Cutting irregular hole in panel
1 Attachment(s)
Mods, please move if this is not in the right place.
I've finally found a steel box to put an isolation transformer in, the front panel is what appears to be 1mm steel. I want to put a standard MK mains single socket on the panel, which entails cutting an irregular hole - almost square, but not quite. What is the best way to cut such a hole (there's also a rectangular one needed for the on/off rocker switch)? I've got no fancy metalworking tools, just a power drill, vice, hacksaw and files. |
Re: Cutting irregular hole in panel
The standard way is called 'stitch drilling'. Mark the hole you want to cut, perhaps on masking tape applied to the panel. Drill a sequence of small holes around, and just inside, the edge you've marked. Join a few of them together with the tip of a needle file, then continue this if necessary with a junior hacksaw blade. Wiggle the waste piece of metal out. Tidy up by hand-filing.
Cheers, GJ |
Re: Cutting irregular hole in panel
Have you considered fitting a cavity wall style plastic Pattress then you could cut a simple square hole.
https://www.screwfix.com/p/appleby-1...B&gclsrc=aw.ds Cheers Mike T |
Re: Cutting irregular hole in panel
I would use a steel cutting blade in my jigsaw, taking it slowly . Mick.
|
Re: Cutting irregular hole in panel
Thanks Mike, I had never thought of a pattress, it would simplify matters a lot. Would need to check if there's enough clearance behind the panel to the transformer.
GJ, that sounds like a straightforward approach. Is it best to use lots of small holes or fewer large ones? |
Re: Cutting irregular hole in panel
Small holes can better follow the shape and leave you less filing to do. But you can't drill overlapping holes with ordinary drill bits, so you leave small spaces between them, then you need to be able to enlarge a few to make space to get a hacksaw blade through to be able to saw the other holes together.
If you go the jigsaw route, Put masking tape on the surface so it doesn't get marked by the sole plate of the jigsaw. Other methods would be: Abrafile fitted in a hackaw frame. Nibbler (Advel, Monodex, or a powered one) It depends what tackle you have handy. |
Re: Cutting irregular hole in panel
A surface mounted plastic pattress would make life even easier.
Alan |
Re: Cutting irregular hole in panel
Quote:
|
Re: Cutting irregular hole in panel
Not sure I understand the potential need for packing Mick. Just screw or bolt the pattress to the panel and fit the socket in the normal way. Hole needed for the wiring of course.
Alan |
Re: Cutting irregular hole in panel
Quote:
Cheers Mike T |
Re: Cutting irregular hole in panel
Corner holes then jigsaw and finish of with a file.
Lawrence. |
Re: Cutting irregular hole in panel
1 Attachment(s)
Mk do a "metal frame for panel mounting" that might do you: I have used them myself for this sort of thing. Screwfix don't do them now but a decent electrical shop should carry them.
|
Re: Cutting irregular hole in panel
Quote:
|
Re: Cutting irregular hole in panel
Once you have drilled a series of holes they can be joined by tilting the drill/metal doing a self supported milling action. This does tend to drift to one side a bit, the correct angle of tilt will compensate. The little bits left joining the two can be snipped with cutters.
|
Re: Cutting irregular hole in panel
Or one of these if you have a 50mm holesaw: https://uk.farnell.com/mk/735whi/mai...020-Desktop-Hi
|
Re: Cutting irregular hole in panel
Quote:
|
Re: Cutting irregular hole in panel
if you mount the socket conventionally you might want to think about if you want the earth on the socket to be connected electrically to the case of the transformer or not, as it will be via the mounting screws.
My transformer uses an all-insulated box and the screws and socket earth are isolated completely from the incoming mains earth. Filtering on the appliance under test may otherwise cause parts in it to acquire a high floating voltage by referencing it to mains earth. |
Re: Cutting irregular hole in panel
Quote:
The intended usage is mainly for live chassis work which would not use the earth pin, but also for small switch mode power supply testing. In the latter case there is access to the transformer output (and socket L/N) to allow a current probe and high voltage differential probe, so the input power can be monitored via a scope. |
Re: Cutting irregular hole in panel
If you use a jigsaw cover the front panel and the saw bed plate with masking tape
this allows you to mark the panel and more importantly will stop the panel having its finish damaged Did this 100,s of time while I was producing control panels etc Trev |
Re: Cutting irregular hole in panel
because I assume you're using an isolating transformer so you can work on something live a bit more safely. If the appliance has components (eg capacitors, especially vintage ones, or a leaky mains transformer) connected between its earth conductor and its live or neutral, and you connect its earth to mains earth, then you are connecting components between the 'isolated' side and the mains earth, so the item under test is no longer completely isolated from the mains earth. Touching the supposedly isolated live or neutral may use you and a faulty component to complete the circuit. You may therefore be under a false sense of security.
If its a 2-wire only appliance eg live chassis radio then the output socket earth wont be connected. But if its an appliance that needs an earth under normal conditions, then leakage to earth may manifest as an earth-referenced live or neutral. When I worked for another company our isolation transformer had a sense relay that cut the power if it saw any voltage coming back on the appliance earth conductor, like a voltage-operated ELCB. I think 8-) |
All times are GMT +1. The time now is 11:32 am. |
Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.