12-13-2013, 02:03 AM
dave102269 Wrote:I have the lapping tool and have used it on a couple Spike's forged uppers with what I consider success. I'm about to assemble an upper on a Mega billet receiver and am concerned about using the lapping tool to check that it is true. If I spin the tool, it will remove the anodizing and open up the possibility of corrosion. Can I assume the Mega billet upper is true? Is corrosion an issue?
While I'm here...This is my first high end billet upper assembly. Will I need to use a torch to get the extension to mate with the receiver? Could one of you experienced guys elaborate on this process?
The only area that the lapping tool should be removing the anodizing is where the shoulder on the tool contacts the front of the threaded section. As stated earlier see LRRPF52's pic. I would not put a torch of any type on the upper to expand it to fit over the extension, (unless you are from Great Britain, they call a flashlight a torch). I don't know the temperature at which aluminum starts changing it's heat treat characteristics, but I would recommend contacting the mfg before heating over anything that needs gloves to handle.
I'm working on my first AR build also, so don't take my word on it. I used to make custom knives and I know a quick pass with a torch to straighten a knife blade just out of heat treat will affect the heat treat and edge holding ability.