board of a rigid plastic material the cutting surface 14 may be of a so called u201c self healing nature u201d when subjected to cutting action laminated thereto is a stock race assembly 16 comprising a disk shaped plate member 17 of rigid plastic which is attached to the opposite surface 14 a of member 12 by gluing as is well known in the art and which on the opposite side thereof has a grommet and sleeve member 19 rotatably connected to a stock race unit 18 constituted of plastic material as shown in fig2 in the exploded transverse sectional view thereof taken along line 2 2 in fig2 the stock race includes a first member 20 of a molded plastic ring shaped configuration having an annular raised portion 22 adapted to receive a series of annularly spaced ball bearings 24 housed in a plastic cage structure 26 which is fully rotatable about a central axis 27 this arrangement in effect causes the top member 12 having the cutting surface 14 to be equipped with a rotatable stock race configuration essentially analogous with that provided for in the u201c brooklyn revolver u201d rotating turntable structure as set forth hereinabove pursuant to the present invention there is provided a vacuum formed spacer 34 which is essentially a ring shaped disk member having.