Silly Putty pressed into and removed from a shallow feature allows you to see the mirror image of the feature in relief. This technique is especially useful for mold makers, since the impression left on the putty would be the same as the impression left on the molded part.

The "flapper" is an effective, easily made tool, which can be used to quickly hone or size poorly finished or undersize inside diameters. The shaft of the tool should be made approximately half the diameter of the hole being sized.

The cloth abrasive formed into a flat loop and clamped into the tool should be roughly twice the diameter (measured end to end) of the hole being sized.

It is important to indicate the spindle directly over the hole so that even pressure is applied. With the eighty-grit paper spinning at 500 RPM, I was able to open the hole in the example photo .001" in a few minutes.

A V-block constructed with shallow V-grooves can be used to effectively hold small diameter pins in a milling machine vise for further machining. One Advantage of using a V-block over using a collet fixture is that Z heights remain constant in spite of slight variations in pin diameter. The copper pin shown in the photo was held in place with a soft piece of plastic to reduce the chances of denting the pin.