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Author Topic: Good Drill Bits????  (Read 3951 times)
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« on: March 05, 2011, 12:43:47 PM »

Looking for recommendations on some good quality Drill Bits for drilling into steel. I'm drilling all the new rivet holes in my steel skins and the 1 1/2" tubular steel. I've tried a couple bits for hardend steel like Dewalt Bits and Cobalt Bits and dipped them in oil before every hole but they still seem to dull quickly. I'm using a small 1/8" bit as my pilot hole and that's the one that wears out the quickest. I've got like a 1000 holes to drill and would rather buy good bits that will last awhile instead of drilling 5 holes and tossing it. Anybody know of any good bits for drilling hardened steel??

Jimmy
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Gerry H
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« Reply #1 on: March 05, 2011, 12:53:23 PM »

Try Carbide, but watch your speed.
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« Reply #2 on: March 05, 2011, 12:55:56 PM »

Try Carbide, but watch your speed.

Carbide bits need to be used at a slow RPM??
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Ray D
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« Reply #3 on: March 05, 2011, 01:05:26 PM »

Get the drill doctor.  I put all new stainless skin on my bus and I drilled every hole with two drill bits, nothing special about them,  they were real short when completed though.  When you get the knack down for sharpening, how much pressure to put and correct drilling speed (I varied both pressure & my speed from slow to medium in spurts), they will stay sharp quite a while.

Ray D
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DaveG
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« Reply #4 on: March 05, 2011, 01:25:12 PM »

Try a "split point" bit, something like Fastenal's Black & Gold. Almost all 1/4" & 3/8" drill motors turn too fast for this type of drilling. Start with a good quality bit (not the most expensive) and control your speed and keep pressure on the bit...you want it cutting into the material, not just riding around and spinning on the material. Also, might want to be careful that your "pilot" hole is too close to the hole size you are drilling.
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Charley Davidson
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« Reply #5 on: March 05, 2011, 01:26:58 PM »

Your using mild steel unless it's stainless so just a jobber bit will/should do the job
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JackConrad
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« Reply #6 on: March 05, 2011, 01:29:25 PM »

Use a good lubricant such as WestLube. Overheating the tip of the bit is the fastest way to shorten bit life (other than breaking the bit).  Jack
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« Reply #7 on: March 05, 2011, 03:11:52 PM »

I would go to an industrial supply place and buy GOOD drill bits.Tell them what you are drilling. Dewalt stuff(almost all of it) is JUNK!!!
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Iceni John
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« Reply #8 on: March 05, 2011, 03:29:10 PM »

I agree that a Drill Doctor is a necessity.   I have to resharpen after two holes in stainless, and after every few holes in the 90,000 PSI steel that Crown used.   I used to buy US-made drill bits, but found they don't always last longer than some import ones.   I got a few bits recently from Ace Hardware, and they're surprisingly good for being Chinese.   I have two complete sets of HSS bits:  one set has 118-degree point angles for harder metals, and the other is 135-degree for aluminum and softer materials.   I also always use cutting oil, either Tapmatic or a sulphured oil, and this helps prolong the bits' life.

John

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« Reply #9 on: March 05, 2011, 03:38:29 PM »

I buy quality bits, run them around 800 rpm and use a lot of pressure.  The bits need to cut, it's when there is too little pressure that they heat up and dull.

HSS bits, I don't bother sharpening them.  i just toss them.

Brian
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« Reply #10 on: March 05, 2011, 05:25:50 PM »

I used split point cobalt drill bits when I did the 1,000 holes in my bus.  I found they drilled the fastest when run at a fairly high speed and they didn't seem to wear out any faster at a high speed.  I dipped them in oil several times per hole.
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« Reply #11 on: March 05, 2011, 05:52:29 PM »

sheeting bits have drill on each end . just swap ends and keep sharp. A 3/16th can be easily hand sharpened on a good bench grinder or if you don't feel confident use a drill doctor. As others have said heat is the enemy! I keep a jar of cheap vasoline and dip bits to help lubricate and cool. Just dip bit in jar at end of each hole.   Bob
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« Reply #12 on: March 05, 2011, 07:26:53 PM »

The trick as mentioned before is drill slow. If you rev that drill up it will eat the edge right off your bit. Make sure you have The Drill Doctor. It cost less for the Doctor than to buy enough bits to do the job. Have about 10 bits and at the end of the day sharpen them all and start fresh the next day.
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« Reply #13 on: March 05, 2011, 09:24:31 PM »

If you can find some of the old stepped bits that Boeing surplus used to sell, they are hard to beat. I still see them at lots of the swap meets although they sell for a lot more than Boeing used to get. I remember buying them for $2.00 a pound ten years ago. They seem to get 50 cents to a  buck for them now but that's still a bargain, I think. Anyway, I had great luck with them. Good luck, Hal   
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« Reply #14 on: March 05, 2011, 10:10:19 PM »

"dipping the bit in oil" will destroy the bit in short order.  Some materials will finish the job quicker but oil will always speed up the dulling.  You absolutely must use Drilling or taping "cutting oil".  I learned this from an old salt machinist more recently that i want to admit.  Now somebody please explain to me WHY cutting oil is so darn expensive considering the ingredients.

John
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