Main AC (IEC) Type Connect

[trem]

I am building a small amp out of an old Sig Gen.
It just had a small hole in the back for a 2 wire power cord. Is there something ROUND I can buy that will accommodate a 3 wire connection.?
I can buy the typical IEC connector, but I am not sure if I can cut a square/non-round whole in the chassis..... if you know what I mean.
What do you guys do to make a "professional" looking AC connection on the back of a chassis.?
Thank You

[Jazz P Bass]

If there is an existing hole in the chassis, I would hard wire the power cable. & use a chassis/ compression strain relief.
You may have to open the diameter a little, depending on the cable.

[Enzo]

I agree, just enlarge the hole only as much as needed and hard wire a plain old round power cord in place of the 2-wire old one. You can either buy an appropriate strain relief piece or just take one off some old piece of equipment to snap around the new cord. Look at a zillion older amps that did not have detachable power cords.

Instead of looking for new power cords, I usually take an old IEC cord, clip the female end off, and strip the free wires.


Now then, cutting the square or other non-round hole. This is not so hard, maybe a bit of work, but the results are a nice modern power inlet. IEC males come in the screw on mount types we see a lot, in their somewhat rounded holes. Then ther are the snap-in ones with a rectangular hole. SOme mount from the inside, and some from the outside. The ones with an outside flange will cover any ugly hole edge you create.

When I first started making stuff, I had to make holes in aluminum chassis. We are talking over 50 years ago. I had no power tools. I had a hand powered drill, an "eggbeater drill," like these"
Tuning an Eggbeater Drill so it ‘Spins Real Good’ - Restoring vintage and antique woodworking tools - wkFineTools.com

To make a hole for an octal socket, or a larger hole for a transformer, I drilled a circle of little 1/8" holes, then punched out the center. That left a real rough edge, which I then cleaned up with files and nippers. A lot of work, but it got me there. These days, power tools are cheap and everywhere. Drill a 3/8" hole, then use a sabre saw to cut out to the edges you want. A cutoff wheel in a Dremel would also work.

But they also make a nifty hand tool called a nibbler, draw your hole, drill a large center hole 3/8" is good, then nibble out little square bites until you have the square hole. Google "nibbler tool."

[Tom Phillips]

Wow. You never know what's going to turn up on this forum.
Thanks for the link to the eggbeater drill restoration page. I have one of those drills and I'll bet that it will get more use if I give it a tuneup. I've never even oiled it.
Thanks again Enzo

[madkatb]

AES sells a nibbler for under $6 that works through a 3/8" hole.
If your going to use a Dremel make sure you wear safety glasses. If you get even slightly off line or out of plumb (ie. sideways torque) with the cutoff blade it will disintegrate with lots of flying pieces. Been there, done that, didn't like it.
Enzo nailed it. The outside mount connectors hide a lot of ugly.

[trem]

I have always wondered what those Nibbler Tools were for.....
I do have a Dremel as well. For the price, think I will try my luck at a bit of Nibbling.
On a typical BF/SF Fender don't the "holes" for the strain relief have some straight sides, or am I imagining that.?
Thank You

[Tom Phillips]

...On a typical BF/SF Fender don't the "holes" for the strain relief have some straight sides, or am I imagining that.?...

You are not imagining. The strain relief holes often do have flats on the sides. They are called 'Double D" holes. This stops the strain relief from rotating in the hole.

[R.G.]

You are not imagining. The strain relief holes often do have flats on the sides. They are called 'Double D" holes. This stops the strain relief from rotating in the hole.

Non-round holes, even complex ones, are - OK, not easy per se, but doable. They just take some time. I've done this a lot.

You lay out a drawing of what hole you want on a drawing program, print it full size, then spray the back side with spray-on pressure sensitive adhesive. Then you cut out the outline, and press it on the chassis where you want the hole. A little judicious work with an awl to mark the corners and to scratch the outline, and you have the hole outline marked on the chassis. Then: drill a hole inside the outline, and go at it with a set of small files. It may take a while, and you have to be careful to color inside the lines, but you get an arbitrary hole. Nibblers are nice for the roughing work, but they are not precise enough for the final holes. The final holes are file work.

[Enzo]

Oh yeah, lots of ways to do that. I used to put down strips of masking tape to cover the area, then draw the outline on the tape. Mill out the hole using whatever metal grinding method you like to the edge of the lines on the tape. When done, pull away the tape. No scratches on the metal. I sometimes cut out a stencil pattern for an odd shaped hole. I use something like a piece of manila folder. Then tape the stencil to the metal.


D-holes and double D-holes do indeed keep the strain relief from rotating, but I really doubt that will be a huge issue for you, so a round hole will work too. I have seen enough commercial gear with round holes, after all.


RG's right, the nibbler isn;t for finish work, but it does work pretty well, and you will probably like it, especially at the price.


Tom, you like the eggbeater? I was of course using my dad's tools as a kid, and he was more of a woodworker. SO he had a brace and lots of auger wood bits. But he also had twist drills with the base needed for the brace, and I used that a lot in addition to the eggbeater. One day I found a large burring ream for the brace, and oh man, I was in hog heaven, it was large enough I could deburr those really rough octal holes. It vaguely resembled a cone step drill.

Brace and bits:
Brace and Bit
Bit & Brace: 9 Brace & Bit, Special Heavy-Duty Hand Drill Bit Brace Online

Burring ream:
CRAFTSMAN 6729 3/4" & AJ No. 7, 2" PIPE BURRING REAM (02/22/2011)...

And one other tool I had to use to drill holes - the Yankee drill.
Yankee Style Push Drills Many Manufacturers

It looks like an oversize screwdriver, but it is spring loaded. You push on it and it collapses into itself wwhile turning the blade end. You could chuck drill bits or screwdriver blades into it. They come in all sizes. If you recall the movie Blues Brothers, They are in the elevator near the end, and Elwood uses a large Yankee driver to take out the screws of the elevator control panel.

[Tom Phillips]

...Tom, you like the eggbeater? I was of course using my dad's tools as a kid, and he was more of a woodworker. SO he had a brace and lots of auger wood bits. ...

Yep. All that you say really brings back memories. I still have access to a couple of braces and a box full of auger bits. They are very efficient tools. I’ll bet that one could put a ¾” hole through a 8” thick doug fur beam with a brace and bit faster than you could do the job with the average home style cordless drill. It sounds better too. Just the crackle of the wood chips being carved out. Wonderful tone.

[Enzo]

And directional ratcheting for when you are right next to a wall or something. And that big wide pivot piece on the end, so much nicer to lean on hard than... well, than most anything else.


Remember those brass nesting screwdrivers?