Drilling Question

[Greg Agresta]

This may sound like a dumb question. Recently, everytime I drill a hole in a knife handle. I've been burning up my drill bit. I have my drill press set to the lowest RPM and try to drill slowly but after one hole, the bit seems to over heat, chatter and stop drilling. Am I doing something wrong? Am I supposed to use a higher speed on the press? And yes, I use a cutting oil and I'm drilling 1095 stelel. Any advice will be greatly appreciated. Thanks

[Alex Middleton]

Are you drilling before or after hardening?

[Jerrod Miller]

If the answer to Alex's question in "after", don't do that.  And don't harden that part of the tang anyway.  Also, normalizing is better than annealing here.  

[Alan Longmire]

This may help too: https://www.custompartnet.com/calculator/drilling-speed-and-feed

You may be surprised at the recommended speeds.  It's not always slow.

[Aiden CC]

7 hours ago, Alex Middleton said:

Are you drilling before or after hardening?

Also, is it forged or stock removal? I've had trouble in the past drilling forged steel. I decided to make some test coupons (forged 5160), and found that samples which were forged and then left to cool in air were essentially being quenched from contact with the anvil (with bainite and martensite showing up in the microstructure). You can solve this by normalizing all of your knives a few times after all forging (heat up then cool in air, though for some steels like O1, air is too fast if the blade is thin). You can also temper knives after you forge them. I've used a torch to heat the blade until I get a sky-blue color in the area I want to drill. This isn't as easy on drill bits, but it works in a pinch and doesn't form scale on your piece.

Hope this helps!

[Joshua States]

9 hours ago, Greg Agresta said:

I'm drilling 1095 stelel.

This is very finicky stuff and can cause tremendous cutting problems after forging and heat cycling. If you are forging 1095, grinding it and then trying to drill it, or cut it with a bandsaw, it will laugh as you toss bit and blade into the trash can. If you do not have the means and equipment to do a full industrial anneal, you will have to settle for the fast normalization to get this steel to cooperate with your drill bits. Kevin Cashen once told me: "Normalizing is more about the rates of heating and cooling than about getting exact temperatures." Heat it quickly to well above magnetic and let cool in still air. That will get the carbon into an even solutions and cool it quickly enough that it will not form carbide sheets, but not fast enough to harden. Your bits may still chatter and squeal, but they will cut.

Then again, you could always spend a few extra bucks and buy carbide drill bits.

[Bruno]

Carbide bit's are awesome.  I've only ever owned 1 used to cut through a hardened stainless blade someone asked me to be a thumb stud in.  Cut like butter.  Otherwise, I've learned how to sharpen drill bits.  Not too hard, just need a good eye and steady hand.    Normalizing several times has helped me in the past but I still get the squeal,  with or without a lubricant.   I find bits around 1/8th inch or so want a faster speed to cut well, which can be tricky, at least for me, since small bits tend to bind and break under pressure. 

All I can offer, is make sure you have no scale on your piece before you drill, as that will dull the bit before it can be of any use.  When you start hearing a squeal, Stop and sharpen your bit.   I can usually get 1/3rd way through a piece before I start getting the squeal, then a good sharpen usually helps it push through the center, which for me seems to be the toughest part.  I don't use 1095 exclusively, but have included it in damascus bars with 52100.  Not sure which causes me the most trouble.   I usually normalize at least 3 times.    A slower cools seems to work better, so I sometimes I let the blade sit in a secondary cold forge, so as the wind that runs through my shop doesn't cause any weirdness.   The insulation of the forge just lets it cool down a little slower.  But not so slow as to attempt an anneal.   I've used ash buckets before for a real slow cool with files and such,  but then I read about those laminar carbides and such, and it would explain previous broken bits.

As far as normalizing, I've read somewhere, probably here,  that when normalizing, go to a really high heat the first time, then go progressively lower heats, for the next couple rounds.   

Hope any of that helps.   

Edited April 17, 2019 by Bruno

[Greg Agresta]

I guess I should have included more info. No, all my drilling problems are occuring before heat treating. I bought already annealed 1095 steel, 3/16x1 1/2x12 off the internet. The first knife went fine, drilled the holes, no problem. The second and third knifes not so much.. After experiencing my first burned bit, I changed the speed of my drill press to it's slowest RPM's but am still experiencing the same problems but to a lesser extent. Does anyone know what RPM's are best for drilling? Putting too much or not enough pressure?

[Alan Longmire]

Probably not enough pressure.  If the bit is not making chips, it's work-hardening the steel.

[Alex Middleton]

You didn't buy left handed bits did you? 

Since you seem to have avoided the common pitfall of trying to "anneal" the steel yourself, you're farther ahead than I was my first few tries.  Like Bruno said, carbide bits are awesome if you have a good solid drill press.  Unfortunately they are quite expensive when compared to cobalt or HSS bits. I've found that cobalt bits are a good middle ground between price and performance.  Run them slow, keep it well lubricated  (3-in-1 oil or tapping fluid, NOT WD-40!), and keep a good constant pressure.  As Alan mentioned, you should see a constant flow of chips, otherwise adjust your pressure one way or the other until you do.  Good luck!

[Joshua States]

On 4/17/2019 at 12:58 PM, Greg Agresta said:

I bought already annealed 1095 steel, 3/16x1 1/2x12 off the internet.

Questionable annealing is my guess. I buy quite a bit of 1095 from a "reputable" retailer and often find that it is a lamellar anneal, not a speroidized anneal. What that means for the layman is that the annealing process was slow, but not slow enough. Steels with more than about 8% C have a weird characteristic caused by all of that carbon. After hitting critical or austenitic temp, with a mild soak at heat, the carbon should be dissolved fairly uniformly throughout the steel. As it cools that carbon starts to form carbide, at first it just kind of clumps, (normalizing in still air) but given more time it forms sheets, because all that carbon starts to migrate. If the cooling process is really slow (like -50*F per hour) down to around 800*F, you get a fully spheroidized anneal, which will cut like butter. However, if the cooling process is in between, you get these sheets of carbide running through the bar. Your drill will cut a little, hit a carbide sheet, dull instantly, and squeal like a stuck pig.

When ever I use 1095, I never accept that the "anneal" is an industrial, spheroidized anneal. I always normalize before machining of any kind.

On 4/16/2019 at 11:23 PM, Bruno said:

I don't use 1095 exclusively, but have included it in damascus bars with 52100.  Not sure which causes me the most trouble. 

They both do. Both of these steels have somewhere between .95% and 1.4% C in the matrix. When I use 1095 in Damascus, the bar goes into the Paragon for an all-night long anneal.

Edited April 19, 2019 by Joshua States

[Bruno]

1 hour ago, Joshua States said:

When I use 1095 in Damascus, the bar goes into the Paragon for an all-night long anneal.

Thanks Joshua ,  I will have to try a slower cool on the next bar and see how it works...

[Joshua States]

For those of you with a programmable HT oven, here is a bit from a conversation I had with Kevin Cashen on machining Damascus bars with 1095:

Joshua, your machining setbacks can be summed up in one word- 1095. It is the simplicity of 1095 that makes its extra .15% carbon so annoying. With no carbide formers (Cr, V etc..) to distract that carbon it forms very obnoxious pro-eutectoid carbide networks rather readily. I think I have dulled more drill bits on 1095 than any other alloy.

To tame it, you approach things from the opposite direction. Keep the annealing temp below critical, (or at least well below the upper critical AcCm). By doing so you have a more slow and controlled diffusion that tends to gather the carbide up into spheroids, rather than lamellae. This eliminates the carbide networks and makes things easier to machine.

Normalize the bar to break up the networks you have, and then heat it (no ramp, just heat it) to 1375F for 1 hour and then ramp down no faster than 50F per hour to below 800F-850F. This is what I do when I need to mill, cut or otherwise machine my steel and want my tools to be fine with it. You will have coarse spheroidal carbides but it will cut like butter.

[Alan Longmire]

And yet some people still sell it as "beginner friendly."  

[Greg Agresta]

Thanks to everyone who responded to my question. I think Joshua may be right. His description of the bit cutting for a while then hitting a hard spot sounds exactly like what has happened to me. This problem began after my second purchase of annealed steel off the internet (EBay) no problems with my first pieces. I think I'll try buying from a known quality seller from now on. Any suggestions??

[Joshua States]

2 hours ago, Greg Agresta said:

I think I'll try buying from a known quality seller from now on. Any suggestions??

Where do you live? A lot of folks like NJ Steel Baron, but the shipping costs from NJ to AZ make it prohibitively expensive for me. I buy my 1095 from Admiral Steel and have just gotten used to subjecting it to normalizing and a full anneal when I need to machine the product.

13 hours ago, Alan Longmire said:

And yet some people still sell it as "beginner friendly."  

It's about as beginner friendly as 52100 or O-1.