An easily used adjustable jig for accurate pre-grinding of TEM specimen discs to a predetermined thickness. Thinning time may be considerably reduced by initial grinding down of thick specimens to the order of 0.005"-0.010" (0.125-0.25mm). A graduated grinding jig can thus save valuable time and produce more accurate results. The Graduated Grinding Jig is made of stainless steel and has click stop graduations of 0.001" on the advance screw. Thus the thickness of a specimen can be reduced in