I just became a member and trying to figure out how to ask a question. I recently received a Rebel t6i. My older camera is a Pentex Honeywell with thread mount lens. Is there an adaptor for between thread mount lens to bayonet lens?
Your Pentex Honeywell camera uses a M42 screw mount. A simple M42 to EOS adapter might work for you and only costs about $10. But... Some lenses have protrusions that might interfere with the mount so it would be best if you went to a camera store to try it out before you buy.
"Is there an adaptor for between thread mount lens to bayonet lens?"
There is no adapter that is worth time nor money spent. You have a nice T6i so move on into the digital age and leave the screw mount in the past where they belong. All modern digital age lenses are better than the old film lenses.