, I think you will see a little over 5/8. I used a bench grinder to reduce that head diameter a little so they would fit into the spot face I cut using the counterbore cutter. Chuck the screws into a hand drill and spin the screws while pressing the edge of the screw head up to the face of the bench grinder stone, you get an even cut all the way around the head of the cap screw that way.
    Once you have them installed into the knuckle using some red Locktight, you will need to do some relief grinding on the screws at 4:00 and 8:00 as well as the 9:00 and 3:00 positions to clear the axle spherical ends. I elected to grind on the cap screw heads rather than the axle housing but you could take metal off either one to get clearance for full knuckle turning travel.

    Don
     
  9. Aug 23, 2011
    CJ Joe

    CJ Joe Truckhaven Tough!

    Pinon Hills, CA
    Joined:
    Nov 9, 2002
    Messages:
    390
    BlueComet,

    Not sure what size chuck you have on your drill press but the spotface arbor size is 1/2". I guess it could be done off-hand but I'd choose not to.

    Keep in mind that Vernco used a different fastener than the button head that I used for that article. The button head "head diameter" is .650" so you would want to use an 11/16" spotface. This will give you a decent tolerance. In fact it will allow a little space for the liberal amounts of Lock-Tite to ooze up around the head. You have two choices for the pilot. The minor diameter of the existing internal 3/8-24 UNF thread is .330" a 5/16" pilot would give you about .018" of slop. Or... you could drill out the existing internal thread with an 11/32" drill and use an 11/32" pilot. This second method is only removing .014" from the weakest part of the existing thread and would have no consequence. I'd go for the second method.

    Also, there is not any need to do any relief grinding on the bolt heads in any of the positions. That was the reason I selected the button head bolt. It has a low profile and a large wide head to distribute the load.

    BTW, it's been over 6 years since I did that knuckle conversion. I've work that axle pretty hard and it's still holding.

    Joe
     
  10. Aug 24, 2011
    OzFin

    OzFin Vintage Jeep Guy

    Michigan
    Joined:
    Jul 16, 2007
    Messages:
    936
    I did mine in a mill so there was no need for a pilot. This is easy work for a fabrication shop, you may inquire locally to see if it can be done at a reasonable expense.
    I also turned down the button head bolts so the knuckle did not need grinding for clearance... and I do have the full turning angle. I got the bolts from Fastenal and threaded them through the existing holes/threads of the knuckle.
    Here are some pictures for ya.
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  11. Aug 25, 2011
    BlueComet

    BlueComet 1962 JEEP CJ-5

    Montrose, Colorado
    Joined:
    Mar 17, 2006
    Messages:
    204
    Thanks to all who posted their advice. It took some planning, but I've decided to go with the 11/16" spotface with an 11/32" pilot, and the McMaster Carr button head bolts as per the instructions in the tech section. I do have a drill press with a 13mm chuck, so the bit I ordered should fit (it has a 1/2" shank).

    I'll update with my progress when the tooling and bolts arrive. I'm learning as I go, and needed some patient guidance ... couldn't do it without your great help!
     
  12. Sep 17, 2011
    BlueComet

    BlueComet 1962 JEEP CJ-5

    Montrose, Colorado
    Joined:
    Mar 17, 2006
    Messages:
    204
    One last question here, so I thought I would resurrect this thread to ask it:

    Does anyone have a torque recommendation for the nuts that go on the new knuckle studs? Should I use red or blue locktight - or none at all? I have some lock washers that would fit. Should I use those?

    Just trying to clean up the details and finish this little project!
     
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