Could use some help on the inside bottom of hollow forms.

[Grey Darrah]

I've got a couple of taller hollow forms (12 to 14 inches) that both have a nub at the bottom. It's about 1/2 inch long, maybe a 1/4 inch wide, a bit fuzzy looking, and dead center in the bottom of my forms. If it matters, they're both maple. I'm using Trent Bosch's stabilizer and 3/4 inch tools for the hollowing. All that happens when I get my tool down on the nub is it bounces around, never seeming to cut any of it.

Is there a secret tool I don't know about that can reach 12 to 14 inches down a narrow opening and snip it off?

I'm not sure how visible it will be, but I attached an image of the nub, looking straight down into the vessel.

All suggestions are welcome and appreciated.

Grey

 

[Bill Boehme]

It's really annoying when you discover a tall thin spike an inch tall and as you said it's all but impossible to keep the tool on that spot. If it's an end grain hollowform you can't break the spike. With hand hollowing on cross grain you can bring the tool from beneath to lift off the nub. Otherwise, coarse sandpaper works for me. In a captured bar system keep the cutter at dead center.

 

[Grey Darrah]

They are both end grain pieces. The sanding is a great idea. I think I'm going to try and attach some 80 grit to a stick and see how it goes.

Thanks.

It's really annoying when you discover a tall thin spike an inch tall and as you said it's all but impossible to keep the tool on that spot. If it's an end grain hollowform you can't break the spike. With hand hollowing on cross grain you can bring the tool from beneath to lift off the nub. Otherwise, coarse sandpaper works for me. In a captured bar system keep the cutter at dead center.

 

[Bill Boehme]

If you can get a sanding disk for a drill with a long extension that would be the most effective way to sand it. I've tried the sandpaper-on-a-stick method and it's really slow.

The advantage of drilling a center hole is that you avoid this problem, but I've found that the best way to learn the right way to do something is to first do it the wrong way. That helps to drive home the message of what I should have done.

 

[hockenbery]

The the cutter needs to be at center. As you know this is a combination of setting the height of the support and the height of the tool rest.

A trick to find center is to use the cutter to strike a line across the bottom
Use an engine inspection light to see which way to adjust the tool rest and maybe the support post.

Once you have center it is light cuts to chop down the hill.
Sometimes you can cut straight at the top and sort of drlll down.

The easiest way to deal with bottom bumps is to not let them form. But that is for the next ones.
I like to use a light to see what is going on as I get close to the bottom
You can also drill a depth hole and just stop cutting when you get to that depth.

Trent tells a story about a guy who paints the top red and sells the hollowmforms with a mini Volcano in the bottom of every vessel.

 

[Michael Nathal]

I have a Jamieson system, and he uses a tool rest with a threaded nut to micro-adjust the tool rest to get the tool exactly on center. When you hit it just right, the nub is removed very quickly. It is not always easy to see when you are on center, especially on deep forms with narrow openings. I tend to do it by feel: moving the nut a quarter of a turn until I get the tool on center. I was thinking the Bosch system would be easier to hit exact center and keep it there, so the fact that this is still a problem is interesting info for me.

Also, installing a sanding disk on a long bit extension in a drill press is another way to sand off the nub.

 

[hockenbery]

getting the tool rest off a little makes the tip cut high or low

Systems like the Bosch and Hope can be set up quickly and repeatable.

1 put a lock collar on a toolrest to repeat the height. Then it is always on the center line.

2 If your lathe is dead level a level on the bar works

I do the initial set up using a center point in the head stock to match the cut line against.


If you use bars with different diameter the tool rest must be adjusted
If you have bars that cut above or below the centerline of the tool you may need adjust accordingly.