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rsser
2nd Jun 2006, 06:36 PM
Picked up some new tricks courtesy of Guilio Marcolongo's demo at the Koonung Woodturners recently.

Below are some pics. The pencil jar is not my best and is only for illustration. It's about 4" deep. The blackwood is gorgeous and thanks to the donor. By way of self-critique, it's too short for its base, the taper isn't big enough (though the macro setting on the camera makes it look like a reverse taper in the pic) and the top rim is too narrow.

To the tricks...

Guilio recommended sanding with wet and dry and keeping the piece wet. Fewer scratches and no heat checks from power sanding. Tried this and found it to be spot on. Down sides: messy and slower. Unexpected upside: easier to keep the crisp edges of the detail work.

He also recommended using a skew and a peel cut to finish the outside of bowls and the like. On this piece I'd started with a roughing gouge and tried to improve on it with a scraper ... which btw was an interlocked grain lump. The results were poor, but a few passes with a very light peel cut improved it out of sight. He advises using a very sharp skew, fresh off the grinder with the cutting edge polished with buffing compound. I used a fine lap which is supposed to be as good, tho slower.

Lastly, I've been doing the bottom of these jars with a round nose scraper. Guilio demo'd a different tool - which I've tried to reproduce, see the pic. He uses these for finish hollowing on concave boxes etc. This worked well prob. because less edge is in contact with the piece than in the case of a bullnose scraper and because the twisting forces are countered by the the offset cutting edge.

In my repro, the cutting edge is too close to the near side; I couldn't move it back since the off-side of the tool I modified had started life with that side ground for other purposes.

May I thank Marco for his generous sharing at the demo and afterwards. He's a real gentleman.

CameronPotter
2nd Jun 2006, 06:45 PM
Thanks to you too Ern for passing along the tips. :D

Cam

hughie
2nd Jun 2006, 07:56 PM
The pencil jar is not my best and is only for illustration.
To the tricks...

Marco recommended sanding with wet and dry and keeping the piece wet. Fewer scratches and no heat checks from power sanding. Tried this and found it to be spot on. Down sides: messy and slower. Unexpected upside: easier to keep the crisp edges of the detail work.

He also recommended using a skew and a peel cut to finish the outside of bowls and the like.


In my repro, the cutting edge is too close to the near side; I couldn't move it back since the off-side of the tool I modified had started life with that side ground for other purposes.


Ern,
Thanks for the heads up. Wet sanding make sense when you think about and your repro looks interesting and should work OK. Skews, hmmm had wondered about that but never got around to taking it any further. mainly cos I do quite a few with rolled over type edges.
The pencil jar came looking OK in the pic, as you say great piece of timber.
hughie

hcbph
3rd Jun 2006, 03:50 AM
That chisel looks much like this: http://www.pennstateind.com/store/lx170.html

I haven't used one myself and always wondered a little what they were best used for. Good info.

Paul

rsser
3rd Jun 2006, 06:59 AM
Hook-nosed scraper eh? I had been thinking of it as a Guilio's lobe ;-}

ss_11000
3rd Jun 2006, 12:16 PM
thanx for the tip bout sanding

rsser
3rd Jun 2006, 04:15 PM
In response to the PM about the pencil jar procedure I used ...

1. Turn square into cylinder with roughing gouge; in this case I used headstock end mounted in Titan chuck with Powergrip jaws and tailstock support; the piece was about 3x longer than needed for this job

2. Turn spigot on tailstock end

3. Remove piece and replace Powergrips with 75mm bowl jaws

3. Reverse piece and round off the square end without tailstock; bit of vibration now due to extent of overhang

4. Mark out and cut profile, inc recess for smaller chuck and 50mm jaws, and deep beading tool cut at top of jar in prep for removal from stub

5. Experiment with Guilio's rec's re cleaner cuts and wet W&D sanding

6. Apply a coat of Rustins Danish Oil

7. Separate the form from the stub with lathe stopped and tenon saw. You can use a parting tool but with a piece this wide overheating, smoke and dulling of tool are likely.

8. Reverse onto smaller chuck and jaws

9. Measure depth of hollowing

10. Mount 2" saw-tooth bit onto Jacobs chuck in tailstock and mark depth (if more depth needed, use morse 2 extension to mount bit)

11. Start cutting in. (And discover bit is blunt and so remove and touch up cutting edges with triangle file). Stop and retract bit often to clear shavings (an alt is to retract a little and get a chopstick in and pull them out while still rotating) but not so far as to clear the entrance). Watch for heating up/timber discolouring. This diam bit is as much as I like to go; shank tends to get chopped up by chuck or extension set screws (aka grub scews). HSS bits are worth the money if you do a lot of this.

12. Once at depth, retract bit and remove tailstock.

13. Reduce wall thickness in stages.

I like a square ended sharp scraper for this (well, not exactly 90 degrees, more like 87-88). It cuts the end grain neatly. Side scrapers in my view just tear out the side grain esp on redgum and jarrah and give you too much work sanding.

Your cutting edge should be just a bit above the equator to allow the bottom nearside edge to clear.

Do this about 3mm width of cut at a time, going down half the depth to near the thickness you want. Then complete to the base but take care you don't go right down. You should end up with steps in the base.

Do one final pass from top to bottom.

In most cases you can't see what you're doing so by eye you line up the scraper edge parallel with the outside edge of the jar.

Feel the cut. Reduce the width of cut if your tool is being pulled sharply down, and also resharpen it. Get your rest as close as poss to the jar.

14. Round out the bottom of the jar/box with Guilio's lobe tool or a bullnose scraper. The deeper the box the harder it is to do this without trouble. 5 or 6 " is hard work.

You aim your scraper downwards somewhat, with a 75 degree bevel, aiming to scrape at the 'equator'.

The Munro hollower is good for this kind of work too.

You will end up with a square shoulder at the perimeter. This doesn't bother me. If it does you, you could grind a scraper with an arc leading to the offside (ie. 12 noon to some hour mid-afternoon) and use this to take out the shoulder.

If you get a nipple at the centre, get your tool below it and square to the centre and raise it first and swing to the left to take the nub out.

15. Sand. The wall: you can do this by hand or with paper wrapped around a dowel. I now use a small drum sander in an electric drill to take out any 'corduroy' and then finish off by hand.

Sanding the base is a pain. I no longer bother. It will be filled with pencils after all. But if you're a perfectionist use your fingers carefully or find a heamostat and make a short cylinder of steel wool and wet and dry to clamp in it.

16. Remove piece and finish inside and outside.

Notes: after turning the outside profile it's worth removing the chuck and piece from the lathe, sitting them upright and checking the form to see if it works.

When sanding change the lighting angles to reveal scraches you may have missed.

Always use fresh sandpaper.

Always start with tools with a fresh edge, and touch them up regularly, esp when end-grain hollowing.

Relax, take things slowly but commit to a cut. There's lots of wood out there. Look for nicely figured blanks. Practice. Do a dozen in a row to refine your techique. They make great gifts and don't use up much scarce timber.

Below is a pic of one of my favourites. 11cm tall, Supplejack. I'm not going to show you all the crappy ones that preceded it :o

Hope this is helpful.

There are of course many ways to skin a cat. Feel free to comment on the above or talk about your approach to pussy ;)

ptc
3rd Jun 2006, 06:46 PM
Ern
tried to give you a Greenie.for the tutorial.
but not allowed at this time.

rsser
4th Jun 2006, 07:31 PM
Thanks ptc.

Hughie, it's still worth a try with a 'bullnose' skew. I just did on a small huon pine bowl and got excellent results - will save a deal of sanding. One tip: if you start to feel some catching, raise the handle a bit.

hughie
4th Jun 2006, 09:15 PM
Hughie, it's still worth a try with a 'bullnose' skew. I just did on a small huon pine bowl and got excellent results - will save a deal of sanding. One tip: if you start to feel some catching, raise the handle a bit.
[/QUOTE]

Ern,
I spent a day at the woodshow and watched RRaffan deftly use the scraper to great effect, almost zero sanding.
Afterwards spent 1/2 an hour or so with Bruce Leadbetter and watched as he gave a demo with his handle-less bowl scraper, very effective. Looked a bit like a french curve :D now I am showing my age :D

hughie

rsser
4th Jun 2006, 09:50 PM
Yeah, got some French curves myself. Only trouble is they're in the shed!

I'd guess a scraper with a burr and a shear cut would give you a similar effect. Was he running it off the rest?

What did the handle-less scraper look like? [Edit: in cross section I mean]

hughie
4th Jun 2006, 10:20 PM
I'd guess a scraper with a burr and a shear cut would give you a similar effect. Was he running it off the rest?

What did the handle-less scraper look like?


Uses it free hand, no tool rest. Spring steel about 1mm thick, size hmmm about the size of the second smallest curve in the set. Shape I'd say, 'volute' is the best way to describe it.
Price $10, which is very reasonable, personal shoppers only. :(

hughie

powderpost
4th Jun 2006, 10:58 PM
Sanding can be kept to a minimum with a cutting technique with sharp chisels, but some timbers haven't read that book. I first saw shear scraping demonstrated in Brisbane by Del Stubbs, in about 1978 or 79. Since then, I have used the method sucessfully on some of the crankiest timbers I have met. Even then sanding is sometimes necessary. I fold the sand paper into a flattish roll and let the natural spring in the paper do the work. Sanding coves. I roll the paper onto a cylinder slightly smaller that the cove and again let the natural spring in the paper do the work. Inside bowls and lidded boxes, I use a side ground shear scraper and a dome shaped shear scraper with the corners rounded. I don't like sanding because the dust gets up my nose and makes me sneeze... ;)
Jim