Hand drill meets thick steel plate
November 23, 2015 10:05 AM Subscribe
Suppose I have a 1" thick plate of A36 mild steel and I want a 1/2" diameter through-hole, but I can't use a drill press. Is it complete folly to consider using a hand drill?
Additional questions:
Is a run of the mill black oxide HSS jobbers bit with average wear and tear going to get the job done or should I be looking for a new bit with a fancy surface coating and/or carbide tip?
How on earth do I start this thing? I was thinking I'd use a center punch and then an 1/8" bit to drill a pilot hole perhaps 3/8" deep or so.
What's my target RPM? How much downward pressure do I need? Cutting fluid? Am I going to have to stop periodically to let things cool? (I'll probably have to anyway, as the shitty hand drill I have gets terrible battery life.)
I don't necessarily care about the dimensional quality of the inner diameter of the hole, but I assume the result is going to be just downright hideously sloppy. Is there any way to clean it up? Is using a reamer (again using only hand tools) an option?
Additional questions:
Is a run of the mill black oxide HSS jobbers bit with average wear and tear going to get the job done or should I be looking for a new bit with a fancy surface coating and/or carbide tip?
How on earth do I start this thing? I was thinking I'd use a center punch and then an 1/8" bit to drill a pilot hole perhaps 3/8" deep or so.
What's my target RPM? How much downward pressure do I need? Cutting fluid? Am I going to have to stop periodically to let things cool? (I'll probably have to anyway, as the shitty hand drill I have gets terrible battery life.)
I don't necessarily care about the dimensional quality of the inner diameter of the hole, but I assume the result is going to be just downright hideously sloppy. Is there any way to clean it up? Is using a reamer (again using only hand tools) an option?
I assume you're doing this in place. Any reason you can't use a drill guide or jig?
These can be as simple as a piece of wood with a hole normal to the work surface (or whatever angle you please) attached with a clamp, to things like this. With a simple wood jig, clearance and oiling will be a problem.
The key is simply to go really, really slow and use a fluid, like oil. For a hole that big, I'd consider making multiple passes. A half-inch hole is huge in one go with a hand tool. Fatigue and good registration are both going to be issues, which is another argument for using a jig.
posted by bonehead at 10:24 AM on November 23, 2015 [1 favorite]
These can be as simple as a piece of wood with a hole normal to the work surface (or whatever angle you please) attached with a clamp, to things like this. With a simple wood jig, clearance and oiling will be a problem.
The key is simply to go really, really slow and use a fluid, like oil. For a hole that big, I'd consider making multiple passes. A half-inch hole is huge in one go with a hand tool. Fatigue and good registration are both going to be issues, which is another argument for using a jig.
posted by bonehead at 10:24 AM on November 23, 2015 [1 favorite]
In my experience, drilling steel with a battery powered drill and plain jane drills is a real pain. I bet you could get it done, but it won't be pretty. Be careful to not snap off the 1/8" drill. And I'd step up from 1/8" to 1/4" to 3/8" to 1/2". Good luck.
posted by mbd1mbd1 at 10:27 AM on November 23, 2015
posted by mbd1mbd1 at 10:27 AM on November 23, 2015
There's hand drills, and there's hard drills. You mentioned terrible battery life, so I am guessing what you have is under-powered and not up for the task. It could be done, but it will take a long, long time (acceptable for a prison breakout over a 30 year sentence).
Go rent a better drill, pay someone else to do it, or patiently drill multiple times using stepped bit sizes and oil.
posted by Diddly at 10:27 AM on November 23, 2015 [2 favorites]
Go rent a better drill, pay someone else to do it, or patiently drill multiple times using stepped bit sizes and oil.
posted by Diddly at 10:27 AM on November 23, 2015 [2 favorites]
Drill speed chart here and here (PDF). About 600 RPM maximum for a 1/2" hole in mild steels. Slower is fine too.
posted by bonehead at 10:27 AM on November 23, 2015
posted by bonehead at 10:27 AM on November 23, 2015
I drilled a few good holes in stainless on a sailboat with a battery drill, took several days of recharging but doable. Get a couple really good bits, a file to sharpen and re-sharpen. A little oil works but a drilling fluid is probably a good idea. Slow, patient, get the first 16th very accurate if that's important. A good center punch will help starting a lot. Did I mention getting a quality bit spec'd to the kind of steel you're working on! Oh and patience and gentle persistence.
posted by sammyo at 10:43 AM on November 23, 2015
posted by sammyo at 10:43 AM on November 23, 2015
Reading your issue closer, going a bit smaller and then opening to size with a rattail round file could be an option.
(will you be on a tippy ladder or dangling upside down? no? 'k just go slow and easy :-)
posted by sammyo at 10:46 AM on November 23, 2015
(will you be on a tippy ladder or dangling upside down? no? 'k just go slow and easy :-)
posted by sammyo at 10:46 AM on November 23, 2015
Yes to pilot hole. Drill it all the way through. Use copious amounts of cutting fluid (I like the CRC stuff). It'll keep things cool.
I'd drill the hole in steps. 1/8, 1/4, 3/8, 1/2. For unhardened mild steel you don't need any sort of special bits. You can rent magnetic mount drills if you need an accurate 90 degree hole but it probably isn't necessary if you are just bolting thru.
Ideally you want a combination of pressure and speed that results in long spiral curls of material being ejected from the hole. Slower is generally better.
I do this all the time both for bolting and for tapping in my job. It is quite doable and I've never bothered reaming in either case. You'll end up with a slightly trilobed hole. Which you could ream if you need something perfectly round. Note that you use a smaller than 1/2" drill to ream to 1/2".
posted by Mitheral at 10:47 AM on November 23, 2015 [2 favorites]
I'd drill the hole in steps. 1/8, 1/4, 3/8, 1/2. For unhardened mild steel you don't need any sort of special bits. You can rent magnetic mount drills if you need an accurate 90 degree hole but it probably isn't necessary if you are just bolting thru.
Ideally you want a combination of pressure and speed that results in long spiral curls of material being ejected from the hole. Slower is generally better.
I do this all the time both for bolting and for tapping in my job. It is quite doable and I've never bothered reaming in either case. You'll end up with a slightly trilobed hole. Which you could ream if you need something perfectly round. Note that you use a smaller than 1/2" drill to ream to 1/2".
posted by Mitheral at 10:47 AM on November 23, 2015 [2 favorites]
If you are a do-it-yourselfer, one of the most practical things you can do is google up your local tool rental shop and put them on speed dial. Life is just too short to waste time on inadequate tools and good tools are too expensive to purchase for one-off projects. For example, you can rent a heavy duty corded 1/2-inch drill for about $15 a day.
posted by JackFlash at 10:51 AM on November 23, 2015 [3 favorites]
posted by JackFlash at 10:51 AM on November 23, 2015 [3 favorites]
Oh and when I need to insert a bolt I generally use an oversize bit for my final. A 17/32nds in this case. Makes it easy to fit the bolt through.
posted by Mitheral at 10:51 AM on November 23, 2015 [1 favorite]
posted by Mitheral at 10:51 AM on November 23, 2015 [1 favorite]
Do drill the holes in steps like other people have said. Do use some kind of drilling lubricant, vaseline works ok.
Do not try to do this with a battery powered drill. It might actually take days to charge/drill/charge/drill.... Buy a $25 corded drill from the local hardware store.
Do let the drill cool off frequently.
posted by gregr at 11:31 AM on November 23, 2015 [1 favorite]
Do not try to do this with a battery powered drill. It might actually take days to charge/drill/charge/drill.... Buy a $25 corded drill from the local hardware store.
Do let the drill cool off frequently.
posted by gregr at 11:31 AM on November 23, 2015 [1 favorite]
If this is a piece of structural steel please do not drill a hole in it.
posted by gregr at 4:41 PM on November 23, 2015 [1 favorite]
posted by gregr at 4:41 PM on November 23, 2015 [1 favorite]
Observe correct rpms. Use several drills to step up to final diameter. Use cutting fluid. "peck" with the drill, boring maybe 1/8 inch , and pulling out to clear the chips. Standard HSS drills should work fine.
posted by 2N2222 at 4:45 PM on November 23, 2015
posted by 2N2222 at 4:45 PM on November 23, 2015
Go to a shop with a metal CNC plasma cutter, and have them make your perfect hole. It shouldn't cost much, and you will be fascinated by how the CNC plasma cutter works.
posted by Oyéah at 6:08 PM on November 23, 2015
posted by Oyéah at 6:08 PM on November 23, 2015
This thread is closed to new comments.
Why not take it to a machine shop and tell them exactly what you want? I can't imagine it costing much at all to do.
posted by Thistledown at 10:13 AM on November 23, 2015 [4 favorites]