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Posted: 7/25/2014 9:51:46 AM EDT
| Ordering some 7/16" end mills for some 80% lowers. Is there an allowance for a radius at the bottom of the milled pockets? In other words, should I order squre end end mills or can I get some with a .03"(or bigger) radius round edge? Thanks for the help. |
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Quoted:
You could cut the floor .03 deeper and use a radius if you wanted too. For that matter you could do almost all of the lower with a small radius cut and only touch up edges that are needed with a square end mill. It's your lower, make it how you want it. I've considered this option. Might just have to try it, just for the hell of it. |
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Quoted:
Ordering some 7/16" end mills for some 80% lowers. Is there an allowance for a radius at the bottom of the milled pockets? In other words, should I order squre end end mills or can I get some with a .03"(or bigger) radius round edge? Thanks for the help. There is no allowance for radius, but there is some tolerance for slop. As mentioned, you could hog it all with a radiused cutter, and just stay the radius above final depth with your quill stop, then finish to depth with a flat end mill. Except for the trigger return spring, nothing else needs the floor of the FCG well pocket to even be there at all. |
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Quoted:
Thanks. I hate sharp corners as they are huge stress points. If I can get away with radius, I always try. There is little stress in an AR lower receiver. Square corners at the bottom of the fire control pocket will never be a problem. Every AR is machined that way. |
| Radius corners are used in structural steel to prevent stress cracks or failure points. But..... we are not talking 50 Kips stress on an AR lower. The original design was for square corners, and I see no reason to deviate from the design that has been working well for close to 50 years, give or take. |
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I can understand where he's coming from here, square corners (sharp cut angles) are stress risers and create possible fracture points.
But as pointed out, the design has been around for over 5 decades and there are still original receivers running. I'd rather have a slight fillet at the corner myself. |
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