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9/22/2017 12:11:25 AM
Posted: 2/11/2006 4:31:25 PM EDT
I've killed 4 TiN drills trying to drill my trunion holes!! Taking it to my brothers mill tomorrow. Anyone else have a problem like this?

Kris
Link Posted: 2/11/2006 4:56:49 PM EDT
NO, but I use a drill press and COBALT bits.
Link Posted: 2/11/2006 5:03:18 PM EDT
[Last Edit: 2/11/2006 5:04:19 PM EDT by shop_rat45]

Originally Posted By vatolocal:
NO, but I use a drill press and COBALT bits.



That is going to be my next option if the mill doesn't work. Heck my 1919A4 bolt and sideplate weren't this hard and this is only 1.0mm sheet metal. Guess this one won't be coming appart anytime soon.
Link Posted: 2/11/2006 6:35:43 PM EDT
Even with my cobalt bits I would still use some oil. Makes your bits last longer. All I can say is the cobalts are worth there weight in gold when dealing with the GT receivers.
Link Posted: 2/11/2006 7:19:48 PM EDT
How fast is your drill bit turning???

Going too slow is better than going too fast.

Link Posted: 2/11/2006 7:39:24 PM EDT
Hope you're not using Harbor Freight TIN coated bits!

I may have Chinese made machine tools, but I don't buy any Chinese made cutting tools or bits. They're awful.

"Morse" brand cutting and tapping fluid has been my favorite for years now. You really have to work to smoke a bit when using it!
Link Posted: 2/11/2006 7:56:52 PM EDT
Minimum Cobalt, the ultimate is carbide. Turn at MINIMUM 1000 RPM and use cutting fluid with the cobalt (not with carbide) and you should be fine. For the record, I always use a spotting drill (center drill?) to start my holes and then switch to a drill bit.
Link Posted: 2/11/2006 8:10:46 PM EDT
I did this same thing with my first 5 receivers or so. No I use good cobalt run slow and start very small and increase size. It does not take as long as I thought it would compared to spinning it fast and I dont swear near as much at 0100 with no place open and dull bits.
Link Posted: 2/11/2006 8:36:42 PM EDT
interesting, I didn't wreck one bit on my AUSA build. Drill press and oil to help the cutting. I can't remember what brand the bits were, I think Skill. Went through like butter.
Link Posted: 2/11/2006 8:59:25 PM EDT

Originally Posted By Sidecarnutz:
Hope you're not using Harbor Freight TIN coated bits!






I think we found my problem. Eh, it's what I've got sitting around. We will use a good center drill on it tomorrow in the mill. If we can't get it then, I'll step up to cobalt.

I'm just really impressed with how hard they are. Heck, I think I've found broken taps that are easier to drill than this thing.
Link Posted: 2/11/2006 11:19:44 PM EDT
i use craftsman tin coated bits with the "point" (know idea what that shit is about but they work)
a drill press (1/3hp)set as low as she will go,..(650rpm),...lots and lots of cutting oil,....as long as i can support the reciver,.. say by having the trunnion in it,...i can just ease through no problem.

now i do have some cheap bits,....and man they suck ass!,...you get what you pay for with drill bits.
Link Posted: 2/11/2006 11:59:23 PM EDT
Not for an AK but for work.

Had a hell of a time drilling 316 SS with bullet bits and cutting fluid. I finally had to use a carbide bit and an industrial dremmel type tool. Just had to drill four .25in holes. took me several hours.
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