'large' tube socket hole-making

[Opcom]

What is the easiest way to make a nice looking tube socket hole for big tubes like the 813 or 4X150, or even monsters like the 3CX3000?

Prefer a method that does not involve stripping the whole chassis.

Fly cutters on thin metal have frustrated me. The metal flexes and bends and the cutter gets hot and dulls. Doing it wrong, no doubt.

Drilling and filing is not fun, takes hours. A jigsaw is OK but hard to turn in such a small circle. I am sot of tired of making ugly holes.

A punch is great but big bucks. I borrowed a punch for a 6" hole in 1/8" aluminum for a CRT. What an arm twisting cheater bar experience! But where can a punch set be had that does not cost $100 a piece?

[WQ9E]

Some commercial electricians will have some very large chassis punch tools so if you have a contact in that group follow up on it.  A large tool rental place might also be a possibility.

The fly cutter works fine on thin metal IF you back up the metal with something to stabilize it.  A sacrificial block of wood works well.  This is the method I used when I built a large amp several years ago.  It didn't take long.

A hole saw will also make the cut although they generally leave a much rougher cut.  It will also need to have thin metal backed up.

With either make sure the material is properly clamped or secured.  Proper bit speed and pressure is also critical to a good cut.

If your drill press and/or the shaft for the cutting tool has excessive run-out then the hole size will be increased.

Other methods that would probably work but I haven't tried would be to rough out the circle and then use a sanding drum mounted in your drill press to smooth the final work. Another possibility is using one of the small router like rotary tools with an outside circle guide and abrasive bit to finish out the hole.

Using any of these make sure you have eye protection in place and don't neglect to properly clamp the workpiece.  A piece that gets caught by a hole cutter can be whipped around with a large amount of torque if you are using a drill press with significant power.

[WBear2GCR]

I use a standard hole saw, the type with the arbor, center drill. The hole saws are typically called "bi-metallic" and come in specific diameters.

A drill press typically will have some run-out, so a test cut on similar material is a good idea, as is relatively low speed on the drill press, plus some lube on the cut. I am lucky (heck, no luck, a lot of looking around and work to get it) to have an old milling machine which has nil runout and does not slow down under this sort of load. The saw and arbor's runout then dominate, which is not bad... Of course some dressing of the cut hole may be required.

And, you have to be able to reach the spot intended for the hole with the machine, be it a drill press or a milling machine.

I like fly cutters but only when I can very very solidly clamp the work to a backing surface before cutting. The typical chassis sheet metal bends too much under the force of the fly cutter to cut smoothly. That's been my experience with them.

                           _-_-

[W1ITT]

About 40 years ago I bought, possibly from Brookstone back when they sold good tools, a circular hack saw.  It has a 3/8" rod for the backing and uses a special saw blade that is basically a thick wire covered with abrasive material.  One drills a center hole, slightly larger than 3/8, and then a 1/8 pilot hole on the radius. Then the saw frame is put into the center hole and assembled onto the radius "blade" and away we go.  I have cut numerous 4-1000 sized holes in chassis plates as well as innumerable meter holes in 1/8 aluminum panels.  All that is required is a bit of touch up with a half-round file to make a nice hole.

I also have a fly cutter that I have used with limited success and not a small amount of spilled blood.  I don't like them.

There's only one blade left for my good old circular hacksaw rig and I'm unable to find another of the correct size.  It's a good old tool that's worth looking out for, perhaps on ebay.  And no, mine's not for sale or loan.   I'm taking it with me.

[KL7OF]

Fly cutters work very well with a wood backer as previously stated....If you sharpen the fly cutter bit so that is has a steep angle and cuts a narrow groove it will work better than the standard 45 degree  angle that most fly cutters come with.....Good Luck..

[Detroit47]

I have rented Hydraulic Green Lee knock out sets before. If you live in a large metro area this may be an option. They are a breeze to use. I have also put holes in on a NC mill. Sometimes it is better just to pay for a little machine work.

John N8QPC

[pa0ast]

some punches,  these are easy to handle by amateurs also if there are already parts mounted on the chassis. And the result looks professional. Should be available in the usa as well.
Hydraulic:
https://www.hbm-machines.com/producten/plaatbewerking/overige-machinesplaatbewerking/hbm-8-ton-hydraulische-plaatpons
Manual:
https://www.hbm-machines.com/producten/plaatbewerking/overigeplaatbewerking/hbm-10-delige-plaatponsset-met-ratel
cheap:
https://www.hbm-machines.com/producten/plaatbewerking/overigeplaatbewerking/hbm-4-delige-plaatpons-schroefpons-set
Even cheaper but only 1 size for this little money .
https://www.hbm-machines.com/producten/plaatbewerking/overigeplaatbewerking/hbm-3-punts-plaatpons-schroefponsen
This will do the job for You. 
RGDS Anton

[N2DTS]

Greenlee makes a nice punch set for electrical boxes, big sizes, bearing punches, with a big ratchet handle that makes things easy.

I also have a set of electronic greenlee punches, if one set is not the right size, the other is.

[w4bfs]

I use an Adel nibbling tool which is fb for aluminum panels to 1/8" thick ... took a quick look on Ebay and found several similar inexpensive tools .... to make an attractive hole will require practice until you figure it out .... the nibbled slugs are ideal to mix with sodium hydroxide and make hydrogen gas to fill balloons

[w1vtp]

Gee, where were you guys when  I built my PP 813 transmitter.  I did it the hard way - drilled a bizillian holes snipped out the undesired piece in the center and used a half moon rasp to smooth things out.

I've attached some photos - two were for meters and one for an ART13 variable inductor.  Oh yes, that was done with a hand drill, center punch - not a drill press..  It can be done just takes time

Al

[W3RSW]

Very similarr to Al, Every large hole I've cut in stock for many years has been with a Black & Decker 7514, 2 speed jig saw, double insulated 110 vac. Blades come in tooth sizes from aluminum to wood.
I've cut everything from standard rack panels to light aluminum project boxes.

Careful placement of pilot holes are drilled so that outside of 3/8 dia. Is tangent to the inside of the larger circle or square to be cut.  Then cut outwards from pilot hole to meet tangent and continue on larger, compassed circumference or line. One hole necessary for a circle, two opposing angle holes for a square or rectangular cut.

In recent years I've found the infinite slip blade, "Quick-grip" mini bar clamps to be really neat.  Clamp down the work securely as close to the edge of the underlying bench as possible as you rotate and cut circle sectors. This eliminates chatter, binding, jumping and blade breakage.  For angle, bar, rod and tube stock, simply use a couple of clamps and make the cut as close to the edge of the work table as possible to clear the blade.

Plan the work so that enough stock is left to adequately clamp with two clamps, the desired piece falling off at the end hanging away from the table or bench.

A good example is my 813's by 572's AM rig too.

[KB2WIG]

A,

Nice work.

 Howdja adjust the swing link?

klc

[N2DTS]

I have used a file a lot in the past, for those holes the punches did not work on, and fan holes (4 to 6 inches).
Sometimes you can use tin snips and a file.
I have a cordless drill, a bunch of files and some hole punches.
Wish I had a brake and a shear for sheet metal work, and a drill press would be handy, but more room for tools means less for rigs and parts....

[WZ5Q]

I tend to use Core Drills for up to 3/4" holes, a Greenlee Step Bit or Hole Saws for up to 1 3/8" depending on the material, Hole Saws above 1 3/8", and the jig saw for the real large holes.
I prefer the variable speed hand drill as I feel I have more control, but the work must be firmly secured.
You must also be sure the saw is very sharp and take it slow especially if it is a steel chassis.
The Hand Nibbler is a must for the small square holes, makes it so much easier.
I clean the hole edges up with a deburing tool and various files.
Here are a few shots of my last sheet metal project.

Take Care,

[Opcom]

Thanks for the great advice. The price of hydraulic punches has really come down. I see that one need not have a lot of room on the chassis, since the unit has a hose. It has also been a chore to make holes for meters, and those are worst because it can't be hidden like a tube socket hole.

[N0WEK]

I've been using one of these for years and they work great. They're rated for 16 gauge steel but I've used them on at least 1/4" aluminum.

Cheap too....at Home Depot or Ebay.

https://www.youtube.com/watch?v=Pj8cyeV4WJ8

[W1RKW]

A quality hole saw with arbor in a drill press works excellent.  Clamp the piece down tight and back it with a piece of scrap hardwood, clamp the hardwood too and go slow with the press. Dress up the hole a tiny bit if necessary with a half round file and you're done.  I find setting the drill press table angle at about 1/2 to 1 degree decreases any possible cutter chatter.

[W4RFM]

Thank you N0WEK for your post.  I had no idea something like that was available. I am getting that tool!
Bob W4RFM

[N2DTS]

+1!

Thank you N0WEK for your post.  I had no idea something like that was available. I am getting that tool!
Bob W4RFM

[Dave K6XYZ]

What is the easiest way to make a nice looking tube socket hole for big tubes like the 813 or 4X150, or even monsters like the 3CX3000?

Prefer a method that does not involve stripping the whole chassis.

Fly cutters on thin metal have frustrated me. The metal flexes and bends and the cutter gets hot and dulls. Doing it wrong, no doubt.

Drilling and filing is not fun, takes hours. A jigsaw is OK but hard to turn in such a small circle. I am sot of tired of making ugly holes.

A punch is great but big bucks. I borrowed a punch for a 6" hole in 1/8" aluminum for a CRT. What an arm twisting cheater bar experience! But where can a punch set be had that does not cost $100 a piece?

Recently I had some parts cut by a water jet guy for reasonable.
Makes a perfect cut regardless of the shape.
A circle would be no problem.
I can easily get this done in Tulsa of all places.

[Pete, WA2CWA]

I've used the General Tools Model 55 circle cutter since the 60's. The thing will cut round holes from 1 3/4 to 7 7/8 inch in heavy aluminum and sheet steel with ease. It's designed to work in a drill press.

[W7TFO]

Well Pat, with the message system FUBAR I'll resort to posting here .

Let me know what size(s) you need, and I'll loan them in my next mailing .

I have most every round Greenlee size up to 5-3/4" .

No point on trying to maim yourself or your budget...

73DG

[Opcom]

Thank you! I sent a regular e-mail. Note my e-mail addr has changed, listed therein.

[VE1IDX]

What is the easiest way to make a nice looking tube socket hole for big tubes like the 813 or 4X150, or even monsters like the 3CX3000?

Prefer a method that does not involve stripping the whole chassis.

Fly cutters on thin metal have frustrated me. The metal flexes and bends and the cutter gets hot and dulls. Doing it wrong, no doubt.

Drilling and filing is not fun, takes hours. A jigsaw is OK but hard to turn in such a small circle. I am sot of tired of making ugly holes.

A punch is great but big bucks. I borrowed a punch for a 6" hole in 1/8" aluminum for a CRT. What an arm twisting cheater bar experience! But where can a punch set be had that does not cost $100 a piece?

FWIW I use a Black & Decker scrolling jigsaw. It has a "steering wheel" on top that allows the blade to rotate 360 degrees. It eliminates most of the problems of fitting and swinging in tight spaces. I also use a reverse cut blade that cuts on the down stroke but you have to hold it down pretty good. A fine blade and high stroke speed but slow feed pace makes nice cuts and the scroll action makes it really simply to cut even really odd shapes.