Originally posted by pentasonic49 The T mounts that I have are held on to the lens with three equally spaced grub screws in the knurled part. You unscrew them a few turns and the mount detaches from the lens. The lens end of the mount is a dovetailed groove.
The grub screws do not hold the adapter to the lens. The adapter actually consists of two pieces. One piece has the camera mount, while the other has the fine threads to connect to the lens.
The grub screws are there to allow you to align the focus and aperture markings so that they are on the top of the lens.
The adapter simply unscrews from the lens. It is simply a friction fit. There is no locking mechanism.
Its possible that the adapter the OP has is really a Nikon F-mount, which is very similar to a Pentax K-mount. Are there any markings on the adapter? If it is a Pentax mount, it should have P/K engraved on it somewhere. If it is a Nikon mount, it will have NI or N engraved.