Silly Chassis Punch Question...
Ok, flame me if you will, but I don't want to punch the wrong size of holes in my nice shiny copper plate.
I want punch two hole sizes, and thought it would be nice to do it myself.
One is for a simple 9 pin socket (for ecc88, ecc83, ecc82, etc..). I estimate the hole should be 22mm in diameter (that is about 7/8 of an inch for those in some english speaking countries).
The other is for a regular 8 pin socket (for el34). I estimate that the hole should be about 27-28mm in diameters or about 1 1/4 inches.
I was looking this up and read somewhere that those greenlee punches don't actually make the same size hole that is written on them...
I don't know if this is true, but it would sure be a help if someone could enlighten me on this. Does a 7/8 inch punch make a 7/8 inch diameter hole???
Any suggestions would be welcome. And yes I searched a bit on this and didn't find a thread that addressed this topic well enough.
I haven't mic'd the holes, but I can tell you for sure that the 3/4" Greenlee punch will accommodate 99.9% of the nine pin minature sockets out there. The 1-1/8" works for every octal socket I've used. For perspective, I've had these punches for more than thirty years and they've been used for a pretty good variety of sockets.
"those greenlee punches don't actually make the same size hole that is written on them..."
I believe the confusion on hole sizes originates in the difference between radio "chassis" punches and electrical "conduit" pipe punches. Chassis punches are marked by the actual hole size while conduit punches are marked by the pipe ID size.
Since "conduit" punches are much more common on places like Epay, one should be careful to check.
1/2 inch pipe punch-- > 7/8 inch hole
3/4 inch pipe punch -> 1.115 inch hole or approx. 1 3/32 inch hole
1 inch pipe punch -> 1.362 inch hole or approx. 1 3/8 inch hole
I believe that Greenlee punch sets may be marked as to the size of the conduit/ fittings (ID) and not the actual hole size.
A hole saw will be the exact size, but can discolor the surrounding area if not careful.
Use a 1 1/8" (28.6mm) punch for:
American 4-pin (28.8mm)
British 4 pin (28.3mm)
McMurdo Octal (28mm)
Use a 1 1/16" (27mm) for:
PTFE Loctal (26.8mm)
Use a 21mm punch for Chinese Novals.
Use a 3/4" (19.05mm) for traditional Novals (18.5mm)
Use a 5/8" (15.9mm) for DIN sockets and B7G sockets (15.6mm).
A well-greased good quality chassis punch produces an excellent hole; Q-max in the UK, Greenlee in North America. Oh, and if you punch through a piece of thin dense cardboard on the face side of your copper plate (cardboard between the plate and the receptacle of the punch), you won't get any marks on the face.
HomeDepot has those Greenlee punches. It may not be listed on the webpages, but you can find them in your local store. Then you can take a close look of the size v.s. the label.
Umm, Greenlee has two lines of punches:
Conduit Punches which are sized to the conduit fittings they are meant to be used with, and the holes punched are larger than the stated punch size.
Radio or Chassis Punches which punch holes of exactly the stated size.
You just need to know which you are buying.
Mine are all radio punches and holes punched are very close to the stated size.
I use 7/8" or 3/4" radio punches for 9 pin sockets, and 1 1/8" or 1 1/4" for most octal and UX4 type sockets.
Look at smoking-amp' s post for conduit punch sizes.
I have lots of Greenlees and love 'em, but there are cheaper alternatives for light duty use.
Note that there is a company in the UK that makes nice "radio chassis' punches for a fraction of what the Greenlee cost. Sescom normally carries these, but seems to be out of stock. I don't know the brand name off the top of my head, but I have some and they are quite nice.
Ocean State Electronics sells a small radio chassis punch kit which is decent for light usage. (Aluminum chassis) I have one that has served me well for about 15yrs, almost worn out now, going to buy another set: http://www.oselectronics.com/ose_p64.htm
Q-max, yep that's the one. Their punches are quite nice at half the price.
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