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#197527 - 12/04/10 05:11 PM Delicate cutting job ahead. Advice?
sparkyinak Offline
Member

Registered: 07/08/07
Posts: 1296
Loc: Alaska
I'm looking at custom building a few control panels that will require several large meters in a small area of a factory built box so I will be drilling/cutting several large holes in close proximity to one another. Hole saws and KO dies tend to buckle the metal and the end visual product is very important. I have consider sending them out but will likely be $$$. With all the cool tools in the trade, any thoughts out there on on something that can cut a 3"+ holes in 14 gauge steel without being so abusive to the surounding area and leaves a clean finish. There will be an inch or so between the big holes. The plate will be swiss cheese by the time I'm done with it and it need to keep its shape.

My best guess is clamp the cover to plywood, layout the pattern, use alot a fenice and hole saw the large holes first and work my way down. I need to find someone with a milling machine.

Any thoughts?
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#197528 - 12/04/10 06:33 PM Re: Delicate cutting job ahead. Advice? [Re: sparkyinak]
wire_twister Offline
Member

Registered: 07/25/07
Posts: 265
Loc: Georgia USA
I have had good luck with clamping the piece to a sheet of plywood or plank, then clamp the whole thing to your drill press table, and use a holesaw with some cutting oil, and take your time. Run the saw at a slow speed and use just enough pressure to get it to cut, use oil or even water to keep the heat down.
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#197529 - 12/04/10 07:04 PM Re: Delicate cutting job ahead. Advice? [Re: wire_twister]
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
iirc, milbank sells the particular gunmetal grey in spraycan for touchup

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#197531 - 12/04/10 07:17 PM Re: Delicate cutting job ahead. Advice? [Re: sparkyinak]
LarryC Offline
Member

Registered: 07/05/04
Posts: 776
Loc: Winchester, NH, US
When I did controls assembly, Greenlee KO punches did a good job. You do have to make sure the KO are sharp. To help start them, try drilling two holes where the punches start. That reduces the load on the tips and keeps the dies sharper longer.

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#197533 - 12/04/10 07:44 PM Re: Delicate cutting job ahead. Advice? [Re: LarryC]
KJay Offline
Member

Registered: 11/27/07
Posts: 763
Loc: MA, USA
If they're just round holes in mild steel, then the Hougan Rotabroach hole cutters with a regular 3/8" drill should work for you. They are available individually in sizes up to 3" and make some of the cleanest holes Iíve ever seen in sheet steel. You really don't need to apply very much force at all for them to cut.
I bought a fabricators set from Colonial Hardware a few years ago, so I know that they sell them.
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#197534 - 12/04/10 09:53 PM Re: Delicate cutting job ahead. Advice? [Re: KJay]
Obsaleet Offline
Member

Registered: 04/05/03
Posts: 361
Loc: Pa
For the 3"+ use a compass and draw the hole out. drill releif holes just inside the line. Use a good jigsaw( I use a bosch) and a metal bit. Clamp the thing to a good table and cut away. A half round bastard file to clean up the burrs and get you to the line. Labor intensive but effective.

Ob
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#197542 - 12/05/10 07:54 PM Re: Delicate cutting job ahead. Advice? [Re: Obsaleet]
NJwirenut Offline
Member

Registered: 09/15/01
Posts: 816
Loc: Bergen County, NJ
I have to agree with LarryC. Short of a CNC milling machine, you aren't going to get cleaner holes than you can make with a Greenlee chassis punch. I haven't noticed any problem with warping of the metal, as long as the punch is SHARP.

The only downside is that a 3" Greenlee punch is not exactly cheap. Figure on at least $400 new, and that's for the manual drive version. Probably double the price for hydraulic.

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#197543 - 12/05/10 09:45 PM Re: Delicate cutting job ahead. Advice? [Re: NJwirenut]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
One tool:
A Dremel, will do this.
Just have a test on a bit of the same material before you start chopping into your panel face.

Punches are OK, if you like the expense of having something you may never use again.
If you don't mind a bit of filing to make the edges a bit more "friendly", the Dremel is the way to go.

One tool I have had for years is what is known as a "Die Grinder" it holds smaller type bits like small grinding bits and also flap-discs.
It is a lot higher powered than a Dremel and uses lower speeds.
I've always found the flap discs great for cleaning up cut out holes in a jiffy and it makes a nice smooth edge to the finished hole.

Coming from an engineering background, I'd recommend you get some of the film that 3M sells, that is used on stainless steel sheets during transit to save any knocks to the finished product from the factory.
It is adhesive and is black on the sticky side and white on the outer side.
I usually do my marking out on this with a mechanical pencil,once the film is in place, you could also do this with a very fine tipped Sharpie pen.

Having said that, I have also cut out reasonably "round" holes with a small angle grinder (always smaller than the final hole size), with a cut-off disc and got them within a ball-park of finishing them off with a die-grinder.

Just bear in mind that when you are grinding away, the hole is getting bigger and never let a grinder of any sort "dwell" on any point of the cut out.

Constantly check your work, it's rather hard to fix up something AFTER you've mucked something up.
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#197546 - 12/06/10 07:52 AM Re: Delicate cutting job ahead. Advice? [Re: Trumpy]
ghost307 Offline
Member

Registered: 05/09/05
Posts: 884
Loc: Chicago Illinois USA
Have you thought about asking any of the folks up there who build or repair their own planes? It sounds like a question that comes up frequently from people who are trying to fit all their stuff in an instrument panel.

I'd thumb through a copy of Kitplanes magazine and see who their advertisers are...or go online to EAA.org and see if they have a chapter nearby you could call on.
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#197548 - 12/06/10 12:15 PM Re: Delicate cutting job ahead. Advice? [Re: NJwirenut]
LarryC Offline
Member

Registered: 07/05/04
Posts: 776
Loc: Winchester, NH, US
As for finding Punches, I see a fair number of them on E-bay. Depending on your lead time and number of different hole sizes, buying online might be worth your time. Also check out local people who build custom boats, airplanes, and industrial controls. If these are standard meters, perhaps a generator repair facility may also have the punches. Have you tried talking with your competitors to see if you can borrow or buy a used punch from them?

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