Correct Size Knock Out Hole Punches

[Pollys13a]

Hi all,
What would be the correct size for a  12AX7  B9A tube socket, a K8A  6V6 octal socket and  if different what might be required for rectifier sockets?
Thanks.

[uki]

I don't think there is a default size, each brand may be different from one another. Mesure the sockets you have.

Here some findings on octal sockets:

Amphenol bakelite 8 pin octal tube socket. Black. Compact MIP. Wrap around silver pins. 1.046"d hole required. Over/under chassis mount. 1.312" c-c mount holes.

Pomona surface mount octal socket. 1.792" diameter base. 0.772" high. Made in the 1960's.

Millen 8 pin phenolic octal chassis mount vacuum tube socket. #4241-1. Missing pin contact #6. Fits 1.05" diameter hole if bottom mounting. 1.3" c-c mounting ears. U.S. made in the 1960's.

from: https://www.surplussales.com/Tube-Sockets/TubeSkts-3.html

[HotBluePlates]

What would be the correct size for a  12AX7  B9A tube socket, a K8A  6V6 octal socket

Did you look at the tube sockets listed in Hoffman's store?

For the socket he sells, 9-pin B9A need a 3/4" hole.  His octal sockets need either a 1" hole or a 1-1/4" hole (actually 1.18" but the nearest size Greenlee punch is 1.25" and the mounting centers are 1.5" for this socket).

But as Uki said, it really depends on the specific socket you use.

[Pollys13a]

OK, thanks for the replies, these are the tube sockets I intend to buy. Ebay UK item numbers 203593328614 and 321001703678
At bottom of listing shows dimensions, in case I get it wrong could someone please advise me which hole size I need to mount each socket either above or below the chassis?
Cheers.

[acheld]

Hi there. 

IF you intend to "drill" your socket holes yourself -- ie, a custom chassis -- a couple of words of advice:

1.  Measure and layout -- check and re-check.  You get one chance to make it right!
2.  For your pilot holes, use a center punch to make sure your drill goes where you want it.
3.  Every socket has a different mounting hole size.  It's just the reality.
4.  You have three choices to make big holes.  Choice one is a hole saw.  Just, no. It makes a mess.
5.  Choice two -- IF your socket has a mounting hole diameter that matches a hole punch, go for it.  Greenlee punches are the most expensive, but there are cheaper "knock-outs" (pun intended).  These produce the cleanest holes, but a hole punch tool only is good for one diameter.
6.  Close behind, and the method I use the most, are the inexpensive step drill sets available everywhere. These have the advantage of producing good round holes in varying sizes, with simple de-burring as the final cleanup.
7.  You may not be aware, but twist drills > about 1/4" do not produce "round" holes when drilling sheet metal.  If you need precise larger holes, then you need to drill small, and use a hand reamer to get your precision hole.   This is NOT needed when drilling stuff like holes for pot shafts and the like. 

[sluckey]

OK, thanks for the replies, these are the tube sockets I intend to buy. Ebay UK item numbers 203593328614 and 321001703678
At bottom of listing shows dimensions, in case I get it wrong could someone please advise me which hole size I need to mount each socket either above or below the chassis?
Cheers.

Both of those ebay listings told you exactly what size hole is required. What don't you understand about that?

[PRR]

Both of those ebay listings told you exactly what size hole is required. What don't you understand about that?

Maybe using a cellphone and couldn't reach the bottom of the page?

Brand New K8A 8 pin octal vacuum tube socket
Panel cut out: 26.50mm

[Pollys13a]

OK, thanks for the helpful replies people :)

[trobbins]

I have a manual hole punch kit with 8 die sizes (same die sizes as a Greenlee kit), and have since purchased two more die sizes to better align with fitting some common parts I use for amp restorations.  Buying individual punches is typically a much much costlier path to take (if you're lucky enough to find a die size that suits).  The kit may use a different mandrel (diameter and/or thread) than any individually purchased punch uses.  I have often chosen the valve socket to suit an available punch size, rather than the other way around - but that was because I have a stash of different reclaimed valve sockets.

[joesatch]

i am considering these, not sure how they compare to Greenlee ( i can bring myself to drop that kinda dough on a punch):

For power tube sockets
https://www.automationdirect.com/adc/shopping/catalog/tools_-a-_test_equipment/hole_cutting_tools/knockout_punches_-a-_accessories_-_fractional_-a-_metric_size/109300


for preamp sockets:
https://www.automationdirect.com/adc/shopping/catalog/tools_-a-_test_equipment/hole_cutting_tools/knockout_punches_-a-_accessories_-_fractional_-a-_metric_size/1097034

[Pollys13a]

i am considering these, not sure how they compare to Greenlee ( i can bring myself to drop that kinda dough on a punch):

For power tube sockets
https://www.automationdirect.com/adc/shopping/catalog/tools_-a-_test_equipment/hole_cutting_tools/knockout_punches_-a-_accessories_-_fractional_-a-_metric_size/109300
Thanks for the info.


for preamp sockets:
https://www.automationdirect.com/adc/shopping/catalog/tools_-a-_test_equipment/hole_cutting_tools/knockout_punches_-a-_accessories_-_fractional_-a-_metric_size/1097034

[sluckey]

i am considering these

I highly recommend you choose your socket first, then buy the correct size punch. I also recommend using only Belton high quality, reliable sockets that Hoffman sells. They are also widely available across the net. Different manufactures may require different size holes, especially if the sockets are made in China.





The nine pin socket requires a .75" hole and the eight pin socket requires a 1.18" hole. So, your choice for power tube sockets is perfect, but your choice for preamp sockets makes a 1.115" hole. Very nice for 3/4" conduit but inappropriate for tube sockets.

Stay away from conduit punches. Search eBay for "greenlee radio chassis punch" and you will find a 3/4" punch that really makes a 3/4" hole and costs less than the punch you linked.

[Pollys13a]

I have a manual hole punch kit with 8 die sizes (same die sizes as a Greenlee kit), and have since purchased two more die sizes to better align with fitting some common parts I use for amp restorations.  Buying individual punches is typically a much much costlier path to take (if you're lucky enough to find a die size that suits).  The kit may use a different mandrel (diameter and/or thread) than any individually purchased punch uses.  I have often chosen the valve socket to suit an available punch size, rather than the other way around - but that was because I have a stash of different reclaimed valve sockets.

Which brand did you buy?

[Pollys13a]

i am considering these

I highly recommend you choose your socket first, then buy the correct size punch. I also recommend using only Belton high quality, reliable sockets that Hoffman sells. They are also widely available across the net. Different manufactures may require different size holes, especially if the sockets are made in China.





The nine pin socket requires a .75" hole and the eight pin socket requires a 1.18" hole. So, your choice for power tube sockets is perfect, but your choice for preamp sockets makes a 1.115" hole. Very nice for 3/4" conduit but inappropriate for tube sockets.

Stay away from conduit punches. Search eBay for "greenlee radio chassis punch" and you will find a 3/4" punch that really makes a 3/4" hole and costs less than the punch you linked.

Thanks for that and the tip about, conduit punches :)

[Pollys13a]

I read that Greenlee can lose their edge if have been used on SS? Any idea of grade, type of steel, has that remained constant over the years? 

[joesatch]

i can literally build an amp for what a greenlee punch set costs

[Willabe]

i can literally build an amp for what a greenlee punch set costs

So.

Good hardened steel with good bearings for smooth cutting cost money. They last a long time. Their tools and good tools cost good money.   

[SILVERGUN]

I own 3 that I snagged off ebay for very good prices. maybe $20 each with shipping(?)
1 3/16"
3/4" and 7/8"
They've worked well for me but I did buy a bunch of sockets all at once and just stick to those.

[Willabe]

I read that Greenlee can lose their edge if have been used on SS? Any idea of grade, type of steel, has that remained constant over the years?

Are you asking what are most tube amp chassis made of?

If so, most are mild steel or aluminum.

I wouldn't try using a stainless steel chassis, too hard to work with. And what benefit do you gain? 

[PharmRock]

Last year I grabbed a set of 8 Greenlee chassis punches off e-bay for $150, which is a pretty good deal.  Greenlee punches are considered the "gold standard" in this category, as far as my understanding goes.  I'm not sure about them losing their edge over time.  If true for Greenlee, its probably true for every other brand in this category.
 
I recommend the chassis punches vs. a step bit, especially for aluminum, because the heat generated with a step bit for the larger octal holes can "goop up" the aluminum.  I learned the hard way that its best to drill a little, then wait, then drill some more.  The chassis punch makes a much cleaner hole and avoids all the metal shavings.

May want to check Harbor Freight...they might have a cheap set, which might be sufficient for occasional use. 

[joesatch]

I've bought some on ebay. What's the deal with the bearing ? Do i need to buy one? What i bought has no bearing afaik

[acheld]

the heat generated with a step bit for the larger octal holes can "goop up" the aluminum.  I learned the hard way that its best to drill a little, then wait, then drill some more.  The chassis punch makes a much cleaner hole and avoids all the metal shavings.

Of course a punch works better -- if you have the correct size.

To avoid heating up your drill bit and for more precise drilling, consider using a cutting fluid such as Tap-Magic. You don't need much.  Works great. Not expensive.  Easy to clean up. 

[sluckey]

I've bought some on ebay. What's the deal with the bearing ? Do i need to buy one? What i bought has no bearing afaik

The bearing requires less muscle power. Usually only found on the larger size punches. Not necessary on most aluminum chassis. Very useful on steel. So is cutting oil.

[HotBluePlates]

i can literally build an amp for what a greenlee punch set costs

Tools is expensive.

DIY for everything means you save on the cost of a single chassis, but spend very much for for tooling.

DIY is economical if you make a lot of amps, but if building just one or two then a pre-drilled chassis is a better deal.

[Soulfetish]

Machining stainless can have some challenges. But it all depends on the grade/temper of the metal, diameter of the hole, thickness of the material, and material of the tooling. But, there are some general things to look out for.
Stainless can gal up and kind of fuse along the cutting edge. Particularly if you cut too fast. I actually ruined an expensive step drill cutting aluminum too quickly in the same fashion.
Also, even though the low carbon grades don't harden with heat, they can work harden very quickly. This can be the problem if cutting too slow, where the stainless can harden along the cutting edge of the tool.
Lubrication helps with both problems.

edit: I should mention that I've never had any problems using greenlee punches the few times I've punched stainless.

[craig.kimble]

I use these.. they are fairly inexpensive, built well, and has no problem with .09 aluminum.

The octal is spot on, the 9 pin punch is a bit oversized but it works.

https://www.automationdirect.com/adc/shopping/catalog/tools_-a-_test_equipment/hole_cutting_tools/knockout_punches_-a-_accessories_-_fractional_-a-_metric_size/109220


https://www.automationdirect.com/adc/shopping/catalog/tools_-a-_test_equipment/hole_cutting_tools/knockout_punches_-a-_accessories_-_fractional_-a-_metric_size/109300

[sluckey]

the 9 pin punch is a bit oversized but it works.

For $26 or less you could get a used .75" Greenlee that punches the correct size hole.

[craig.kimble]

For $26 or less you could get a used .75" Greenlee that punches the correct size hole.

I've looked all over for one, but haven't had any luck..

[sluckey]

Plenty on eBay. Wide range of prices.

     greenlee 730 radio chassis punch 3/4

[uki]

I do it with a driller and a file. I know the puncher is faster, but I got the right size every time no matter the size of the socket.

[PRR]

Greenlee radio punch history: