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how to make hole in transistor can without shavings?
Posted by
coppercone2
on 15 Feb, 2024 08:40
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I want to make a hole in a can (sheet metal) but I want to guarantee that there is no shavings inside.
What is the best tool for this? Assuming I can flush it out with liquids. This hole is maybe 3/32 of an inch.
If I used a standard 2 flute drill I expect possibly curly shavings getting stuck inside.
I thought the best ways might be either
1) grinding
2) some kind of cutting tool with way too many faces running at high speed and low feed to discourage proper chip formation. (dust maker)
For 1, is there any tools that might be suitable? I thought maybe some kind of CBN coated grinding rod, perhaps meant for jig grinders? It should be dimensionally stable. I think ideally it would be like a micro ceramic hole saw? Could a diamond core saw work?
For 2, recommendations ?
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#1 Reply
Posted by
guenthert
on 15 Feb, 2024 09:39
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I got no experience with it, but my first thought was to use a laser cutter. For a few mm sheet metal, power requirements ought to be modest.
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How big of a hole and how thick is the metal? I wonder if you might be better to punch a hole in the metal instead of drilling it? A sharp punch should be capable of making a hole and leaving all of the metal attached instead of liberating flakes, shavings, etc. If you must drill or grind then setup a vacuum suction device such as a household vacuum cleaner near the site and run it while you drill and attempt to catch any particles as they're being created.
If your transistor is in a metal can, can you de-lid it and then drill a hole in the lid, clean it and then reattach the lid?
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#3 Reply
Posted by
jpanhalt
on 15 Feb, 2024 14:48
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I have used heavy grease when installing a Helicoil in stripped spark plug threads in aluminum heads. That catches most of the chips. Then very carefully clean with towels. Of course, the holes were bigger. Slow speed and decent pressure helps get bigger chips that curl outward and are easier to see and remove.
Using more flutes and high speed will only make smaller ships that will be harder to remove and possibly fall into the hole.
For your specific problem, I would consider a larger, sharp bit to get through most of the metal. Clean. Then for the very last thin portion, you might use a pick. Alternatively, etch the last bit -- either with acid/FeCl3 or by electrolysis. Since the case is probably magnetic, adding a strong magnet to your drill might help capture chips.
Grinding small area to get it thin could also be done. But, I would not grind through to make a hole, if particulates are an issue.
EDIT: How about doing it upside down so gravity is on your side?
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#4 Reply
Posted by
KrudyZ
on 16 Feb, 2024 04:50
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You could try twisting or shearing off the entire can and then replace it with a machined piece with a hole of the desired dimensions.
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Anything that removes metal - grinders, sanders, mill bits, drills WILL get stuff inside the can with one specific and fairly difficult to achieve exception. The exception is if you grind the top (or saw or mill) to foil thickness and then carefully puncture/tear the remaining foil. Even tearing and puncturing can, but usually doesn't leave flakes inside.
Another feasible approach is using a rolling cutter similar to that used to cut copper pipe to cut through the lid. Not totally debris free but better than most drilling/milling/grinding operations.
Finally, think about the risk of displacing debris that is already inside the can from a harmless location to someplace that matters. Most are fairly clean inside, but not all, and at least some manufacturing processes have a "mechanical getter", a patch of sticky substance to grab and control anything that has found its way in. Getting such hot while shaking and vibrating the package is likely to release any such debris.
The only times I have been involved in such operations they have been small hobby/research type things and involved post de-lidding cleanup and much larger feature sizes than are common today. Perhaps large operations have developed solid processes for this, but I think most of their effort is getting it right the first time. Only the reverse engineering and other spy types really do a lot of this.
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One option is to use a pipe cutter (the version with a round wheel). Another option is to simply use side cutters and nibble parts away.
A third option is to use an iron saw, and then not cut completely through the can, but only "alsmost" though it. Then you can create a weak line around it's perimeter, and do the last part with brute force. Intermediate filings can be removed with compressed air, sticky tape, a magnet or blue-tac.
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I was hoping I could pour out the grindings by putting water in there and ultrasonic cleaner for a short duration to agitate it and pour it out a few times, I figured maybe this makes a bond wire but I never knew there was a mechanical trap in there (glue?) for debris. sounds like its better to cut it off and resolder
I wonder if I can cut it with a thin dremel wheel (to-3 package) half way, modify, then replace the cover back in place by spot welding a tab to it for a third hand, filing them so they fit right, and soldering around the perimeter.
I don't like the idea of a 'pipe' joint with solder on such a thin can but it should work. 'bridgit' solder should be good for this application.
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#8 Reply
Posted by
tooki
on 16 Feb, 2024 22:30
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Why do you want to open the can anyway?
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sun roof
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#10 Reply
Posted by
KrudyZ
on 17 Feb, 2024 03:54
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I just tried it with side cutters along the lower edge of the package.
Comes out quite clean with no debris that would interfere with the transistor.
It's more of a beach blanket than a sun roof though.
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#11 Reply
Posted by
tooki
on 17 Feb, 2024 17:28
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#13 Reply
Posted by
tooki
on 19 Feb, 2024 07:41
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Transistors don’t need sunroofs. Also, they aren’t cars.
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You could try it upside down to minimize the chips inside. Mount the transistor so it spins in a drill-press chuck and mount your drill pointing upward in a vise that is clamped to the drill press table.
Actually, a center-cutting end-mill would work better because the point of a standard drill might contact the transistor die as is punches through.
You will need to guard against the end mill being pulled through abruptly at the last minute. Maybe a sleeve on the mill to keep the maximum depth to a safe depth. Go slow, especially just before getting through the inner surface. There is a good chance that a burr will exist on the inner surface so that may need to be dealt with. There is a possibility that the vibration will kill the transistor.
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This could be done in a good drill press, not a worn or cheap loose one. Hold part firm, zero movement, this may be an extensive set up. Chuck a sharp 3 or 4 flute Center Cutting Endmill, descend slowly. Chips stay out. the whole is clean and burrless, but the disc falls through.
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#16 Reply
Posted by
floobydust
on 05 Apr, 2024 16:43
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I have used a hacksaw as the shavings are large, and then a magnet to pick up metal chips.
