Milling Enclosure Cut-outs

[Reddinr]

I need to make a number of cut-outs of various sizes in a NEMA 12, 12-gauge steel painted enclosure door. I can remove the door to mount on a milling machine. This raises the metal about 1/2" above the table due to the door flanges (or I can mill from the back side if that is better?) What are recommended end-mill type/size, feeds/speeds for this? I want to avoid the saber-saw approach for larger cut-outs so the results are cleaner. I also don't want to over-heat the paint when cutting. I have one chance to get it right, else it's another $300 cabinet... Thanks.

 

[kenscabs]

You don't state the size and shape of the cutouts. Simple holes, use a hole saw. Since it sounds like you're concerned with the finish, display module maybe? I'd put down blue tape, lay it out, drill and rough cut it with a saber saw, then clamp it on the milling machine with a piece of plywood under it and mill to the final dimension.

 

[Reddinr]

You don't state the size and shape of the cutouts. Simple holes, use a hole saw. Since it sounds like you're concerned with the finish, display module maybe? I'd put down blue tape, lay it out, drill and rough cut it with a saber saw, then clamp it on the milling machine with a piece of plywood under it and mill to the final dimension.

The holes are various sizes. There are several 22mm holes for buttons and a couple of large cut-outs (22" x 20" for example). It will include a large touch-screen. I'm thinking about adding a decorative bezel made from ABS if the hole is not clean looking enough. Why pre-cut and mill vs. just mill?

 

[derf]

If you can rough it out with a saw, it leaves less to machine. The less material you have to remove, the less heat it creates. Milling on only one side of the cutter is easier, and the cutter will not want to walk like when plowing through material on all sides. Like kenscabs said, back it up on the face side with plywood or mdf.

 

[Reddinr]

If you can rough it out with a saw, it leaves less to machine. The less material you have to remove, the less heat it creates. Milling on only one side of the cutter is easier, and the cutter will not want to walk like when plowing through material on all sides. Like kenscabs said, back it up on the face side with plywood or mdf.

Thanks. That makes sense. Any advice on endmill, type / flutes, feeds/speeds for thin steel like this?

 

[gymbo]

Google 22mm knock out punch for 25.00/35.00 bucks you will save yourself a lot of grief on the button holes, for the square holes a jig saw and a file are your friend. Lay everything out with pencil (which will wipe off with a little varsol) Drill centre holes for the buttons and four corners on the square , masking tape helps to eliminate scratches but you won,t burn anything.

 

[JimDawson]

Like @kenscabs states, I normally use plywood or MDF as a spoil board. The biggest problem is that there is no really good way to anchor the work down near the cut. And the spiral on the end mill tends to want to pull the work up. On the large cut out, a few screws anchoring the waste piece to the spoil board would be very helpful.

For the 22mm holes, a 1/2 inch conduit hole punch is exactly the correct size. Most of the big box stores sell conduit punches in the electrical section.

I normally use a 3/16, two flute end mill for panel cutout work. A 3/16, straight flute, carbide tipped router bit works well also, and you can bring the spindle speed up a bit, and they don't pull the work up. The material that the panels are made out of is a bit gummy and doesn't machine well. Play with the feed and speed a bit to find the best combination. Do it in two passes, a roughing pass, and then a final clean up pass to get a nice edge. Use some kind of cutting fluid, WD-40 would be fine.

If you are doing this on a CNC machine, I would start out at about 5 IPM and about 1500 RPM and adjust as needed. Maybe start with a .032 DOC.

 

[dogma]

If your willing to consider non-end mill options, for thin sheet metal, I've had good luck with rotabroach cutters (annular cutters that work with a drill chuck) and step bits. Rotabroach hole edges are fairly clean, even from a hand drill.

 

[Reddinr]

Thank you all for the advice. My cabinet should be here in a week or so and I'll have at it. I have knock-out punches for the small holes and will try the straight-flute approach for the large cut-outs.