Making a Floating Reamer Holder for Chambering Barrels

A simple floating reamer holder for chambering barrels in the lathe

First, as always, gather your materials.  You’ll need:

  • A piece of scrap ~3″ long by 3/4″ diameter
  • One ball bearing, as close as you have to 1/2″ is handy.  You can adjust this to any size over about 3/8″ – but 1/2″ or thereabouts is probably ideal.  An even easier alternative is to find a “Tooling Ball”.
    • A piece of aluminum at least 1″ in diameter by ~3″ length.
    • A piece of steel 3/4″ diameter by 1″ or so.
    • A bolt 3/8″ x 6″ or so.
    • two 1/4-20 setscrews or similar
    • a roll pin ~1/8″ diameter

    To begin, grab your 3/4″ stock face it off and turn one end down to the diameter of your ball bearing, or a little less, for about 1″.

    Facing a shaft for the drive ball portion

    Center drill it and use a countersink to open the hole to the full diameter at the mouth.  If you’re using a tooling ball, drill the shaft to accept the ‘handle’ of the tooling ball you’ll use.

    Cupped shaft, ready to accept the ball bearing or tooling ball

    If you bought a tooling ball, the work is easy, but if you have just a ball bearing, here’s how to proceed.

    Braze your ball bearing to the stock – I filled much of the cavity with flux before brazing, then just brazed it in with some brass brazing rod.  I quenched the brazed part as soon as I was done brazing in the hopes that my ball bearing wasn’t badly annealed.

    The ball bearing, brazed to the fixture

    A few minutes on the buffer and the piece cleaned up nicely.

    The brazed-on ball after cleaning up on the buffer

    Now turn the other end of the shaft to a diameter that will fit in your lathe tailstock chuck.  (1/2″ in my case)  I turned mine for a length of 1.125″, because that’s about as deep as my tailstock chuck.

    Turning the back of the shank to fit in the tailstock chuck

    The finished shank installed in the lathe tailstock chuck

    Now chuck up the aluminum stock and face an end.  Drill it 7/16″ all the way through.  (This is the diameter to hold your reamer.  If your reamer is some odd diameter you’ll need to adjust accordingly.

    The body of the reamer holder faced and drilled through

    Now for a little calculation – add 0.035″ to the diameter of your ball bearing.  My bearing was 0.560″, so my calculated value was 0.595″.  (Note that this dimension isn’t terribly critical either, so don’t sweat it if you’re a little off).  Bore the aluminum out to your calculated diameter for a depth of 1.75″.

    Boring the guide end of the reamer holder

    Now make a cleanup cut on the outside of the aluminum if you want your tool to look nice, chamfer both ends, and lightly countersink the larger (guide)  hole.

    Finally we’ll make the steel plug.  This is the surface on which the ball-bearing will bear.  We want to cut it so that the guide hole side is shallower than the guide is long, with a little bit to protrude into the reamer side.  It’s basically a stepped plug with two diameters – one the diameter our reamer hole (7/16″) and the other the diameter of our ‘calculated value’ from before.  Turn these to spec, a little over won’t fit, but a little under won’t hurt.

    First turn the reamer diameter.  I have about 1.355″ left in my 7/16″ hole, so I’ll turn only a 1/4″ stub to .375″.  Make sure to cut a square shoulder.


    Turning the steel bearing plug for the reamer holder

    Next turn the ‘calculated’ value.  I went for ~1/2″.  Polish the face of this end to a mirror finish.  Don’t worry too much about the edges – we’re only concerned with the areas the ball bearing can touch. The aluminum piece makes a handy handle for polishing.

    The polished plug, still in the holder body which was used as a handle while polishing

    Drill and pin the steel piece into the aluminum tube.  Push the steel piece in place, making sure it is fully seated.  Measure the depth to the polished face.  Add 3/8″ to that value and drill through with a 1/8″ drill bit.  Pin the piece in place with a 1/8″ roll pin.

    The steel plug has been pinned in place

    Install the set screws to hold the reamer.  The reamer goes in the 3/8″ hole, so measure it’s depth and drill and tap for two 1/4-20 set screws to fit in the allotted area.  I ended up with a depth of ~0.900 so I placed the set screws 0.400″ apart starting 0.300″ from the end.


    Setscrews installed to hold the chambering reamer

    Finally, install a handle on the aluminum piece.  I used a 3/8″ bolt, with the head rounded off.  Make sure the handle is short enough that if it were to come loose and spin, it won’t hit the ways on your lathe.

    Finished reamer holder

    This holder is for use only with piloted reamers.  It allows you to apply forward pressure with the tailstock, while allowing the reamer pilot to guide the reamer into the barrel.  If the reamer should catch while turning, simply allow the handle to slip from your grasp and spin freely while shutting down.



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    2 Responses to Making a Floating Reamer Holder for Chambering Barrels

    1. Calin Brabandt says:

      Great idea to use a tooling ball! I was trying to figure out how to easily afix a ball to my tailstock. Being worried about annealing a ball bearing, I’d considered scuffing up one side of the ball and just gluing it with JB Weld to the end of a cheap (machinable) modified dead center. I won’t worry about the hardness or robustness of a tooling ball.

      Thanks for the ideas.

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