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Boring deep pilot holes for vases

Randy Anderson

Randy Anderson

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I'm looking for ideas on boring deep (up to 25") pilot holes for hollowing large vases and keeping them on or close to center. It's very hard to keep the pilot hole on center once you get out past 15 inches or so. If you've ever hollowed something very deep with a pilot hole opening that is off center you know how challenging it can be. You're already extended far off your tool rest and if your opening is way off center it can be brutal to try and get it back centered to finish hollowing. Plus, getting the bottom and bottom curve transition consistent is key to minimizing cracking.

I currently use Milwaukee switchblade bits for doing my pilot holes. The largest I use is 2 9/16". I drill a 1/2" center hole to about 5", then switch to the Milwaukee bit, then drill another 1/2" hole, then switch again, etc. Things usually go well for the first 15 inches or so. The Milwaukee bits have a self feed tip that fits well into a 1/2" pilot hole. I repeat this step process all the way to the bottom. Once you get long extensions on your bits a slight wobble can easily begin to become a spiral, especially if the pith and wood grain begin to lead the bit astray. I drill on my lathe with a Jacobs chuck and #2MT.
 
Are you familiar with the tally ho boat building project on YouTube? They have had to drill some very long very accurate holes. I sort of remember them doing it with an auger with the lead screw ground off. Might be worth binge watching the entire saga to see what they did...
 
Trent Bosch has a gun drill for hollowforms. You can see how it works with Air to clean the shavings. Fast straight holes.

You can extend the depth by modifying the handle (after opening the hole)
You can by longer bits

Gun Drill – Trent Bosch Tools

trentboschtools.com trentboschtools.com

You might be reaching diminishing returns on drilling deeper. Just use your hollowing tools on center assuming you are using something like the jaimeson system.
 
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The old method for this was a hollow center in the tailstock and you used it like a drill bushing. In your case this will take some effort to work around the extensions. You can get gun drills with coolant holes all the way through them. For wood you use compressed air instead of coolant to blow back the chips. But at your depth of 25", runout of the hole is not going to be eliminated. I would work in stages for about half that depth, then use your hollowing rig. Chip removal from 20"+ is going to require more relief than just sending a drill bit that deep. You will need a bigger cavity to handle the chips. Another method would be to hollow from both ends. For weed pots with really tiny entrance holes, I turn a tenon on the bottom and then part off a disc from the bottom of the blank. Hollow into the vessel from a larger hole in the bottom. Then glue in that bottom disc back in, making sure to line up the end grain. Then you can flip around your blank and hollow out the top half, driving the blank on that tenon you made on the bottom disc. Here is a used .5" x 22" gun drill for $30. https://vbindustrialsupply.com/prod...b19c81250437cd47a2f30330f0ed03551c4efdaf3409e
 
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Isaac, I found the video in their library of them using the long auger bit. They certainly were able to drill a straight hole. Something to consider for my initial pilot hole to guide the much larger dia switchblade bit. Thanks.
 
Al, I have a variety of hollowing tools depending on what I'm doing but my main one for deep hollowing is an 1 1/4" OK Spindoctor boring bar. I've pondered putting a bit on the end, locking the bar into position with the frame and tool rest support tube and just driving it in manually for my initial hole. I believe if I can get an initial 1/2" straight hole to the bottom the switchblade bit will follow it well enough.
 
If you do want to try gun drills this is my solution. The drills with the mounting thread in 3/8", 1/2" & 3/4" were purchased at Boeing surplus when I went to the symposium in Tacoma. The process of getting the drill out & hooking the air hose takes more time then the actual drilling.
DSC00849.JPG
 
Dean, there's a plan and goal behind my efforts. I have an opportunity to place some large pieces into some galleries plus I like making what I call floor vases - 24 to 30 inches tall. I've been on the journey to get there for about a year now. Doing pieces of this size and caliber is not something many people take on. That's what drove my initial interest. It's fairly unique and it's a whole different category of wood stock requirements, equipment to move and handle them, tools to turn and hollow, boiling, drying, finishing, etc. The list of things needed has been a real journey but a fun one. I'm almost there.

Here's a 26" black cherry I recently finished turning. A long way from done but should be a nice piece.
 

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Randy, about 2 years ago there was an online 'travelogue' of someone turning a 5 or 6 foot deep vase. It came out in periodic installments and was fascinating to watch, even though I could never imagine turning such a piece. Maybe someone on here can remember where to find the videos, and will share. If you haven't seen them, it would be 'must watch.'
 
Randy Anderson said:
I've pondered putting a bit on the end
Click to expand...
I use a boring bar from Advanced Lathe Tools (Steve Sinner's company). The bar is made to accept a Forstner bit, which is secured in an adapter for the bar (also from Advanced Lathe Tools). I have drilled to 22" with a 1 3/16" Colt Maxicut bit. The bar is pushed in and pulled out, about 1" at a time. It actually goes fairly quickly, which I attribute to the quality of the Maxicut bit. If the bit enters the HF on center, my depth holes stay on center. The other important factor is that the boring bar is very stout. With all that said, I would suggest seeing if you can adapt your boring bar to accept the drill bit.
 
I second the gun drill. They are self-centering. My gun drills are 3/4" on the mounting end so you might adapt them to your boring bar. Heck, I might try to adapt some to my boring bar. Thanks for the idea!
 
Darryn Achall said:
I second the gun drill. They are self-centering. My gun drills are 3/4" on the mounting end so you might adapt them to your boring bar. Heck, I might try to adapt some to my boring bar. Thanks for the idea!
Click to expand...
Note the gun drills have a hole thru them for coolant when using them with the intended metal however they do an excellent job on wood also and that coolant hole will work well to clear the chips if you apply compressed air. The use of a boring bar to hold the drill would not have a way to connect an air supply. The most accurate method I have found is to make a shallow starting hole then push the drill in by hand with air applied and the drill will self guide.
 
Just a note about gun drills. The tips are almost always ground for cutting metal. Trent Bosch sells gun drills optimized for wood. The tip geometry is complex, there looks to be 5 or 6 different angles, so you can't simply stick it in a Drill Doctor and change the bevel yourself. Using a metal-cutting tip still works but you have to push harder. Watch Trent's video on using it, he makes it look effortless. My gun drill requires a lot more force. Sterling Gun Drills has a lot of info on their web site
 
are your turnings thin, as well as tall? I have drilled some pretty deep hollow forms, but the bit drifting somewhat wasn't an issue because I had plenty of meat left in the sides of the piece... piece....
 
Don Wattenhofer said:
Note the gun drills have a hole thru them for coolant when using them with the intended metal however they do an excellent job on wood also and that coolant hole will work well to clear the chips if you apply compressed air. The use of a boring bar to hold the drill would not have a way to connect an air supply. The most accurate method I have found is to make a shallow starting hole then push the drill in by hand with air applied and the drill will self guide.
Click to expand...
Yes, you would need to do some machining to adapt the gun drill to whatever equipment you want to use. I also use the gun drill by hand with an air hose fitting adapted to the end. I have seen a tailstock piece made with an I-beam that allows the gun drill to be fed through a sleeve in the I-beam.
 
I use a gun drill for drilling the hole in lamp bases. My bases are basically solid wood......12" tall or so....maybe a little larger. I use a "starter" drill in a drill chuck mounted in the tail stock. Just to help me get on center.
Then I hold the gun drill up there and place my compressed air up to the opening on the drill. Start drilling. They work very well. I have never modified the gun drill tip.
 
Hugh said:
I use a gun drill for drilling the hole in lamp bases. My bases are basically solid wood......12" tall or so....maybe a little larger. I use a "starter" drill in a drill chuck mounted in the tail stock. Just to help me get on center.
Then I hold the gun drill up there and place my compressed air up to the opening on the drill. Start drilling. They work very well. I have never modified the gun drill tip.
Click to expand...
I too have not modified the cutting tip and I don't have to use excessive force to push the drill in like someone had previously mentioned. I have had difficulty pushing it in if I tried to drill without the compressed air though.
 
Darryn Achall said:
I have seen a tailstock piece made with an I-beam that allows the gun drill to be fed through a sleeve in the I-beam.
Click to expand...
I would think that the sleeve would need to be precision machine tool accurate not your typical wood lathe accuracy. The gun drills I have are only at the drill size at the cutting tip so the sleeve would only work to start the hole and when the cutting tip passes through the sleeve it is back to self guiding/centering.
 
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Don Wattenhofer said:
I would think that the sleeve would need to be precision machine tool accurate not your typical wood lathe accuracy. The gun drills I have are only at the drill size at the cutting tip so the sleeve would only work to start the hole and when the cutting tip passes through the sleeve it is back to self guiding/centering.
Click to expand...
Custom deep bore setup An example of a custom tail stock and rail for deep boring in wood. It can get as complex as you would like to make it.
 
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