sheet metal drill bits? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: May 03, 2022, 04:05:49 am
content: Does anyone know of a drill bit set meant for drilling sheet metal that has the geometry required to make nice holes? I don't mean a step drill, I mean like a twist drill with special points.I see some theories about something along the lines of crown point drill bits for drilling sheet metal nicely. I got a set of acrylic drill bits a while back and I am very happy I got that, so I was thinking it might be nice to have for sheet metal.I.e. something like thishttps://qrpbuilder.com/wp-content/uploads/2016/11/sheet-metal-drills-a.pdf

author: bdunham7
author_rank: Super Contributor
timestamp: May 03, 2022, 04:12:53 am
content: Black and Decker 'bullet' drill bits are sort of like that.

author: WattsThat
author_rank: Frequent Contributor
timestamp: May 03, 2022, 04:41:34 am
content: Standard bits work fine using this machinists old trick. (start at 5:50 if you just want the method without the drama):

author: metrologist
author_rank: Super Contributor
timestamp: May 03, 2022, 04:42:10 am
content: Also maybe you seen the YT vids of the machinists fold a small piece of denim cloth over their hole and drill through that. The swarf get wrapped up with the cloth and bit which prevents it from grabbing and tearing through. I haven't tried it.

author: coppercone2
author_rank: Super Contributor
timestamp: May 03, 2022, 04:46:07 am
content: I was hoping there was a drill bit solution, those cloths look great but I find myself dealing with sheet metal enough that I don't think I would mind buying a specialized drill set, if it exists. That might be useful if you need a non standard hole and like letter drills on a sheet metal. For number drills I don't know, they seem too small for a cloth.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 03, 2022, 10:22:29 am
content: Any single point cutter will work, particularly if done in a rigid setup. Of course, step drills are in that category, but you eliminated them from consideration.When working on aircraft sheet metal, a wider included angle (i.e., 135° vs. 118°) is often used. That helps with small holes. In fact, they are sometimes referred to as "aircraft drills." You can get sets in number, letter, and other dimensions.

author: langwadt
author_rank: Super Contributor
timestamp: May 03, 2022, 11:40:42 am
content: https://youtu.be/XA8L4L30TyI

author: eugene
author_rank: Frequent Contributor
timestamp: May 03, 2022, 02:55:24 pm
content: Maybe not "machinist approved", but at home I use bits intended for wood to drill sheet metal. The B&D Bullet drill sets are available at your local hardware store. Or:https://www.mcmaster.com/drill-bits/point-style~brad/

author: metrologist
author_rank: Super Contributor
timestamp: May 03, 2022, 04:22:57 pm
content: Most that do enough of this will look at a punch.

author: coppercone2
author_rank: Super Contributor
timestamp: May 03, 2022, 04:46:06 pm
content: How similar is the hand ground drill to the pilot point drills? So I guess I basically want a 135 degree pilot?

author: TimFox
author_rank: Super Contributor
timestamp: May 03, 2022, 04:57:10 pm
content: I know you rejected step drills, but I find them very useful for sheet-metal drilling.My favorites are the "Unibit" brand (Irwin) that have a single cutting edge, and leave very clean round holes in metal, say 1/16" thick, starting with a pilot hole equal to the minimum diameter of that bit (e.g., 3/16").The larger ones are designed to enlarge holes, and need an initial hole cut with a self-starting bit (such as the 3/16" minimum type).(I prefer them to competitors' products that have multiple cutting edges.)They are available in fractional inch sizes (minimum 3/16 inch diameter), but also in metric (even mm values, minimum 4 mm diameter).https://www.irwin.com/tools/browse/drill-bits/unibit-step-drills

author: BrokenYugo
author_rank: Super Contributor
timestamp: May 03, 2022, 05:02:42 pm
content: AFAIK step drills are more or less the gold standard. Hand grinding/sharpening a brad point is tricky and I doubt those pointy tips last long cutting metal.

author: alpher
author_rank: Frequent Contributor
timestamp: May 03, 2022, 07:21:06 pm
content: As somebody suggested, don't drill, punch ✊

author: jpanhalt
author_rank: Super Contributor
timestamp: May 03, 2022, 07:52:03 pm
content: Quote from: BrokenYugo on May 03, 2022, 05:02:42 pmMost important, it appeared he was using too fine a stone for re-contouring. Notice the bluing he got. The problem I have had doing work on small aircraft is that you usually need to go through more than one thickness for rivets. Moreover, it is rare to use anything more than 1/8" on ordinary sheet metal. That is where the 135° bits come into play.Quote from: BrokenYugo on May 03, 2022, 05:02:42 pmAgeed. Redoing a drill's point by hand requires skill. "A drill follows its point." That is why I like my drill sharpener (a great TDR/SRD unit). It's old but like new and not worn out (attached). I have known far better machinists than me who could do that by hand.

author: coppercone2
author_rank: Super Contributor
timestamp: May 03, 2022, 08:28:41 pm
content: I think maybe the step drills I have are dull, I might buy a extra set for thin metals and another set for 1/8+I might have ruined it drilling 10+ gauge steel a few years back, it does not feel sharp compared to a fresh one. The bit went from welding thickness metal to being used on essentially tin cans and that might be the problem, people seem to agree the unibit is better then the other bits.The only benefit is that you can be sure you wont over size a hole freehand using a modified bit.I was doing holes in thicker metal (maybe 12 AWG) and the bit felt very grabby/inconsistent.What is the highest quality step drill brand? Maybe I will see if norseman sells it. Is M42 or maybe carbide a good choice for material for this?How about those hole saw drills sold in the electrical section of the hardware store? (i.e. klein), they look kind of like magnetic drill hole saws (usually SDS), the electrician ones have carbide teeth.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 03, 2022, 08:36:26 pm
content: Get a good bit of HSS and learn how to sharpen it. Doesn't change the diameter much. My Unibit with 3/8" long steps (max 1/2") is at least 40 years old. Still works great.

author: TimFox
author_rank: Super Contributor
timestamp: May 03, 2022, 08:54:43 pm
content: I don't recommend the electrician's-style hole saws for good holes in sheet metal.There is another style, more expensive, designed for sheet metal that I have used for shallower holes:https://www.mcmaster.com/hole-saws/hole-saws-for-sheet-metal-11/cutting-depth~1-8/There are also ones with more depth than 1/8 inch. Full list:https://www.mcmaster.com/hole-saws/hole-saws-for-sheet-metal-11/For step drills, I recommend the Unibit brand from Irwin. They are available in different formulations.

author: themadhippy
author_rank: Super Contributor
timestamp: May 03, 2022, 08:58:28 pm
content: holesaws tend to leave a rough edge,ok if your putting a bush or grommet in,but need a bit of filing to get a smooth finish.

author: TimFox
author_rank: Super Contributor
timestamp: May 03, 2022, 09:11:05 pm
content: That's a problem with the "electrician's" hole saws. I've had better luck with the shallow-cutting ones I cited above.

author: eugene
author_rank: Frequent Contributor
timestamp: May 03, 2022, 09:11:23 pm
content: I have a few punches for larger holes, but who has every size that might be needed? They're relatively expensive. Also, I don't know what sizes are available, but there is definitely some minimum hole size that is practical.Step drills are useful for a few holes, but tend to be slow.I'm going to reiterate my support for the kind of bit in the OP; something with a sharp point at the center and two 'fly cutter' points that are sharp and shaped well. Depending on the size of the fly cutting points and the thickness of the sheet metal, comparatively little material gets cut. You end up making little washer shaped things. It's quick and results in a very clean hole. No pilot hole is required as with a punch or step drill. The sharp point means that even a center punch isn't necessary (especially if, like me, you tend to put the punch in the wrong place anyway.)I doubt aluminum is any harder on the tool than wood. Even with mild steel they should last a long time. Toss it out and buy a new one when it reaches end of life. Cheaper than step drills or punches.

author: alpher
author_rank: Frequent Contributor
timestamp: May 04, 2022, 12:26:53 am
content: For smaller holes in sheet metal nothing beats an "ironworker",But at home this thing costs less that quality drill set and does much better job in sheet metal than any drill bit you can afford:https://www.princessauto.com/en/metal-punch-kit/product/PA0008019921Princess Auto is pretty much a canadian Harbor Freight.

author: metrologist
author_rank: Super Contributor
timestamp: May 04, 2022, 05:20:15 am
content: Or maybe a Rotex or TinKnocker is more appropriate for a home-ish kind of shop?https://www.penntoolco.com/tin-knocker-18-station-hand-turret-punch-tk-18/

author: coppercone2
author_rank: Super Contributor
timestamp: May 04, 2022, 05:28:00 am
content: I thought maybe if I was to do punches I would get a micromot mini-press and dies for it, but I am not sure at the moment what it could handle. or some larger arbor press. With a chuck and bushings/pins it looks like you might be able to get any sized hole you want, so long the bushing can be fixtured somehow, perhaps in another larger chucknot sure what the force requirement is. that thing does 250lbActually I am thinking, you can do this in a drill press... its already heavy duty, enough for dealing with shields and screenshttps://www.americanmachinetools.com/tonnage_punch_hole.htm

author: coppercone2
author_rank: Super Contributor
timestamp: May 04, 2022, 06:52:53 am
content: I had another idea, maybe its possible to work harden metal by peening or something, then drill it?I wonder if that would make it better or worse, might try tommorow

author: jpanhalt
author_rank: Super Contributor
timestamp: May 04, 2022, 09:43:41 am
content: Another perpetual thread on how not to drill a simple hole?How about using a TiG torch with the gas turned off. Then grind the edges? If that doesn't work, turn the argon on. Ordinary stick welding is also used. Of course, don't forget the ballistic method(s). That allows a wide choice of diameters...

author: metrologist
author_rank: Super Contributor
timestamp: May 05, 2022, 02:57:39 pm
content: Just for fun, I stumbled across this DIY small hole punch system on this very forum.

author: coppercone2
author_rank: Super Contributor
timestamp: May 05, 2022, 03:18:45 pm
content: Does anyone sharpen their strait edge step bits?I tried the technique with the dremel point using a silicon carbide stone (the one that looks like a cone), but its still not as sharp as a new one. Someone that does alot of work told me their not really sharpenable. But I did see a interesting video where you rub it on a diamond hone plate to sharpen it.. is that worth a try? The edges are like borderline OK right now for thicker materials, I am scared to mess with it because it might get ruined (its a $40 milwakee bit)

author: metrologist
author_rank: Super Contributor
timestamp: May 05, 2022, 05:54:48 pm
content: Yeah you better be careful. You're sharpening the inside flute, right?

author: abquke
author_rank: Regular Contributor
timestamp: June 04, 2022, 03:27:31 pm
content: I impulse bought a hand punch once and it works great for thin-thin steel and thin aluminum. Faster and better results than drilling.https://www.mcmaster.com/hand-punches/compact-portable-lever-operated-hole-punches-8/

author: coppercone2
author_rank: Super Contributor
timestamp: June 05, 2022, 01:17:47 am
content: Quote from: metrologist on May 05, 2022, 05:54:48 pmbought new drill bit instead, I got tired of experimenting with the sharpening stuffI want those factory sharpened because if I make a weak edge or something, I thought it might get jammed and try to spin the drill on me and hurt my wrist at a random time if I am using it on thicker metal (I like using the magnetic drill or drill press if possible on things like that, but there are always exceptions). I learned to use a weaker drill with these ... I think the factory made one will wear smoother. I can handle the milwakee m12 fuel when it does that, but if I was using a 18V big brushless drill, I think it could hurt. Granted you are supposed to use two hands but the problem is usually that its sometimes nearly impossible to fixture and you need to brace what you are drilling with your hand/body because of vibration to have any semblance of 'work flow' unless you are 'the clamping doctor' with unlimited floor space for weird fixtures.

author: Smokey
author_rank: Super Contributor
timestamp: June 14, 2022, 04:23:24 am
content: Quote from: langwadt on May 03, 2022, 11:40:42 amSo this dude made his own brad point drill bit?https://www.mcmaster.com/brad-point/

author: langwadt
author_rank: Super Contributor
timestamp: June 14, 2022, 06:09:37 am
content: Quote from: Smokey on June 14, 2022, 04:23:24 amthose are for wood and such