Similar to a Liner bushing, but with a head to resist hevay axial loads. Head liners are permanent bushings used to hold renewable drill bushings. The head liner's ID has a precise sliding fit with the renewable bushing's OD. The hardnened head liner accurately locates the renewable bushing and protects the jig plate from wear cause by frequent bushing replacement.
Note: The "length" listed for a head liner refers to its overall legth, not its length under the head. Metric head-liner bushings are the same as metric press-fit bushings.