Best Way to Expand/Increase Diameter of Existing Panel Hole

[Todd, KA1KAQ]

I have a bit of a predicament to figure out. I've got a panel with an existing hole maybe 3/4 inch or so (think of one of those large pilot light jewels nearly the size of a quarter) and I need to expand it to a larger opening, around 2 inches or so. Along the lines of the meter opening on a Ranger or such.

The panel is steel, not terribly thick but thick enough that you can't flex it by pushing on it. And it's fixed in place. Removing it is possible, but requires some serious dis-assembly. If it ends up being the only way to get it done I'll have not choice, of course.

I've got one of those nifty cutters that fits in a drill and tries to break your wrist when it catches, but it needs a small pilot hole to keep it aligned. The opening is already too large for that. And torching is out since it needs to be a precise opening to hole the meter housing properly.

Some sort of reamer would appear to be the solution, just not sure that make them that large. Figured folks here would be the best bet for finding a solution if one exists.

[w8khk]

Two options:

For this task, I prefer a chassis punch.   Less vibration, nice clean cut hole, even in steel.  But the punch is expensive, especially if you use it only once.

Make the pilot hole smaller.  I have used a fly cutter like you have in the following manner:  Use machine screws to bolt a scrap plate of steel, or thick aluminum, to the back of the panel.  Drill a pilot hole of the proper size in the exact location.  Then use the fly cutter to make the larger hole.  If possible, drill the smaller meter mounting holes first, then mount the scrap plate using those holes.   Alternatively, you could mount the backing plate using holes within the circle you are cutting, far enough in that the fly cutter will clear the machine screws.   If you have other holes in the panel outside the circumference of the proposed meter hole, use those holes to mount the plate, and it will be more stable when the hole breaks through the panel.  I would be concerned about vibration from the fly cutter damaging fragile components behind the panel, if any exist.

[Ralph W3GL]

Hey Todd

If you can get behind the panel easily, see if you can find the
size for your hole in a Greenlee knock-out punch...  (Check
an electrician friend to possably borrow one for the job)

Then twist the bolt with one of your Crescent Knuckle Busters.
Use a big one to get the leverage to cut the steel...

     

Edit:  Yeah, Ricks got you covered... But, fly cutters on hand drills
          really are asking for trouble

[K9PNP]

The only way I have been able to use a hole saw in that situation is if the panel is loose and I can use the drill press:  clamp the panel where you need it and not worry about the pilot hole.  

Don't own any chassis punches meter-hole size.  And unless you have a good quality Greenlee with the good bearing using one that size on steel could be fun.

I have also done it by marking the outline of the required hole and using narrow blade on a hand-held saber saw to rough out the opening then finish it out with a bastard file.  Labor intensive, but it works.  You can make it as accurate as you want to if you take your time.  Of course, what else is around the original hole may cause you to modify that method somewhat; vibration and cuttings are definite problems at times.  Have done it with just the files, but that is usually reserved for minor size adjustments unless you have more patience than I.

Hopefully, someone else has discovered a better, easier way.

[w8khk]

Edit:  Yeah, Ricks got you covered... But, fly cutters on hand drills
          really are asking for trouble

Yes, as Mitch says, it is safest to have the panel clamped down in a drill press.  But that of course means removing the panel. 

When I use a fly cutter freehand, I use an 18 volt Porter Cable variable speed drill.  This one has fine control at very low speed with reasonable torque, so it is much safer than the higher speed hand drills.  Use very little pressure, and take your time.  A bit of oil on the steel panel helps keep the cutting tip sharp.

As stated previously, Greenlee punches make this a trivial task.  Lubing the bearing and the threaded screw on the punch makes it cut through steel like it was butter.

[MikeKE0ZUinkcmo]

I've used all three mentioned methods for making holes and have settled on hole saws for a variety of reasons.    First, the initial tool cost is nearly the same as a single Greenlee Chassis punch, but additional sizes are A LOT less expensive.   Second, there isn't any concern about the cutter digging in, and the associated havoc THAT causes.   Third, No having to fiddle getting it adjusted to the proper diameter.   Fourth, no big worries using them in a hand held drill, and having to clamp the work piece down.

Don't "chince" on the tool quality though, get the good one it'll outlast you for sure.   Good bi-metal hole saws come in diameters from around a half inch up to over 6 inches or so, in 1/16" increments.   Keep in mind though that SPEED as a general rule is the enemy of cutting tools so whatever you use you want less than 6 to 7 hundred RPMs or so.

One of the other fellows mentioned installing a patch, but I'd just use a couple of POP rivets to hold it,  then re-establish your pilot hole position.    Since you're working with steel, the job can be a little cleaner if you place a several of those small rare earth magnets just under the hole to catch the chips.

Good luck on your project.

[WBear2GCR]

Todd,

can you post a pic of the exact item?

I'd go with Mike's idea for hole saws, but much depends on if you can mount with screws or clamp a bit of backer plate steel or aluminum to the panel. And then what is behind that hole. Then you can drill the pilot hole for the hole saw in the backer plate and do a slow cut. If you own a very big geared down drill, one with that extra handle to keep it from rotating when lugging through major heavy cuts by hand, that would be ideal for hand held cuts like this with a hole saw.

I just found a neat Miller's Falls monster drill, massively geared down, heavy cast metal body at a yard sale... has what looks to be 3/4" pipe threaded into the side for that extra handle.

                       _-_-

[KA2DZT]

Use a Greenlee punch.  A hole saw can be used but you need a 1/4" pilot hole.  You have too large a hole there now.

Here is what you can do.  Get a small piece of scrap metal,  drill two small holes, one on each side of the existing hole.  Drill same two holes in the scrap piece.  Nut and bolt the scrap piece over the existing hole.  Now drill a 1/4" pilot hole through the scrap piece.  Now you can use the hole saw.  You'll need a slow speed drill for the hole saw.

Work slowly, you should be able to drill the larger hole.

Fred

[W7TFO]

Hi Todd,

I have a pretty complete set of Greenlees, from 1/2" to 5-1/2".

Opcom did his 'scope hole' with the big one a while back

I'll be glad to loan you right one for your job, and you probably won't need to take anything apart...

73DG

[N0WEK]

I use these...

http://www.ebay.com/itm/Malco-HC1-Sheet-Metal-Hole-Cutter-for-1-4-Inch-or-Large-/370838462310?pt=LH_DefaultDomain_0&hash=item5657b1df66

http://malcoproducts.com/product/hvacr/metal-duct/power-assisted-cutters-shears/gold-standard-malco-hole-cutters

They make chips, which the Greenlees don't but the are infinitely adjustable from 2"-12" and the large model does 2" - 20".

The same thing applies to creating a new centering hole with a metal scrap.

[W1RKW]

Not the best way but if using a hole saw: Since you are enlarging a hole, make a template with another piece of stock of the desired hole size, then clamp that into place on the panel and start cutting. I had to enlarge a hole for a new lock set in a door. I used the above method to enlarge.

If you have access to a drill press that would be even better.

[WD8BIL]

Nibbler and a file.

[W1ATR]

Depending on the brand of arbor you have, mine are Lennox brand, enough threads stick through the installed holesaw to screw another smaller holesaw on a couple turns and use it as a pilot in the existing hole. I do it all the time with ac linesets. 

[Todd, KA1KAQ]

Not a bad idea, Jared. Hadn't thought of that. Trying to mount something to drill a new pilot hole and have it come out right is about an impossibility for my skill level.

Seems like the punch would be the easiest/fastest/cleanest approach. Not sure why I'd put them out of my head, probably because every time I needed a Greenlee, it was a one time shot and the cost was too high. Seems perfect in this case since removing the panel isn't easy.

Thanks for all the ideas, and apologies for not responding sooner, was traveling. TNX too for the offers of loaner punches. If I can't pick one up reasonably, I'll take one of you up on it.