Machining electrical enclosure doors

If I only have to put some holes in an enclosure for cord grips, it's easy enough to use a step drill. I'd like a better solution for more complicated door panels. For example, the most recent door was 10x12 and has 8 round holes ranging from 7mm to 31mm and a 45x92mm rectangular hole for a 1/2 DIN panel meter.

At a previous job we would take large, complicated doors off the cabinet and have them waterjet, but that's not really an option here.

What I ended up doing was locking the door shut and clamping it to the mill. I drilled the holes with a step drill on the mill, so I could use the DRO. I then milled the rectangle with a 1/2" cutter (5-flute from Helical). This left a lot of cleanup to do with a saw to get the corners sharper and get rid of the burrs from the step drill. The step drills also don't break a chip well, so the swarf scratched up the paint.

I would like a way to mill this complete, but the door is relatively flimsy and vibrates, so when I tried using a smaller cutter, it quickly snapped. Even using stout 1/2" drill bits and cutters, Things weren't very precise. The 1/2 DIN cutout came out undersize.

Any suggestions? I can't dismount the doors on the smaller cabinets, but on a larger cabinet I could.

Greenlee knockout punches. Drill hole for the cap screw, assemble the cutter, wind it through. Clean perfect holes, even square or rectangle. Or you can drill a hole, use a nibbler, and file to shape.

I use the punches for conduit holes. I could buy the ones for 1/2 DIN and 22mm as well, but that still leaves me with laying everything out by hand and dealing with the small holes. On disconnect switches for example, you need a 31mm hole, closely surrounded by four 7mm holes. I'm hoping someone has a trick for milling these.

At the very least, I wonder if you could put a column of 4x4 in the cabinet to support the door. You could fix in place by nailing it to 2x4s. This might give the door panel the rigidity you'd want when milling.

Hand held plasma to gut the door (torch rides along edge, doo from inside)
\leaving 1/2"-1" wide edge.

plasma/laser/waterjet/cnc mill flat panel goes on outside, stich weld
from inside

Masking tape over working area. Layout with pencil. Drill 1/16" pilot holes on center and at corners. Use step drill where it works. Use jig saw for rectangles and hole saw or punch for rounds. Remove tape.

My main panel shop has been doing it this way for years.

2¢

I have made many custom electronic assemblies, all of which required holes of various sizes and shapes.

My main "trick" was to layout the panel in my 2D CAD program and then print it 1:1 on label stock (peel and stick paper with adhesive on the back). I used a label stock with a removable adhesive. The print was accurate enough to do the work directly from it.

Small' round holes, under 1/2" diameter were drilled. The center was punched and I started with a drill in the 1/8" range for holes of that size and larger. Smaller ones were drilled with the final diameter drill right off. A step drill is very useful for the final diameter and I always used the depth stop on my drill press to chamfer the top edge of the hole while drilling it. The steps on step drills always have a small radius and that works perfectly for a chamfer. Then I flipped the panel over and immediately chamfered the back edge with the same depth setting. Fast and very neat,

For holes larger than 1/2" and non-round ones I almost always used chassis punches. I have a rather large collection that includes round sizes from 1/2", up to above 2", by 1/16s. I also have three square ones, a couple of rectangular ones, some D and double D shaped ones, and at least one for a D-subminiature conector.

For large and odd shaped rectangular holes and even others with more than four sides but still with 90 degree corners, I use the square and rectangular punches. For instance, a 1.5" X 2.25" rectangle can be cut with six punches with a 3/4" square punch. I layout the six centers where I drill a hole for the draw bolt on that 3/4" punch and the outline of the final hole. I have CAD "parts" that I can call up for each of the square and rectangular punches so I only need to place them to cover the larger hole.

After I print the pattern on the label stock, I paste it on the panel. Center punch, drill, chassis punch, and deburr. Sometimes a bit of filing is needed to smooth out the junction where two square punches were made.

These techniques can be used on your doors and will produce professional looking results. And using the chassis punches is faster and easier than milling. All the electric and electronic parts that I have used are made with a tolerance for slight variances in the hole sizes and spacing so the accuracy of this technique is quite good enough for them. Most data sheets for these parts show a recommended hole pattern with dimensions.

I have done some panels using a milling machine. You still need to do the layouts and often need to make compromises at corners (overshoots or filing to square it). Drilling and punching is much faster.

DanielG said:

I use the punches for conduit holes. I could buy the ones for 1/2 DIN and 22mm as well, but that still leaves me with laying everything out by hand and dealing with the small holes. On disconnect switches for example, you need a 31mm hole, closely surrounded by four 7mm holes. I'm hoping someone has a trick for milling these.

Click to expand...

DanielG said:

I would like a way to mill this complete, but the door is relatively flimsy and vibrates, so when I tried using a smaller cutter, it quickly snapped. Even using stout 1/2" drill bits and cutters, Things weren't very precise. The 1/2 DIN cutout came out undersize.

Any suggestions? I can't dismount the doors on the smaller cabinets, but on a larger cabinet I could.

Click to expand...

I remove the door and attach a 3/4" plywood scrap to the backside. Using either small C clamps or or wood screws in the positions for future holes.
Then hold plywood in a vise or clamp to table. Always works.

If the small doors can't be removed then a plywood piece on the backside will be enough support.

We have taken a completely different approach to this kind of thing.

Layout your button / HMI cutouts in CAD and send off to a laser shop and have a complete panel laser cut from brushed stainless - MAKE A NOTE ABOUT NOT MARRING!

Include corner / perimeter square mounting holes for #10 stainless carriage head screws or larger for bigger panels, we have gone as big as 36 inches by 42 inches for control consoles . . . and then receive / inspect and ship to the laser marking vendor who puts your button / switch labels on along with your company name and logo.

Then just cut one big rectangular hole in your cabinet or console along with mounting screw holes (small holes with a jigsaw and drill, or larger holes on our planer mill), mount your bezel, components, wire, and done.

Alternately, we will wire it on the bench and then install . . . makes for faster, neater, easier work.

Here is a reject console cover that we did for a Herkules Roll Grinder that we retrofitted a few years ago. This was a console hinged cover replacement and made of 10GU stainless - it got scratched up so we replaced it with new. The holes in the bottom are hinge mounts and the holes above were quarter turn clips.



The laser does a nice job of cutting the keyed button mounts and the laser marking doesn't rub off after years of use and abuse.

DanielG said:

I use the punches for conduit holes. I could buy the ones for 1/2 DIN and 22mm as well, but that still leaves me with laying everything out by hand and dealing with the small holes. On disconnect switches for example, you need a 31mm hole, closely surrounded by four 7mm holes. I'm hoping someone has a trick for milling these.

Click to expand...

use a decent 31mm holesaw - like these Starrett SM31 Metal Hole saw, Stainless Steel Sheet, 31 mm: Amazon.co.uk: Business, Industry & Science and make up a simple frilling jig that locates in the 31 mm hole with the 7mm holes as guides ?

DanielG said:

I use the punches for conduit holes. I could buy the ones for 1/2 DIN and 22mm as well, but that still leaves me with laying everything out by hand and dealing with the small holes. On disconnect switches for example, you need a 31mm hole, closely surrounded by four 7mm holes. I'm hoping someone has a trick for milling these.

Click to expand...

use a decent 31mm holesaw - like these Starrett SM31 Metal Hole saw, Stainless Steel Sheet, 31 mm: Amazon.co.uk: Business, Industry & Science and make up a simple drilling jig that locates in the 31 mm hole with the 7mm holes as guides ?

Same with your ''odd shaped'' holes, make up a drilling jig for the corners then chop the waste out with the jigsaw ?

I use these hole saws from McMaster carr



and cut squares with a 3" cutoff

At work we have a Greenlee punch for 30.5 mm pushbuttons. It makes the hole and the four anti-rotation notches in one shot.

Knockout punches are too slow though for what you are asking, I like motion guru's approach for small panels with a non-removable door.

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motion guru said:

Here is a reject console cover that we did for a Herkules Roll Grinder that we retrofitted a few years ago. This was a console hinged cover replacement and made of 10GU stainless - it got scratched up so we replaced it with new. The holes in the bottom are hinge mounts and the holes above were quarter turn clips.

View attachment 272787

The laser does a nice job of cutting the keyed button mounts and the laser marking doesn't rub off after years of use and abuse.

Click to expand...

Well CRAP!

Now I HAVE to start doing it this way.

Looks super clean, like it was made by professionals in a factory.

Thanks for sharing Guru.

I used to do a lot of test equipment back in the day. Hell we didn't even have a real mill, masking tape and a sabre saw. Honestly the step drills are going to be faster than Greenlee punches. I think you speeds and feeds are off, you ought to be able to get square cutouts etc done without an enormously time consuming burr. Mebbee a 3/8 three flute at modest spindle speed. Triangular file in the corners should take a couple minutes to clear up. Maybe you jsut need to rough and finish to get rid of that burr.

Removing the door and laying it face down on a piece of plywood with some hold downs would probably be my choice.

If you are doing dozens of the same ones, having another piece of plywood, clamp it down on top and mill the first one through it, then it is just a vibration control [and damage control]device