01-17-2014, 01:47 PM
KTC,
I checked my CMT billet upper and it is square. However, I had a slip fit, but no "wobble". The barrel extension IIRC was .9965. I decided to put mine together without loctite for now. I wish it had been a tighter fit, but I may do a before and after comparison if accuracy is suffering.
The main reason for doing it is to make sure that the face is square to the bore. Like others have said, it may affect accuracy and also help address the issues with broken bolts. Once I get some "used" brass, I plan on lapping my bolt also to make sure it is square, and has even contact.
Hopefully a CNC machine would have tighter tolerances, however machines tolerances deteriorate and wear, and if the machine has been "crashed" (hit something it shouldn't have been cutting or bumped into something) then the indexing on those 4 or 5 axis's could be off. I don't know how often the heads are indexed, but I'm pretty sure it's not every day at the start of the shift.
If you decide to loctite, as was already said, no open flames (to hot for the heat treat on Al), use a heat gun, heat evenly and penetrating oil. Loctite the barrel extension, not the threads.
I checked my CMT billet upper and it is square. However, I had a slip fit, but no "wobble". The barrel extension IIRC was .9965. I decided to put mine together without loctite for now. I wish it had been a tighter fit, but I may do a before and after comparison if accuracy is suffering.
The main reason for doing it is to make sure that the face is square to the bore. Like others have said, it may affect accuracy and also help address the issues with broken bolts. Once I get some "used" brass, I plan on lapping my bolt also to make sure it is square, and has even contact.
Hopefully a CNC machine would have tighter tolerances, however machines tolerances deteriorate and wear, and if the machine has been "crashed" (hit something it shouldn't have been cutting or bumped into something) then the indexing on those 4 or 5 axis's could be off. I don't know how often the heads are indexed, but I'm pretty sure it's not every day at the start of the shift.
If you decide to loctite, as was already said, no open flames (to hot for the heat treat on Al), use a heat gun, heat evenly and penetrating oil. Loctite the barrel extension, not the threads.