Cutting Holes In Sheetmatal

[EdK]

(05-17-2016, 05:44 PM)TomG Wrote: or just drill a bunch of small holes around the periphery, knock it out and file to make it pretty.

This is kind of what I'm leaning towards, even though I'm a lazy bastard.

Ed

[Vinny]

Forget the HF set, it doesn't go to 2.5"

[wawoodman]

I would use the hole saw. Of course, I've been collecting them for so many years, there aren't too many sizes I don't have...

On the other hand, http://www.ebay.com/itm/Greenlee-2-1-2-D...SwYmZXHm0T

[EdK]

(05-17-2016, 06:53 PM)wawoodman Wrote: I would use the hole saw. Of course, I've been collecting them for so many years, there aren't too many sizes I don't have...

On the other hand, http://www.ebay.com/itm/Greenlee-2-1-2-D...SwYmZXHm0T

That's definitely not an option.  

I have a 2.5" hole saw and may try it on the first one and if it goes well I'll use it on the second one. I've mostly used hole saws on wood so don't have much experience using them on metal.

Ed

[Vinny]

or http://www.ebay.com/itm/Greenlee-2-1-2-C...SwZJlXNNKz

[arvidj]

(05-17-2016, 05:40 PM)DaveH Wrote: The way I have done it is to place the part to be cut on a thick piece of wood on the floor. Then stand on it (nicely)
Use an electric hand drill on the slowest rpm with a bit of cutting fluid and 'waggle' the drill in a slow circular motion. Slow and more slow.
The pitch of the teeth is fine - one tooth will travel 8'' along the metal in one revolution.

When I say the pitch of the teeth is fine, I don't mean the physical placement of the teeth is fine, I mean it will be fine to use.  
Although the pitch may seem coarse, the application it is being used for the pitch is OK.

 
DaveH

+1 on Dave's approach. The slower the better. I'd put it on the drill press, make sure everything is firmly attached to the table, turn the variable speed pulley down as far as it would go ... about 150 rpm i think ... then turn the vfd way down. Light presure,some lube and patience.

Having put a number of 4.5 inch speaker holes in car door panels the excitement usually occurs when one side breaks thru, with the key being to not let the teeth catch on the breakthru edge.

[pepi]

(05-17-2016, 05:40 PM)DaveH Wrote: The way I have done it is to place the part to be cut on a thick piece of wood on the floor. Then stand on it (nicely)
Use an electric hand drill on the slowest rpm with a bit of cutting fluid and 'waggle' the drill in a slow circular motion. Slow and more slow.
The pitch of the teeth is fine - one tooth will travel 8'' along the metal in one revolution.

When I say the pitch of the teeth is fine, I don't mean the physical placement of the teeth is fine, I mean it will be fine to use.  
Although the pitch may seem coarse, the application it is being used for the pitch is OK.

 
DaveH

That's the way I have done it, slow speed is the key, folks run hole saws to fast. 

Another description of the drill motion, rock the drill in a slow circular motion.

If you spin a coin as it slows down it has a rocking motion.  As the coin is rotating only part of the coins circumference is in contact with the surface, that's the way the hole saw needs act.

Greg

[Dr Stan]

Ditto on pepi's & DaveH's comments.  I'd go with the DP as you'll have much more control over the entire process.

One other option would be a plasma torch & a circle cutter if that is available.

[Hawkeye]

When I'm doing service upgrades, I sometimes need holes around that size. I've done it quite a few times with a hole saw. Since I'm not in my shop at the time, I use my 1/2" battery drill (on slow, of course). It's always worked for me. The metal thickness is around what you have, maybe even thinner. It's not a really precise hole, but a mill/drill should do better.

[awemawson]

If used carefully it's surprising what a good hole saw can do. I now only buy Starrett. Go slowly and use plenty of cutting fluid. I've cut 6" holes in 1/8" plate to mount coolant motors, and 35 mm holes in 1" plate for attachment pin holes for my digger. (and many things between these extremes)

It is quite surprising how good a finish you actually can achieve on thick plate with such a crude device.