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> No Messin' Around Drill Bits For Steel
Jimthecopierwrench
Posted: July 08, 2018 12:37 pm
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Started skinning my bus yesterday - 3000 solid rivets per side.

Going in with a smallish bit until I feel I'm a bit under the flush part of the head, then hogging with a 1/4" until the head spins off. Works, but tedious. 3 minutes per rivet.

Ryobi cordless and Rona twist drills - surprise!

The rivets are quite hard. Work hardened from installation?

A proper drill will be in order, best bits for the job though? Don't mind spending real money if there's something that will cut well.

I suppose I'll have to go to a machine supplier anyway to get them, but any suggestions?

I assume anything at the home depot regardless of their fancy wolverine adamantium sputtered coatings will be all but useless.



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MacFromOK
Posted: July 09, 2018 12:21 am
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Harbor Freight has some surprisingly good quality bits. And I bought a NiCad variable speed drill w/keyless chuck from 'em on sale (probably a closeout) for something like $16 - and it's waaay stronger than my old B&D ever was.

As a general rule IME, genuine HSS (and especially titanium-coated HSS) are usually pretty good, even the cheap ones. Got some nice B&D coated ones from Walmart.

YMMV. beer.gif

EDIT: FWIW... if the rivets are actually hardened, a dremel (or similar type small grinder) with a small wheel would probably be faster. Hardened stuff grinds a lot easier than it drills. wink.gif


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kl27x
Posted: July 09, 2018 08:50 pm
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I assume you could drill out these rivets in 20 seconds, IF you could fit them in a drill press. If they are taking 3 minutes, I am thinking same as Mac. Grinding might be faster.

This feels like giving Michael Jordan advice on his jumpshot. You have way more experience than me at machining things. But have you tried a die grinder with a carbide bur?

If you have never used a carbide bur, it's basically a high rpm rotary file. Since it's carbide, you can't really overheat and ruin the cutting edges. It is a lot easy to control by hand than a carbide endmill. The cutting edges have a big negative rake so they can't dig in too deep and grab. They work great on the (tiny) rivets I use. You just come in at a shallow angle, as perpendicular to the rivet as you can comfortably hold the tool and work around in a circle to keep the crater significantly larger than the radius on the bur (else it will start to grab). You need to use a bit more pressure than with a cutting disc, but a lot less than with a twist drill.

Another thought is a step drill. They hog steel like crazy. Maybe a small pointy one will fit in a pilot hole and cut a big rivet. The main problem is that the more bite you get, the more you will just spin the rivet.

Personally, I don't think there's that much to steel twist drills. If there's anything better than regular HSS or cobalt bits you can get at HD, then that will be news to me. I don't pay any attention to the coatings.
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Jimthecopierwrench
Posted: July 10, 2018 01:42 am
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Might be something to the burr - but I'd have to rig up a jig. Something like a magnetic base version of a drinking bird.



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AwesomeMatt
Posted: July 10, 2018 03:38 am
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DIY Mag-drill using an MOT, a thrift store wine corking plunger, and a drill?

I'm liking the idea of coming at them from the sides with a grinder. Maybe die grinder if full grinder is scary.

Maybe those $20 Princess ultra-speed die grinders too (dentist drill speeds). They'll chew through soft aluminum and are spinning far too fast to rotate the rivet.

Maybe plain ol' Dremel with a drillbit (some models have mini jacob's chucks instead of collets) would work. It's not steel.

There are many wrong ways to do this.
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kl27x
Posted: July 10, 2018 06:21 am
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Odd the timing on this. My GF brought in the mail a bit after I responded to this. My first 6mm carbide burrs just rolled in on the slowboat from China.

My crappo electric die grinder is still on that boat, and it's a little late to fire up the compressor. So I still haven't tried them.

The little Dremel can chew up some steel (wood and aluminum, too) with the 3mm burrs, though. I originally bought 10 of the same burr, years ago, thinking they chip and dull like end mills. I have yet to change out from the first one.

https://i.imgur.com/29Bbvzz.jpg

+1 on the angle grinder, if you are just going to scrap the sheet metal. 3000 rivets x 3minutes each with a hand drill, I figure you are planning to put it in the stock pile. And yes, you should be scared every time you use an angle grinder. I won't use an angle grinder, free-hand, unless I need to, and this is one of those occasions. Where I live, one angle grinder ER bill will buy several top end die grinders. (Better than one table saw surgery bill; that will buy a new car.) smile.gif

It is odd you can buy a good angle grinder for under $50.00. But a name brand electric die grinder starts at over $100.00 and go up to $300 without help from Festool or other insane German brands. But considering I have injured myself with almost every tool I own, the die grinder isn't so expensive for me. If the chinese import isn't concentric enough to run a burr, I'll just use it with cutoff wheels and pony up for a good die grinder. Heh, I just answered my own mystery. An angle grinder probably works fine with much looser tolerances. I have one of the world's worst rotary tools, but with a cutoff disc you would never know the difference. The disc just wears down to match the runout. And any edge wobble just makes it cut like a dado wobble stack.
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Sch3mat1c
Posted: July 10, 2018 10:45 am
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I picked up a 1/8" carbide tipped jobber's drill (from McMaster, it was, what was it, $20 or $30? -- might as well be a whole finger), since I poke a lot of holes in FR-4 as well as metal. Needless to say, it's staying much sharper than the chinesium it replaced. smile.gif

Might also grab a diamond grit sharpening "stone" / plate for touching them up, I assume you know the angles alright.

Wouldn't suggest a battery powered drill, though if you have to, you can cord it anyway, there's not much meat inside the cheapos.

Here's a hack: https://www.seventransistorlabs.com/Images/...edlessDrill.jpg
Original HF special, NiCd pack toasted from continuous charging (no logic in the charger, just a tranny, diode and LED). Trashed the pack, wrapped wires onto the terminals. Fast forward, I need to use it from a 12/24V system, so I made an 18V output converter box. Add 12V battery, and voila, a corded battery powered drill. biggrin.gif

Tim


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AwesomeMatt
Posted: July 10, 2018 06:47 pm
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QUOTE
Here's a hack:


Tim you should be ashamed, that looks like somethin' *I* would build. I've been meaning to build. It's on the list.
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kl27x
Posted: July 10, 2018 10:38 pm
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Behind the times... Li ion tools are here, and they are not shit.

Granted, I don't install decks or frame houses. But I have never run out of battery with my Li ion Bosch drill, nor have I ever waited even 1 second for the battery to charge. Even though I lost the spare battery within a month or two.

I have a cheap chinese "Worx" driver. For 3 years, I hardly ever used it. I bought it on a lark because it had a novel bit change system. It has an internal battery and a tiny barrel jack where you plug in a tiny wall wart. I randomly came across it in the closeout bin at the box store. Since it looks just like a POS and it was practically free, I assumed it was NiCd or NiMh. And from my sum past experience (with B&D tools that looked identical), I assumed it would be dead every time I picked it up or that it would die halfway through the job. After 3 years, I had to resort to using it enough times to notice; everytime I picked it up, it worked, and it finished the job without slowing. So 3 years later, I finally consider it a practical, dependable tool. Then one day I looked at the fine print, and see it has a Li ion battery. smile.gif

If you're going to do a battery conversion check out RC li ion packs. Quadcopters and whatnot have created a competitive market for premade packs with crazy discharge rates. Prices are very reasonable. I've strapped a small 4S 2000Ah 50C(!) pack to a Proxxon rotary tool some years back. It's still small and light enough to hold like a pencil, and it dusts the power and torque of the standard transformer. I have yet to use up more than a tiny fraction of the capacity in a go, and my charge rate is only limited by my PSU. Super cap? I think they're dead. Anything they can do, Li ion can do better. If I could manage to stall/seize this thing, there would be a mess of melted windings on fire.

Check it. Even if the C rating is overblown by 10x, this tiny battery would still easily power a typical hand drill.
https://i.imgur.com/cJHtJab.jpg

Incidentally, the bit in there is the most excellent 1/8" fine carbide burr I have found. If I remember correctly, it is a Dremel grout removal bit which I snapped in half and ground the end flat with diamond. It leaves a nice smooth finish and is very controllable. This is what kicked off my carbide burr fetish, like ten+ years ago. It is still my go-to for modifying enclosures and plastic connectors, free-hand. But the tool needs to have fairly low runout to use a burr. If you buy a dremel from Princess Auto to run a burr, you might as well buy a lottery ticket while you're at it.
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Sch3mat1c
Posted: July 12, 2018 06:52 pm
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Oh absolutely, batteries can do time constants of minutes these days. Hard to say if they'll ever do seconds or less; this is where supercaps shine. Say if you need to go 0-60 in literally two seconds, and can't afford the weight of batteries to dump that much (this is the difference between a Tesla and an electric dragster). Although to be fair, the weight of supercaps to do that isn't much less, so you'd probably end up with a hybrid of both in such an application.

Tim


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kl27x
Posted: July 12, 2018 07:31 pm
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^yeah, weight I guess. Maybe extreme temps are another place.

Just an FYI on the die grinder I just received.

The cheapest electric die grinder money can buy? I'm floored. It works. What I got is hilariously labelled "Die Grinder." (On the back, S1J-25 3104, 400W, 25000 RPM, 120V-60Hz) It's only about half a horsepower. But that makes it 3-4x the power of a Dremel. Runout is shockingly good. Burrs run great. It has enough torque and concentricity to cut, optimally, with burrs or cutoff wheels.

I opened it up to do a slight modification. What I notice is that unlike a rotary tool, the motor on a die grinder is better isolated from the spindle. The motor has a pair of ball bearings on its axle on either end. Then that is coupled with a plastic coupler to the spindle, which has its own pair of ball bearings. A rotary tool has the plastic coupler, but it only has 2 bearings, not the 4. So side-load and bit vibration shouldln't wear on the motor contacts as much, and even though the motor hasn't been balanced perfectly and there's a bit o vibration, the runout is very good, nonetheless.

Looking at reviews for these cheap grinders, the main complaint is the 6mm collet that won't take a 1/4" shaft. I tried putting my air grinder collet cone in it, but it doesn't fit. In the US, at least, it looks like all of the cheapest grinding points/stones, diamond burrs, and carbide burrs come in 6mm shafts, anyway. So for the home gamer who doesn't buy their stuff at the autoparts store or tool truck, this isn't necessarily a dealbreaker and actually has some benefit.

The only thing I want but can't find in 6mm is a cutoff disc mandrel/arbor. A 1/4" cutoff disc arbor is only $5.00 or so. I took one and tapered the shaft down to 6mm just using a dremel with stone bit and the old hand and eye. Ran a file over it. Sandpaper. And it runs true. If I needed to do this to the occasional steel shafted bit in 1/4", I could live with that.

The plastic is very rigid and is fiberglass reinforced. The slide switch interrupts both live and neutral. The fits of the halves is extraordinarily tight. Most impressive to me is that holy cow, they didn't save 2 cents on the screws. The screws are sufficiently beefy in diameter and have very hard heads that do not deform in the least against the bit.

About the only thing that is chintzy is the power leads to the motor don't have a proper place to route. It takes a bit of fiddling to get this thing back together, pushing around these wires with a stick to snake them around the housing bits and screw holes.

This is basically a larger Dremel. Still small enough to use with one hand for certain apps/bits. And it was under 30.00, delivered. Color me impressed. I have many rotary tools, and this was less expensive than all but one of them (and that one is crap).
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