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Discussion Starter #1
Been drilling the trunion holes on a NDS-2 AK-74 receiver, never worked on such a hard receiver before! And using new cobalt and titanium bits! When they say 100% heat treated you better believe them.
 

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Drilling at the proper rpms? Using lots of cutting fluid? I don't remember having too much trouble with my last NDS-2. I always end up messing things up if I try to use cheaper titanium oxide coated bits. I've had great luck with good quality name brand cobalt bits.
 

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They really did get some of those suckers hard huh? I've had a few of those.

This may sound stupid, but I've had the best luck running the drill at the slowest rpm, using cutting fluid, and using regular HSS drill bits. If you want to save yourself some grief, do this.

Go to home depot, get some blu-mol HSS drill bits. Get a 1/8, 9/64 and 5/32, get 3 of each.

On the hole that you're having trouble with, reduce the speed on the press, then pop in the 1/8 bit, then step up until you're up to 5/32, or if you're doing the rears, go up to 11/64, but you get the idea.

Some of these cobalt and titanium nitride coated bits don't work for beans when the coating wears off. If you've gotten the bit hot, forget about it, throw it away.
 

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Discussion Starter #4
m0ondoggy said:
They really did get some of those suckers hard huh? I've had a few of those.

This may sound stupid, but I've had the best luck running the drill at the slowest rpm, using cutting fluid, and using regular HSS drill bits. If you want to save yourself some grief, do this.

Go to home depot, get some blu-mol HSS drill bits. Get a 1/8, 9/64 and 5/32, get 3 of each.

On the hole that you're having trouble with, reduce the speed on the press, then pop in the 1/8 bit, then step up until you're up to 5/32, or if you're doing the rears, go up to 11/64, but you get the idea.

Some of these cobalt and titanium nitride coated bits don't work for beans when the coating wears off. If you've gotten the bit hot, forget about it, throw it away.
Yes, the bits got quite hot then became dull. :razz:
And they were Bosch and DeWalt which were the most expensive ones at Home Depot. And using cutting oil to boot! Will try those blu-mol and will let you know. Thanks for the tips!
 

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Discussion Starter #5
m0ondoggy said:
They really did get some of those suckers hard huh? I've had a few of those.

This may sound stupid, but I've had the best luck running the drill at the slowest rpm, using cutting fluid, and using regular HSS drill bits. If you want to save yourself some grief, do this.

Go to home depot, get some blu-mol HSS drill bits. Get a 1/8, 9/64 and 5/32, get 3 of each.

On the hole that you're having trouble with, reduce the speed on the press, then pop in the 1/8 bit, then step up until you're up to 5/32, or if you're doing the rears, go up to 11/64, but you get the idea.

Some of these cobalt and titanium nitride coated bits don't work for beans when the coating wears off. If you've gotten the bit hot, forget about it, throw it away.
Yes, the bits got quite hot then became dull. :razz:
And they were new Bosch and DeWalt which were the most expensive ones at Home Depot. And using cutting oil to boot! Will try those blu-mol and will let you know. Thanks for the tips!
 

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I believe the dewalts are titanium nitride coated, and once you wear that off, they're done. The blu-mols are actually the cheapest ones there. Just buy a few and don't use them for more than a couple of builds and you'll be ok.
 

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Discussion Starter #7
I got the blu-mols and finished the job, using cutting oil and a lot of patience. Phew!
 

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Set the pulleys on the drill press to the lowest possible speed!

Mine is set at under 100 rpm. Can't remember the exact number right now.

That makes a big difference and keeps heat down so your bits last longer too.
 

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Discussion Starter #9
Mine is a cheap HF drill press, lowest speed is 620 rpm which is what I used. Oh well...
 

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Cobalt drills, to my knowledge aren't coated. They are basically a variation of the HSS bits, but with more cobalt in the alloy. The hold their hardness at higher temperatures and are recommended by professionals for use when drilling stainless steel or hardened steel. GO SLOW is the best advice anyone can give you. Smoking and chattering are things you don't want to see and hear while drilling.
 

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For drilling using solid carbide drill (ideal for cutting heat treated steel)
Alloyed Steel, Hardened and Tempered Steel, Tool Steel with:
BNH from 250 to 350 SFPM (surface feet per minute 150) 150/0.156 (5/32 Drill) X 3.82 = 965 RPM
BNH from 350 to 400 SFPM (surface feet per minute 125) 125/0.156 (5/32 Drill) X 3.82 = 3060 RPM
Calculating Carbide Drill speed.
http://www.precisiontwistdrill.com/tech ... de_amg.asp

Purchasing a full carbide drill bits will kill you at about $10 a pop.

Try more speed you may be just work hardening the area you are trying to drill.

I use these with decent luck. They have a better wear rating than HSS, are for high-tensile alloys, titanium etc.
http://www.use-enco.com/CGI/INLMKD?SIIT ... &SICOUNT=1


ADDED
High Speed Steel RPM formula
NDS receivers (4130 range likely) FPM 50 Roughly
HSS RPM = Cutting speed X 4 / Diameter = 50 X 4 / 0.156 (5/32 drill bit) =1282 RPM Use lots of oil keep your drill bit cold!!!
http://its.fvtc.edu/MachShop1/drillpress/cutspeeds.htm
 

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I use solid carbide for ANYTHING that is even remotely hard. As long as you take care of them they last forever. IMHO I think they're worth the extra $ that you pay for them...
 

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"This may sound stupid, but I've had the best luck running the drill at the slowest rpm"

NOT stupid... I learned this from experience on Elk River (Global Trades) receivers. Slowed down? Sears Cobalt bits go thru damn near anything... even Mosin receivers.
 

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Sidecarnutz said:
Set the pulleys on the drill press to the lowest possible speed!

Mine is set at under 100 rpm. Can't remember the exact number right now.

That makes a big difference and keeps heat down so your bits last longer too.
this is what my dad always told me and I learned through trial and error over the years,too dumb to listen to those in the know when I was young :sad:
 

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slow speed; plenty of cutting oil; and a Drill Doctor..a properly sharpened bit will zip right through a NDS receiver like it was a tin can ..yes even the El'Cheapo Chinese drill bits. Grind your bit with a split point, and you wont have to center punch the center of your hole. If you do alot of drilling or have an expensive set of bits the Drill Doc is a must have.
 

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gundoc said:
slow speed; plenty of cutting oil; and a Drill Doctor..a properly sharpened bit will zip right through a NDS receiver like it was a tin can ..yes even the El'Cheapo Chinese drill bits. Grind your bit with a split point, and you wont have to center punch the center of your hole. If you do alot of drilling or have an expensive set of bits the Drill Doc is a must have.
Those are great, but for the price of one, I'd have to buy a few hundred bits to amortize it. My dad has one, and it's great, but too expensive imo.
 

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m0ondoggy said:
gundoc said:
slow speed; plenty of cutting oil; and a Drill Doctor..a properly sharpened bit will zip right through a NDS receiver like it was a tin can ..yes even the El'Cheapo Chinese drill bits. Grind your bit with a split point, and you wont have to center punch the center of your hole. If you do alot of drilling or have an expensive set of bits the Drill Doc is a must have.
Those are great, but for the price of one, I'd have to buy a few hundred bits to amortize it. My dad has one, and it's great, but too expensive imo.
Thats why I said if you do alot of drilling. I have a few sets of Snap on 115 pc drill sets one is HSS the other is M42 Cobalt .I like to keep them sharp . For myself I have so much $$ invested in tooling the expense of the Drill Doctor was well worth it...you can find them on Ebay used most of the time for a very reasonable price. Just make sure you buy a machine that can grind split points. I bought a top of the line model used like new for less the 50 bucks.
 
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