Rick wrote in with a drill bit question:
I’m having trouble drilling holes thru a threaded rod. Any advise for the best metal drill bit? Also, is 3in1 oil ok for a cutting oil? I’m about 75% thru the rod and can’t seem to go any further. I started w/ an 1/8″ bit all the way thru and am now using my second 1/4″ Dewalt Titanium bit.
Here’s what I’m trying to drill thru: http://www.mcmaster.com/#
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Okay, so here’s what we know:
- Material: 1″-6 ACME threaded rod, low-strength steel
- 3-in-1 oil is being used as cutting oil
- Started with 1/8″ drill bit with success
- Running into problems with 1/4″ drill bits
Cobalt steel drill bits are great for drilling through tough materials, but they can be brittle and usually must be used in a drill press. The threaded rod is made from low-strength steel, and so regular drill bits should be okay.
I would use a regular high speed steel bit. This sounds like a tough cut, so I would make sure to use an industrial brand, such as Precision Twist, Cleveland, and the like.
If ordering from McMaster, I would probably try something like this one, a “Heavy Duty Chip-Clearing High-Speed Steel Jobbers’ Drill Bits.”
I would also add at least one more step in there and try using a 3/16″ drill bit as an intermediate between 1/8″ and 1/4″ sizes.
As for cutting oil, I would use a proper cutting fluid. I like to use “safe” fluids, such as Tapmatic Natural or Aquacut.
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Lastly, try to watch your drilling speeds. Irwin has a nice PDF download that could help you determine the proper speed, and there are plenty of online references as well. You could also refer to this Fermilab PDF chart (oh boy would I LOVE to tour a place like that!), and another reference. Both say that speeds should be at or slightly over 1,000 RPM. Irwin’s reference leads to a rough speed recommendation of about 1,000 RPM as well.
Summary: I would use an industrial bit, or rather at least two bits (3/16″ and 1/4″), a proper cutting fluid, and I would ensure I’m running at a relatively appropriate spindle speed.
If you still cannot drill the remainder of the hole, the steel might have been hardened by the previous drilling attempts, in which case I’m not sure what to recommend. At that point I might try a cobalt steel or carbide bit.
All you metalworkers out there, do you agree with my recommendations, or would you advise differently?
Allen
I wouldn’t think a pilot hole would be necessary. Sometimes that hurts more than helps.
Useing a hand drill or drill press ? Most likely the problem is that the material, drill or both are moving. Is he on the second bit because the first broke or he thought it was dull ?
You have to have things lock down right, and make sure you are drilling straight. Now that he has a pilot hole, come in from the other side to finish it.
Cutting oil does help, but on something that small anything should work.
Jer
This, step drilling is usually detrimental. Let the drill do the work, when you step drill the drill is working a more dificult manner.
Josh
Norseman makes some great drill bits. Their molybdenum steel bits might work well for this – they’re strong like cobalt steel but less brittle, so they can have a thinner web. Their. normal HSS bits are great too; you can get them from Harry J Epstein’s
Controlling the drill speed and alignment are crucial; a drill press is a huge help.
Mike
Steel may have hardened by rubbing of drill, flip rod over and drill out from other side.
Make sure all broken portions of previous drill bits are removed from the hole. If the edge of the new drill hits them it will damage the edge of the new drill.
Do not use made in China drills, especially the one available from mcmaster or msc.
fred
work hardening may indeed be an issue.
depending on the size of the hole needed – you might try treading a nut onto the rod, center-punching the nut and then drilling.
fred
Threading not “treading” – and probably a square Acme nut (McMaster-Carr should have them)
Rod
Most likely, the material is work-hardening at the point where the drill bit is cutting. This can result in small chips in the cutting edge of the drill bit causing further problems. “Speeds and feeds” are important. If the problem is work-hardening, try increasing the feed and slightly reducing the speed. If you suspect that small chips of the drill bit are embedded in the material, a carbide or carbide tipped bit may be the only way to get past the spot at which you’re stuck.
Your Titanium bits only have a coating of titanium nitride that chips off fairly easily and is probably not helping you.
Carbide can generally be run faster but I would increase the speed after it get past the hard spot.
Cutting oil may not make much difference. It’s primary role is to keep the cutting edge a stable temp and 3-in-1 oil will do that.
Unfortunately, it sounds like to finish the job you will have to invest in a couple more drill bits. I hate when a seeming simple job keeps getting more expensive!
Tim
I’ve had really good luck using black oxide drill bits when drilling through metal. They seem to hold up way better than titanium coated.
Hang Fire
Drill rod is not hard enough to require Cobalt drills. Most any lubricant will do.
Grind a flat spot. Start a hole exactly where you want it with a center drill. Finish the hole with a standard drill bit. That’s it.
If you need a small hole and the standard drill bit flexes too much, break it off and resharpen it as short as you can get it.
porphyre
I’m curious as to the direction he’s drilling. Is it parallel to the length or perpendicular? Is he trying to hole a bolt for safety wire or something. Or drilling the length so it’ll slip over something? What level of precision is needed?
Above good advise included, if he’s drilling the length, maybe flip it 180* and come at it from the other side and meet in the middle.
KL
Yep, it’s been work-hardened. You can get under it with a quality, sharp bit with heavy feed but it’ll be a sacrificial bit. I’ve had great luck w the Triumph Thunderbits w 135* point in such instances. Available in the Hot Deals catalog at use-Enco.com. I hate the ones with 3-flat shank but these are good for use in a hand drill.
Paul
I would try the Ridgid cobalt bits (145*) that home depot sells. I’m no expert, but I believe, that when it comes down to it the material you are drilling must be softer on the Rockwell scale than the drill bit itself. So the harder the better if the work piece is work hardened, right? The cheap titanium coated bits seem to be good for one use if that.
I use the craftsman brand cutting oil when drilling mild steel plate and if I ever get stuck I make a pass with the bit the next size down so the tip of the bigger bit can sink down farther and get a better bite. I’m not sure if its just the work hardening that stops a bit in it tracks or that if you don’t keep a constant feed it “polishes” the hole leaving nothing for the cutting edge to catch.
http://www.homedepot.com/p/RIDGID-Coldfire-21-Piece-Cobalt-Drill-Bit-Set-4516767/202251098
glenn
Place the rod in a vice with soft jaws, centre punch a start point. Use a 1/8 (3.2mm) cobalt (if not cobalt at least use HSS) bit to drill a pilot hole and use a high speed on the drill ie; 2400-3000 rpm. Don’t force the drill, take it easy, let the bit do the work and let it cool off in between drilling.
A “lubricant” is not necessary for the odd one off hole. In fact its not a lubricant that is needed anyhow, but a coolant or cutting fluid, If you are doing something like a production run, I would be buying a product similar to this in the link below, But for drilling a hole here an there in steel thicker than sheet, water will suffice as a coolant if used before the bit gets too hot.
https://www.rocol.com/products/rtd-liquid-reaming-tapping-drilling
When you go to the next size up, use a lower rpm, @ 1000 and again, don’t force the drill.
And don’t waste your time using using those cheap “titanium” coated bits. They are little better than case hardened cream cheese.
Jerry
Use a cordless drill-driver with the clutch set low enough so that the chuck stops turning before the bit breaks. Start at a low setting, and tighten it a little at a time until it drills normally without slipping with normal pressure. When the bit binds, the clutch should slip, and save the bit. Reverse the bit out of the hole, and look to see if you chipped the edge. Touch it up if you did. A chipped bit builds up a lot of heat quickly. Use a slow bit speed on anything that has the potential to work harden, it may take longer, but reduces the chances of tempering what you are drilling. Also, when drilling through fairly thick metal, you may be producing as much (or more) heat and friction from the flutes of the drill, as the cutting edge. As a twist bit wears, it gets a minute amount of ‘taper’ which you will likely never notice until you drill a deep hole in steel. Use cutting fluid to cool and lubricate the bit. If you can drill a small pilot hole no problem, but the larger bit sticks and breaks, chances are you need to reduce your RPMs. Larger bits produce more heat. Lastly, try drilling the pilot hole through, then drill about halfway through, then try from the other side. One thing to watch when drilling steel, is drilling too large a pilot hole. The pilot hole should be about the size of the ‘point’ of the bigger bit (ideally). Drilling too large a pilot hole puts all the force on just the ‘corners’ of the cutting edges, making them more prone to chip.
Eric
Does nobody sharpen drill bits anymore? Touch the bit up on a bench grinder, and finish the job. Don’t worry about work hardening or the fancy coating on the bit, a couple drops of 3’n1 and a sharp bit should have no problem with grade 2 steel.
Sean
Put a nut on it, drill through the nut and rod at the same time.
Noah
This is the kind of job that I would do on a drill press, because it would allow everything to be clamped down and held tight.
If I had to do it hand held in the field, the most important thing would be to be patient and drill slowly. Don’t just pull the trigger and blast away.
Ryan
Is it mild steel? depends on the bit I guess. but, a handy little formula if you know the type of steel is 4x cutting speed (for the type of steel) example…mild steel is about 100, but with a high speed bit, cut that number in half and then divide that top equation into the diameter of the hole you want. 4xC.S./D
Ryan
I should have mentioned that should give you the approximate RPM you need to drill easier.
E L
An old Electricians tip :
Get a jobbers bit and some sugar and water
mix it to a little more than paste then dip the bit and drill away .
works with anything metal that needs a hole thru it
will make a holesaw last forever
SteveR
As Noah suggested, this job would be easier on a drill press. I don’t have one myself to keep the rod locked down (i.e., not turning), and to insure a straight-in hole. For that I’d recommend a Big Gator Tools V-Drill Guide, available on Amazon and elsewhere. I’ve got one that runs from 1/8″ up to 3/8″. The nice thing is that it has a V-shaped underside which permits it to ride on the rod (threaded or smooth) to keep it place and your hole oriented 90 degrees to the material you’re drilling into. You will also need a spring clamp (one of those with the orange vinyl tip covers made by Pony, or similar); a C-clamp may also work to hold the drill guide in place.
I would use a liberal amount of cutting oil as a coolant; stop periodically to clean out the chips and recoat the area. I would also start with a new drill bit; a dull bit might be what’s preventing you from finishing the job. If that doesn’t help, you will need to flip it 180 degrees to finish drilling the hole from the other side, as others have suggested. And, as Noah also mentioned, drill slowly and carefully; you’ll get there with less drama if you let the tool do it’s job.
JRE
I used similar material on a recent project (McMaster-Carr Stainless Steel Acme Threaded Stock). It is a difficult material to turn or drill. I broke off a 4-40 tap in one piece despite drilling one number size larger than usual and plenty of cutting oil. I rarely break taps – this stuff is just tough – but had no issue drilling the hole. Speeds and feeds are important as are sharp tools. The parts I was making had the holes drilled perpendicular to the centerline, completely through the material. I milled a 1/4″ diameter flat at the hole location with an uncoated HSS end mill, center drilled first and then followed up with a sharp HSS drill bit (bright finish, no coatings). The cuts were made at 750 RPM with the workpiece clamped firmly in a vee block. Chips were cleared every 3-5 seconds along with application of WD-40 to the bit each time the chips were cleared. I did observe that the threaded surface appeared harder to cut initially but was softer in the center, supporting the observation of work hardening (which is expected for this material). Perhaps the issue is that your drill was dulled by the initial cutting?
Stuart
Stainless is typically tougher to drill through than plain steel.
Some Acme threaded rods are also case-hardened for greater durability and wear resistance. They’re not fully-hardened, except at the outer surfaces where the extra hardness is needed most.
ccr
You have dulled your drill or work hardened the steel as this is just soft 1008 threaded rod and about the softest grade of steel you will find. There is no need to run out and buy some expensive drill bits as others have suggested. Simply sharpen the drill bit you already got or get a cheap carbide tipped masonry bit and just punch it on thru if you have work hardened the steel. Run a 1/4″ drill about 800 rpm (200 divided by diameter for soft steel). The 3M oil is not the ideal cutting fluid, but for soft threaded rod it will be fine and you could probably just spit on it and it would work!
Michael
If all materials are steel, I would put a torch to heat it up then immediately drill the hell out of it.
mike
Funny how these types of posts bring out the garage hacks that think they know whats up.
Chuck it in a lathe and plow that thing,if its really mild steel doubtful its work hardened and Dewalt titanium bits suck. Get the proper stuff for the job before you hurt yourself.
75sfm is sufficient for most any mild steels,45ish sfm for stainless. WD40 is a better cutting oil than 3 in 1,but ideally you should use cutting oil and you can get that at hardware stores easily. CRC even makes cutting oil in a spray can.
Machine stainless and mild steels all day long everyday,this rod is like a 5 min job.
Shawn B
For sure. I read this and thought “what’s the problem ? it’s just some soft A108.”
I don’t think he’s trying to drill the rod on axis though, so finding a shop with lathe probably isn’t the solution. But then I thought: if the 1/4″ Dewalt TiN bit is like the ones in my jobsite bag, with the funky modified brad/pilot point.. well there’s the problem. Those bits suck for steel.
If I were this guy, I’d: 1) try and find a 1/4″ screw length 135° split point bit. Or 2) get one of those (Milwaukee, whatever) 1/4″ jobber length black oxide 135° split point at any hardware store.
Clamp the acme down. Peck it with a smaller bit to set a “spot”. Switch to 1/4″ (don’t pilot thru-drill it, waste of time), and getter done. Either the original bits are wrong (wood) geometry, or they are dull. Use a sharp 135 point. Should be easy.