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Drilling a 4" diameter hole.

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Forum topic by opticsguy posted 11-28-2021 10:38 PM 837 views 0 times favorited 27 replies Add to Favorites Watch
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opticsguy

14 posts in 1226 days


11-28-2021 10:38 PM

Needing to drill a 4” diameter hole through 5” thick wood. These need to be perpendicular to the surface and fairly accurate. Was thinking a 4” diameter forstner bit

Any recommendations for tooling and etc? Thank youi!!


27 replies so far

View Eric's profile (online now)

Eric

2817 posts in 1204 days


#1 posted 11-28-2021 10:48 PM

That is a big hole to drill. Are you using a drill press or hand drill? With a drill press you could use a hole hole saw in stages, at each stage drill a few smaller holes with in and break the meat out if the hole with the grain. Then back to a 4” hole saw.
I would a small long drill to create a pilot Al the way through first.

-- Eric, building the dream

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splintergroup

6319 posts in 2553 days


#2 posted 11-28-2021 11:13 PM

4” is fairly common for recessed light fixtures so you might be able to find a reasonable quality hole saw.

Beyond that, 5” thick, yowza!

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nickbatz

894 posts in 1411 days


#3 posted 11-28-2021 11:22 PM

If your drill press can reach 5” and has enough muscle to do it with a forstner bit, sure.

If not – and I’ve never tried this – but here’s one thought:

1. Use a hole saw to make a template for a plunge router. You could use a scrap piece of plywood, for example.

(“Hole saw” is the actual term – if you look it up you’ll see what I’m talking about.)

2. Clamp the template to your 5” piece in a way that you can put it in the exact same spot on the other side of the board when you turn it over (see step 4).

Alternative: I think the hole saw will cut out a circle with a center hole (it’s been years since I used one, so I forget). Put that circle back in and use the center hole to drill through the board so you have a center hole on the other side to align the template when you turn it over.

3. Cut as deep into your 5” piece as you can with the hole saw, and route out the wood inside the cut using the template.

4. Keep doing that until you get as far as you can before the router runs out of room, then turn it over.

Hopefully you can get reach 2-1/2” deep. If not, you’ll probably have to use some kind of hand saw to remove the remaining piece.

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Madmark2

3247 posts in 1919 days


#4 posted 11-29-2021 04:19 AM

Pilot thru. Use 4” hole saw as far as it will go. Chisle slug out as best you can. Repeat. Do both sides.

-- The hump with the stump and the pump!

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Lazyman

8755 posts in 2718 days


#5 posted 11-29-2021 06:11 AM

I would probably drill a pilot hole the same size as the pilot bit of the hole saw and then drill half way in from both sides. If you get a deep enough hole saw, you might not have to do any chiseling and you won’t get any tear out as you break through.

For a cleaner hole and to minimize burning, drill several relief holes just inside the wall. This gives the sawdust a place to go, making the process easier.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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CaptainKlutz

5148 posts in 2825 days


#6 posted 11-29-2021 06:45 AM

+1 forstner bit is best

Going to be a very expensive hole, considering a high quality long reach Bormax has retail price over $1000!
Carbide Processors has it for only $369?

Cheaper tooling would be Chinese made Carbide bits. Shopfox and other sell the Roman Carbide brand.

Only way to safely and accurately drill a hole that large is in the drill press.
If you don’t really care about accuracy; still need a 2 handed Milwaukee Hole-Hawg Drill and must be young enough to enjoy physical punishment of using one.

A much slower and time consuming method is as MadMark and Lazyman suggest with hole saw. Drill a pilot all the way thru, drill some swarf relief holes on plug side, use hole saw to cut ~1.5” deep, chisel out plug, and repeat twice on each side.

What ever method is used, be sure to keep the cutting edges cool. It is easy to overheat cutting edge on deep hole, especially in hardwoods or wet pitch filled softwoods. Clear chips often. Use compressed air to clear chips can also help cool edges too.

Best Luck!

-- If it wasn't for bad luck, I wouldn't have no luck at all, Doom, despair, agony on me… - Albert King - Born Under a Bad Sign released 1967

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Madmark2

3247 posts in 1919 days


#7 posted 11-29-2021 07:29 AM

4” forstner is going to need big drill press. Mine runs out of gas at 2-1/2”, you’ll need a monster to turn a forstner that size.

4” hole saw bit can be hand drilled with a corded VSR drill, plumbers do it all the time, although not normally thru anything thicker than 2X stock.

-- The hump with the stump and the pump!

View TopamaxSurvivor's profile (online now)

TopamaxSurvivor

23254 posts in 5006 days


#8 posted 11-29-2021 08:47 AM

It did not say if it is in hardwood or soft. I have drilled a few 4” plus holes in softwood. A Forstner Bit will be interesting to force through without a screw point. A wood auger will be nearly impossible to control the drill motor. If you are using a drill press, you will not need a pilot hole for hole saws. I would hole saw a series of smaller holes and work up to 4 inches. You can chisel out the scrap as you go. Keep the hole saw cool.

If I were using a handheld Hole Hog or another drill motor, I would drill the pilot hole for the hole saws. Start all of the hole saws working up to 4” about 3/4” deep. Remove the pilot drill and progress keeping the hole saw cooled and chiseling out the waste.

Good luck. I can’t imagine doing it in hardwood.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View sunnybob's profile

sunnybob

95 posts in 96 days


#9 posted 11-29-2021 10:40 AM

Just to be different…. Mark out the hole on the wood, saw the wood into two halves on the bandsaw, including going around the hole.
Stick the two halves back together again.
I’ve used this system several times.

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LeeRoyMan

2375 posts in 1057 days


#10 posted 11-29-2021 01:40 PM

I would turn a 4” hole on the lathe, then take the hole and glue it into my piece.

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Lazyman

8755 posts in 2718 days


#11 posted 11-29-2021 01:46 PM



I would turn a 4” hole on the lathe, then take the hole and glue it into my piece.

- LeeRoyMan

You just described what a Ringmaster does.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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LeeRoyMan

2375 posts in 1057 days


#12 posted 11-29-2021 01:54 PM


I would turn a 4” hole on the lathe, then take the hole and glue it into my piece.

- LeeRoyMan

You just described what a Ringmaster does.

- Lazyman


I use the new and improved Holemaster instead…
It comes with handles, making it easier to hold the holes.

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Lazyman

8755 posts in 2718 days


#13 posted 11-29-2021 04:14 PM

It is really hard to get the glue to stick and clamping is a bitch.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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LeeRoyMan

2375 posts in 1057 days


#14 posted 11-29-2021 04:36 PM


It is really hard to get the glue to stick and clamping is a bitch.

- Lazyman


LOL,
Clear glue works best, but clamping IS difficult. :)
Pneumatic air clamps maybe..

View splintergroup's profile

splintergroup

6319 posts in 2553 days


#15 posted 11-29-2021 05:36 PM

A Zen optimist would say the hole is already there, one just needs to clean the saw dust out to reveal it.

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