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TTIT
11th June 2009, 11:05 PM
I'm working on my biggest hollow form so far (380x280) and I'm having a bit of trouble getting the inside smooth with so much overhang from the toolrest. The entry is big enough to fit my arm through (just) and feel the 'ribs' on the wall surface and I'm gradually wearing them down with a shear-scraper but it's taking forever so I started to wonder if...
(a)... there is some secret easy method for evening out the surface after hogging out.:doh:
(b)... the pro's leave it rough and use tiny entry holes so that nobody can get their hand in to feel the ribs.:;
(c)... I'm just too impatient :B

Anyone have any tips/shortcuts???

I've never actually seen a large hollow form turned by a pro - what condition is the inside surface usually in ????? :shrug:

INVENTOR
11th June 2009, 11:16 PM
If the entry is large then you could use a extended rest, like the Kelton hollowing gate, or similar. That way you don't have the overhang and your tool has support. Its when you have a small entry and large overhang (on large diametres) that things get interesting. With too big a hole, the more you see and can feel. With a small hole it is difficult to sand but not impossible. Use a powered sander with a long shaft. Can't tell you all the secrets.

Skew ChiDAMN!!
11th June 2009, 11:24 PM
After observing a few blokes I know who are into it, I'd reckon the answer is mainly (B)...

...with a little bit of (A), where the "secret" seems to be $$$ invested in a deep hollowing rig with a laser pointer.

It's also amazing how well a handful of grit (coarse sand or gravel fines) thrown into a form to dry tumble for a while can smooth the inside... :wink:

joe greiner
11th June 2009, 11:25 PM
(b) (B) and [B], hands down, according to a few pro's I've consulted. If the hole is still too big, add a collar.:wink:

Cheers,
Joe

jefferson
11th June 2009, 11:36 PM
My aging father makes polishing machines for cleaning up antique bottles. The device is fairly simple - a continuous cycle motor, with the "aged" bottle suspended in a cannister filled with cutting compound. The trick is getting the right amount of compound in there to take the rubbish and high spots out. After the first cut, he polishes.

Perhaps the same sort of thing could be useful? Slow speed on the variable lathe with cut copper less the cutting compound to take the high edges off and smooth?

Jeff

tea lady
12th June 2009, 12:05 AM
:think: Maybe you could do it like a ball mill. Big marbles little marbles and grit. :shrug: Maybe tumble some wooden pebbles while you are at it.:cool:

Cliff Rogers
12th June 2009, 01:15 AM
All the pros I've asked reckon that they use trained termites. :D

Paul39
12th June 2009, 05:18 AM
Saw a discussion of these on the Practical Machinist site. The abrasive part might have to be shortened a bit.

http://stores.shop.ebay.com/Pixelman-Digital-Products__W0QQ_armrsZ1QQ_fsubZ11

rsser
12th June 2009, 07:18 AM
Some pro turners in the US no longer bother with getting a fine finish on the inside, and some just use a toothpick cutter to turn 'corduroy' as a decorative thing.

Course it helps to have a narrow opening so sticky beaks can't get their hand in ;-}

If you have a fair finish off the tool Vern another option might be the home-made flap sander. Know this one?

TTIT
12th June 2009, 09:29 AM
:think: Maybe you could do it like a ball mill. Big marbles little marbles and grit. :shrug: Maybe tumble some wooden pebbles while you are at it.:cool:


My aging father makes polishing machines for cleaning up antique bottles. The device is fairly simple - a continuous cycle motor, with the "aged" bottle suspended in a cannister filled with cutting compound. The trick is getting the right amount of compound in there to take the rubbish and high spots out. After the first cut, he polishes.

Perhaps the same sort of thing could be useful? Slow speed on the variable lathe with cut copper less the cutting compound to take the high edges off and smooth?

JeffMight not have explained it well enough - it's not the finishing that's a problem, it's getting an even line before the finishing starts. Easy on the outside where you can see the ridges and even on small forms where you can 'feel' them with the tool but once you have about 150mm overhang, the drag on the toolrest makes it hard to find the bumps to work on them. At the moment, each time I cut one down I tend to leave a new one each side of it :C - running out of wood :B


Some pro turners in the US no longer bother with getting a fine finish on the inside, and some just use a toothpick cutter to turn 'corduroy' as a decorative thing.

Course it helps to have a narrow opening so sticky beaks can't get their hand in ;-}

If you have a fair finish off the tool Vern another option might be the home-made flap sander. Know this one?I thought about using a flap sander but I still wouldn't be able to tell if I'm working high spots or making new low spots :doh:
This was my first real test for the laser guide too but it appears they are only a rough guide at best. When you're scraping the wall of something that size, ridges 1mm or so high don't show up at all.
Might have to just keep plugging away at it one ridge at a time... grooooaaaannn:C

Grumpy John
12th June 2009, 09:31 AM
I used to wonder the same thing Vern until I saw a Raffan video. The cheeky bugga makes the vesel in two halve,s gets a perfect finish then glues them together (cheater :D). When he turns the outside he puts a bead at the join to disguise it.

hughie
12th June 2009, 10:40 AM
Vern, check your pm box, have a prototype that'l help

woodcutta
12th June 2009, 11:31 AM
Vern,

How about one of these mounted on the end of the tool and the screen on the handle?


http://www.fiberscope.net/servlet/the-VideoScopes-cln-Portable-Videoscopes/Categories

woodcutta

TTIT
12th June 2009, 11:50 AM
Vern,

How about one of these mounted on the end of the tool and the screen on the handle?


http://www.fiberscope.net/servlet/the-VideoScopes-cln-Portable-Videoscopes/Categories

woodcuttaInteresting idea Andrew :2tsup: Twould make lining up on the ridges easier to start but it would be hard to see through the cloud of shavings once you got going. Main problem is that the only ones I could afford have a minimum focal length of 150mm so I wouldn't be able to get back far enough to focus in most forms :C

Ed Reiss
12th June 2009, 12:49 PM
TT...along with the arsenal of flap and disk sanding, proper turning prep is essential. There is no way that taking the "ribbing" out is going to be a quick task. I just finished off a "simple" vase shape about 200mm high and 135mm wide and I spent over 2 hours preping the interior for sanding.
After roughing the main area out and leaving about 3/8" wall thickness at this point the controlled, tedious work begins.
First with a rounded HSS tool bit in the holder, start to take light cuts straight in for about a half an inch from the rim. Now stop the lathe and either vac out or blow out the cut bits and dust. Now repeat for the next 1/2". for each section cut, stop the lathe and get rid of the dust and shavings that are there....this gives you a clear view of hills and valleys.

Once you've got the wall thickness you want, there will still be "ribbed" areas that need attention...here's where I employ my secret weapon - a 5/8" carbide ball mill. It is large enough to bridge the valleys and cleans up the hills and leaves a relatively smooth surface. Just run it along the surface, it takes off small imperfections easily

Now to sanding...I generally start at 120 or even 220 (others may have to start at 80, depending on the prep. Do I use power sanding...you betch'a, but only after hand sanding first. Different size H&L holders come into play 1", 2", 3", and 5", as well as different size flapwheels in different grits.

Well, there you have it...lots of starting and stopping the lathe, taking small controlled cuts, and patience will yield a "baby" smooth surface

wheelinround
12th June 2009, 01:20 PM
Vern you are the Pro

besides a picture is worth a few laughs :D

TTIT
12th June 2009, 04:12 PM
I used to wonder the same thing Vern until I saw a Raffan video. The cheeky bugga makes the vesel in two halve,s gets a perfect finish then glues them together (cheater :D). When he turns the outside he puts a bead at the join to disguise it.Hmmm - so it's left to us amateurs to push the boundaries then eh!:;


............my secret weapon - a 5/8" carbide ball mill. It is large enough to bridge the valleys and cleans up the hills and leaves a relatively smooth surface. Just run it along the surface, it takes off small imperfections easily
...............That's a newy on me :o definitely food for thought! (hey Hughie - you taking notes here :;)

wheelinround
12th June 2009, 04:24 PM
wots needed is an expanding adjustable cutter head that beats as it cleans as it sweeps

dai sensei
12th June 2009, 08:34 PM
What about a sanding head on the end of a flexible shaft that fits within the entry. If the entry is big enough for your hand, you should be able to fit a 75/50/25 head. Put the head in, hold the end with one hand, the other hand on the drill or dremmel. Start with say 120 grit and using the largest head that will get to where you need to, it will ride the ridges and sand them flat.

mkypenturner
12th June 2009, 09:47 PM
vern
i just got the may 2009 woodturning mag ( 200 th ) issue there is a new sanding tool for bowl tall vases and hollow forms on page 92 pm me if u cant get it and want a pdf copy
troy

or any body else that wants a copy just pm me with your email address

TTIT
12th June 2009, 10:07 PM
What about a sanding head on the end of a flexible shaft that fits within the entry. If the entry is big enough for your hand, you should be able to fit a 75/50/25 head. Put the head in, hold the end with one hand, the other hand on the drill or dremmel. Start with say 120 grit and using the largest head that will get to where you need to, it will ride the ridges and sand them flat.Thought about it but the entry only just allows my hand/wrist through - even the cable of a flex-tool won't squeeze in with it. If I enlarged the entry I would still be up the veritable as the shape would not allow the handle/cable enough room to apply the pad squarely on the surface. Even the flap sander idea has been dropped as the angle of the wall will mean the flap sander will only cut with the corner for about 3/4 of the surface......... if all that made any sense at all :shrug:
Starting to wonder if it would be worth mounting on of those self-powered sanding heads
on an extension handle with an adjustable pivot of some sort that allows it to sit flat on the surface. Loaded with a coarse enough grit, it might just even things off a little.

TTIT
12th June 2009, 10:09 PM
wots needed is an expanding adjustable cutter head that beats as it cleans as it sweepsIf ya got a spare one I'll borrow it then eh!:;

Ed Reiss
14th June 2009, 12:23 PM
TT.... here's a few pics of a maple piece just compleated yesterday. 150mm high x 140mm wide x 4mm wall

I tried my best to get nice inside shots that would show off the smooth interior by using the method I alluded to earlier in this thread...you'll just have to take my word that the insides are smooth and not rippled

wheelinround
14th June 2009, 12:38 PM
Vern http://www.gambier.d.reeks.btinternet.co.uk/tools.htm

an idea Ed provided part of solution
using a deep hollowing bent shaft attach a flexi shaft drive and use http://etoolshop.co.uk/cart/images/282443.jpg

TTIT
14th June 2009, 11:29 PM
vern
i just got the may 2009 woodturning mag ( 200 th ) issue there is a new sanding tool for bowl tall vases and hollow forms on page 92 pm me if u cant get it and want a pdf copy
troy .............Got that issue - wouldn't mind the sander but it's a bit pricey - maybe one day :B


TT.... here's a few pics of a maple piece just compleated yesterday. 150mm high x 140mm wide x 4mm wall

I tried my best to get nice inside shots that would show off the smooth interior by using the method I alluded to earlier in this thread...you'll just have to take my word that the insides are smooth and not rippledI don't have any trouble on open forms like that Ed - just when I can't see what's happening and there's a bucketload of overhang.

I have wrapped him up in paper now after persisting with the shear-scraper. Took a while but I managed to get the surface even enough for now - could lose the whole thing during the drying process so it could all be for naught! I haven't done anything with Kauri pine before so I don't know how it will behave. I didn't worry about bagging it after the first hollowing session and came back to it a couple of days later to find some pretty big cracks around the mouth. Have kept it bagged since so the next few days with it wrapped up will be interesting :shrug:

Paul39
15th June 2009, 04:00 AM
I didn't worry about bagging it after the first hollowing session and came back to it a couple of days later to find some pretty big cracks around the mouth. Have kept it bagged since so the next few days with it wrapped up will be interesting :shrug:

I have had good luck with wet or dry pieces by liberally applying boiled linseed oil in and out and wrapping in newspaper when I stop turning. If it is ready for the last sanding steps, I'll wet sand with 220 and Tung Oil (my usual finish) then apply more with a rag, wrap in news paper.

I am amazed how much linseed oil was absorbed by a root / stump two days out of the ground. The sister piece that I soaked in detergent and water for a week and then microwaved twisted and split all over.

I think Richard Raffan wrote that one can do all sorts of things to prevent splitting, or do nothing, and the result is some split and some don't.

TTIT
15th June 2009, 09:29 AM
.............I think Richard Raffan wrote that one can do all sorts of things to prevent splitting, or do nothing, and the result is some split and some don't.That's pretty much my philosophy also - wood's not that hard to find. I didn't want to cover/treat this one with anything at all because I plan to have a go at using aniline dyes on it. Once it's dry, I'll 'borrow' my sons air-brush and have a play ............ and if that doesn't work I've left the walls at 10mm so I can always carve it up a bit - the Kauri is just too plain on its own :shrug:

Ed Reiss
15th June 2009, 11:37 AM
I don't have any trouble on open forms like that Ed - just when I can't see what's happening and there's a bucketload of overhang.

OK, TT....that takes us back to the carbide ball mill for taking down the ridges. One major plus with the ball is that there is no way in hell that it will catch, so turning "blind" and also with lots of overhang is no problem.

Good luck with the piece your working on...looking forward to seeing a pic of the finished product.

hughie
15th June 2009, 11:53 AM
Hi Vern,

In past I have coated the inside with BLO and its helped alot with cracking etc . But if its gonna twist, it will, no matter what we do...well thats my opinion :U

Jim Carroll
15th June 2009, 06:39 PM
When using the scraper on the inside of a hollow form it is best to use the largest teardrop cutter you have so it will ride on top of the bumps easier. If you use a small cutter it will do as you say get rid of the high spot and create 2 more humps.

By getting a peice of toolsteel and shaping in a radius like the teardrop with about an 80 degree angle. Most readily available ones only have about a 40mm radius so 50-60 would be better and mounted onto a rigid handle with the ability to tilt on an angle of 45 degrees.

This way are riding over a couple of bumps and able to get a rid of all the little ones on between.

artme
15th June 2009, 08:34 PM
From a technical point, Jim has the answer.

It's a fascinating subject this, and one that brings differing opinions to the fore, especially with regard to competition pieces.

one view is that since you don't see the inside of the vase why bother too much with perfection.
The other view says everything should be perfect.

I often wonder if is fair of judges to come equipped with mirrors arthroscopes, lasers, echo sounders, ground tracking radar and whatever to "judge" a piece.
It appears the only ones who can meet these exacting means of judging need to spend thousands on the necessary equipment. Is it worth it???

KenW
16th June 2009, 12:03 AM
Like Jim, I use a large teardrop cutter (the largest that will fit through the opening), the only difference is that my cutter is sharpened to 45 degrees. The sharper angle will take much finer cuts when presented at 45 degrees to wood. I fit this cutter on to my Stewart system for short hollowing and onto a Rolly Munro hollowing tool for deep hollowing. The Munro hollower is not meant to have such a cutter fitted, however it works fine. For the initial hollowing I use the Munro hollower with it's correct cutter.

TTIT
16th June 2009, 09:28 AM
When using the scraper on the inside of a hollow form it is best to use the largest teardrop cutter you have so it will ride on top of the bumps easier. If you use a small cutter it will do as you say get rid of the high spot and create 2 more humps....................


Like Jim, I use a large teardrop cutter (the largest that will fit through the opening), ......................With 2 suggestions for the same solution I'll have to play politicians and treat that as concensus :U I'll make a much bigger teardrop and give it a spin when the form dries out - if it stays in one piece :B

WOODbTURNER
16th June 2009, 02:46 PM
Vern,
Have you seen Enzo's new Ultimate sanding attachment. It's on his web site under "New".

jefferson
16th June 2009, 09:27 PM
My wife doesn't like you guys overmuch. I have no deep hollowing tools.... Hmm.

Please tell me the rough cost of a decent setup for my Vic. I promise to break the news to her at the appropriate moment. Must be suitable for redgum.

Alternatively, one of the Vic crew might talk quietly with the spouse on the weekend and let her come up with the idea.

PS. Guard dogs and my son here at Kiewa over the weekend, so pilferers don't bother.

Jeff

Bagmann
16th June 2009, 09:40 PM
Nice idea Ed. Just a question is the 'handle' for the ball anything special or just normal mild steel?

Cheers
Simon

TTIT
17th June 2009, 12:04 AM
Vern,
Have you seen Enzo's new Ultimate sanding attachment. It's on his web site under "New".Could be worth a shot even though it still doesn't overcome the problem of 'feeling' the high spots with the tool. Just got an order through from Enzo last week - might give him and the plastic a rest for a week or two while the form dries out :;:U

Ed Reiss
17th June 2009, 12:09 PM
Nice idea Ed. Just a question is the 'handle' for the ball anything special or just normal mild steel?

Cheers
Simon

Simon, the ball mill has a 1/4" shaft, so it will fit any of your hollowing tools that accept a 1/4" shaft. .the mill itself is carbide, cuts nicely. I've used it on approximately 30 pieces and it is starting to get dull...so will be ordering another soon.

bobsreturn2003
20th June 2009, 09:29 AM
if you use a stewart system you can feel the ridges . and use a rounded cutter ,and steady hand , takes practice , cheers bob