Small Machinist Jack

[Paul Jones]

Last week I was working on a project where I needed a very short machinist jack but instead had to improvise. I wanted to be better prepared the next time so I machined a 1.3” to 2” tall machinist jack from 7/8” dia. 1018 cold rolled steel (CRS) rod and used a ½-20 hex bolt for the jack screw. These machinist jacks are used for support and positioning parts for milling operations and also used as packing materials for cutting short stock on a horizontal bandsaw.

Using the lathe, I reduced the rod diameter to 0.864” to better fit a 21 pitch knurl and reduced the top of the jack base using a cutting tool with a 0.125” radius (see photo below). The internal thread of the base goes completely through and also provides a think 0.1” rim around the base bottom for better seating. An 8-32 x 1” stainless steel socket head cap screw provides a "handle" and another way to lock the jack screw. Using the jack base as a mandrel, I faced the steel hex bolt top flat, drilling 0.5” deep and then reaming a 0.251” hole in the top for any future attachments like a swiveling top, V-groove top, pointed rod, etc. (see http://www.homemadetools.net/machinist-jack-accessories ).