Making or sourcing ~20mm metal circles? (not legal tender or holey) - Page 1
Forum section: electronics / beginners

author: Whales
author_rank: Super Contributor
timestamp: August 23, 2020, 03:01:33 am
content: I'm trying to make a special battery adapter for a particular product my work has a lot of. Having access to ~20mm metal circles/rounds of some description that I can solder to would make my life a lot easier. Preferably something I can make myself or source from within Australia (or otherwise avoid the 1-3months of China shipping I'm seeing at the moment).Ideas so far:Coins:would be almost perfect (depending on solderability of alloy), sadly defacing coin of the realm is illegal.Coin blanks:I've only seen slow overseas suppliers OR precious metal ones from within AusWashers:hole in the middle causes me problems with my battery contacts, unless the hole is really small (<4mm)Hole saws:again creates a hole in the middle.Custom PCBs:I feel like this might be technological overkillAny clever techniques or methods that I could make some out of flat metal sheet? Or any known supplies of pre-made ones? Any thoughts or advice appreciated, I'm going in circles.

author: sleemanj
author_rank: Super Contributor
timestamp: August 23, 2020, 03:09:37 am
content: Thin nickel sheet might be suitable to punch with a circular craft punch die available at your local crafty type store.

author: Monkeh
author_rank: Super Contributor
timestamp: August 23, 2020, 03:11:37 am
content: A hole saw should work without a pilot in a press.You could also part off from round stock on a lathe or even just a band saw.

author: Whales
author_rank: Super Contributor
timestamp: August 23, 2020, 03:22:45 am
content: Quote from: sleemanj on August 23, 2020, 03:09:37 amOoh, I didn't realise you could easily get punches this big. Looks like there are a few places in Australia, thankyou.Quote from: Monkeh on August 23, 2020, 03:11:37 amI'll give this a go. I'll get a new (cheap) holesaw, my sets are all too large.Quote*jealous glare*I do have brass round stock of the right size and a band saw, but it's a tiny 140mm blade-length unit that blunts easily and wanders whilst cutting.

author: DrG
author_rank: Super Contributor
timestamp: August 23, 2020, 05:05:12 am
content: For sourcing, there are lots of suppliers along the jewelry / tag / token / hobby markets. Here are a few to give you some search options.https://www.aliexpress.com/item/32716955260.html?spm=a2g0o.productlist.0.0.2f952084QZxOYi&algo_pvid=0e4feabd-a56f-480d-a110-05c09ae5210c&algo_expid=0e4feabd-a56f-480d-a110-05c09ae5210c-21&btsid=0ab6fa8115981585640436065eee76&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_https://www.etsy.com/listing/605668731/10-deburred-choose-your-metal-12?ga_order=most_relevant&ga_search_type=all&ga_view_type=gallery&ga_search_query=metal+stamping+blank&ref=sr_gallery-1-9https://www.dhgate.com/product/58mm-aluminum-stamping-blanks-2-28-inch-diameter/401215302.html?skuid=383440067284910080#s1-24-1b;srp|3229652801

author: Kasper
author_rank: Frequent Contributor
timestamp: August 23, 2020, 06:55:31 am
content: I'm guessing you already looked here but its not in your list so...https://www.digikey.ca/en/products/filter/battery-holders-clips-contacts

author: Domagoj T
author_rank: Frequent Contributor
timestamp: August 23, 2020, 07:39:35 am
content: Specifying thickness, material and quantity could help us with suggestions.It really is a different story if you need 200 or 200 000.Anyway, when I needed some thin, but large plastic washers with small hole, I used a lathe to put a hundred or so roughly cut pieces on a mandrel and turned them all at the same time. They had to have a small hole in the middle, though (but in my case that was needed anyway). If you can live with a 5 mm hole, the process should be possible for you as well.If not, or you don't have access to a lathe, and need fairly small quantities look into having it laser or waterjet cut.Laser is fairly cheap, but some shops may refuse to cut copper alloys. That was the case when I had to have some things cut from bronze sheet (something about reflections damaging the laser).I ended up waterjet cutting. There is basically no restriction on material there, but it is a bit more expensive.If you need large quantities, punching will be much cheaper, after the initial setup fee.

author: voltsandjolts
author_rank: Unknown
timestamp: August 23, 2020, 08:42:13 am
content: All of this sounds like a real kludge.

author: nali
author_rank: Frequent Contributor
timestamp: August 23, 2020, 09:29:21 am
content: Putting "20mm brass disc" into Fleabay brings up a bunch of hits - they're used by engravers & for dog tags that sort of thing.

author: Whales
author_rank: Super Contributor
timestamp: August 23, 2020, 10:11:05 am
content: Thankyou for all of the suggestions.eBay and Alix:economical shipping from overseas means 1-3 months of shipping at the moment, I'm not willing to wait.digikey:I'll take a look and see if they have any huge ones. EDIT: sadly look to be all square, not round. NB broken link, possibly due to silly geo-region redirects?lathe:*seething jealousy overflowing further*quantity:circa 50thickness:around 1mm. Thinner than a coin (<2mm) and stabler than foil (>0.3mm)I've modified a 22mm hole-saw to remove the center-drill and so far it appears to be a promising option when paired with my drill press. I've made some neat 18mm circles out of FR2 but I will have to see how it performs on some thin metal sheet stock.

author: Whales
author_rank: Super Contributor
timestamp: August 23, 2020, 10:13:23 am
content: Quote from: voltsandjolts on August 23, 2020, 08:42:13 amA circle is a circle, no matter if bought from someone else or cut yourself

author: Domagoj T
author_rank: Frequent Contributor
timestamp: August 23, 2020, 03:23:58 pm
content: If the hole saw works for you, great.As for the lathe, get one. It's an amazing tool to have. Even small desktop ones are very usable. I bought mine three years ago and it's the best money spent, used almost on daily basis.

author: tszaboo
author_rank: Super Contributor
timestamp: August 23, 2020, 03:49:32 pm
content: Just make a drawing for it, send it to a local shop.It is really easy, if you did it once. We literally have one every second corner in an industrial park, and they do these kind of things all the time. They can laser cut this in an hour.

author: mathsquid
author_rank: Frequent Contributor
timestamp: August 23, 2020, 04:20:32 pm
content: A lathe would be nice, but for cutting 20mm round stock, you could use a small or mini chop saw.

author: voltsandjolts
author_rank: Unknown
timestamp: August 23, 2020, 04:30:18 pm
content: Quote from: Whales on August 23, 2020, 10:13:23 amSure, but I was refering to the root problem - a plethora of batteries, holders and packs already exist so you don't have to kludge a battery pack together with washers.But what you are trying to adapt is a secret, so who am I to 'judge your kludge'

author: Doctorandus_P
author_rank: Super Contributor
timestamp: August 25, 2020, 12:03:13 am
content: You can make some kind of jig and clamp a piece of material between 2 ball bearings, and then use a bench grinder.This tends to work best if the axis of the bench grinder is around 80 degrees from the rotation axis of your jig, so it "grinds a lot" and "rotates your jig a bit.For 50 it might be a good idea to make some kind of pendulum of spring loaded jig that pushes the part with the right force into the grinding wheel until it stops at an endstop. And make 2 pieces of the ball bearing part of the jig, so you can mount a piece of material in one jig, while the other is grinding.

author: themadhippy
author_rank: Super Contributor
timestamp: August 25, 2020, 12:46:07 am
content: off the wall idea,knock outs from metal electrical back boxes

author: Brumby
author_rank: Unknown
timestamp: August 25, 2020, 12:55:42 am
content: Quote from: Monkeh on August 23, 2020, 03:11:37 amMy first thought also.Have done this with plywood. Cutting metal shouldn't be a problem, just go slow and steady. Digging the blank out from the teeth will be fun, though.

author: Monkeh
author_rank: Super Contributor
timestamp: August 25, 2020, 01:23:28 am
content: Quote from: themadhippy on August 25, 2020, 12:46:07 am16 per box for a 2-gang 25mm, for 50p.. Why didn't I think of that?Not sure the aussies use equivalent boxes though.

author: Nusa
author_rank: Super Contributor
timestamp: August 25, 2020, 01:42:08 am
content: QuoteGiven that you only need 50 of them, what about coins of other realms? The 5 cent euro coin comes to mind as likely to be available at money exchange places, but there are probably many candidates (Canadian and US nickels are the same size).

author: vk6zgo
author_rank: Super Contributor
timestamp: August 25, 2020, 02:52:28 am
content: Quote from: Nusa on August 25, 2020, 01:42:08 amOr pre-decimal Oz pennies?Nobody seems to care about defacing them.I know some stuff from that era is now valuable, but pennies were around in huge quantities.Another point, are they used in-house, or are you selling the devices?If the former, is it that important that the spacer be a full disc?A square with the corners cut off may do the job OK, although it probably wouldn't look good enough if you have to sell them.

author: BrianHG
author_rank: Super Contributor
timestamp: August 25, 2020, 02:55:08 am
content: How about a source for tokens used in arcades.

author: themadhippy
author_rank: Super Contributor
timestamp: August 25, 2020, 03:18:15 am
content: Quoteclipsal are aussies and they do a few metal boxes,for example part no SB471

author: Raj
author_rank: Frequent Contributor
timestamp: August 25, 2020, 04:32:35 am
content: Do what they did-https://hackaday.com/2014/02/08/behold-lil-screwy-a-homebrew-100-ton-press/

author: kaevee
author_rank: Regular Contributor
timestamp: August 25, 2020, 07:00:27 am
content: I have about 100 Nos of Aluminum circles of 25mm dia / 0.8mm thick. Will they do?If you need any other metal/alloy, they can be manufactured.

author: Raj
author_rank: Frequent Contributor
timestamp: August 25, 2020, 03:45:05 pm
content: Btw, If you have a vice, I can make you a die set that can do the job, if you intend on using thin sheet metal...But can you answer me a few questions?Why aren't you simply getting round PCB? they can make PCB in any shape now.Why can't you bend a wire to act like flat contact like the one in attached photo?What size of battery is it?Do you need to solder onto it? if yes, aluminium won't work.Is it a one time purchase or multiple?How many do you need?How dimensional accurate do they need to be? if it's just 10 or so,and they don't need to be accurate, you should be using a hacksaw or dremel to cut em out

author: girishv
author_rank: Regular Contributor
timestamp: August 25, 2020, 04:45:08 pm
content: As an after thought, how about "Slide-in Battery Contacts" from KeyStone.https://www.keyelco.com/category.cfm/keyelco/Slide-In-Battery-Contacts/id/1039These will work for custom battery case and probably works for all kinds of batteries.

author: Whales
author_rank: Super Contributor
timestamp: August 25, 2020, 10:09:08 pm
content: Thankyou everyone, I was not expecting all of the suggestions to keep coming.Project is on hold. I made some bad assumptions about parts I could 3D print -- the places I would normally go to and ask if I could borrow their printer are shut with the pandemic and the commercial operations seem to want 1/3 of a price of a printer to make a few FDM parts.Quote from: voltsandjolts on August 23, 2020, 04:30:18 pmNot intending to sound secretive, I'm just caught up in circlesI didn't expect as much interest as this.X-002.99.382 batteries cost $100-200AUD. Inside each are lots of spot welded strips, plastic frames, plastic shims and 3x NiMH AAA batteries.82.5mm long, 26mm diam:I have a stack of 20 "bad ones" on my desk that I have been sorting through (we've also been seeing bad contacts -> not charging) and I know we waste more than we should.I have been looking at ordering some generic alternatives, but from the outside they look identical, so by the law of packaging inertia I suspect they are made in the same way. I'm going to grab some anyway and see when they arrive.Whilst generics are much much cheaper I would still prefer an option where the AAA cells inside are easily replaceable. This would set us up for life and let us control the datecodes on the NiMH we put inside.Quote from: Nusa on August 25, 2020, 01:42:08 amI would prefer not to deface legit coin from any legal country, even lesser ones like New Zealand.Quote from: vk6zgo on August 25, 2020, 02:52:28 amHmm, I'm under the belief that (with something like 2 exceptions) all currency ever issued in Aus is still considered legal tender. In practice though you're probably right, no one would care.Regardless: I have some better options now so I'm going with them.QuoteIn-house. Initially for fun, to see if it's possible to replace the big waste we have at the moment.Quote from: girishv on August 25, 2020, 04:45:08 pmQuoteYes. Social acceptance is an important engineering requirement for this project, it has to look similar to the existing ones. Rejection reduces the fun factor.I could get away with hand-cut metal discs (eg sqaurish with the corners cut off), but this felt a bit silly to me given how many circles are surely made in punching processes & thrown out. Hence why I made this topic: the quest for circles has become a drive of its own, perhaps more important than the battery holder itself.My fallback is to use ~5mm bent metal strips (ie nickel-plated spot welding strip) as a thinner contact for the ends. It wouldn't look pretty and it would have to be anchored, but it should be enough to contact the battery springs in the holder. This side-steps the need for any circles, pre-made clips or other more complex parts.Quote from: BrianHG on August 25, 2020, 02:55:08 amHmm. Looks like there is at least one local guy selling some:https://www.ebay.com.au/itm/1-8-kgs-bulk-mixed-metal-world-tokens-incl-car-wash-arcade-gaming-etc/293696574774?hash=item4461ae1536:g:ZRIAAOSwXMxb8QvT&frcectupt=trueSadly I would end up throwing most of them out. Only a few would match my needs, I can't make a shell that fits all size variants and not all would be solderable.Quote from: kaevee on August 25, 2020, 07:00:27 amThankyou for the offer kaevee, appreciated, but I have to say no. I can't easily solder to aluminium.QuoteI prefer options where I can do this myself.Quote from: Raj on August 25, 2020, 04:32:35 amO.oI do have a press... oh god. This might be less insane than I think if my holesaw catches/tears the metal sheet.Quote from: themadhippy on August 25, 2020, 12:46:07 amI will see if I can get one of these boxes from my hardware + test soldering onto the zinc.Quote from: Raj on August 25, 2020, 03:45:05 pmAs per original post: overseas shipping is horrible at the moment + I think PCBs are compete overkill for this.(I think I've mostly answered your other questions in other parts of this post)For now I'm sticking with a holesaw modified to remove the centre drill. Thanks again to everyone.

author: Whales
author_rank: Super Contributor
timestamp: August 25, 2020, 10:33:07 pm
content: To jump ahead a bit and answer a question that might come up: employee/employer relations & funding. I suspect some of you will pickup on the $$$ disparity between how much these batteries cost and how much I'm prepared to pay in this project.I don't work for a place that thinks in terms of R&D or such, they're purely operations and "throw money at external vendors for supplies". Regardless, if I'm stuck between the options of (1) doing the same work forever or (2) coming up with fun work-related projects in my spare time, then I'll go with (2) even if it has to be a bit self-funded. If it does become useful for the company then I'll make sure they pay for every cent of my time & parts, yes I know that's still not optimal.

author: Nusa
author_rank: Super Contributor
timestamp: August 25, 2020, 11:09:47 pm
content: Looking at the entire problem rather than focusing on one part, my suggestion would be to create an X-002.99.382 sized case for an a 18650 button-top cell (size is in the name: ~ 18mm x 65mm). Once you've done that, your original task is also done. 3 AAA battery holders to replace 18650's are an off-the-shelf item. Sometimes included with 18650 flashlights.

author: Whales
author_rank: Super Contributor
timestamp: August 26, 2020, 12:29:03 am
content: Quote from: Nusa on August 25, 2020, 11:09:47 pmThought of that, sadly not possible. Charger is built into the units that take the batteries.

author: tszaboo
author_rank: Super Contributor
timestamp: September 10, 2020, 09:43:08 pm
content: I would guess that they use hermetically sealed, medical grade, certified, super expensive battery for a reason?

author: sokoloff
author_rank: Super Contributor
timestamp: September 10, 2020, 10:32:49 pm
content: Quote from: Whales on August 25, 2020, 10:09:08 pm3D printers are incredibly cheap. The commercial operations are charging for the time and fiddly nature of printing other people's one-off parts.A $200 US Ender 3 Pro is a pretty reasonable piece of home shop equipment. As you're making the first few pieces and coming up the twin learning curve of designing parts and printing parts, you'll likely figure out why they don't sell the service for $10/part.Quote from: Nusa on August 25, 2020, 01:42:08 amRandom but relevant trivia: It's specifically illegal to export, melt, or treat any US pennies or nickels.https://www.law.cornell.edu/cfr/text/31/82.1

author: Monkeh
author_rank: Super Contributor
timestamp: September 10, 2020, 10:36:32 pm
content: Quote from: sokoloff on September 10, 2020, 10:32:49 pmSo every person to have left the US with loose change, myself included, is a criminal. Ahhh, American laws..

author: Nusa
author_rank: Super Contributor
timestamp: September 10, 2020, 11:03:06 pm
content: Quote from: Monkeh on September 10, 2020, 10:36:32 pmNaw, he failed to quote the exceptions to that law in the very next section:https://www.law.cornell.edu/cfr/text/31/82.2So the "exporting" part is all fine and dandy for all you pocket-changers and money-changers. And the OP isn't subject to US jurisdiction, far as I know. But even if he was, I suspect this would cover it: "The prohibition contained in § 82.1 against the treatment of 5-cent coins and one-cent coins shall not apply to the treatment of these coins for educational, amusement, novelty, jewelry, and similar purposes as long as the volumes treated and the nature of the treatment makes it clear that such treatment is not intended as a means by which to profit solely from the value of the metal content of the coins."Which explains how the penny press machines at some US amusement places are legal, since the output is no longer recognizable US currency.As for why the law exists: there was a point in US history where the 95% copper/5% zinc penny was worth more than a penny, so loads of them got melted for scrap metal prices. That's also why US pennies have been 97.5% zinc with 2.5% copper plating since 1982, which is a far more effective deterrent than the law. Still some old ones in circulation.

author: vk6zgo
author_rank: Super Contributor
timestamp: September 10, 2020, 11:45:56 pm
content: I've definitely seen Oz pre-decimal coins incorporated into various tourist ge-gaws, pretty much always old pennies & halfpennies, so it looks like the authorities don't much care.Perhaps coins from no longer extant countries may be another possibllity.The successor regimes probably recalled most of them, but there may be many floating around which were carried as loose change in tourist's pockets.The history about the old copper US coins is interesting, when the first Oz 50c coin was issued, with an inrease in the price of silver, the coin's value from its silver content was more than its face value.They were withdrawn & the present style of cupro-nickel one was issued.