Punching through two sheets of steel....

[JacksonburgFarmer]

Has anyone SUCCESFULLY punched through two sheets of steel with a greenlee hydraulic knockout punch? I have a 6X6 trough INSIDE of a homemade steel enclosure (12 Gauge thickness). I would like to punch through the back of the trough and the "outer enclosure".

Ultimate goal is to get a 1 1/4" RMC into this trough. Dont want break a die or punch trying this if it wont work....thought I would ask here before I tried it.

This is a pretty common setup in my area on farms around older grain handling setups. They would fabricate a enclosure (varying in size) to house a panel, motor starters, start/stop enclosures, ect. The idea was to "protect" electrical equipment from the elements, and to allow the use of NEMA 1 enclosures.

Oh what fun....another day in paradise....

 

[wireguru]

I would use a carbide hole cutter.

 

[Buck Parrish]

It would likely work fine. But as you may know, knockouts can be finicky some times,
How about a hole saw. That's what I would use.

 

[12345rsmith]

yes, but it is not what I would call a recommended activity. My preference would be a hole saw on high torque and slow speed to keep the heat down. But I realized that that has its own limitations.

 

[infinity]

I've done it many times over the years. Two panels side by side nippled together comes to mind. Drill once, punch once. I have broken the stud on the punch once or twice while doing so. :roll:

 

[JacksonburgFarmer]

Uh....well....I thought about the hole saw route....but holesaws are not my favorite tool to use....granted I will have to holesaw for my punch....but that is only a 1/2" holesaw.

 

[nakulak]

it might cut em both if its nice and new and really sharp and the metal isn't too thick. then again, it might not. I'd drill it too.

 

[nhfire77]

exothermic cutting system? Do you own a plasma torch?

Seriously though, carbide tipped hole saw is my vote. Slow and steady.

 

[hurk27]

Uh....well....I thought about the hole saw route....but holesaws are not my favorite tool to use....granted I will have to holesaw for my punch....but that is only a 1/2" holesaw.

Ever hear of a Step bit, or uni-bit?

I have one that goes to a 1" conduit size, I use them to make a larger hole for the KO punch, which makes it much more easier to remove the slugs after punching a hole. doing a double punch will depend upon how sharp your punches are, and how thick the metal is, I have done it, but I have also come very close to breaking the punch, but the nice thing is, once you have made the partial cut in each place you want, then just separate the two box's and finish punching out the holes one at a time, at least they will line up.

 

[JacksonburgFarmer]

hurk27, yes I have a unibit, several of several sizes actually. Seperating the enclosures would be the ideal way I agree, however, this is in a existing installation. Seperating the trough from the outer enclosure would be a monumental task, and is not praticle to do. I have to make the hole where it is.

 

[220/221]

Once you use these, the hole saw will be your favorite tool.

1 1/4" hole is nothing. It only take a little bit longer than a 1/2" hole. You will be done in less than a minute.

Over 1.5" you need to punch but for small holes, a good hole saw is the ticket.


IMO, step bits are awesome for making a small hole larger but you have to remove too much material using a step bit to drill a hole..

 

[jrannis]

If you are above 12 gauge, use a hole saw and tap majic, dont blow out your KO set.
I have had to punch one enclosure and then bolt them together then use the first hole as a guide for the second hole.

 

[LarryFine]

I, too, would use a carbide hole saw, cutting each layer from its own side, if space permits. Medium speed and medium pressure works. I use cutting oil.

For those who break pilot bits when the cup hits the surface, try shortening the bit so the edge of the bevel is on the same plane as the tips of the teeth.

 

[Cow]

Use the good carbide cutters like 220 suggested. I typically use them up to 1" and anything past that I punch out. But for situations like yours with extra thick steel, don't take a chance on breaking one of your studs or punches, just hole saw it.

 

[ohmhead]

Well when greenlee test there cutters they punch thur thicker metal but that said all we do everyday is distrbution lots of side by side panel nipples before we hang them we save time pre punching these never broke one yet .

This way your exactly lined up .

Greenlee is tuff the only broken stud or cup was from a helper not scewing fully on the threaded stud or trying to use a regular cutter on stainless thats always fun .


1 1/4 or less is ok with a hole saw i agree .

But think how many 1/2 drills have burned up cutting 4 holes all day we only use cutters on most projects and yes uni bits are the best for just about any electrical work .


Our shop sends our cutters out to a metal shop and has them sharpened when they get dull this increases the life of that cutter for many years of use .


Plus when you put them back in the box cutting edge up not down and keep them coated with 30 wd oil everyday wipe them off ive got a greenlee set from 1977 and its stiil cutting .

 

[jrannis]

Well when greenlee test there cutters they punch thur thicker metal but that said all we do everyday is distrbution lots of side by side panel nipples before we hang them we save time pre punching these never broke one yet .

This way your exactly lined up .

Greenlee is tuff the only broken stud or cup was from a helper not scewing fully on the threaded stud or trying to use a regular cutter on stainless thats always fun .


1 1/4 or less is ok with a hole saw i agree .

But think how many 1/2 drills have burned up cutting 4 holes all day we only use cutters on most projects and yes uni bits are the best for just about any electrical work .


Our shop sends our cutters out to a metal shop and has them sharpened when they get dull this increases the life of that cutter for many years of use .


Plus when you put them back in the box cutting edge up not down and keep them coated with 30 wd oil everyday wipe them off ive got a greenlee set from 1977 and its stiil cutting .

So Ohm<
How thick is the metal you are cutting?
What do you consider the max of the hydraulic knock out?

 

[ITO]

Has anyone SUCCESFULLY punched through two sheets of steel with a greenlee hydraulic knockout punch? I have a 6X6 trough INSIDE of a homemade steel enclosure (12 Gauge thickness). I would like to punch through the back of the trough and the "outer enclosure"....

One of my electricians broke the stud off a $1,500 Maxis stud punch doing exactly what you are talking about, and I have a tool room full of the broken hydraulic punches from the same thing over the years...JUST DRILL IT, and save your self the heart ache.

 

[Smart $]

hurk27, yes I have a unibit, several of several sizes actually. Seperating the enclosures would be the ideal way I agree, however, this is in a existing installation. Seperating the trough from the outer enclosure would be a monumental task, and is not praticle to do. I have to make the hole where it is.

If you decide to go the hole punch route, I recommend the punch be of the slugbuster type if possible. Also, predrill small holes (1/4" perhaps) on the periphery of the hole where the punch first contacts the metal. This saves the punch from having to push through the extra thickness and lets it start sheering upon applying pressure. Also helps tremendously if the punch is rather used and dull.

 

[ohmhead]

So Ohm<
How thick is the metal you are cutting?
What do you consider the max of the hydraulic knock out?

Well i guess your standard panel can sizes commercial types 16 ga just a guess .

Greenlee cutters can cut 10 ga normal cutters but you can get 8 ga cutters from them if you like a better cutter .

If you look at 16 ga to 10 ga its fine 10 ga is twice the thickness kinda makes it a easy cut if you take care of your tools .

Tools are made to use and they will break we just never had one break on a double panel cut ever and we kinda do it everyday.

We use a big greenlee C clamp on pre fab panels we set them bottom to bottom clamp them with vise clamps and punch away no problems most jobs were talking hundreds of panels to punch out pre fab is the key to electrical work today .

We dont do this with stainless !

We plasma cut stainless or use stainless greenlee cutters one panel at a time .





One small hole set the C clamp and punch now with this cutter we use a 8 ga cutter .

Take care

 

[blueheels2]

Broke the stud when I tried.