[uncola]

Hi I'm going to be drilling my first case for a ksa-5 clone using a pcb from china.. 
 
What's the best way to make the IEC hole?  I saw people recommending making a paper template and taping it to the backplate, then chain drilling around the edge, then using a nibbler.. except my backplate from modushop is 3mm aluminum so it's too thick for a nibbler..
 
Should I drill the corners, then use a dremel to cut out the iec and a flat file to make it square?
 
Other holes like RCA, pot hole and headphone jack hole are around so I'm pretty sure I can just do it with a stepped drill bit.
 
Any tip for making the holes for the pcb standoffs?  I was just going to put the pcb in the case, and then use a fine tip sharpie to make a dot in the mounting holes of the pcb, then drill.. 
 
 
edit: I see some people also recommend drilling the corners then cutting the iec using a jeweler's saw

 

[HiGHFLYiN9]

   
Should I drill the corners, then use a dremel to cut out the iec and a flat file to make it square?
 
Other holes like RCA, pot hole and headphone jack hole are around so I'm pretty sure I can just do it with a stepped drill bit.
 
Any tip for making the holes for the pcb standoffs?  I was just going to put the pcb in the case, and then use a fine tip sharpie to make a dot in the mounting holes of the pcb, then drill.. 
 

 
That's exactly what I do, measure the IEC (or use the data sheet), mark up the hole with a sharpie, drill the corners with a drill press, then using a dremel cutting disc to remove the square, then a flat file to finish it off. Then lay it in, and mark the screw holes with a sharpie. If you're rich, you can buy a GreenLee IEC punch for a mere $300. 
 
Regarding the holes for the standoffs, yes that's the best way to do it. One thing you should get is a deburring tool (Skaviv makes them for $5-10) so you can remove the metal burrs that pop up when you drill a metal chassis. 

 

[uncola]

thanks HiGHFLYiN9!

 

[David Aldrich]

I'm a fan of corner drilled and a jigsaw. Then file and sand to perfect. I'm lazy though.
 
For the PCB, if you can whip up a dimensionally accurate print then you can tape down the template and center punch for drilling.

 

[MisterX]

I've scanned PCBs to make mounting hole templates a few times.
More times then not I will just use the pcb and a square and a scribe (a small sharpie is usually not much help) .

 

 

[MisterX]

BTW, these wheels from McMaster kick the crap out of the "reinforced" Dremel branded cutting wheels.
 
 
http://www.mcmaster.com/#1257a31/=wru01l

 

[uncola]

One of my internet friends says he hates stepped bits because the hole sides won't be straight, they'll have a taper.. and I should use regular twist drill bits.. is this a valid concern?

 

[HiGHFLYiN9]

It wouldn't really matter with most things you are mounting to a chassis as you have the red/white washers with the RCAs, the locknut with the power switch, etc. which cover up things like that if you are drilling really thick metal. But sure, you can use a straight bit too. I use a set of Cobalt Dewalt bits for chassis work, they hold up to abuse a little better than standard bits. 
 
 
Mr X thanks for the disc recommendation. I saw that it doesn't use the proprietary lock system from Dremel, assuming you just use the little screw bit, maybe with a lock washer?

 

[mcluxun]

  One of my internet friends says he hates stepped bits because the hole sides won't be straight, they'll have a taper.. and I should use regular twist drill bits.. is this a valid concern?

i cant find proper size taper for larger holes like D-style (15/16 inch), and stepped bits do a nasty job on thicker panels.

 

[MisterX]

Yeah, the taper on step bits doesn't mean much on thin stuff and they suck for thick stuff.
Works better then a hole saw though.

 
IIRC I also ordered a standard screw type arbor from McMaster for those McMaster wheels.
Will look around later and see if I can find it...
The quick change deal is nice on those Dremel arbors but my last McMaster wheel has done a bunch of amp builds and is still going strong.

 

[uncola]

hey misterx can you help me figure out the transformer I need for my ksa-5?  the aliexpress listing for the pc says 18-25v ok, 40 watts+ needed.. that means I need a transformer like this one?
http://www.antekinc.com/as-1220-100va-20v-transformer/
 
20v times 2.5 amp = 50 watts?  the 100va part doesn't factor into it does it?
 
this is the transformer I ordered which I think will be too weak..  http://www.antekinc.com/as-0520-50va-20v-transformer/
20v secondary windings(dual) * 1.3 amps is 26 watts?  or should I factor in both secondary windings and double that?  in that case would it be 52 watts and good enough for the ksa-5?