Enlarging knockouts & drilled holes

[Phoenix]

Those QMax punches are very good, expensive for the number of sizes required though, I have about 4 I think, not sure that they are any quicker than a hole saw, but, they are much neater as long as the enclosure does not twist and distort.

Pretty sure they are slower in most cases, but a lot easier in where you've got to add holes to trunking and theres not enough room to get a drill in squarely below, just drill a pilot at a crazy angle rather than try and start a cutter bit at a crazy angle!. They go through some quite thick metal as well, have used one on the back of those blakely transformer units in school science labs, which have a good few mm of metal to them (and weigh as much as a very heavy thing!)

I witnessed one electrical contractor get one heck of a "row" for drilling through the top of a panel to put the mains in without protecting the control gear inside.The end customer insisted on the machine builder replacing ALL the control gear at the electrical contractors cost, machine was new

Choice they had not!

Cost them 5 figures IIRC.

Main isolator, breakers, contactors, I/O, PLC including rack, and various other bits, all because they guy installing the cable did not follow the accepted and stipulated working practice.

Funnily enough don't remember seeing him on the site after that!!!

Pet hate of mine, seen at least one panel where there was the waste from a 20mm cutter bit sitting neatly on a section of breakers (it was a sectional panelboard with several sections of mcbs as well) from where they drilled a hole up the top for a stuffing gland for fire alarm cable, it was those 1970's federal stab-loks as well, plenty of exposed busbars that it could have fallen onto!

I like to use an apprentice holding a plastic tray to catch the bits that come out, still a bit scary drilling into a live board though!

Even collared a site agent once to hold a vaccumm cleaner nozzle in a fire alarm panel that I had to drill and tap new cover fixing bolts into cos someone had swept the others up for me headbang

 

[pickleye]

Thanks for the suggestions. :Salute :

Sadly I am the apprentice so I do the drilling, cleaning wiring texting etc etc while my guy smokes himself to death.

He's not big on passing on experience and expertise.

Thanks for the replies and to the forum for filling a missing part of my apprenticeship.

I'll have to get myself one of those oops cutters. Maybe I should look for some oops snips, oops knife... :run :run

 

[batty]

CEF used to do a thing called a reload arbor which was designed for making holes bigger and making changing holesaws quick. They were good because one you could go from 20/25mm up to a lot larger sizes. Not sure if they still do them. I have loads of holesaws with the bosses on but have mislaid two of the arbours that I had. I don't tend to use CEF these days but may pop in one day to see if they still do them because they do make making holes bigger easy.

 

[Apache]

No Andy, then they would not be sharpened they would be recut, I used to have a guy that could do that too!

I'd imagine in most cases a new holesaw would be cheaper!

 

[Sidewinder]

Not actually Patch, depending on size of course!

He could do them in minutes!

 

[steptoe]

sheet metal punch? q max | eBay UK makes a neater hole than a cutter bit as well

I didnt even realise you could still get those,

bloody brilliant bits of kit,

esp as has been said when space is limited.

good find.

 

[thomas123]

i fit the smaller holesaw into the larger one, small holesaw then acts as the arbour.

 

[Larnacaman]

Most of the electrical contractors i've known on my projects have used cone cutters to open up smaller sized holes, they come in several different sizes and are both quick and easy to use in the majority of cases.... If going from 20mm to 32mm then the first stage would be to use the 20 to 25mm, the the 25 to 32mm. You can get them to go from 20 to 32mm, but can be a little on the inaccurate side, on the final aperture.

 

[ian932]

Step cutter is the way to go I find holesaws you end up with a hole bigger than you want if you get a bit of drift on when drilling, I use my step cutters on unistrut with no problems so a knock box is no problem for it.

 

[Sidewinder]

I agree ian, holesaws almost always cut oversize.

IMHO it's a combination of tolerance stck up between all the different parts, also, they are rarely truly round.

Cone cuts/step drills are easier to get a much more accurate hole diameter.

I tend to use more cone cuts as that's what I have obtained over the years.

Step drills will give you a more parallel sided hole than a cone cutter, so in that aspect better.

Also you tend to have standard size steps ont he step drill thus easier to get the correct size first hit.

It is more difficult though is it not to go in between the steps I find, you?

With thin sheet the tapered hole is normally not a concern.

 

[Evans Electric]

Thanks for the suggestions. :Salute :Sadly I am the apprentice so I do the drilling, cleaning wiring texting etc etc while my guy smokes himself to death.

He's not big on passing on experience and expertise.

Thanks for the replies and to the forum for filling a missing part of my apprenticeship.

I'll have to get myself one of those oops cutters. Maybe I should look for some oops snips, oops knife... :run :run

Your "Guy" needs a kick up the ar$e , for not passing on his experience.