Author Topic: Punching powder coated steel?  (Read 665 times)

S. cerevisiae

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Punching powder coated steel?
« on: September 01, 2015, 04:19:56 PM »
I am in the process of laying out a small control panel for a single heated vessel 120VAC 20A electric brewery.   I brew primarily 3.5-gallon batches, which start off as 4.5 to 5 gallons of wort, so a limit of 2400W is not a problem.  I am able to boil this amount of wort on an portable 1800W induction range, which is not as efficient as an immersed element.  I have also installed a 10-gallon 120VAC 20A BoilCoil installed in my PolarWare 361BP 10-gallon Brew Pot (the made in the U.S.A. Polar Ware kettle with factory welded ball valve and thermometer fittings), but I brew 5.5-gallons batches so infrequently that I having to wait a little longer until the wort comes up to a boil is not a problem.

With that said, I have managed to assemble a fairly decent collection of different vintage Greenlee 730BB round punches over the years (1/2", 5/8", 13/16", 7/8", 1", 1-1/16", 1-3/16", 1-3/8", 1-1/2", and 2").  They have been used primarily for the task for which they were originally designed; namely, punching holes in metal chassis for tube sockets and other tube-type-era electronic components (a technology that is is still used in guitar amplifier and radio transmitter linear amplifier design).  Most of the work that I have performed in the past has involved punching holes in unfinished/anodized aluminum or cadmium plated steel chassis. I have avoided punching painted chassis because they tend to chip.  Has anyone punched powder coated steel?  If so, did the punch chip the finish on the die side of the hole?  I need to decide if I want to use a punch or a bi-metal hole saw for the larger holes.  I will need to use the 2" punch for the flanged NEMA power connectors.  That punch is a monster. It requires one to drill or punch a 3/4" hole for the draw stud.
« Last Edit: September 01, 2015, 09:18:52 PM by S. cerevisiae »

Offline Stevie

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Re: Punching powder coated steel?
« Reply #1 on: September 01, 2015, 05:02:26 PM »
Don't the components have a bezel?

Offline ocddot

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Re: Punching powder coated steel?
« Reply #2 on: September 01, 2015, 07:19:04 PM »
I would cover the punch area with tape to prevent the coating from chipping. Not sure if that's a solution, but its what i would try do to remedy the chipping

Offline metron-brewer

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Re: Punching powder coated steel?
« Reply #3 on: September 01, 2015, 08:12:18 PM »
It can be done but it depends on a number of factors. First being the paint itself. Some coatings are more brittle than others and lend themselves to chipping. Also the tooling involved, how wore out is it, fresh clean edges yield better results. Taping the surrounding area is a good idea. In addition you could try one of the smaller holes in an area of the 2" cutout. Since you will need to have a 3/4" hole anyway, you could try it there or off center so if you need to use the hole saw you still have the option of drilling the correct pilot in the center.
Ron B.
White Bear Lake, MN

S. cerevisiae

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Re: Punching powder coated steel?
« Reply #4 on: September 01, 2015, 09:32:01 PM »
I prefer to draw a punch with the die on the outside of an enclosure. All of the components have a lip or a mounting flange, so small chips will be covered.  Large chips will more than likely result in a post-machining refinish job.  I thought about using a plastic or fiberglass enclosure, but both of those materials have down sides as well.

Offline duboman

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Re: Punching powder coated steel?
« Reply #5 on: September 02, 2015, 01:28:50 AM »
Sorry to say, in my experience with powder coating, either punching or drilling there is most likely no way to avoid a chip in the coating. A good coating of duct tape over the hole will minimize the likelyhood but not guaranteed. If the fitting you are inserting has a outer flange or you can use something that would cover the edge you can probably hide a chipped edge.

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Offline wingnut

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Re: Punching powder coated steel?
« Reply #6 on: September 02, 2015, 01:50:20 PM »
i work with powder coated electrical panels for a living.  We use tape over the hole (masking tape) and put the cup on the inside of the panel door.  The minimal chipping has always been to minor to note.  (until this post, I never even thought about it) (Keep in mind that nema rated panels usully have devices that are installed with a rubber gasket... so they more than cover up any tiny chips that may occure right at the cutting point of the punches)
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