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Best place for carbide bits... update with sort of finished 80% project on pg 2

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RobertH:
shooter, who makes that jig?

zofoman:
OSG is the brand that most of the high-end shops use.  Many are DOD contractors and their tolerances are extremely critical.
Sound advice is to invest in the right tools the first time.  You just increase your overall costs when failure occurs and you have to replace that bargain tool with a better more expensive one...not to mention cost of your potentially damaged product.   Just my .02

OSG Tap & Die cutting tools
402-980-1714

SS_N_NE:
I am a machinist and have finished a forged 80% lower.

Carbide bits are expensive, fragile and expensive. Carbide requires rigid machine setups and are not the best choice for occasional, lighter or more manual (like drill press and jig) work. High Speed Steel (HSS) is more forgiving and will machine aluminum very effectively at a much lower cost. Use WD-40 to keep the aluminum from cold welding (sticking) to the cutters and drills. It is best to have compressed air available to frequently clear away chips (there will be a lot for such a small project). Carbide is awesome material but can be easily chipped by handling and application errors. A sharp HSS tool will last a long time in aluminum and resist a number of errors plus a very low cost. STILL...try to stick to name brand tools bits, there are some cheap import tools that are just "look like tools" (Harbor Freight), the low cost import tools at a place like Enco, will be up to the job. It is difficult to explain the difference, but just to be aware that there is some true junk tooling out there.

Enco is a reasonable resource and allows choice of cutter quality...the cheapest tooling will work fine and do dozens of lowers if not abused (intentionally or unintentionally...machine work generally involves a lot of trial learning...the hard way).

Placement of the holes for trigger group and safety are the most critical part of finishing the lower. A decent jig makes that part fairly fool proof. Squaring up to your fixture will be critical or you can force a drill to go off course. I machined my own fixture, basically to hold the receiver for machine work and line up the jig in a milling machine so the jig guide holes are not really touched during the drilling operations. Better jigs will have hardened bushings to give more life to less sophisticated machine work, like using a drill press.  As pointed out previously, carbide will cut hardened bushings and that their own path if set up incorrectly. The HSS bits are less likely to cut drill bushings (but great care should be taken to make the bits run as true as possible). Running the bits into a hole and backing out frequently will clear chips and make for truer holes (lots of WD-40). Drills do not make nice holes. Cutting undersize and using a final size reamer will produce the better results.

The lowers are forgiving to small amounts of error. A unit trigger group could possibly save a botched job. The balance of the cavity work is less critical than the trigger/safety group holes and can allow significant error and produce a functional receiver. Sticking to measurements is important, but difficult to get "mil spec" in the "drill press" type machine work many people are doing.

00BUCK:

--- Quote from: Ivars on November 07, 2014, 12:53:30 PM ---Fastenal has end mills in stock for a reasonable price.  If you plan to use a drill press, good luck. 
 

--- End quote ---
No luck needed, just get a basic understanding of milling (use conventional not climb) and A LOT of patience. You are not using a milling machine and drill presses don't like a lot of side pressure, so TAKE IT SLOW and only remove about 1/8" of depth per pass. Understand that it won't be perfect and pretty like a CNC job, but done right, you will have a completely functional lower.

RobertH:
well i jumped on a Modulus universal jig and two end mill bits (in case i broke one).  it came to $198 shipped.  Modulus Arms and 80% Arms both have Black Friday deals going on now.  i picked Modulus because their jig can be used with New Frontier Armory billet lowers and 80% Arms cannot.

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