The drilling jar connecting with drill tool and working with drill strings is a downhole stuck freeing tool in drilling operation. When drill tool is happened to be stuck in downhole, the stuck drill tool can be released by in time starting the drilling jar to provide continuous up jarring or down jarring . It is a desire tool for directional well, complicated well and deep well.

The drilling jar is consisting of ZSJ type drilling up jar and ZXJ type drilling down jar , both can be used mutually or operated separately . The up jarring section takes use of hydraulic mechanism; the jarring force can be adjusted according to up elevating load but can not exceed the max. load for tool load rated. The down jarring section takes use of mechanical friction mechanism; the jarring force is well pre-adjusted by adjusting device before put into down-hole. No re-adjustment can be allowed after jar is put into down-hole.