Best drill bits for 5160 steel.

[ZachNiedjalski]

Hey Everybody,

First of all I apologize if there is a topic on this already, but I'm wondering if anyone has suggestions for drill bits that can drill through 5160 without taking an hour.  The drill bits i have are not doing the trick.  Any help would be much appreciated.

 

Zach

[ThomasPowers]

Is the 5160 hardened and if so to what degree?  Also the set up for drilling is very important, slow speeds, slower than systems designed for drilling wood, and greater rigidity are required for best performance.  

I know folks drilling car leaf springs as heat treated for automotive use,  using a Cole drill---which is hand powered!

[Sanderson Iron]

Don't know if it's an option, but any 'ol HSS drill will handle 5160 if it's annealed.  (Well, that is, if the drill's sharp.)  Use lard oil if there's a problem.  

I have good luck annealing 5160 by heating it to above critical, letting it soak in the fire a few minutes, then burying it in wood ashes overnight.  Usually the next morning it's still too hot to touch but soft enough to machine.  

Joel

[BIGGUNDOCTOR]

By hand or with a drill press? What size hole?

HSS in a drill press should be no problem. Slower speeds, and good feed pressure with a good cutting oil should do the trick.

[Kozzy]

With most drill bits, you will find an order of magnitude difference in the ease of drilling when using good quality bits vs what is normally available at the home center.  Even what looks like a "brand name" at the usual home center is generally a pretty lousy quality bit.  I'm not sure who handles machinist supplies in your area but typical quality brands are "Precision Twist Drill", "Hertel", "Chicago-Latrobe" and several others.   There are mail order sites for machinists supplies but I won't list them here due to the general terms of use that the moderators prefer.

Even though you'll pay more, the value from that extra cost more than makes up for it.

As to actually drilling your stock, others have covered that pretty well. One mistake people often make is not maintaining enough steady pressure to keep the bit cutting:  Once you let a bit spin at the bottom of the hole, you've often ruined the cutting edges and it will end up being a fight to finish the hole or make another.  With tiny holes done in a hand-held drill, maintaining pressure can be tough as one twitch can end up snapping the bit.  Always use a drill press if it's an option.

For the average user, fancy gold or purple (etc.) coatings are usually of little benefit if any at all.  Those tend to only help when pushing drills near their limits or for specialized stuff like gummy metals.  With average steel drilling, a plain old well-ground finish is adequate.   Cobalt bits (not the home center version) can help with some tough to drill materials like 300 series stainless.  Carbide bits are horribly brittle but once in a while can solve a bad drilling problem--at a high cost.  HSS covers 99+% of most people's needs.

Oh...and the same holds true for taps and dies---but with an even greater payback when you buy quality.  The difference in ease of use on these is almost to the point of amazing over the usual home center offerings.

[JNewman]

Listen to Kozzy this is very good advise!!!. The only thing I disagree about is when buying the drill bits they are often cheaper than the local hardware store if you approach it right. A drill index full of drills will be much more expensive than the home center although worth it.  What you want to do is figure out the couple of sizes you will be drilling a lot and go in and buy a sleeve/envelope of them. Industrial supply houses typically don't post prices and often have minimum cash sales.  I pay about $3cdn each for high quality 1/4" drills. Less than $2 each for 1/8"  a sleeve of them is 10-12.

Figure out what you want save up  and plan on going in and spending $30-50 and stocking up.  If you are the guy that takes up a lot of time for a tiny order you will pay for that.  The industrial places are used to and rely on selling lunch bag sized packages with $1000s of dollars of carbide in them.  If you wast their time you will either pay dearly for your drills or you will get told "industrial sales only"   Buy together with some friends If this method is too expensive.

[BIGGUNDOCTOR]

Zach, I sent you a message with some of the suppliers I have used in the past, and they should cover Canada.

[Sanderson Iron]

A pilot hole will help a lot if you can get your speeds right.  Don't know what you're working with.  

[beaudry]

 I almost always use ''screw machine'' length drills rather than ''jobbers length'' because they are shorter and stiffer for the size.  I usually use Hertel or better bits  with the black oxide coating HSS to hold the coolant on the surface. I buy them in bulk from MSC. Sharpen them or toss them when they get dull.  

Lately I've become a big fan of a product called Syn Kool, a water diluted cutting oil that seems to work really well and does'nt leave such an oily mess to interfere with subsequent welding or finishing.

Cheap bits and taps will end up costing you more than they are worth most of the time.

[BIGGUNDOCTOR]

Forgot to mention, if the drill bit says made in China - don't buy it.  I have had good luck with USA, and European makers. Black oxide and bright finish are fine for your uses.  Split points are nice, but unless you can recreate it when you resharpen them you will lose that feature when you do.  You can do it freehand with a good bench grinder and a sharp cornered wheel. Once you learn to sharpen a drill bit on a grinder you can play with angles, and modify points for various jobs. I put a brad type point on the drills I use for sheet metal so they cut a disc out, and I flatten the cutting edge when drilling brass so it does not suck itself in.