Chambering Through Headstock - Shims

Discussion in 'Gun Project Questions & Gunsmithing' started by GSPV, Oct 12, 2018.

  1. GSPV

    GSPV A failure to plan is a plan for failure. Gold $$ Contributor

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    Guys,

    When chambering through the headstock, where the chuck jaws contact the barrel, the barrel needs to be able to pivot rather than be bent to get the barrel bore concentric with the spindle bore

    Some people use a loop of thick copper wire. Some use copper pennies.

    Someone on here has a set of shims that I thought was a brilliant solution. Anyone on here know who does that or has a pointer to a thread to find them?

    Regards,

    Greg J
     
  2. GSPV

    GSPV A failure to plan is a plan for failure. Gold $$ Contributor

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    642A106E-F0D2-4A38-BEBF-4F9355EC477D.jpeg Like this. This looks like it’s in a spider on the outboard side.

    How would you do it?
     
    Last edited: Oct 12, 2018
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  3. Shawnba67

    Shawnba67 Silver $$ Contributor

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    Build a big spider on your chuck. I like to use tool balls between the blocks and the bolts to allow free pivoting. Use as fine a thread adjust bolt as you can makes the last tenths easier!
    They also sell bolts with pivoting balls built into the end I think they are called clamping screws. Lots of ways to skin this cat.
     
  4. Ggmac

    Ggmac

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    Take a 1" or larger aluminum square solid extrusion , drill a 3/4" or larger hole , cut diag in quarter . Make to size of barrel OD
    Or take 1" X.5" alum and pair 2 together and drill hole . Make 2 sets .
    It doesn't need be exact
    Or take 1"-1" alum , cut hole center and split , make 2sets .
    You get the idea
     
  5. Bamban

    Bamban

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    That looks like the outboard of my 1236. Here is the chuck side. The barrel pivots on ball bearings on the finger clamps.

    20180729_183637.jpg
     
  6. Bamban

    Bamban

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    Here is the one in my Jet 1024.

    20170502_234847001.jpeg
     
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  7. sdean

    sdean Silver $$ Contributor

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    Stan just think how small you would shoot if you chambered the correct way? You need to read the other thread to learn what material to use for pillars.
     
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  8. Bamban

    Bamban

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    Stan,

    The old heads in this game are all doing it right in their own ways, different as they may be. I have a lot of respect for the people like you, who have been doing this stuff for years, I read a lot and asked those older gentlemen I know in the business for advises. For myself, being a total rookie, with no preconceived biases, I jumped in with both feet and eyes and ears wide open. I am doing what I am doing because I am comfortable with it and it works for me within the limitations of my machines.

    Ignorance is bliss, I learned a lot along the way.

    Nez
     
  9. Daveinjax

    Daveinjax Silver $$ Contributor

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    That’s some sexy chit right there ! Too busy to clean up the part offs !
    It looks like you use brass for the shims. Is that brass or an artifact of the camera ? What all have you tried as shims ? Your thoughts on materials for shims ?
     
  10. shortgrass

    shortgrass

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    Many "don't know what they don't know", Stan. There's huge difference between applying practical machining experience and learning on your own off of the web.
     
  11. butchlambert

    butchlambert Site $$ Sponsor

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    Bamban understands machining practices and what is important in the final product. His setup does not bend or stress the barrel.
     
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  12. Bamban

    Bamban

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    I tried aluminum, and settled on brass. Don't know if I can tell the difference.
     
  13. butchlambert

    butchlambert Site $$ Sponsor

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    Bamban has been a friend for a few years. Both him and his wife are retired engineers. He has a great mind and is always studying different machining methods, looking for better methods. Bamban never criticizes others or their methods, He watches, ask questions, and evaluates all of this.
    Bamban is one of the best Service Rifle smiths in the nation.
    I knew he was good when I saw that his wife could always park her car in the 2 car garage with the machine tools. Among other tools he has 2 lathes.
    I don't chamber the same way as Stan, but I do know he has chambered several successful rifles. As said many times in the past, several good ways to skin the old cat.
     
  14. alphapygmy

    alphapygmy Silver $$ Contributor

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    I use a similar setup. The adjustment screws have ball bearings pressed into the ends and fit into dimples in the aluminum blocks. This barrel is threaded for an Ezell tuner and getting a touch up on the crown.
    chuck.jpg
     
  15. Cloudrepair

    Cloudrepair Gold $$ Contributor

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    20181014_105739.jpg 20171215_212207.jpg some of the ones I've done that work great.
    Just used 3/8-24 set screws and turned a .375 full radius on one end and used a .375 ball mill for the seat and part them off.
    I have used a radius on the inside of the shim and a flat both work perfectly fine.
     

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  16. Keith Kilby

    Keith Kilby

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    I milled half round cuts in jaws of 4-jaw. Made half round steel inserts that are just held in place by tension against barrel. Ends up acting like a true gimbal and allows you to hold barrels that don't have a cylindrical section at breech. You do need a barrel that extends outboard the head to hold in a spider there. You can watch indicator move at breech end as you adjust screws in outboard spider...with finger pressure only. Pivots quite nice in jaws. I have done quite a lot of barrels this way and never had one slip. Also works same way when you turn barrel around to crown/thread muzzle. Found this in the Aussie book by W. Hambly Clark. I'm not very good at posting pics but I'd be happy to text one to anyone that wants or doesn't have the book. PM with info to get pic
     
  17. Alex Wheeler

    Alex Wheeler Gold $$ Contributor

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    My thoughts are the outboard spider should not be doing anything. Design your chuck right and you can chamber a barrel holding it only with the chuck and the entire muzzle end can float. The spider is lightly snugged up only as extra support , but it should not be needed. If your using it to push and hold a barrel your bending it, if it doesnt have the clamping power to hold a barrel alone, the barrel with probably move during machining. If a barrel moves when you loosen your spider, your bending it.
     
  18. alintx

    alintx

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    Ever tried putting nylon tie wraps directly on the jaws?? Works like a champ and they're always handy. I chamber on centers, but they also prevent marring a finished surface
     
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  19. clowdis

    clowdis

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    Are the bolts holding down the ball bearings flat faced?
     
  20. Bamban

    Bamban

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    They are cup face screws that I touched up with 1/4 inch ball end mill.

    To secure the Bald Eagle spider to the faceplate I used plain old Unistrut 3/8 nuts that straddle over the slots.
     

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