Screw Jack

Here are 4 different size jacks that work with a simple screw design.  You will need one base, one screw, and one saddle.  

There are 4 sizes.  5_8 indicates that the jack is 5 inches tall when fully screwed in and 8 inches tall when the screw is screwed into the base 1 inch.  So functionally it will raise from 5 to about 8 inches.  Likewise the 8_14 screw and base would extend from 8 inches to 14 inches.  You could mix and match if you wanted to, but you wouldn't get the full range out of both parts.

I printed my examples with 6 wall thicknesses and you shouldn't need any support.  Mine turned out just fine without support.  

It should go without saying, but I'll say it anyway.  I'm not claiming any safe working load for this jack, and I can't recommend using it in any situation where its failure would be a hazard to your or anyone else's safety.

I designed this using Solidworks.