This information is from Maritool's website www.maritool.com. 

Maritool makes outstanding tools at a great price.  I highly recommend you visit them.  Especially those using the new Tormach MX with BT30 tooling.

https://www.maritool.com/faq/collet-questions  Question #2

How much should I torque ER style collets nuts?

The following torque ratings are for solid ER style collets nuts. Bearings collets nuts are not as strong so reduce these values 15%

When clamping on shanks 30% smaller than collets maximum capacity, reduce torque value 40%.

In most cases a light oil film on tool holder thread is adequate. Collet and collet seat should be clean and dry. 

Below values can be exceeded 5% when using our full round torque wrench adapters.

ER8      10-12 FT-LBS 

ER11     15-25 FT-LBS

ER11M   15-20 FT-LBS

ER16     30-45 FT-LBS

ER16M   25-35 FT-LBS

ER20     50-55 FT-LBS

ER20M   40-48 FT-LBS

ER25     70-80 FT-LBS

ER32     90-110 FT-LBS

ER40     100-130 FT-LBS

ER50     140-150 FT-LBS