punching large holes in a chassis

doing the metal work on your own amp is one of the most difficult parts of building an amp from scratch! unfortunately, the tools to make the large holes in your chassis can also be expensive. here are just a few options.

chassis punches

these are what you really want, if you can afford them! they are a great investment but can be very expensive. a chassis punch mostly consists of a bolt a cutter and a nut. you simply drill a hole to accommodate the bolt, place the bolt through the hole, attach the cutter and nut, then tighten the bolt. the cutter cuts through the metal as the bolt is tightened. you get a very nice looking hole! try to find a standard size to accommodate your most used 8 and 9 pin sockets.

drill bits

you can purchase drill bits for large holes, but this is probably not your best option. the bits can be expensive and they will need to be sharpened quite often. luckily they can be sharpened quite easily.

stepped drill bits

these drill bits are like 5+ bits in one. these also can be expensive. one other drawback is that each time you use the bit you will wear down smaller hole sizes. my stepped drill bit is pretty dull. i can only use it on cake pans.

hole saws

i have never tried this method, nor have i ever heard about anyone else trying it, but i'm sure it can be done! you may get only a few holes per bit, however

spade bits

these bits are made for boring large holes in wood. i had heard of others using them on thin aluminum chassis (like the hammond chassis.) i have tested it out on cakepans and hammond cassis and it indeed worked. This could be a very cost effective option since these bits are almost disposable at their low cost. i wouldn't try this on a thicker chassis however, as you bit probably won't last long. so far on smaller chassis i have got about 7 holes drilled from one $3 bit.

general punching tips

when ever you are cutting metal, use a lubricant! it will cut down heat, make the cutting process easier and extend the life of your tools! use wd40 or even 3-in-one oil if it is all you have. I have not been able to source a proper cutting oil yet. Please comment if you know where to get some.

cut surfaces are sharp and can have burs and barbs on them! use a deburring tool of roundish file to disarm your chassis holes. these buts really hurt!

what about holes that aren't round?

great question! often a feat that requires some ingenuity. square chassis punches do exist put run in the hundreds of dollars. here are some other options:

drill bits and saw

drill out the corners and saw the length using a metal saw such as a hacksaw or jigsaw


many people make a template for their hole, then drill a hole to accommodate a router bit, pop in the router and cut away the material they don't need. i have never tried this, but it sure sounds fun!


these little tools "nibble" away material a piece at a time. slow and steady does the job. it would probably be a little more efficient to drill a hole to remove most of the material and then nibble away the rest. i use a nibbler to make mounting holes for EIC sockets. I start with a 3/4" hole, then nibble away what's left. not bad tool to have around.

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