I have an small adapter that goes into my tripod head socket and makes
it fit on the smaller male post of the tripod legs. I don't recall if
the size is the same that you mentioned though. I suspect that bigger
camera stores should be able to help you. You might check the
bogen/manfrotto web site for parts too.

Yes, it's a standard part that's often included with tripods
and/or heads. It's usually a small insert that you can
either screw into the head to make it 1/4" or alternatively
screw over the tripod thread to make it 3/8". Any dealer
that sells tripods/heads should have one.

The Manfrotto item is 088LBP in Europe. If you're in US it will have a
different Bogen number, but I expect if you are you'll be able to do a
search on it and get the number you need.  Hope this helps.
Mark

Yes, Linhof has packaged one, that works very well. It is stainless steel (
most are brass and crack easily), and I keep about 3 around various camera
bags. Most pro-photo shops carry some version, but after a dozen cheapies,
I've standardized on the Linhof and have never broken a single one over 15
years.

Hunt

According to woops <w3cyykcv7q8gjpv@jetable.org>:

    Yes.  I have several which came with various things.  Your ball
head (especially if new) should have come with such an adaptor.  They
are typically a collar threaded externally with the 3/8-16 and
internally with the 1/4-20.  They typically have a bit of a flare (like
a countersunk screw except that the overall diameter is just a little
beyond the OD of the 3/8-16 thread (to keep the adaptor from going too
deeply into the hole in the camera or the ball head in this case), and
they also typically have a slot bridging the 1/4-20 hole so you can use
a coin as a screwdriver.

    O.K.

    Check the packaging for your ball head.  I find it difficult to
imagine it being shipped without one.

    Yes -- you could *buy* one.  Try going to your camera store and
seeing what they have.  I would expect them to be in a blister pack on a
rotating rack somewhere.

    Or -- if you have a lathe, turn the 3/16" OD with a bit of a
chamfer at the end, thread it using the lathes' threading gears, drill
through the center with a #7 drill bit (tap drill for 1/4-20, and tap it
to 1/4-20, and only then part it off.  I would suggest brass as being a
good material for the product.

    If you have a milling machine, also set up to mill a slot for
use in removing it when the time comes that you need to do so.

    Grinding is probably a poor way to make one.

    Enjoy,
        DoN.