JT taper for drill chuck

[bryan]

I have a R8 arbor for a drill chuck but I don't know what JT taper it is to get a chuck for it. It measures .813 at the aft end and .765 at the narrow end. What is the jt taper?
Internet didn't do me any good on this one
Thanks
Bryan

 

[JerrySharrett]

According to Machinerys Handbook it is a #3, pretty standard of the Jacobs tapers. (0.8110-0.7461") You measured the small end as 0.765" but I'll bet that was to the top of a radius. The #3 measurement above is to a sharp corner.

 

[bryan]

Thanks, Jerry

I just did a quick measurement with a caliper, thinking a JT6 or whatever would be a lot different.
Now I know what chuck to get.
Thanks again....
Bryan