Drill bits, question for the pro's or someone that knows.

[da King]

I have bad luck when it comes to buying drill bits for a hand drill. Seems like there's a lot of choices out there, hardened steel, carbon steel, carbide tipped etc.. and the advise I'm getting doesn't jive with performance.
Anybody know drill bits? What type of bit would be best for general shop use, building a kit etc. Do you sharpen your bits or just chuck'em when they quit cutting? How often do you sharpen? 20 uses - 50?. What about those Drill Doctor bit sharpeners? Always thought those were for house wife's but if I sharpen a bit on the grinder - well its hit & miss, & way more miss than hit, maybe I need the house wife thing.
A quick lesson would be appreciated.
Thanks
Finn

[Jeff Kleiner]

Plain ol' black oxide bits. Drill your 1/8" rivet holes with a #30 rather than 1/8" bit. When cutting slows down DO NOT push harder; instead stop and run it across a Drill Doctor (yes, they work).

Jeff

[Bob Cowan]

I like to use titanium coated bits. They seem to work well and last a long time.

I real key to longevity is to use cutting oil, and don't let the bit overheat.

I use a Drill Doctor to sharpen the bits when needed. They are really simple to use, and only takes a couple of minutes to sharpen the bit. It's nice to say, "I'll just buy a new bit, they're cheap". But what happens when it's Sunday evening, and you're halfway through a project? You can wait until tomorrow, then go to the store and buy a new bit. Or, you can take a couple of minutes and sharpen the one you have.

This is one of those tools that will pay for it's self in a fairly short period of time.

[frankeeski]

I'm with Jeff, black oxide bits will cut a good long time and #30 are just a bit bigger and allow the rivets to work better. A Drill Doctor works well to keep your bits sharp, I use mine all of the time. As far as sharpening, you'll know when they need it. The single best advise I can offer for drilling is constant, medium pressure and varying speed (on and off the trigger). Varying the speed allows the bit to clear the shavings and will keep the bit heat down. Also if you are varying the speed, if a bit breaks, (this happen more with smaller bits) you'll be less apt to mess up the material you are drill into.

[GWL]

For many years, I bounced around with what ever I had in my tool box. HSS and black oxide and titanium coated bits were easy to come by so that is what I had. When I started my build, I needed a set of numbered drill bits.

Due to a recommendation from a forum post I bought a cobalt 135º split point set from Pan American Tools. These bits just don't wear out (almost) and are tough enough to drill through stainless steel too. They are harder so will last longer and withstand heat better than HSS or the black oxide coated HSS. Since they are harder they are more prone to break if not drilling just right. I've used them (#10 & 30) in my small Bosch battery powered drill and haven't broken one yet. Besides the set, I bought ten extra of #10 & #30 bits as these were the ones you will use the most in your build. Usually the only reason I use a new bit is because I've misplaced one of them.

Most of the time, I will center punch my drilling location but the split points start more easily in metal than the standard 118º standard point bits you'll find in most hardware stores.

In addition, if you are familiar with Insti-bits they make drill adapters that will mount a drill into the adapter that allows it to quickly mount and dismount the bit from a quick change chuck. It makes changing from different drill sizes to countersinks and to drivers a breeze.

A bit more expensive but well worth it. Pan American link for sets:
http://www.panamericantool.com/cobalt-drills/cobalt-drill-sets.html

Insti-Bit link:
http://insty-bit.com/drill_adapters.html

George

[2bking]

My experience is that you get what you pay for. Harbor Freight, Northern Tool are cheap places to get bits but stick to name brands like Cleveland to get better quality. I'm using Cleveland and they cut very fast. The harbor Freight TI coated ones, not so good.

[Bill Waters]

As George suggests, quality cobalt bits are superior to others by a wide margin. Properly sourced, they are not that much more expensive. A local industrial supplier (no Web site) named Threads for the South (770-456-6446) sells them in any quantity. It only took two of them to drill all of the holes on my roadster.

Bill

[CHOTIS BILL]

I have never heard that 135* drill bits are any harder than 118* drill bits and I have my doubts that they are. The material determines how hard they are made not the angle of the point. The 135* drills easier because of the way the tip is ground to relieve the very tip. I have been in machining for over fifty years and learned early on how to sharpen drill bits by hand but if you haven’t done it a lot or very often then a machine like the Drill Doctor is a good investment. For hand work high speed steel or cobalt steel is a good choice but stay away from high carbon steel ones.

Just my opinion and I may be wrong,

Bill Lomenick

Here is a link that has some explanation of different types of drills.

http://www.mcmaster.com/#standard-drill-bits/=orklph

[Tuck60]

The harder the material the larger the drill point angle. 118 degrees will be fine for mild steel and alum. Cobalt adds some higher heat tolerance. Split points are for drilling without centerdrilling. When drilling dont force it; let the drill cut. High rpms generate heat which will dull a drill quickly, though aluminum can be drilled at any rpm. When drilling steel low rpm is correct.

Mike

[skullandbones]

Hi Finn,

Good advice above. I consider most of my drill bits as expendable. So the black oxide double ended ones are great for drilling the small rivet holes. I think I may have used three packs of those during the alum panel stages. I have all grades of quality in my various sets so I treat them differently. On the better quality ones, I use them til they are dull and then place them back for sharpening. At a point where there are enough to do a batch, I sharpen on a angle piece held by vice grips on the grinder then harden and temper them when I have time. But most of the bits are throw aways at some point.

Don't put very much pressure and let them cut using oil. If they won't cut at that pressure, they are dull. Get another. You will save much more time by following those rules.

http://secrets-of-self-sufficiency.com/hardening-sharpening-and-tempering-tools

You may find the link useful if you have bits you really want to spend the time, bringing them back.

One note: I find the step bits very good in certain applications. After a little practice, they are very helpful if you are shaping a hole or don't know exactly how large it must be. You will see what I mean when you have tried them.

Good luck,

WEK.