Drilling Deep HF

[Tom Storey]

A question or two on preparing a deep hollow forms. Do those of you who turn deeper hollow forms, say to 12 inches deep, drill the centre down to near the full depth? And if you do, what is the drill bit type and diameter of choice?
My thoughts are to use a ½ inch or so forstner bit with an extension chucked in the tail stock. Forsner bits come with flat and sawtooth bottoms...which would be better for this 'deep' drilling. Types of wood I'll be using are walnut, cedar, birch and like that.
Any hints, pointers and cautions on this operation would be much appreciated!

Thanks, Tom

[Nathan Hawkes]

Tom, I haven't done hollow forms that deep, but I have used an auger bit to drill a depth hole in pieces that I can't core with the mcnaughton. I think it is a bit more stable than a forstner bit with an extension, but I already had the auger bit before needing it to bore a hole in a turning blank.

[Kirk Miller]

Tom I have drilled my HF with a forstner bit in just the fashion you spoke of and it does work. You have to be patient and go really slow though. The bits heat up very fast. On the other hand the last HF I did I used nothing but a Sorby Multi Tip. I think it wokred pretty well and maybe went a bit faster than with a Forstner. Hmm Just reread your post. I havn't done any HF's that are that deep yet. Good luck

[Jeff Nicol]

Tom, I use my own creation that uses a reground drill bit that I use as my hollowing tool. If you go to the gallery sticky you can see some pictures of it and there is a video of me using it on Youtube. It can cut, drill and get you to the depth you need. In my post where I met Steve Schlumpf he shows me with my very deep hollowing tool and says I look like Ahab waiting for the whale! There a lots of ways to get there when hollowing you have to find the one that fits you best.

Jeff

[George Guadiane]

Tom, I use my own creation that uses a reground drill bit that I use as my hollowing tool. If you go to the gallery sticky you can see some pictures of it and there is a video of me using it on Youtube. It can cut, drill and get you to the depth you need. In my post where I met Steve Schlumpf he shows me with my very deep hollowing tool and says I look like Ahab waiting for the whale! There a lots of ways to get there when hollowing you have to find the one that fits you best.

Jeff

I have seen this method and it works well!
I use a forstner bit to start a hole - if you are going for 12 inches in depth, a one inch hole is certainly small enough - once I have a starter hole, I use a modified auger bit (with the screw tip ground off - otherwise it's WAY too aggressive) to drill to depth... The old augers come in some pretty remarkable lengths, and 12 inches isn't too difficult to drill. Properly sharpened, the finished hole bottom is very good, no pints sticking down, and the auger clears the chips nicely.

[Bernie Vail]

The old time auger bits I have seen and used have a square shaft end to fit the v-shaped jaws of the old time brace. How do you chuck the bit in a lathe? Grind off the flats on the bit and use a Jacobs chuck?

[Mike Minto]

i use a forstner bit, too, about 1" on an extension to enter my hollow forms. sometimes i have to bore in about 5", turn and hollow, then re-bore to a deeper depth with the forstner - sometimes the bit will catch and rotate my chuck in the tailstock, but not too often, or i'll do it in stages if i'm boring so deep that the extension flexes too much. clear those chips often, and watch the heat build-up! mike

[Richard Madison]

As mentioned, the chips do not clear easily behind a forstner, so you must back the bit out frequently to clear the chips. If the chips pack sufficiently behind the bit it can actually become trapped in the hole, and you may have to turn down to the bit to recover it. Of course this has never happened to me. Yeah, right. An auger, or aforementioned multiple stages of drill and turn, drill and turn, should work.

[Wally Dickerman]

I use a hand held 3/8 in. 16 in. long, regular drill bit. It has a handle shaped about like a door knob. Makes it easy to push it in with the palm of my hand. Drill an inch or two, pull it out to clear chips, then back in again. Takes no more than a minute or two.

With a deep piece you have to proceed carefully because it's easy for the drill to wander off line.

Drilling a center hole serves two purposes. It makes it easier to hollow by cutting from the center out. It serves as a depth gauge. When you reach the bottom of the hole, STOP.

Wally

[Bernie Weishapl]

You guys drill a hole in a hollow form to start????

[Ryan Baker]

The size of the hole depends on the size of the opening you want to end up with to some extent. Most often, I use about a 1" forstner and an extension (if necessary). A good forstner will not clog too much, but you do need to keep cleaning out the cuttings (no big deal). I used to use a smaller hole (3/8 or 1/2"), but drilling it out is faster and easier than any other method so you might as well take out more with the drill. If you use a forstner, you will need a minimum of about 3/4-7/8" or it won't clear the extension. I won't use an auger because of the screw tip (grinding the tip down may work).

Of course, you can do it without drilling the hole first -- and that works better with some methods (e.g. Jeff's tool) than with others. As Wally said, it makes the job easier and it establishes the depth.

[Tom Storey]

I'm practicing on a small end grain hollow form and I've found that normal bowl gouges arn't the best choicehttp://www.sawmillcreek.org/images/icons/icon11.gif they seem prone to catching! This hf is about 7" deep and I've drilled in a few inches with a 1/2" forstner, hollowed, and drilled again. I think that this method will work but on deeper vessels but I'll need an extension. I've been using a home made hook tool to do the hollowing so far; I'll try a termite bit next.

I've not been able to find a close-up of Jeff's drill hollowing/drilling tool and I'm not sure how it is ground; can you direct me to a close-up of the buisness end Jeff?

Bernie W, what sort of tool bit do you use if you don't drill?

Thanks for all the input folks!

[George Guadiane]

The old time auger bits I have seen and used have a square shaft end to fit the v-shaped jaws of the old time brace. How do you chuck the bit in a lathe? Grind off the flats on the bit and use a Jacobs chuck?

Actually, I cut that part off. And yes, a conventional Jacobs chuck works fine after that.

[Art Kelly]

I just made some vases with glass tubes for holding flowers with water.

Some of the holes were almost a foot deep, and I put a 3/16" od nylon tube on the bit to cool it and eject the chips.

The first photo shows the bit just entering the hole so you can see the end of the tube; the second shows the bit about 3" into the hole with the chips flying. I run about 20 psi air which doesn't use a lot of cfm through the 1/8" id tube.

It also works with Forstners.

Art