Hollow form questions

[bob svoboda]

Ok, today I began the learning curve of HF-definitely at the bottom end of the curve, but determined to master it. The main question I have now is, how do you turn away the pyramid of wood in the center bottom and make it smooth? Also, do most of you start your hole with a drill bit, and if so, about how large of a bit do you generally use? Thanks for any advice offered.

[Steve Schlumpf]

Bob - I do not drill a hole - I just start hollowing. As far as getting the center smooth - you have to have your cutter at the center line and be able to sweep into and past the center to smooth it out. If you hesitate at the center - it will divot, to high or low and you will leave a bump.

What style of form are you creating? How deep? What tool are you using?

[Mark Hubl]

Bob,

The little pyramid on the bottom is a pain. I sneak up on it with a straight tool, kinda from the bottom and cut upward, very little at a time. Takes forever. That is why on most forms I drill a hole. In smaller forms you can do this with your straight tool. I prefer to use a long drill bit tool or forstner bit. For small openings I use a long 3/8 bit and drill to the final depth. This eliminates the nub and sets the depth. (Yeah, right, how come I still make funnels.) For something with a wider opening I may start with the 3/8 tool and then use a larger bit to clear out the top and give me some room.

[bob svoboda]

Bob - I do not drill a hole - I just start hollowing. As far as getting the center smooth - you have to have your cutter at the center line and be able to sweep into and past the center to smooth it out. If you hesitate at the center - it will divot, to high or low and you will leave a bump.

What style of form are you creating? How deep? What tool are you using?
I've started with basically a sphere, about 5" wide and 5" tall. I'm working end grain with the Derry ornament hollower and also using the Sorby multi-tip tool. I have the Derry captured system w/laser, but haven't begun to use it as of yet.

[Steve Schlumpf]

I'm not familiar with the Derry system - but at 5" you should be able to take care of the bump with the Sorby.

First - you need to know where the tool is hitting the bottom of the form. Keeping the tool in the same position as when you are hollowing - with the lathe off - move the cutter horizontally back and forth a few times so that it scores the bottom of the form. Grab a flashlight and check out where your tool is cutting. You can then can adjust your tool rest 1/2 the distance and you will be on the money.

Big thing to remember is to keep the cutter moving. When you go to cleanup the bottom area - sweep through the raised area. Once your cutter gets to the other side of the bump - the direction of travel for the wood is away from your cutter - so you won't have a catch or dig further into the wood. Just a nice steady sweeping motion...

[Richard Madison]

I like to drill a "depth gage" hole to almost the intended final depth, usually with a 1" forstner, being sure to account for the drill point. Makes hollowing easier for me, as you can cut side grain from the hole outward instead of cutting end grain (for end grain hf's).

[Mike McAfee]

I don't drill and yeah the nib is a pain in the butt! Steve's suggestion is about as good as it gets although I wish I had some deep dark secret method other than that!

Get into tall hollows and small openings and don't sweat the nib, no one will ever know!:rolleyes:

MMc

[George Guadiane]

I don't drill and yeah the nib is a pain in the butt! Steve's suggestion is about as good as it gets although I wish I had some deep dark secret method other than that!

Get into tall hollows and small openings and don't sweat the nib, no one will ever know!:rolleyes:

MMc

Here's a "dark secret method":
Make an open bowl.
Leave a nub in the center ON PURPOSE.
Use the tools you would for hollowing and (paying careful attention) watch and feel the process of removing the bump.
Start over a few times and when you get comfortable, close your eyes and just feel the bump being removed.
Once you have the muscle memory, you should be able to do it in the bottom of a hollow form.

[Thomas Canfield]

I started out using a 3/4" Forstner bit on an extension to drill, but later got a 5/8" twist bit with #2 MT to fit direct in the tailstock and that works better. The Forstner bit required backing out often to prevent chip plugging. I also often will just use a 3/8" spindle gouge to plunge a hole if not too deep. In any case, a depth hole helps for bowls to gauge the bottom, and for end grain hollowing to pull the tool out to do the cutting.

[Bernie Weishapl]

Ditto what Steve said. I don't drill either. I like to open my HF and turn from there. I don't like drilling because I find it harder to hollow properly and find myself going to far. I like to hollow the top 1/3 and keep as much mass as I can in the lower 2/3. I finish it before going on to the second 1/3 and when the 1/3 is finished I go about finishing the lower 1/3.

[bob svoboda]

Thanks guys, for all the great suggestions. This is a great example of why this forum is so valuable. Now to the shop to try to develop (or get) a technique!

[Reed Gray]

While I don't do that many hollow forms, I tried the forstner bits, and found that I could hollow with the tools a lot faster. Do practice on a more open form where you can see that cone, and work it in sweeping motions, side to side and up and down. Dave Ellsworth shows this in one of his DVD's. If you leave the cone, it can catch the back side of your tool, pull it under the cone, back up and around, and slam it back onto your tool rest. Explosion, and bad words will be said. I try to take the cone out as I go, starting in the center and working back up to the top.

robo hippy

[Ryan Baker]

I almost always drill a hole first, because it sets the depth and it simply makes it a lot easier to not deal with the center nib. I used to use a 3/8" twist bit. Now I usually use 1/2" because the larger hole gives easier access to the tools that follow. Sometimes I will use a larger Forstner, depending on the opening size I am making. Drilling is usually faster (not with forstners) and easier, so do what you can with the drill.

If you are removing the nub by hand, you need to develop a feel for it. You can find the "dead spot" -- the center -- gently with the tip of your straight tool. Then slowly work the tool from the center point: dip down slightly and make a light cut coming back up to center. Then sweep slightly left and back to center. Repeat. Be very gentle. It works but it takes practice. Don't alloe the nib to build up much size before you take it out or it becomes much more difficult to cut out.

If you are working by hand, do not move the tool past center to the right, especially with a small opening. That is dangerous, and will almost always result in the tool being kicked or twisted with upleasant results. Steve can get away with that method because he is using a captured arm system that will keep control of the tip.

I agree with George. If you can practice the technique on an open bowl you can see into, it will be much easier to figure out what to do.

[Jeff Nicol]

I don't drill like normal, I use my drill bit cutter to start and cut to depth of the HF I am working on. I can go 18" deep with the handle it is mounted in. When I start to finish the inside I will change from the drill cutter to a round or egg shaped cutter to do a finish shear scraping action and I can get the bottom nice and clean. The rounder scraper is easier to take small amounts off to clean the bump off the bottom.

Hope some of this helps,

Jeff

[neil mackay]

today I began the learning curve of HF-definitely at the bottom end of the curve, but determined to master it. The main question I have now is, how do you turn away the pyramid of wood in the center bottom and make it smooth? Also, do most of you start your hole with a drill bit, and if so, about how large of a bit do you generally use? Thanks for any advice offered.

Bob,

Some drill a small hole to the required depth and some use a Forstner bit. If I do drill I like to use a Forstner bit of around 1.25-1.5" This gives me some working room at the bottom of the hole.
Do I drill all the time? No, it depends on what I am doing and how hard the timber is. If its dried old man Jarrah thats been down for 100 years or so. I will drill the biggest darn hole I can get, drillin' is easier than turnin' in this case.
If you using an Oland type hollower you will find it can drill and hog out for you and take the 'pyramid' off the bottom for as well.

[John Tomasello jr]

Usually on HF & goblets I will drill a little smaller then my finished hole size to a little less then my finished depth. Try to use forstners when ever possible. With nasty hard end grain on goblets I will cut with a bigger forstner to a depth were the out side of the cup start to taper back to the stem then switch to a smaller bit to get a deeper hole. I fell like I am cheating when I do it this way, but until my skills improve drilling will be my method of choice.