How to choose a Chuck JT taper

This is a follow up to a previous topic I have submitted.

I am about to buy a keyed 2mm -13mm chuck and mounting Arbor for the 2MT fitting on the tail stock on my small lathe a Proxxon PD400. The intended new chuck has a Jacobs Taper (JT) mount and the chuck is available in 6JT and 2JT. At the point of placing the order for chuck and arbor I had to state if the chuck was to be a 6JT or 2JT mount in order to supply the appropriate 2MT Arbor. In my limited experience I have no idea why or how a 6JT or 2JT Chuck Mount is what I need. I will be grateful if someone can take the time and trouble to point me in the right direction.

I have looked on the internet and got nowhere. I made enquiries at 3 quality outlets for engineering supplies and tooling, and was told the following;

1. The various sizes of JT mounts is to enable a buyer to use an existing arbor.

2. 6JT mount chucks have a boss and therefore stronger.

3. Some JT mount sizes allow the chuck to be interchanged with other specialist equipment.

It's worth looking at the dimensions **LINK** , to inform your decision.

JT6 is pretty bulky for a modest size chuck.

MichaelG.

My Jacobs #34 chucks, 1/2", have a JT 6 taper, two of them with 2 MT, and the other with a 1/2" parallel, it fits in my wall drill that was designed to tale Blacksmith drills. I think one 16 mm chuck is also 6JT/2MT, and the other is 6JT/3MT.

Ian S C