Hole saw technique?

[zakthor]

I put a 6" hole through the wall of my 50 year old house to hook up portable air conditioner.

All went well except for using the 6" hole saw with arbor bit.

I used an old dewalt 1/2" corded hand drill with a side handle.

Drilled a pilot hole, then started on the inside. Drywall was fine, then insulation. Once 7" deep I hit the first 3/8" plywood, then a second 3/8" plywood, then 1/2" of vertical cedar. I did the final outer layer of shingles from the outside.

The plywood was so difficult to drill. Very hard to keep the hole saw flat against the plywood and it would bind in the groove causing drill to buck. Once the blade was through some of the plywood it was binding really bad and impossible to hold steady.

Best approach seemed to be letting drill spin up with lowest power, lightly contact and hold as steady as possible until it bound. Usually it bound in less than 10 seconds.

Took me about 90 minutes to make the hole but some of that was working with key saw to get pieces out.

I imagine some tripod thing to make a horizontal drill press would be great but I don't have that. What is the trick? Build a jig? I got a great hole but the process sucked.

Would have been more comfortable to use a clutched driver so drill didn't try and kill me every time the bit stopped.

[Rusty Heap]

wonder if some WD-40 would of acted as a cutting fluid and lube?

[911 Rod]

I've found just rocking it back and forth worked well.
I also used a more robust drill.

[GH85Carrera]

Hole saws can be a real challenge. I have an old (1950s) 1/2 inch hand held drill that will throw the operator right on his butt and make you punch yourself with the torque if you don't let go fast enough. And you sure don't want to lock the power on!

I drilled some 2.25 inch holes in some 2x4s to run the central vacuum system in my attic. I was pushing straight down, and it would spin me like a top if I got just a little off center.

It is not a fun job.

[LEAKYSEALS951]

This hurts my wrist just thinking about it.

[zakthor]

Originally Posted by Rusty Heap

wonder if some WD-40 would of acted as a cutting fluid and lube?

Hmm. Yeah the teeth on my hole saw were really sharp and aggressive, like needle sharp. They dug in fast and then bound. Lube might have helped prevent that. Marine grease.

Now I'm wondering if I should have tried running it backwards...

Originally Posted by 911 Rod

I've found just rocking it back and forth worked well.
I also used a more robust drill.

Robust? This thing was maybe too robust.

Another idea: maybe if I'd used an extension I could have better wrapped myself around the drill to support it. As is it was me gripping the drill handle and the cutting happening in the wall.

[908/930]

6" dia is quite large to do by hand, there are drills intended for drilling larger holes like a hole hawg where the handle gives more leverage. A old 3/4 drill with a 4' long pipe handle and two people would probably work. Jig saw would have probably been easier for that size hole.

[herr_oberst]

Originally Posted by 908/930

6" dia is quite large to do by hand, there are drills intended for drilling larger holes like a hole hawg where the handle gives more leverage. A old 3/4 drill with a 4' long pipe handle and two people would probably work. Jig saw would have probably been easier for that size hole.

I was just about to say, you needed a hole-hawg. And those will break your arm if you're not braced.

(And the jigsaw or a sawzall with the correct blade and a deft touch - would have - could have - been a good second choice.)

[MBAtarga]

Were the teeth sharp when you finished the hole?
Plywood glues can be brutal on non-carbide teeth. It's likely the heat on the hole saw caused metal expansion which also caused additional binding and even more heat.

[Nickshu]

Start w/ smaller hole saw and the double them up on the arbor as you go up in sizes.

Like this:
https://youtu.be/9-pBlZa1RBI

[LWJ]

I have many construction clients. Big hole saws take skill to run and still send lots of folks to the ER.

If you are done with your hole. Consider it a win.

[zakthor]

Originally Posted by LWJ

I have many construction clients. Big hole saws take skill to run and still send lots of folks to the ER.

If you are done with your hole. Consider it a win.

Thanks for this. No er but the whole process felt dangerous. Figured I was doing something stupid, and maybe it was. Hole is perfect.

Originally Posted by MBAtarga

Were the teeth sharp when you finished the hole?
Plywood glues can be brutal on non-carbide teeth. It's likely the heat on the hole saw caused metal expansion which also caused additional binding and even more heat.

I don't think so. I spent way more time recovering from the binding than actually drilling. Teeth are still super sharp. Drill was toasty though, had to stop and run it to let the hot air out because the heat was hurting my silky hands.

[NY65912]

You cannot use too much pressure. You have to feed slowly and let the teeth cut. I have done a ton of holes in all sorts of materials. You need poser but have to finesse the feed rate.

We use Hole Hawgs on jigs strapped to the pipe we're punching holes in for mechanical tees and its all about the feed rate. We also use magnetic drill presses on steel beams with annular cutter, same principle.

I screwed up arm when I was drilling 1" holes through joists with a Milwaukee ˝" Magnum Drill, thought it was gonna rip my arm off. I was pushing too hard.

[908/930]

Yes Zakthor you were likely using it correctly, it would be better if the manufacturer of the hole saw had a different rake on the front of the cutter to make it less likely to bite, not as efficient but. Pretty sure the people designing these never actually use one by hand. To not get hurt is another accomplishment. Some of the new high torque drills have sensors in them so if the bit catches it will sense the motion in the drill and shut it down, my large Hilti TE80 ATC-AVR has this function, for good reason.

[masraum]

As has been stated, using a larger diameter bits get harder and harder to do in handheld drills. Ideally, you'd have some sort of jig or press that could be used. The issue is that if the angle of the drill/bit ever changes, then things can get dicey really quickly. going from 1/8" -> 1" -> 3" -> 6" each jump is huge. And it sucks no matter what, whether it's a hole saw, paddle bit, or Forstner bit.

Take it slow, be careful, use a more powerful drill that's got better/more holding options (side handles and the like).

And yeah, I know a guy that broke his wrist using a drill that caught and twisted his hand around.

[dad911]

Originally Posted by zakthor

.....Best approach seemed to be letting drill spin up with lowest power, lightly contact and hold as steady as possible until it bound. Usually it bound in less than 10 seconds.
......

If a bit is not making chips, it's just making heat. Was the drill variable speed or gear reduced? 6" hole saw should not spin fast. I still have an old corded Milwaukee angle drill for stuff like that, but I'd probably use a sawzall with a metal blade (so as not to chip the wood siding) and once the drywall was cut to make sure there are no wires or pipes, I'd probably work from the outside.

[BK911]

I tried hole sawing through some hardy plank.
Ended up drilling dozens of 1/8" holes around the perimeter, then finishing up with the hole saw.

[Zeke]

I won't even buy a 6" hole saw blade. I might if I had to install retrofit can lights in drywall. Then I'd get the masonry model. Not really perfect for drywall but safer. On DW one could use a tooth model in reverse. DW can bite you too. Plywood? That's a big 10-4 good buddy.

[Chocaholic]

Perhaps a peripheral query..but a 6” hole is a somewhat permanent modification for a portable AC vent. Was there no window to vent it through with a window kit?

[peppy]

My uncle had a tool for this called a hole hawg. From what I understand it would break your arm if it was not braced against something solid.