I may have mentioned before that it’s really hard to drill a hole through composite steel, since (sometimes) the metal hardens from the heat of drilling through the layers. Thus, you get a ways into the piece and think “this is going well” and suddenly all activity ceases until you re-anneal the work.
Now that I understand what’s going on, I can handle it predictably, but it’s still not a lot of fun. The last carbide bar I made, I had a brilliant idea: “why not drill it when it’s red hot?”
Here’s why not; this is something you probably have never seen before:
It’s thermodynamics 101: the contact-point between the drill and the hot steel is small, but it’s going to transmit heat fairly quickly. At that point, the smallness of the drill kicks in – it can’t shed the heat very quickly, either. Then it starts to melt.
This was a hand feeling I have never experienced, before. Everything was (apparently) proceeding fairly smoothly but suddenly the drill went forward quickly and I pulled it back, thinking it had pierced through the work-piece. Imagine my consternation when I looked at the glowing red-hot bar and couldn’t see any sign of a hole. Then, I looked at the drill.
By the way, I was wearing welding gloves, so if I had whacked a knuckle on the bar, it would have alerted me to that fact when my gloves started to smoke.
Deploying patience allows you to give the steel an annealing cycle or two. Drill it a bit, heat it and anneal it, drill it a bit, etc. Then, when the hole is all the way through, it’s time to run an 8-32 tap through it. Normally, tapping annealed steel is easy, but in this case there are randomly located layers of hard stuff as well as soft stuff. It took me about 1/2 hour with a hand tapping wrench to carefully tap the hole. I managed it without breaking a tap. Breaking a tap is not merely a badge of dishonor for a machinist, it’s a nightmare: now you have a piece of ultra-hard tool steel threaded into your work-piece and if you’re not extremely lucky in how the tap breaks, so you can get pliers on it and get it out, you’re left trying to drill a hole in the tap for a screw extractor. Basically, it’s time to break out a diamond drill. Or, you grab a chop-saw and cut the end off the work-piece, fire up the forging press, and make a new end. “Knife-makers don’t make mistakes, they make shorter, thinner knives.”
Back in the 70s, I was working at Allegheny General Hospital in Pittsburgh building a prototype for an EKG machine with a microprocessor in it (implementing my boss’ PHD thesis in a more practical way).
I once had the need to drill and tap an 1/8-inch thick piece of very hard steel. I didn’t break the bit, but I did break the tap just as you described. I wheeled the device I was working on to the hospital’s maintenance department and they were able to fix it for me, but I was very ashamed.
(I was an electronics guy at the time; and my knowledge of metalworking was, and is, pretty much limited to finding the right size bit by looking it up in Machinerys Handbook.)
Lasers.
That is really impressive, and no, I’ve never seen that before. I have to say, when you have an “incident” it’s certainly very interesting. I hope you could at least get the drill bit back out, once things had cooled sufficiently.
Reginald Selkirk@#2:
Lasers.
I’d jump straight to regime change, if I had powerful “lasers”
Seeing that photo makes me wonder if there’s a market for joke drill bits that spontaneously melt or disintegrate. “Haha, made you ruin 8 weeks of work” I think I’d put them on the shelves next to the regular drill bits at sliightly lower prices. That’s how you get people to take note of your brand quickly.
billseymour@#1:
I didn’t break the bit, but I did break the tap just as you described. I wheeled the device I was working on to the hospital’s maintenance department and they were able to fix it for me, but I was very ashamed.
Everybody who has ever tapped something, has broken one and had to figure out how to remove it.
My first was when I was modifying a burglar alarm controller cabinet for Moore Security back in 197?5. I went and found Mr Moore and asked him “what do I do?” and he came down and looked at it, then took a ball peen hammer and hit it so hard it popped right out the other side. Then, he took a larger drill and a larger tap and explained that “sometimes, you use a 10/32 to mount the alarm sounder, instead of an 8/32, and this is why.”
High-powered tactical squirt gun.
https://www.engineering.com/AdvancedManufacturing/ArticleID/12716/An-Engineers-Guide-to-Waterjet-Cutting.aspx
You have a real penchant for creating odd and interesting disasters. I just never know what’s coming next.
That’s pretty impressive. You should definitely save that, maybe make something out of it, like a decoration or something. piece of jewelry? paperweight? imbed it in your next resin creation? I dunno, I’m not the artistic sort, but that needs to be preserved and displayed somehow.
How about drilling with those hollow drill bits for glass, have you tried that?
This is indeed the first time ever that I have seen a bent drill bit. I have broken my share, and keep on breaking, but bending? Nevah.
I had a joke drill bit back in the 80’s, the first time I’d seen a spiral flute unwind and go the other way. I kept it in the bits box to remind me of the folly of buying cheap drill bits. It still managed to drill pine though.
Drilling hot steel is pretty much impossible. From memory the best way to drill hard steel is to regrind your drill bit to a shallower angle, proceed slowly with lots of coolant and firm pressure. Many years ago the small engineering shop I worked in got a regular job of drilling 7/8″ holes in spring steel for an agricultural machinery shop down the street. We had a power feed drill press that wouldn’t stop for anything much. Frequent resharpening was the order of the day. No pilot drill, either.
Gaze Upon the Black Magic of Electrical Discharge Machining
Eh, i have a bent 2mm drill bit sitting next to my mill. turns out that tang was harder than i expected.
@komarov that market is already dominated by cheap, hardware store drill bits. steel is cheap, but when you make that many drill bits shit steel is still a cost saving.
One thing about your mistakes–they’re always instructive (and amusing).
publicola@#14:
One thing about your mistakes–they’re always instructive (and amusing).
Thank you. As long as I can find a way to learn something, it’s a bit less mistakey and more of an “experiment!”
Reginald Selkirk@#12:
EDM is droolicious.
A lot of those systems are in the “just barely affordable” range but you pretty much have to set up a fabrication shop around them, to get them to pay for themselves. I know a guy who did that – retired from his IT job and bought a $16,000 Tormach CNC mill and learned to use it. A year later, he had a work-queue that was miles long, from other people who wanted CNC services, and he was officially un-retired and running a busy service business.
There are really interesting trade-offs, too. A $250,000 CNC machine, or a CNC EDM or a CNC water-jet, you can build a service business around and you have to, until the machine is obsolete and someone buys the next generation and can undercut you and you’re dealing with a worn machine that’s less reliable and you have to fab parts for it. Then, you’re chasing your own tail really hard.
At least anvils don’t need system administrators.
Lofty@#11:
I worked in got a regular job of drilling 7/8″ holes in spring steel for an agricultural machinery shop down the street
An old machinist told me that he used to have that job and would just blast a hole in it with an OA torch with a tiny little nozzle and a great deal of air. I guess it depends how thick the material is and whether you can cool around the about-to-be-hole.
Charly@#10:
How about drilling with those hollow drill bits for glass, have you tried that?
I hav some that I’ve used for drilling glass. The problem with those things is that they don’t have the twists like a conventional metal drill, for carrying away the chips. The diamonds chew through stuff, sure enough, but they just create a slurry of powdered mush that used to be stuff, and you have to air blast the hole every second, and re-lube it.
Masonry drill bits – flat carbide spade bits – same problem.
As I understand it the blacksmiths of old would favor punching a hole by driving a square edged punch rather than drilling. Of course you need to work fast and wack it through in one smooth perfect motion with punch and impact being perfectly aligned and before heat can transfer and soften the punch.
The alignment, accuracy, and rapidity of placement and blow would be critical. Seems like you would have a fraction of a second to complete the operation. A bit more if you were driving a solid carbide punch.
I’m thinking you could use a nail gun. I would go with extending the drive rod by welding on your carbide punch or substituting the carbide tool for the existing hardened steel rod on the manufacturer’s rod. I might try it with easier to work with hardened steel. Perhaps using tungsten-carbide is over thinking it.
Of course with most punch operations you want the leading edge to be a bit larger and the body relieved a bit so it isn’t fighting the material all the way in, and doesn’t get stuck. Most nail guns retract the rod well enough that I don’t think that will be an issue, but one can’t tell for sure without testing.
You should be able to get a used nail gun for a hundred or so. Harbor freight sells a functional framing gun for about the same, perhaps little less. If you get a popular model obtaining spare driver rods from parts supplier.
Ever thought of building the thing by yourself ? Would be orders of magnitude cheaper.
daverytier@#20:
Ever thought of building the thing by yourself ? Would be orders of magnitude cheaper.
I have, and I’ve decided not to. My reasoning is that, at a year shy of 60, I haven’t got the runway left to learn whole new stacks of theory and practice; I’m not able to tackle 20 things at once, like I used to. So I’m trying to stay focused. I’m quite sure I could build my own CNC machine, but for a steel-capable CNC machine, I’d rather have a bunch of people at Tormach, who have focused on that problem (and made all the mistakes) for decades working on it, rather than me re-inventing all the mistakes.
(I did back Snapmaker a year or so ago, and I believe I may have a 3D printer show up some day. I really don’t know if I’ll want to dig into figuring it out; I may prefer to spend that time working on investment casting.)
I’m even reluctant to try stuff like 3D printing, because it means having to learn Blender, too, and multiple other stacks of knowledge, when all I want is a few poly models of knife guards that I can cast in bronze. The same applies with the CNC milling machine: I could use a CNC mill to cut outlines of something, but since I am doing one-offs, it’s actually faster to cut them with and angle grinder and a diamond cutoff wheel – so long as I don’t need the kind of tolerances a CNC mill can achieve, I’m faster doing it the old school way.
Marcus Ranum@#21.
Oh, I didn’t mean a whole CNC machine, that’s a lot of work. I was thinking about something like a small static spark drilling rig. Just to drill a straight hole down. Nothing fancy.
daverytier@#22:
Oh, I didn’t mean a whole CNC machine, that’s a lot of work. I was thinking about something like a small static spark drilling rig. Just to drill a straight hole down. Nothing fancy.
Oh, well – for that, I can afford to waste many drills, before it becomes a fair trade-off to build something like that. I could send it out; the machine shop in Clearfield has a very nice water-jet machine that they don’t charge nearly enough for.
What I really want to build, but am not sure if I want to run the risk, is an inductance crucible. Basically, it’s a microwave oven’s heating unit, wrapped around an alumina crucible. You can get them to 2500F in a few minutes if they’re well-insulated. (It’s what Bob Kramer uses to make his meteoric metal smelt-downs) The temptation to be able to electro-melt my own wootz is huge. But I’m waiting patiently – Dragonfly Forge is doing a class this summer (I am already enrolled) on Japanese-style smelting tamahagane (jewel steel) – if that is fun and interesting then I will begin researching how to make a water-cooled electro-melter. That design is all within my abilities except for the electrical engineering problems.
Bob Kramer melting steel in his induction crucible.
Yea, induction melting is cool. Not even that difficult to build, there are even tutorials. Wanted to build this. https://youtu.be/WRPoOaaJCIA?t=130 but then I realized I had no practical use for it.