Current specs for the swivel cap retainer on the MK 20 and Mk 25 call for 70 inch pounds (5.8 ft pounds) on the brass bodied first stages but only 35 inch pounds on the ultralight first stages. To use a torque wrench you obviously need a socket ending in a 7/32 allen head.
One thing about torque wrenches is that they are only really accurate in the middle third of the range, so you end up needing 2 wrenchs to do a good job on a reg.
In the abscence of a torque wrench and a suitable allen head socket, you are far better off tightening the swivel retainer cap by feel with a T-handled allen wrench than by trying to use a ratchet and socket.
The SP specs for the Mk 20 and 25 also indicate you should be torquing the seat retainer to 130 inch pounds and the yoke retainer nut to 266 inch pounds and, on DIN regs, the filter retainer to 35 inch pounds.
The yoke retainer is pretty important as it is both easily over torqued and also at high risk of coming loose if inadequately torqued. Every tech should be using a torque wrench on this. But every now and then I encounter a reg where this nut has been badly over torqued and can be very difficult to remove when the excessive torque is combined with a couple years of corrosion.
SP uses the phrase "tool tight" for things like HP and LP plugs as well as for the cap itself and this gets extended by many techs to things like the seat retainer and swivel cap retainers.
To be honest, I do not get overly concerned about torquing the swivel cap retainer on the brass bodied regs if I am doing something in the field. If you are using a T-handled allen wrench on this item and have some experience you are extremely unlikely to break anything (unless you are conan the barbarian), will have a very good feel for how things are progressing and, with adequate experience, you will get it torqued close to the mark as the torquing of the allen wrench itself is in fact a simple torque indicator. This is probably the most fragile part in the reg and I tend to think that there is also a risk of a torque wrench failing to release, or more often of the operator failing to notice the release at the low pressures involved are more of a risk than doing it by feel with a T-handled allen wrench.
And if you look at it, the 3 ft lb torque used in the aluminum regs is adeqaute to hold things together so on the brass bodied regs you really have a fairly wide 3 to 6 ft lb range to land in and the biggest risk is that of over torquing which can happen accidently with a torque wrench at the low settings involved particularly outside a shop setting.
