Machining Hammond plastic enclosures - Page 1
Forum section: electronics / general

author: Sariel
author_rank: Regular Contributor
timestamp: September 08, 2024, 06:59:57 pm
content: Hello,Hammond makes great enclosures for housing of circuit boards. But most of them are sold without any cutouts for connectors.What tools (entry level or a bit above), would you recommend to buy for home (hobby use) so that I could use to do the cutouts myself.( I am an electronic engineer and not mechanical), so it should be something that I could use easily with too much setup complexity.Thanks

author: Infraviolet
author_rank: Super Contributor
timestamp: September 08, 2024, 07:09:20 pm
content: For enclosures you might do better to 3d print them, custom designed to your own needs. That way you can shape them exactly as needed for a given project. They won't be as weather resilient as purchased ones, but purchased ones in to which you've cut entry and exit holes wo't be that weather resilient either. 3d prints can also be made a bit more weather proof by coating in some sort of epoxy layer. Ofcourse, printing would require you to learn some sort of CAD package first, so although the equipment needed is cheap (an adequate basic FDM printer can be <£300, printing plastic is <£20/kg which and enclosure boxes don't use much mass of plastic each) and easy to use the time to learn CAD could be extensive.

author: tooki
author_rank: Super Contributor
timestamp: September 08, 2024, 07:25:08 pm
content: I like the Hammond extruded aluminum cases, as long as the connectors and controls can all fit on the end panels. Then it’s easy to just drill holes, and drill/saw/file other openings. (And they sell spare end panels as spare parts, so if you really mess one up, it’s easy to replace.) There’s also a version with a slide-out “belly plate” that I’ve used to hold a bunch of coax connectors on a PCB.At work, even though we have a full complement of machines (other than a laser cutter or water jet), making oddball holes is still always more work than round ones, so whenever possible, I try to select connectors that only need round openings. So for example, if a connector exists with either D-shape (circle with a flat side) or flange mount, I’ll choose flange mount. The flange needs extra screw holes, but they’re all round holes, so much less work.We do some 3D printed stuff too, but honestly, it never looks as professional. The surface finishes just suuuuck on most 3D printing methods.As far as machining the plastic cases, they’re easy to drill and file, and some shapes can be nicely tweaked with a scalpel. A Dremel or Proxxon rotary tool can also be good, but seek out the special bits Dremel sells for plastic. The thing I hate about plastic enclosures is the horrible mess the shavings make. Metal shavings just fall to the ground, but plastic ones are statically charged and stick to things, making it much harder to clean up. I highly advise working with a vacuum cleaner actively sucking the dust away as you work.Working plastic with water cooling is actually not a bad idea if you can do it safely, since plastic easily gets warm enough to foul tools. The downside is that this creates microplastic debris in the water.Also, regardless of material: protect all the exterior surfaces with painter’s tape before you start working on the enclosure! You don’t want to spend tons of time marking and drilling and filing, only for the file to slip and mar the surface. (Been there, done that.)I usually draw a cutting template on the computer and print it out, cut it out, and then put spray adhesive on it to stick it to the painter’s tape I already applied. This is more precise than trying to use a ruler or whatever. Then use a center punch to accurately dimple each hole. That makes a HUGE difference in hole location accuracy compared to not using a punch, which allows your drill to wander, especially if handheld.

author: rhb
author_rank: Super Contributor
timestamp: September 08, 2024, 07:28:04 pm
content: Depends on the shape and layout. I have a $50 USD drill press with a $35 XY table and $5 XY DRO. Great for getting holes all in a row at 0.1 mm spacing. Check projects-in-metal@groups.ioFor other shapes I recommend a jeweler’s saw or coping saw with a fine pitch blade. Jeweler’s being better.Layout skills matter most. A perfectly drilled set of holes in the wrong spots is a FAIL. Practice on paper.I was driven down the path of fabrication by enclosures.Have Fun!Reg

author: themadhippy
author_rank: Super Contributor
timestamp: September 08, 2024, 07:30:23 pm
content: Quotea selection of drill bits and a set of needle files is a good start.

author: abeyer
author_rank: Frequent Contributor
timestamp: September 08, 2024, 07:37:11 pm
content: For premade enclosures that don't take a separate panel, I like the approach of just dremeling out a large rough opening for the whole panel, drilling some mounting bolt holes around it, and bolt on a finished panel. Then you have flexibility for the panel itself to use whatever process is convenient/best fit for your current project: you can 3d print, laser cut, get a fr4 or aluminum "pcb" fabbed with routed holes, machine out a nice metal one, etc...

author: abeyer
author_rank: Frequent Contributor
timestamp: September 08, 2024, 07:45:39 pm
content: Quote from: tooki on September 08, 2024, 07:25:08 pmYou won't get finished results right off the printer, but even a cheap fdm print can produce results that look nice for a panel design. If you print on a glass built plate with the panel surface down you're 90% of the way to a smooth surface finish. One coat of filler primer and 5 minutes of sanding will get you the rest of the way, and then just a couple coats of paint to finish.

author: tooki
author_rank: Super Contributor
timestamp: September 08, 2024, 08:22:04 pm
content: That seems like ahugeamount of effort compared to just drilling a piece of anodized aluminum sheet metal (like the end plates of the extruded cases). Maybe if I needed some really weird cutout shapes that would need lots of intricate filing.Not to mention the need for a dust-free place to do painting, lest dust ruin the finish.

author: Benta
author_rank: Super Contributor
timestamp: September 08, 2024, 09:03:00 pm
content: Are we talking die-cast, extruded, plastic, whatever emclosures here?The question is too vague for an informed answer.

author: abeyer
author_rank: Frequent Contributor
timestamp: September 08, 2024, 09:24:12 pm
content: Quote from: tooki on September 08, 2024, 08:22:04 pmSure, if I had both tools sitting next to one another and equally available, that's probably the way I'd go, too... but given that OP asked about home hobby use, I wouldn't assume that to be the case. Idohave a small bench mill at home, and access to a bigger CNC... but still will print small things often, particularly if it's not a "showpiece" and I'm just using the bare plastic and not worrying about finishing. I'd spend as much time setting up/tearing down/cleaning up after the mill (or planning & travelling to use one) as it takes to do a cad design & print. I can reasonably keep a printer and even an improvised spray booth in a cabinet in the corner of my home office... not so much a mill.

author: shabaz
author_rank: Frequent Contributor
timestamp: September 08, 2024, 09:47:12 pm
content: Not a complete solution (doesn't replace drills etc), but sometimes a hand-punch tool can be a great problem-solver. It makes nice holes in metal and (some typical enclosure) plastics.I use one very similar-looking to the one in the photo, it has quite a deep neck, and can also pass over most lips of enclosure covers. You can't use it for the top surface of the enclosure of course; just the sides of the enclosure, or the rear cover.You're restricted to the sizes of the supplied punch/dies, but the one I've got is good enough for SMA connectors, typical toggle switches, LEDs, M3 and M4 screws, etc. And I have a larger screw-in type of punch for BNC sockets. The tool is quite accurate too, because the punches have small centering dimples that protrude out, so you can align that to a pen-mark, or a pushed-in dimple where you want the hole to be. For BNC etc., I usually don't take the time to make a D-shape (and D-shape punches are expensive) so instead I use epoxy glue to prevent rotation. Not ideal, but fine for my purposes anyway.I managed to complete a whole project with zero drilling the other day, just using the hand punch. But often there is a blend of tools. The holes are clean/crisp, and so quick. Also, great for using with metal tins where a drill would not be as easy.A drill is more versatile of course, but the punch is also a great tool where it works.EDIT: Also that type of hand punch in the photo has low costs over time, if you choose one where spare replacement punches+dies are often sold cheaply. Photo shows hole quality in metal cookie tins (SMA- and BNC-sized holes). The quality in typical plastic enclosures is just as good; but acrylic and some plastics may crack of course.

author: jpanhalt
author_rank: Super Contributor
timestamp: September 08, 2024, 09:49:01 pm
content: I Haven't seen "step drills" mentioned. They are great for thin materials and particularly plastic. Another term for them is single-point cutting. Of course, they are for round holes mostly, but they are rigid enough to push against them to make oblong cutouts.

author: Smokey
author_rank: Super Contributor
timestamp: September 08, 2024, 09:56:35 pm
content: One of those desktop gantry cnc mills would probably be great for something like this. Make sure the box fits in the world envelope.

author: aeberbach
author_rank: Regular Contributor
timestamp: September 08, 2024, 10:25:05 pm
content: In a metal case if you want to put holes in a panel accurately you have to have a centre punch. Automatic is good, spring loaded, put the tip where you want the punch and press in and a spring-loaded bang makes the mark. Then your drill will hit that mark and that is where it cuts rather than wandering all around before biting in somewhere nearby. You can use these on plastic but check your plastic first, if your punch is wound up too tight or plastic too thin it will crack it, ruined panel. Controls that are supposed to be aligned lookterribleif one is out of line by even a small amount.A drill press is also a very good idea for accuracy and almost a necessity if you want to use stepped drills (or even any drills) for various round hole sizes without the risk of the panel catching in the bit and spinning it around like an inefficient saw blade. Efficient enough to tear up your hand of course.Greenlee-style punches are excellent if you can justify the cost but even the knockoffs can be expensive, probably too much money for one-off.Nibblers are good if you want an odd-shaped hole and your panel is not too thick and you are prepared to carefully finish it with a file (or the thing you mount has a flange and will hide the rough edge).Finally don't ignore laser-cutting services. They are surprisingly affordable and can cut a wide range of material as well and can make a panel as accurately as you can make the design in a vector graphics program like Inkscape. Well worth it for a project that you want to look its best.

author: tooki
author_rank: Super Contributor
timestamp: September 08, 2024, 11:13:35 pm
content: Quote from: abeyer on September 08, 2024, 09:24:12 pmI didn’t say anything about a mill. Just drilling.

author: tooki
author_rank: Super Contributor
timestamp: September 08, 2024, 11:17:01 pm
content: Quote from: Benta on September 08, 2024, 09:03:00 pmThe thread title is “ Machining Hammondplastic enclosures”. I just mentioned the aluminum ones as an alternative because they’re almost as easy to modify, and I find the chips easier to clean up. But OP was clear about their intent.

author: pqass
author_rank: Super Contributor
timestamp: September 09, 2024, 12:50:12 am
content: For quick-n-dirty layout just overlay a largish perfboard on the panel or enclosure. Use the 100mil pitch grid holes as a drill-guide. No fine measurement or punching necessary. Perfect alignment every time.Initially drill the first two holes on opposite corners of the panel (or as far apart in your design) and use a couple of finishing nails to keep the perfboard aligned to the panel as you drill the remaining holes. Use a drill of the same hole diameter; usually 3/64" (1.2mm).Drill the outline of rectangular openings (7-seg. LEDs, rocker switches) then finish with a flat file to exact dimensions.Drill the center of circular openings (pots, T1 3/4LEDs) then finish with correct diameter bit.