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determining bat pin locations

updated tue 21 may 02


Joseph Herbert on sat 18 may 02

Bud Tustin writes:
How can I figure where to drill the holes for the pins, so that they
correctly positioned, so that when I put a plastic bat on them, it will not
wobble ? Not a math wiz, at least not since the aneurysm.

Before you start, you really must know how far apart the holes in the bats
are and what size the holes in the bats are.

Usually the bat pins are ¼ inch socket head screws. The heads have an outer
diameter of 3/8th inch. These screws have a hexagonal recess in the head
that takes an Allen wrench. These screws are available in stainless steel
for about 50 cents, depending on length, and stainless wing nuts are about
65 cents. Why would you have any thing else. Of course, beryllium copper
is nice…

The holes to be drilled in the wheel head have to be large enough to allow
the ¼ inch body of the socket head screw to pass easily. In my machine
assembly days, I think we used a letter O drill – 0.31 inches. You will
need at least a 1/32 larger or 9/32 inch.

To assure accuracy in locating the holes, a prick punch or center punch is
necessary. Also, metal dividers with a screw adjustment and a metal rule or
straight edge and a scriber of some kind. It is possible to do the layout
with pencil.

Clean the wheel head so it is nice and shiny. With the wheel slowly
rotating, move a pencil or scriber across the wheel surface toward the
center. At each stage, the marking device draws a smaller and smaller
circle. When the marker makes a very small circle or dot, stop the wheel.
Place the point of the scriber in the center of the small circle and hold
the scriber vertical. Rotate the wheel and look for any movement of the
point. If it appears stationary while the wheel rotates, you have found the
center. Lightly mark the spot by tapping the center punch with a hammer to
mark the spot. Check to see the punch mark is in the center by the same

Put the point of the scribe in the center mark and slide the straightedge
into contact with the scribe. Hold the straight edge firmly in place and
scribe a line across the wheel head. This is a diameter line since it goes
through the center of the wheel head.

Since you have already determined the distance between the centers of the
holes in the bat pins, you can set your divider points to half that
distance. With one point in the center mark, scribe an arc across the
diameter line on either side of the center. Punch mark the place where the
arc and the diameter line cross.

Check the distance between the punch marks to assure they are the same
distance from the center and that they match the distance between the holes
in the bats.

Block or clamp the wheel head so it cannot rotate during the drilling

Using a 1/16 inch drill bit, drill a vertical hole through the wheel head at
the punch marks made where the arcs cross the diameter line. Do not drill
at the center punch mark. After the pilot holes are drilled, drill the
holes for the pat pins with a 9/32 inch drill bit. Remove any burrs from
the holes with a file or abrasive paper.

Test the socket head screws for fit. If all is well, fasten with lock
washers and nut on the underside of the wheel.

Measure twice, drill once.

Good Luck


GlassyClass on sun 19 may 02

Thank you everyone for giving me such clear directions on how to do it, and
also all the suggestions on how to make it easier.