Drilling Tool Stock with solid carbide bits

[littletoes]

Any machinist types around here???


I have used, with mixed luck, solid carbide drill bits to drill out extremely hard materials.

The biggest problem is that carbide bits are extremely brittle! And EXPENSIVE.

I've tried cobalt bits, but they don't seem to even scratch some materials, and you need carbide.
Even a 1/4" carbide bit with spiral flutes is over $20, straight flutes about $18. If you can imagine, I don't like breaking those, especially when doing a "favor" for a friend....

The problem is that when drilling through tough stock, the material that is left after almost getting through, is enough to chip the bits. Even when clamped to wood.

Now I'm wondering if clamping the stock to mild steel might help???

Any ideas guys???

 

[Milton Shaw]

Get a set of BAD DOG drill bits. They will drill anything hard, such as files etc. They have a life time warranty so breakage would not cost much other than shipping charges. They operate at a lot higher speed than most drill bits and as a result don't seem to break as easy. I don't use mine for everything but for really hard stuff like some stainless steel knives and other objects that regular bits just dance around on and don't even scratch the surface.

 

[littletoes]

Read the discription, BAD DOG are COBALT drill bits Milton...

I'm drilling materials that Cobalt won't touch, including BAD DOG. Ever drill out an Easy-Out? Or a broken tap???

You would have to use a solid carbide drill bit.
THAT is what I'm talking about.

With this drill bit, you could drill a hole through a bad dog;
https://www.mscdirect.com/product/details/79892527

 

[kazlx]

What are you drilling and why? Just FYI you aren't supposed to peck drill with carbide twist drills.

 

[Hephaestus29]

Can you anneal it first or is it attached to something that you can't risk damaging ?

 

[littletoes]

First, a broken/hardened stud. Couldn't touch it with a cobalt, then 1/8" flat plate tool steel.
Cobalt DEFINITELY wouldn't touch that. But the carbide went right through...my problem was, I lifted up off the work, and left a tiny bit...and when I started into it again, it chipped off one side...

Bummer....and either sharpen, or new drill bit. I had two more holes to punch too.

Can't anneal-there is no way to re-temper the area.

 

[Hephaestus29]

Yeah, carbide drill bits are very brittle and break fairly easy, at least the ones i've used anyway.

Is the stud in a cylinder head or the flat plate ? If it's in the flat plate or you just want to drill the flat plate, have you tried a carbide milling bit ? I seem to have better luck with mill bits unless you are just free handing it with a drill.

You might try a heavy cutting/threading oil or Anchor Lube.

 

[Provincial]

Try an end cutting carbide burr. I used one on a hard area in a welded repair. I used it like an end mill at a fairly low speed in a mill drill. If you are "drilling" a hole, you will need to lift the bit and clear the chips often, as they don't have any flutes to work the chips up out of the cutting area.

I used lots of cutting oil and it worked fine.

 

[Gemp]

Rigidity is your friend,make sure your set-up is solid as it can be.

I have had good luck drilling harden tool steel (52-54 rc) with these. They fairly cheaper than solid carbide.

http://www.mcmaster.com/#carbide-tipped-drill-bits/=zz7mvt

 

[70Chevy]

As said, rigidity is what you need. Stub length drill, flooded with coolant.
Are you using a machine or hand drill?

 

[littletoes]

Yeah, carbide drill bits are very brittle and break fairly easy, at least the ones i've used anyway.

Is the stud in a cylinder head or the flat plate ? If it's in the flat plate or you just want to drill the flat plate, have you tried a carbide milling bit ? I seem to have better luck with mill bits unless you are just free handing it with a drill.

You might try a heavy cutting/threading oil or Anchor Lube.

Thanks for the help!

Just a flat plate right now, I've just had a bit of problem right at getting through the plate, chipping the end of the last drill bit on one side. Bummer!

I guess I shouldn't have to use any type of backing material, just clamp it down in the press really well, to prevent any movement.

Do you like cutting oil, or paste better??? I have no experience with cutting paste. I've only used various oils.

 

[bullnerd]

I used to drill a lot of Thompson hardened linear bearing rails.

Straight 2 flute carbide. Constant heavy pressure. No coolant/lube-can actually shock the carbide which it doesn't like either. The 2 flutes you can hand re sharpen if your careful.

In the case of your 1/8, yes very well clamped backer would really help. Better if you can do it in a milling machine rather than a drill press. As mentioned , more rigid the better.

As far as drilling taps and easy outs, the interrupted cut busts them up pretty quick. Any local shops have an edm or tap buster? That would be quicker and less frustrating.

 

[Kevin54]

I've taken out thousands of easy-outs and broken tapos in my 30+ years of being a Toolmaker. I will tell you that a carbide drill will snap nine times out of ten. I always use a four flute carbide end-mill in a mill to remove them. A four flute center drill gives you more cutting area than a drill bit does. The problem with using a drill bit is the flutes of a tap, and the flutes of the drill don't match up. And once a small piece of the tap or easy out releases itself, it will jam into the drill bit and snap it. With an end-mill the size of the hole, you are constantly milling the top off of what is in the hole, and the end-mill will turn the tap or easy-out to dust and not allow the pieces to break off, or break off as much. It constantly pushing down on what is in the hole. I usually have about a 90% success rate on removing a tap or easy-out. But even at that, once you use a carbide end-mill to remove the tap or easy-out, the end-mill is usually shot, as in dull as can be. I keep a few carbide end-mills just for use of removing something like that. I've even removed broken carbide end-mills using a carbide end-mill. It will heat things up red hot, but it will remove it if you use care.

BTW.....it is best to use a carbide end-mill or a carbide drill bit in a mill and not a drill press due to having more control over things and also the rigidity of the mill. A drill press has a little slop in it, which carbide does not like.

 

[littletoes]

Awesome replies guys!

Thanks!

I don't have an end mill, but now I know what to recommend to folks when they ask me to do it.
It will save ME money, and some frustration.

 

[bullnerd]

Kevin is spot on, good call on the 4 flute end mill, I've done the same, it works.

 

[endmill]

try carbide masonry bits they are cheap compared to carbide drill bits.

 

[gsloan]

I grind an old carbide end mill shank into a spade drill. I then crank up the spindle speed to around 4000 rpm and start drilling. I've seen The drill glow for second and then it cuts right through. A spade drill won't clear the chips like a twist drill, so you will have to peck. Just don't start pecking until it has started cutting and has a smooth surface. Sometimes I will grind it left handed for a broken tap just in case it helps it come loose or spin out. Super easy to sharpen if it does chip the cutting edge. I have had great luck with this and done it many times.

 

[OccupantRJ]

try carbide masonry bits they are cheap compared to carbide drill bits.

I have also used these, and hand sharpen them the way I want them.

 

[littletoes]

Made it simple, clamped it in the drill press, and had no problem with the carbide drill bits. Sliced right through it....amazing!

 

[OccupantRJ]

Made it simple, clamped it in the drill press, and had no problem with the carbide drill bits. Sliced right through it....amazing!

Carbide, or carbide tipped?

 

[littletoes]

Solid carbide.

I didn't use the straight fluted version, although they are supposed to be a little tougher.