Machinist's Jack

This is a machinist's jack I made for use on the milling machine. At the minimum height (62 mm} it is level with the base surface of my milling vice when mounted on top of the aluminium t-slot covers. It can also (obviously) be raised up higher as required.

This photo shows the jack with the top (loose) piece removed. All parts were made out of the same block of 40 mm diameter EN1A. The diameter was chosen partly as a result of a conveniently sized piece that I had available, but also in an attempt to make its radius span the distance from the middle of one of the t-slots to the fixed jaw of the vice. It isn't quite big enough to reach that face, but it will work for all but the smallest parts.

The bore through the middle of the top knurled part is 12 mm; this allows the top loose piece to rotate freely (so it can stay still as the jack is raised underneath it). It also allows an 8 mm hex key to pass all the way through (more on this later).

This photo shows all the parts that make up the jack. The top left part (base) is 40 mm diameter and 40 mm long. It is internally threaded M28×1 to a depth of 25 mm and then a 18 mm diameter facing cut was made on the bottom surface to remove the cone shape produced by drilling. The hole that goes through the middle is 10 mm. This allows the jack to be clamped down to one of the t-slots with a cap-head screw if required.

The threaded part in the top-right of the photo is the adjuster screw. This is 35 mm long and threaded M28×1 for all but 10 mm of its length (the remainder is left as 40 mm diameter). There is a 12 mm hole all the way through: as mentioned above, this is used to mount the loose piece and also allows hex-key access if the jack is clamped down to the table. The bottom end of the adjuster screw (shown at the top end in the photo) is counterbored 18 mm to allow clearance for the cap screw (so that the adjuster can go further into the base.

The part in the bottom-right of the photo is a simple knurled locking ring. It is 5 mm thick and internally threaded M28×1.

I'm expecting that at some point in the future, I'll cut a v-slot in the loose top piece (or a new one made for the purpose) to help with supporting round stock. I haven't had a need for this yet so it hasn't happened!

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