Knockout punch sizes

[Cifte12AU7]

I found a local place that will rent me a Greenlee hyrdaulic knockout punch kit.

The dies rent separately so I wanted to rent as few dies as possible to keep costs contained.

The tube sockets will sit below the aluminum surface of the chassis so I need to accommodate not for socket diameter size but for maximum tube glass diameter.

If I'm building the Tubelab SSE I would think that I would need the following punch sizes for my aluminum chassis:

1. 2 1/2" to accommodate the KT66 (largerst power tube): max diameter is 53mm or 2.08 inches

2. 1 1/4" to accommodate the nine pin 12at7: max diameter is 7/8"

3. 2" to accommodate the GZ-34 or 5AR4: max diameter is 1.5"

Am I accurate? I was concerned about going any smaller because it could make rolling/twisting tubes on exit difficult.

Thanks in advance for any insight!

 

[PDL]

Don't forget, knock-outs are sized as NPT sizes which are not the same as actual inch measurements.

 

[rayma]

Don't forget, knock-outs are sized as NPT sizes which are not the same as actual inch measurements.

That's to allow for the clamp to be inserted through the hole and tightened on the cable.
You may be able to buy several punches for the cost of the tool rental.
Hydraulic Punch Driver w/ 5 Hydraulic Punches & Dies
Knockout Punch Kit 10 Pc

 

[Cifte12AU7]

Thanks guys. I'll need to reconcile my measurements with the knockout punch sizes. Now, I'm leaning towards buying so I can ensure I don't make any mistakes.