I’m considering purchasing a plasma cutter to make large robot plates (mostly 1/4" thick steel and aluminum, maybe a few 1/2" steel plates). I normally water-jet these plates, but I can’t afford a water-jet, and sending them out is insanely expensive…I understand that plasma-cutting won’t give me as good of tolerances as waterjet, but the price of the plasma machine is workable. Would anyone please be willing to chat with me on the phone for 10min on your experience with making intricate parts (e.g. a 2 or 3mm hole that I can later drill out and tap)? My cell is (650) 283-0963, and my email is [email protected] Thanks so much! --Reuben (www.reubotics.com)
You won’t be able to cut any holes that small. I would say the absolute smallest hole you can cut with a plasma torch would be 1/8" in 16 gauge steel and that is pushing it. For holes that small you would want to do a peck to mark the hole and then drill it. I have achieved acceptable results cutting holes on a one to one ratio. i.e. 1/4" hole in 1/4" material. For best results you would want to go even bigger, perhaps 2:1, especially with thicker material where you will get some bevel.
Note that plasma cutting a hole hardens the rim, A LOT! Drilling out will be difficult. I recommend for accurate holes use the Peck and Drill method @72Pony recommended.
For the peck-and-drill method, does the hole go all the way through the material (or is it just surface-level, like a dimple)? If so, do you have a rough idea of hole diameter?
The hole cutting can be a bit of luck. Erik gave a good example of the smallest hole that you can make and have the holes columnar with nice, straight sides.
Now I say they are nice, straight sides but not as precise as you might need. That is why most of us try to make the holes with some allowance.
The second part of the problem is explaining what Tom said:
That means even if you make a hole that would be sufficient as a pilot hole, the variations in the hardness of the sides of the hole will lead your drill bit a little astray. Results may vary. You are likely to ruin your first drill bit on the very first hole. I use lots of cobalt bits and they have more trouble with these holes than you might imagine.
I’d use an Easyscriber if you desire a precise drill point on anything you’re cutting out.
The Easyscriber only lightly scratches the surface of your material so you won’t get that “dimple” you’re wanting, but it can precisely draw a tiny circle for your drill point.
After which you just fire up the plasma cutter, reinstall your consumables, then run your normal cut program.
If you use sheetcam for Cam, you create a tool and name it center punch, peck are whatever want to name it. It will leave a small dimple in material and not work harden the material so it can be easily drilled. The mark will look just as a center punched dimple for drill bit o center. Works great I use all the time when I need precise true holes…
on 1/2” plate i get virtually no bevel. there is a tiny amount , but it’s hardly noticeable, and if I were to loop the corners, it would be even better. that’s at 65amps with a hypertherm.
Everyone’s setup is different but holes are one thing that my table does a very poor job of. I have got it better, but not perfect and precise holes just have to be drilled. The hardened edges on steel are a huge PITA. If you have a drill press or mag drill then you can sometimes just hog into them and cut past but I have broken a lot of drill bits doing that. Then the hole inevitably ends up in a slightly different spot on each piece… in my case it’s just single hole tabs and fabrication parts that don’t really matter but if you need multiple precise holes in one piece, plasma is not your friend.
All that said, admittedly, I am not really willing to put a lot more time into perfecting my table. It’s always been “good enough” and better than that involves investing money and more importantly, shop space for an air drier setup. I’m short on space and am at the point where upgrading the table is not worth the effort for the results I would get.
@rat196426 I am curious about this peck tool. I am very familiar with SheetCAM, what settings do you need to configure in that tool to make it do that? I am envisioning a plasma tool that just briefly fires the torch?