Drilling through stainless 3/8" steel bolt

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I am trying to drill though a stainless 3/8" steel bolt (grade 6) on a poo l pump. How long should it take to go 1/2 inch? I think after an hour, I managed to get through 1/8 inch using oil as a lubricant. I am using a 1/4 Dewalt Cobolt bit from Lowls (listed for stainless steel). Is this better than the Irwin titanium bits? I have some diamond bits from Harbor Frei ght tools, but it seems as if the diamond dust was scraped off very quickly . Any suggestions on what else to do, i.e. take it to a mechanic who will cha rge $50 an hour. Are there any suggested drill bits made from industrial di amonds or are they overpriced?
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https://www.youtube.com/watch?v=NtqXlOX_kF4
drill a pilot hole. Black Oxide bits
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On Mon, 13 Jul 2015 01:02:49 -0700 (PDT), Deodiaus

With a good bit you should be through it in about 10 minutes. When we work on molds at work, my maintenance guys do it easily on 10 mm bolts. Get a good bit at an industrial supply house. Check www.mcmaster.com for the right type.
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a constant pressure on the bit at all times. MAKE the drill cut. If it skates and heats, the stainless hardens like glass, and NOTHING will drill it. Start over with a fresh bolt. Clamp it in a drill press vice. Run as slow as possible (or even slower) and keep pressure on the drill at all times. A power feed press works best - cuts fresh stainless like butter.
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True dat!
By "skate", Clare means "not cutting". IOW, if chips are not coming off the work, it's "not cutting" and will harden the SS. Make sure "chips" are being created and the drill bit is not merely spinning in place. If the chips are dark blue/purple, you are feeding the drill with too much pressure. Back off until the chips are jes bluish.
nb
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!?!?!?!?
Using what? A hand drill?
nb
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On 07/13/2015 03:02 AM, Deodiaus wrote:

Sheesh
Do not start out at the full size, use a smaller bit first... maybe 1/8" or even smaller
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philo wrote:

For a quarter inch hole ? I 've never had a problem unless I let the bit rub and work-harden the SS . Heavy pressure and a low speed are key .
--
Snag



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On 07/13/2015 11:36 AM, Terry Coombs wrote:

Yes...as he said it was stainless steel...otherwise a pilot hole would probably not be needed.
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I disagree.
I think the poster claimed he was using a 1/4" drill bit. I'd start the hole with a no. 2-3 "center drill"[1] and finish with a 1/4" HSS twist drill turning at about 750 rpm[2].
[1] <https://en.wikipedia.org/wiki/Drill_bit#Center_and_spotting_drill_bits [2] <http://www.smithy.com/machining-reference/drilling/page/22
Do NOT heed the previous advice to drill "slow". The bit may "catch" on the material and snap the drill bit. Drill at the recommended drill/feed speeds (the smaller, the faster). Special purpose drills like carbide, diamond, etc, are unnecessary, as a properly sharpened std HSS twist drill will work just fine. If you have or plan to purchase "center drills", make sure you run them faster or as fast as the recommended twist drill speeds. ALWAYS use a lubricant. Serously, dirty oil off yer car's dipstick is better than nothing. ;)
nb
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On 07/13/2015 12:00 PM, notbob wrote:

A pilot hole is never a bad idea no matter what.
Many years ago I got a good laugh when I saw my boss trying to drill a 1" hole through an i beam with no pilot.
I was not really paying attention to what he was doing until I came back into the shop an hour later and saw him still trying to drill.
He might have been stupid but at least he was no one to give up.
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with a 1/4" drill is 1280 RPM, but I find that still too fast usually (Speed in sfpmX4/ decimal inch diameter of drill - in this case80X420 devided by 0 .25= 1280 rpm) I like 600- 750 - or closer to 500 RPM for a .5 inch hole. If I'm drilling on the lathe I'l use 300-ish and use the power feed set to about 20 threads per inch
Back up the exit with hardwood or aluminum, or even mild steel so the bit doesn't catch coming out the bottom.
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My bit must have been too worn. I was giving thought to sharpening it using a grindstone. Well, it just got worse. I got a new bit and drilled a 1/8 pilot hole. The guy at HD talked me into getting a screw extractor. Well, shit, the screw extractor snapped off the tip and is now lodged in my pilot hole!! I guess I am going to have to drill 3 holes around the extractor bit in order to pull it out. One of my friends was doing the same thing, and said that even after he got the flange bolts out, the metals had rusted together. Apparently this is a big problem with pool water pumps. The back housing that I am trying to salvage sells for about $100. Almost wondering if it is worth trying. Never thought that this would be as difficult.
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On Monday, July 13, 2015 at 10:00:09 PM UTC-7, Deodiaus wrote:

Oh yeah. The old "Easy Out" (talk about false advertising) They're never easy and usually won't get it out On steel bolts, I've taken to using reverse cobalt drill buts. If yur lucky, only takes about one per frozen/broken bolt & ya gotta drill dead center thru the bolt. (not that easy)
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On Monday, November 9, 2015 at 2:58:22 PM UTC-5, Shade Tree Guy wrote:

Maybe even harder now that there's part of screw extractor stuck in the bolt.
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On Monday, November 9, 2015 at 3:09:47 PM UTC-5, DerbyDad03 wrote:

Time to give up on the drill and use a popper.
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Yes, I am using a hand drill. THere isn't enough clearance to get it on a drill press.
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On Tuesday, 14 July 2015 06:02:29 UTC+1, Deodiaus wrote:

ive used a hand drill with a good cobalt drill bit and a coolant paste start small and work up use the right drill speed TTP Hard Drills are the brand we use see www.ttp-hard-drills.net
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On Mon, 9 Nov 2015 10:36:30 -0800 (PST), snipped-for-privacy@googlemail.com wrote:

When I see hand drill, I think that it's one you crank.
Is that it, or is it a hand-held electric drill that is meant?
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On Monday, November 9, 2015 at 5:23:46 PM UTC-8, Micky wrote:

Haven't seen a "hand powered" drill since cleaning out my deceased parents garage years ago.
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