Replied by OleCowboy on topic AR10 80% magwell EDM
As a former machinist (AFL-CIO-IAM Dallas Love Field Local) in the airlines industry and in the manufacturing sector (munitions) I can assure you standard mechanical machining practices will give the same results at much lower costs. EDM is superior to conventional tool work, but I know of no requirement even with a 3 degree offset to mill out to the millionth of an inch, its simply not that critical, nor do I see a significant benefit in doing so. There are applications of this technology that lend itself to enhanced accuracy and for those who shoot a tighter group than a pie plate.
You will find there are even some AR 308 manufacturers that employ forging for their lowers rather than milling so the tolerances just are not tight.
If you want use EDM that is certainly your choice and you stand to lose nothing in the process, but your weapon would be better served if it applied to the bolt bore and races. Maybe you can get a better cost by having them do more work with the EDM, most shops will discount for more work performed. Let us know what you do on this...
Replied by OleCowboy on topic AR10 80% magwell EDM
There is your justification for sealing the deal.
As an engineer who practiced and lectured, if there was one thing I wanted my engineers and students to walk away with was: FORM FOLLOWS FUNCTION! A screwdriver is not a wrench, wrench not a chisel etc. You have clearly analyzed what needed to be accomplished, then chosen the RIGHT tool for the job I like that...
EDM is a proven method of "cutting" the magwell on lowers. A few manufacturers use this process as they already have the EDM machine and this saves on equipment (Cutting Dies and press).
Most magwells are cut on a CNC mill then a cutting die forced through to cut the corners of the magwell square to finished dimensions. (FYI most mill one side halfway through then flip the lower/tool head and do the other side. If this scares you keep in mind, in the 1800s the railroad used to cut tunnels through hundreds of feet of rock from both ends of the mountain and meet in the middle often only being off by a couple of inches)
In the garage the job could be done with careful measurement, a drill press/power drill and a file. A couple wood blocks and a steady hand and the 3 degree tilted magwell on the AR-10 would be no more difficult.
If you go garage on it with a hand drill (or anything for that matter) learn how to make a jig for the job.
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