Help with a... "goblet..." of sorts.

[Skew ChiDAMN!!]

The Nunawading exhibition is coming up and I've left my run a bit late for this year. :- Actually, I've made a few pieces to enter but none of 'em turned out as desired and I don't see any sense in wasting entry fees on 'em. :rolleyes:

So, I've started on a concept piece, a "petalled" goblet. Because of the way I've done it, I can't reverse chuck it to turn the underside of the petals... You can see from this pic that I turned the bowl very, very thin, less than a mm in fact! I guess that's pretty obvious from the gaping holes in the side, but believe it or not they are deliberate. :p The lip is quite a deal thicker, but once the piece comes off the chuck that'll bve carved too, to form a scalloped edge of the same thickness.

44765

I hollowed under the petals as far as I felt safe, then trimmed away the excess from the wings so I could better see how to proceed. Now I've come to my problem...

44766

The 6mm square bedan (which I've reprofiled to an 85° scraper for just this job) is the only tool I have which fits the clearance available. :( Even then, from the pic you can see that the handle is hard up against the headstock and the ferrule/top end of the handle is rubbing against the chuck. (I'll have to make a new handle after this. [sigh])

Because of the long overhang, about 2½-3", and the thin tool steel chatter is extreme, to say the least. Not something I want to try finishing cuts with, nor do I particularly fancy having to hand sand in there if I can't cut it cleanly. I've tried a swan-necked Oland-style tool, but for some reason it persist in grabbing badly. Those petals are also pretty thin and I don't particularly wish to glue 'em back on later. I suspect this is because I'm both going straight into end-grain and it's impossible to present the cutting edge at the correct angle.

So... I'm open to suggestions. A different tool? A safe way to reverse mount so I have better access? Help? (Something tells me I may not have any show entries this year...)

PS: I also thought of using a donut chuck, but the bowl is really, really thin. It won't take much pressure to crush it along the grain, either. Wish I hadn't thought of going that way. :(

[DJ’s Timber]

Certainly looks like you have reach a stumbling block there Skew.

Can't really think of anything at this stage, will stew over it for the night and see if I can come up with any ideas

[Bruce101]

Hi Skew, I have never tried such a turning job, and I'm nowhere near this level and I may be way off track, but (for what it's worth) could a plug with a very (very) neat fit be made for the bowl and perhaps secured with a number of hits of hot glue? then reverse the chucking end.

Like I say, for what it's worth.

Hope you sort it out.

[BernieP]

G'Day Skew

Of course I can be of little use to solve such an involved problem, but have wondered if you have thought along the lines of this blokes machined coach bolt for a screw chuck? http://www.woodturns.com/articles/tools/mounting_wood.htm

Cheers anyway and keep us posted how you get on and a finished pic of the goblet would be appreciated.

Cheers
Bernie

[thefixer]

G'day Skew

I'm by no means an expert and am a long way from trying anything like that. Your'e a very brave man IMHO. Have you tried putting the tool rest under the chisel just forward of the ferrul to support the tool and reduce chatter.


Cheers
Shorty

[Frank&Earnest]

Skew, you say
"I've tried a swan-necked Oland-style tool, but for some reason it persist in grabbing badly."

If that tool would do the job if it did not grab, and assuming that it has a flat profile (or you are willing to flatten it a bit), a possibility would be to clamp it to the tool rest with a small G clamp and move it little by little as it reaches the end of the useful arc allowed by the pivot. This might require modification of the tool rest, though.

Good luck!

[OGYT]

Perhaps a 'reversed swan-neck' with a support leg on the right side... sort of the opposite of the Al Basham tools???
Don't have an idea... I guess... just ramblin'...........
Yer a gutsy bloke, Skew.

[Skew ChiDAMN!!]

Perhaps a 'reversed swan-neck' with a support leg on the right side... sort of the opposite of the Al Basham tools???

Yeah, that's what I'm thinking, too. And maybe an extension on the headstock spindle, to move the chuck further down the bed. But as mt tool handle's already rubbing on the chuck, I'm not sure whether that's worth the effort.

I tried mounting the cutting head upside-down on my existing swan-neck, but without a supporting leg it was too risky to use. I wonder if clamping a cross-bar on would work as a support? Probably not, it might just roll in the clamp. But I'll give it a try on a scrap piece mounted in t'other lathe and cross my fingers...


Yer a gutsy bloke, Skew.

Gutsy? No, just stupid. Hang on... make that "overambitious." Same thing, but the latter sounds better. :wink:

[OGYT]

Yer up late, too.... or is that early??? Yeah, overambitious does sound better.
Quote: I wonder if clamping a cross-bar on would work as a support?
It might work if you put a set screw on it to keep it from rollin', but that might put a scar on the tool shaft. You may have to make a special tool for this job.
If it had a little bit o' cant to the end of it, so it would sort of shear/scrape (oxy-moronic, that), then you turn the speed way up high, and with a steady hand, slide it in there, and then shave it lightly as you pull the tool out... :yikes:
Mind you, I couldn't do that... but someone with a steady hand might. :D

[Skew ChiDAMN!!]

Quote: I wonder if clamping a cross-bar on would work as a support?
It might work if you put a set screw on it to keep it from rollin', but that might put a scar on the tool shaft.

Hmmm... I wouldn't mind drilling a small dimple on the top of shaft as then it wouldn't catch on the rest when used normally. And I could run the leg to either left or right should the need arise. Thanks! :thyel:


You may have to make a special tool for this job.
If it had a little bit o' cant to the end of it, so it would sort of shear/scrape (oxy-moronic, that), then you turn the speed way up high, and with a steady hand, slide it in there, and then shave it lightly as you pull the tool out... :yikes:

I know what you mean... and I can see myself making one, later. But I've only a matter of days before this has to be finished, and I want several coats of Danish on it yet. Time, time, so much to do and there is no time. :(

Ah well, I'll finish it when I finish it and bother the deadline. Who knows, I may just make an uber-version for next year's exhibition instead, using lessons learnt from this 'un. :)

[joe greiner]

You mentioned reluctance to reverse-mount with a donut chuck because it could crush the bowl. Maybe you could reinforce the outside of the bowl with a gap-filling foam sealant within a larger round container and chuck against that. Product I have in mind is called "Great Stuff" by Dow Chemical; might be something similar in Oz. It's usually used to seal around wall penetrations for plumbing, ductwork, and such. Package says "Cures Rigid & Trims Easily." Unfortunately, it also says "Bonds to Most Materials," so you'd need to put a bond breaker on the outside of the bowl for cleanup. Might make final finishing problematic. Just food for thought, but I'd definitely test the idea on some scrap first.

Joe