I have a couple wrenches that came with my mini air powered die grinder. I want to put a hole into the top so that I can attach a wire or string so I don't lose them.

I used a punch to put a dimple into the wrench. I am trying to drill a pretty small hole maybe a bit bitter than 1/8". I put a cobalt drill bit into my drill press but it just doesn't seem to make any progress. I don't have a cutting liquid - was thinking of getting one. The wrenches are probably 1/8" thick.

Any other thoughts? What are the best bits for drill metal? What type do they use in heavy industry to drill through hard metal? Carbide? I probably have the drill press going too fast but I got it used and have never adjusted the speed. Given the size of the hole I am trying to drill it just seems like I shouldn't need the perfect setup to get a hole.

I adjusted the drill press speed to 620 rpm ( the slowest it can go - it was set at 3100 ) and I tried using a new cobalt bit with some spit on the wrench I had not previously tried to drill but it didn't seem to make any more progress than my previous attempt. I have some cutting oil and the HI-Molybdenum M7 Drill Bit Set on order so either I'll give those a try or next up I might try diamond or carbide bits.

I tried cutting oil - oatey 30201 -, setting the drill press at 3100 rpm, using a new cobalt bit, using a new spot and apply significant downward force - ending up breaking the bit.

I used my MAP torch to heat one of the wrenches to red hot and let it cool over night. The next day I used the same 3100, new cobalt bit, cutting oil and similar force. The drill bit went through ! You can see the line of the heat on the wrench. I didn't get around to trying a few of the other options yet. I'll probably give the diamond option a try on the wrench I haven't heated. Nice to have more than one trick in my bag.

Thanks for all the suggestions! I feel like I used a bit from each answer.

small wrench in drill press

success drilling

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    Spit is a better cutting oil than nothing at all. However I think the core issue is feeds and speeds. – Harper - Reinstate Monica Apr 26 at 19:20
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    Feed being pressure and speed being RPM. – isherwood Apr 26 at 21:14
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    Use a good cutting oil, a cheap bit, and slow speed. This video shows a great experiment cutting through armor plating with a cheap bit, and "tap magic" cutting oil. youtube.com/watch?v=v6QCrV4ZOiU The brand of oil seems to make a big difference, and allows you to just a cheap bit. – Steve Sether Apr 27 at 5:49
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    @CaiusJard The other end of the tether is attached to the loop on your belt. I started making loops, straps and carabiner hooks with and without shock absorbers for my tools for climbing rebar walls in a harness about 7 or 8 years ago and similar gear has even started showing up at work clothing stores in Canada. – K H Apr 27 at 8:55
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    Drilling a hole through a tool sounds like a fine way to cause it to snap under tension. – Valorum Apr 27 at 11:55

11 Answers 11


Anneal The Butt of the Wrench First

When you view this question in the general since of "how to I drill steel that is too hard to drill with the tools I have", annealing it first is one possible solution.

Depending on how steel is cooled, it can form different kinds of crystalline structures that give it its unique properties. In the case of the steel in your wrench, it was likely heated and cooled to different temperatures and at different speeds in a kiln until finally being quenched to give it that nice combination of hardness and toughness that makes it so good at applying force without breaking. The hardness part that you are having a difficult time overcoming comes from that final quenching where it is cooled quickly in oil or water (depending on the exact alloy).

So, to make the steel softer, you just need to heat the butt of the wrench with a blowtorch until it glows a bright red. If it gets too hot you risk decarbonizing and/or melting the steel which will ruin it; so, be careful not to let it get to being white hot. You also do not want to heat the head or neck of the wrench as this may ruin the original temper and make your wrench bend next time you try to use it, but since the butt experiences the least amount of stress in use, softening that steel will generally not be a problem. Then you want to let it air cool. You don't want to cool it in water as this will just re-harden the steel. You also don't want to fully anneal it by kiln cooling it either as you only need it to be soft enough to drill... not soft enough to bend in your hands.

... or if you just want to solve the actual problem (hanging metal tools that are otherwise hard to hang), you could just try a magnetic wall strip. If cost is an issue, you could instead put two nails in your wall that are far enough apart for the handle to fit, but closer together than the width of the head. Then you can hang the wrench upright between the nails instead of upside down on 1 nail.

These methods requires no actual modification of your tools, just your work space.

enter image description here

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    @FreshCodemonger You're unlikely to get the cooling profile right (you don't even have a way to measure the temperature of hot metal, do you), so I'd just leave it as it is. Heating it again could further compromise the properties of the business end, quenching it incorrectly could make it too brittle (useless/dangerous) or destroy corrosion resistance. – TooTea May 3 at 12:59
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    Yes, I agree with TooTea: trying to retemper it is not a good idea without more specialized tools and experience, but since it's just the butt of your wrenches, they should be fine as is. – Nosajimiki May 3 at 13:17
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    @FreshCodemonger if you do quench, be sure to not use water- use oil. Grapeseed oil is OK, but there are quenching oils that can take the heat away in a better manner than your common kitchen oil – tuskiomi May 7 at 15:29
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    @tuskiomi It's a bit more complicated than that. Different steel alloys should be quenched in different mediums for best results. When you buy steel stock, the manufacturer will often tell you exactly what medium it is best quenched in. Some alloys actually should be quenched in water and not oil... so when you buy a tool made from an unknown alloy, you are kinda guessing. – Nosajimiki May 7 at 16:36
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    It's kinda hard to go completely wrong when quenching too. The goal is to harden the steel, and in some form, that's what will be acomplished. – tuskiomi May 7 at 20:03

With a sharp drill, oil and patience, or with carbide. But Why make a hole?

enter image description here

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    This. Or cable tie it to a loop of rope/string. Not worth the hassle of drilling. – pcdev Apr 27 at 4:25
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    I'll see if a cable tie might work - I like simple. Also like the idea of figuring out how to drill through metal. I had a stainless steel strainer for pasta/produce but the weld came undone and I ran into the same problem - was hoping to fix it with a small bolt and nut but couldn't get the hole drilled. – Fresh Codemonger Apr 27 at 5:02
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    Not carbide drill for concrete, it has to be designed for metal, with sharp cutting edge. Or a carbide bit for millling. – bobflux Apr 27 at 8:31
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    Zip ties for the win! One around the tool and the tether and Bob's your Uncle! – FreeMan Apr 27 at 12:10
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    @bobflux For small diameters, "milling drills bits" or "drill mills". For larger diameters "center-cutting end mills." – Brent Apr 27 at 23:07

A challenge at home. Good tools are hardened to near Rockwell C hardness 40. Cheap tools can be much softer. A professional machine shop can drill up to HRC 40 , so they could slowly do it. You have a chance with a new HSS bit , high sulfur cutting oil ( you will probably need to find some old oil as likely it is now illegal) , low RPM , pressure . If the bit turns a few times without cutting , it is been made dull - get a new bit. Start with a small bit like 1/16 , then a large one for final size. You can not drill in a spot where you have made a mark by another try- the steel in that spot will be work hardened to much higher than HRC 40. You can hope the tools are not very hard , a reasonable possibility.

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    I never considered my own work hardening the spot I'm trying to drill. Thank you for that insight! – JS. Apr 27 at 20:31
  • Why not heat the section up and drill a little at a time? Just curious why not as I have seen it done. – DMoore Apr 29 at 16:57
  • If it is a Chrome /moly like 4140 , hardened to HRc 40 ,it would need to be heated over 800 F to begin softening . A carbon steel would start softening a little lower like 700 F. But the cutting action itself heats the steel ; blue of purple turnings at a professional machine shop show the chip was heated to roughly 700 F by the cutting. HSS alloys are used for cutting tools because they can keep cutting to 1000 F and higher. I doubt that heating work would make a difference. – blacksmith37 Apr 29 at 19:22

Without cutting fluid chances are you melted the cutting edges of your bit. Use a sharp bit and any oil you have lying around, along with a slow speed.

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    I saw an automated version of this in a machine shop. The drill was going slowly and oil was being applied continually. It might take a very long time, since you want to avoid overheating the drill bit. – Yehuda_NYC Apr 26 at 19:05

If you have the chops and some electrical equipment, you can use EDM to put a small hole in the wrench with a relatively quick pace.

enter image description here

There is a popular YouTube video with a simple methodology here

While the application is very niche, I figured that I would post it because it is by far the fastest method to remove material at home, and you don't have to (possibly) ruin any drill bits.

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    Looking at that video. The arc generator alone is about E3000 and out of stock, then you have the CNC motion control stuff which was about $700. The CNC motion is listed as 1,169.99. I suspect all those prices are excluding tax/shipping. – Peter Green Apr 28 at 1:01
  • @PeterGreen Right, that's more of a high-level solution, you could put a hole in the wrench with a car battery, aquarium pump and a few lengths of brass tubes if you're 'gung ho'. I wrote this more out of an urge for completeness. – tuskiomi Apr 28 at 1:05
  • This is the best answer. – Tony Ennis Apr 28 at 22:36
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    @Sam is that a challenge? – tuskiomi Apr 29 at 16:24
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    I'll pay you 50 Euros if you get something rigged and "drill" a hole in a wrench with a car battery within a week. (I think it would be a great addition to this site!) Perhaps others pitch in to make it worth your while? – Peter - Reinstate Monica Apr 30 at 0:04


Get a pack of magnets. Each one can hold a wrench to the side of a toolbox, refrigerator or other steel surface.

  • I like the magnet idea if the tool was never to leave my shop or had a dedicated place. Most of my tools are stored in bags ready to take to jobsites. I typically attach grinder wrenches to the grinder cord so they are always with the tool. Most of the newer drills that take a chuck key have a nice rubber or silicon chuck key holder that attaches to the cord. My makita D drill has a dedicated hard recess for the chuck key. I am really just trying to replicate good design that works for tools on the go. – Fresh Codemonger Apr 27 at 16:04
  • @FreshCodemonger A grinder wrench? As in a thin plate? You can definitely put a hole in that with a die grinder or dremel and ball diamond bits, with or without lubricant. You should perhaps include the types of wrench in your question. – K H Apr 27 at 23:47
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    They make magnetic strips that may be perfect for this... However some steel doesn't hold well to a magnet so I would test it out before you go that way. But a really strong magnet cut in a 1" strip would probably hold well and allow you to pluck it off with out a ton of effort. You could even go a second strip if the wrenches get a little too big. – DMoore Apr 29 at 18:43
  • Every so often I buy some more magnets for one purpose and in a short amount of time I end up using them for something entirely different. Good thing we don't use floppy disks any more. – manassehkatz-Moving 2 Codidact Apr 29 at 18:46

Have you considered wrapping them with paracord?

enter image description here

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    The end of that knife has a hole in it. That's what OP is trying to make. – JS. Apr 27 at 20:32
  • I get the impression this was a general illustration, and attempting to be a better looking version of bobflux's answer, rather than specific to how the paracord is tied on this one knife. – BMitch Apr 27 at 23:22
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    I've done numerous paracord wraps and this would definitely bypass the need for a hole. The paracord grips the handle and it's not difficult to add a durable loop of your own design at any point in the binding. Not a bad answer given the prevalence of the XY Problem on stack exchange. – K H Apr 27 at 23:44
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    Because I've now found a grinder wrench is among the wrenches OP wants to retain, I would note they often don't have a taper for the cord to grip, so it would be wise to use an angle grinder to put a few grooves to prevent the rope from slipping off the end. – K H Apr 27 at 23:53

Reality check: Drilling does not make heat.

NOT drilling makes heat! :) if the drill isn't cutting effectively, it's sitting there getting hot (and work hardening the metal and dulling the drill).

Once I was drilling holes in mild steel on a mill, working fast - drill, index, drill, index, drill. I was making nice long chips that came off like noodles. Immediately after the last hole, I grabbed the drill bit by the flutes and loosened the chuck, and put the chamfer bit in there to chamfer the holes.

How did I know the bit would be cool to the touch? By the chips. In this material, the nice long noodles said I was drilling, not making heat.

And that worked because I had the "feeds and speeds" correct: I got the "speeds" by looking up in a table the correct RPM (itself derived for me from the surface feet per minute ideal for that material). I got the "feeds" by touch and feel: when I got happy chips, I knew the feed rate was correct. This worked because with speeds known to be correct, I only had to explore for one variable.

Do the same and you'll be starting on the right foot.

And if the drill even starts to get hot, stop immediately. You are not drilling, you are in a hole so stop digging!

A drill bit that has gotten red-hot is now irreparably damaged.

For a 1/8” drill bit I would expect a correct speed very coarsely around 3000 RPM,

Reality check: slower is not better

A lot of novices go "I'll just err on the side of caution on feeds and speeds". Wrong. There is no 'caution' in that sense in machine work. Feeds and speeds are not maxima... they are correct values, and other values are wrong.

Granted, there's a lot of tolerance - but think of it like water skiing... or flying a fixed-wing airplane. Too slow means you are not doing "the thing" at all!

"Too slow" typically means "work hardening", which makes it only harder to get started again, whilst dulling and heating the bit.

Reality check: oil does not cool

Cutting oil is for cutting. That's why they call it cutting oil. As discussed, cooling doesn't help drill because if you're making heat, you're not even drilling. All it will do is forestall the hot drill's destruction a little bit.

Water will at least boil at 212F, and take away tremendous amounts of heat via the "latent heat of boiling". Oil won't do that (unless you're on the verge of ignition), so its ability to remove heat is very limited and you'd have to use very messy amounts of it to gain appreciable cooling. Larger manual machines have a cutting fluid collection system on their bed, a pump, and a "bendy snake"-like nozzle which can be aimed at the work area. CNC machines have a liquid-tight enclosure, and they just blast the cutting area with multiple streams of oil/coolant.

Drill quality is not the deciding factor

I see you reaching for the "top shelf" drills, thinking they are required. Not in this case. It's about techniques far more than tool quality, i.e. top shelf drills won't save you here, you're just throwing money away.

What "better" drills generally do for you is give you longer service life... giving you, say, 200 holes until dull, instead of 100. In my experience the drill is far more likely to suffer some other casualty long before that, due to the high variability of hand-drilling, say.

To actually get to where the drill reaches its service life, you'd have to be under controlled conditions with a big machine, such as the high-rate work I was doing where I had my technique "dialed in". Or better, using the auto-feeder (where the machine advances the bit for you). In that case, you set it from the "feeds" data from the machinist's tables.

  • So it sounds like I should wait for my cutting oil to arrive, set my drill press to 3100 rpm and try again. My first attempt sounds like it was close to ideal minus the oil - I had it set to 3100 rpm and I was using pretty good pressure via the press wheel. My hope was that by getting top shelf drills I could make up for my beginner techniques. My brain wants to think that given the size of the hole I am trying to drill it should be easy and I should almost be able to look at it and have the hole appear. Reality is proving much different. – Fresh Codemonger Apr 29 at 6:07
  • Have to disagree about speeds - they are the 'Optimum' speed rather than the one and only 'correct' speed - slower is not going to be a problem, just that it will take longer than necessary. – Mike Brockington Apr 29 at 14:34
  • @MikeBrockington The tolerances are pretty broad, granted. "Slower" by 10% of what the book says won't do too much harm. But it's like water skiing, or flying an airplane - too slow means you are not doing the thing. "Slower" by 80% puts you into the "not drilling" zone where you're work-hardening the material and dulling the bit. – Harper - Reinstate Monica Apr 29 at 16:11
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    Drilling and all metal working cause heat. The trick is that when done properly, most of the heat comes out accumulated in the chip material. Lubricants help reducin the heating from sliding the cutting edge on the worked material and it helps spreding the heat from the cutting point. – Crowley Apr 29 at 17:30
  • Cutting actually makes way more heat (than non-cutting) unless you are putting too much pressure on the material. Years of cutting through stone/granite I can assure you that cutting creates heat - probably a good source is materials grinding after cut (not cleaned out). For instance water on my bit will cool down my bit and hopefully flush as much debris away. I somewhat agree with you on the speed thing but you have to go slow to get a divot to start the hole. After that you should be at higher RPMs in busts with low pressure. – DMoore Apr 29 at 18:17

Another option I've gone with is to weld a loop onto the tool. That said, for extremely hard metals you can work your way through pretty much anything with a diamond bit and patience if specialized drill bits and cutting oil don't work. If you can stand a 1/4" hole a diamond hole saw will probably do the trick. There are also ball head type diamond bits you can get for a dremel, but these aren't great for drilling straight holes because of the low velocity at the center of the shaft. I use that type of bit to engrave hard tools, but I cut with the side of the ball, which is at high velocity.

If you have a significant number of tools you want holes in, you could consider getting quotes from laser or water jet shops if there are any near you.

Diamond doesn't require a great deal of pressure to cut and as long as you lubricate well and don't overheat you can spin the bit at fairly high velocity to help your cutting rate. it helps to drill horizontally to help clear the gap.

  • Or weld a hex nut on the spanner. – Tim Apr 27 at 12:30
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    @Tim I like to take a loop screw or eye hook of suitable size and cut a suitable loop from that with an angle grinder. Nice and smooth and round. – K H Apr 27 at 12:32
  • I saw today they have diamond hole saws smaller than 1/4" (I think it was 3/16") common stock at my local tool store. – K H Apr 27 at 23:40

Your explanation that it's to attach a mini grinder wrench to the tool so they stay together made me see the problem (the shape of the wrench is not conducive to attachment) and also a fairly simple and obvious solution

It doesn't actually have to be a hole. Take that mini grinder and use it to grind two slots in either side of the handle so there is a narrow spot, then tie a wire around that spot

enter image description here


According to https://carbideprocessors.com/content/drill-speed.pdf you should be using 3,000 rpm and cutting oil.

The oil doesn't have to be fancy. Just grab some motor oil and a spray bottle or a spoon and keep things lubricated.

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