Stumped! Goblet turning problem

[rsser]

Trying to turn one out of horizontal scrub, a gift from a forum friend.

Outside shaping was no real drama; the wood is hard but responds to a burr or a sharp edge.

The hollowing's a puzzling. Will take teensy scrapings but any more and it's instant chatter tool. The upper wall is fine though is still around 4-6mm thick, and the base is fine ... just on the transition.

Have tried everything in the kit, from Munro hollower, Oland tool, gouge to scrapers.

Stem diam is 23mm; overall length is 170mm.

Got me beat.

Any advice?

[DJ’s Timber]

G'day Ern

Sounds like the stem might be flexing. I normally hollow it out before shaping stem. Maybe try a steady if you have one

[Skew ChiDAMN!!]

Have you tried a round bedan? I make mine from BIG old screwdrivers.

I assume that by "outside shaping" you mean the bowl only (leaving the stem for later) and that you're cutting from the middle out to the rim? I only mention it 'cos some people think "it's a bowl, so you cut towards the center" but either forget that hollowing a goblet is usually end-grain work or don't understand why you cut that way.

(Not applying this to you, just making sure it's said for anyone else who reads this post. ;) )

[ss_11000]

I assume that by "outside shaping" you mean the bowl only (leaving the stem for later) and that you're cutting from the middle out to the rim? I only mention it 'cos some people think "it's a bowl, so you cut towards the center" but either forget that hollowing a goblet is usually end-grain work or don't understand why you cut that way.



ta much, i didn't know that but when i try it, i now know.

cheers

[Captain Chaos]

G'day Ern,
Am I correct in assuming that the chatter is occuring where the base of the interior melds into the side of the goblet? I experienced a similar problem a little while ago whilst turning a small goblet / vase from Broughton Willow. I think that the chatter occured because I could not get the tool rest close enough to the surface that I was cutting at the time & subsequently had an excess amount of tool overhang. Also, because the tool rest has been rounded on the tool support face, there seems to be minimal tool support as it rests on the tool rest & thereby allowing the tool to move & shudder as it is cutting. This jumping around seemed to multiply on itself the more I cut & tried to stabilize it.
To remedy part of the problem, I fabricated a tool rest from 7/8" square bright steel stock & welded it to a 6" length of 1" Ø round bar stock. I am able to get into the interior of goblets with this tool rest & support the tool much more securely & also get much closer to the cutting area.
Dunno if this is of any help to you Ern, but it worked for me when turning my little fiasco.
Regards,
Barry.

[Skew ChiDAMN!!]

ta much, i didn't know that but when i try it, i now know.

Stirlo, here's a quick diagram to help you see the difference. No matter what you're turning, you should try to cut so that the grain is supported by the grain beneath it. If you work in the wrong direction you start "lifting" the grain and end up with a lot of tearout. It's the same problem you get with spindle turning, but exaggerated.

It makes all the difference between a simple, easy finish and bashing your head against the wall, needing to spend an hour or six with the 80 grit gouge.

To be honest, 'cos I turn so many goblets I sometimes fall into the same trap and start turning bowls wrong... :o Habits can be nasty things. :rolleyes:

[rsser]

Thanx guys for responding.

DJ, could be ... it's a fibrous timber so could be whipping about. But on a short stem of nearly an inch?

Skew: wouldn't an Oland tool really be a round bedan? Any case, light scrape cuts from the rim down are no prob, end grain cuts from the inside out ditto; yep Barry, wot you said. There's even a knot near the stem but that's not doing it.

Barry: yeah, willow 'resonates', pardon the pun, but there's very little overhang. I've gone 4-5" overhang into hard redgum before getting this kind of high freq catch/chatter. And the opening is too small to get any special rest into it ... well maybe; now you've got me thinking. Might be able to get something in closer. Will have a look

Or will have to settle for removing microns at a time.

[Edit: Skew, it's not grain tear-out, it's full blown chatter]

[Skew ChiDAMN!!]

Unless you have a BIG oland tool (I wish! $$$) there's still a degree of flex in the shaft. As I said, my round bedans are made from big ol' screwdrivers and if they start flexing I know my toolrest will be flexing too! ;)

Mebbe not tearout as such, but it often only takes the merest "grab" of the tip to initiate a major chatter session, especially in the whippier woods. Sometimes tearout is the cause, but you just don't see it 'cos the chatter has taken out the evidence.

But I'm inclined to point the finger at the stem... in my books that's a no-no. The stem is turned last for good reason, even if it is only an inch long. You not only increase the chance of lateral flex in the bowl section, but the reduced diameter of the stem means it can "wind up" which exacerbates chatter (once it's started) in a major way. Basically you end up with both lateral and rotational vibration.

Given all the reading I do, you'd think I'd be able to find the words to explain it clearly, wouldn't you? :(

[cedar n silky]

Skew- you are so "eloquent" in your advice!! As is everyone else. And RSSR, realy good of you to post these questions for all of us out here in wood turning land.:D
I get so much from this forum- Particularly since I have not turned a goblet yet, but intend to, just for the challenge- if nothing else!:rolleyes:

[cedar n silky]

Unless you have a BIG oland tool (I wish! $$$) there's still a degree of flex in the shaft. As I said, my round bedans are made from big ol' screwdrivers and if they start flexing I know my toolrest will be flexing too! ;)

Skew would you mind posting a photo of your improvised Screw driver/s!!
I'm running out of ???:eek: And I love your improvisations! I am about to tackle the international leaf springs with the thin angle grinder wheels for my scrapers.
Cheers:)

[Skew ChiDAMN!!]

Here's the top & profile pix I posted elsewhere on a similar thread. Apologies for the quality, but I'm a turner, not a photographer... and I hate my camera. :rolleyes:
http://www.woodworkforums.ubeaut.com.au/attachment.php?attachmentid=26478&d=1152948925
http://www.woodworkforums.ubeaut.com.au/attachment.php?attachmentid=26477&d=1152948925

That particular one was originally a small phillip's, but my main ones are made from mechanics' flats with about 12mm shafts; which also had a hex section near the handle for using a shifter.


Skew- you are so "eloquent" in your advice!!

If that means it takes me a 1,000 words to say "yes" then I plead guilty as charged, yer honour! :D

[cedar n silky]

Appreciate the photo's. thanks:)

[rsser]

K, tried Barry's suggestion of getting a rest in close (overhang maybe three quarters of an inch in old money), used the normally trusty 5/16" Oland tool (pretty similar to your screw driver Skew) and got better results but still a long way off what I'd expect or need.

The 1" btw was the stem diam.

Think it must be the timber flexing. Done this kind of thing before with soft or medium density timbers without drama.

Guess it's micron ribbons or nothing. Not up to a steady rest at this stage. Might manage some steadying fingers.

Hollowing the inside first is real 'mess with my mind' stuff but I guess it could be drawn on paper and a template produced.

Maybe flex in the brainbox is the real issue :rolleyes:

[Skew ChiDAMN!!]

The 1" btw was the stem diam.

My mistake. :o I should've realised that's what you meant. If the flex is that bad, it may be time to resort to [gasp] the 80 grit gouge! :eek:


Hollowing the inside first is real 'mess with my mind' stuff but I guess it could be drawn on paper and a template produced.

Maybe flex in the brainbox is the real issue :rolleyes:

At least it keeps you on your toes, mentally. :)

Some people like to hollow to depth, then shape the walls from there; I can't work that way. I shape the top 3/4 or so of the outside of the bowl, then hollow the inside shaping and finishing (inside and out) the walls from the rim down. This way I can get the walls down to almost transparent thickness without major headaches. Once I've started hollowing past what I've already shaped on the outside I'll start switching back'n'forth between inside and outside, completing perhaps 5mm of the wall at a time.

This allows me to get the transition right while still keeping the walls nice'n'thin. It also means the "stem" section gives the maximum support it can to the area I'm working. Sounds fiddly, but it's really quite quick.

[Captain Chaos]

"The 1" btw was the stem diam."

Yeah, sorry 'bout that Ern. I forgot to mention that.:o
Have you tried setting the toolrest above centre when cutting with scraping tools ( when performing internal cuts )? I've found that toolrest height can sometimes alter the cutting position of the tool enough to stop chatter etc. Plus, use Rooolly, rooolly sharp tools. ;) I know that I'm preaching to The Boss, but I thought that I'd just run it by you just in case.
Sounds like it may be a harmonics thing, so what you could try is wrapping a bit of firm foam rubber etc. around the exterior & securing it in position with masking tape, electrical insulation tape or racer tape. This may give added support to the goblet in the critical area & move the harmonic frequency to a different level & reduce / stop the chatter. I've always been going to try this myself but never actually gotten around to it - not because I don't get tool chatter with my turning. I think that I actually invented it! :eek::(
Could you work the tool with one hand & support the exterior surface with the other hand, you know just letting the fingers rub against the goblet?
This may help as well.
Regards,
Barry.

[rowie]

g'day Ern,
although turning the stem first has caused most trouble, being a small internal transition(curve), you may find that using a tool with a similar sized curved cutting edge that there is too much tool touching the wood at one time, causing mini catches/chatter. Going to a smaller radiused tool(like your Oland?) reduces the amount of edge in touch with the wood, decreasing the chatter.

[hughie]

Appreciate the photo's. thanks:)


I kinda have something very similar although its made from a bit of 3/8 round HSS tool steel I had lying around, set in a piece of 3/4 round bar. A bit unwieldy at times but it gets the job done

Other than that Ern it looks like microns...maybe some sort of steady if its harmonics..... i hate it when i cant lick the problem....:mad: ggrrrrh

[Captain Chaos]

"maybe some sort of steady if its harmonics" - Hughie

G'day Ern,
Didn't you make a flash harry ( with no disrespect to the Harrys on this forum ) rest for supporting bowls a while back? Perhaps you could set that up & give it a try.
That's it for me Ern, no more pearls of wisdom from this "Stroke of Genius" challenged old timer. :D;)
Good luck Ern,
Barry.

[ptc]

Ern
have you cracked it yet.?
I told you the make great axe handles out of it !

[rsser]

Yep, ptc, if I could make a hatchet handle to beat the bejesus out of what I'm trying to turn ... ;-} ... or are you, as they used to say, 'having a lend of me'? Don't mind the challenge, but if it gets harder than this, no more marmalade!

Yes Barry, had a bowl steady that I hope the current owner of the old Vicmarc 175 is benefitting from! Good memory you have.

All your good advice has been composting in the back of the head. Only got half an hour on the beast today after having done a roast for the family celebration of me mum's 86th. (Lot's of good wine and talk, and one of me juniors remembered the other with a gift of a seriously big stogie, bless him).

So tried a steeper angle with a tight curve on a scraper and got better if still slow results. Only half way there still. So thanks Barry and rowie.

And skew, your advice is still stewing ... the link btwn chatter and tear out.

[ptc]

Ern
You know what it is ?
You need a good run on your bike.
I Have not cut the big bit yet,
will try to get Chris to ship it for me.

[rsser]

lol, yeah, let the adrenaline wash out the frustration.

Just took her in today for the quote. If it's repairable it'll be about a four week job.

Got some more time in the goblet last night. Results improved with some more RPMs and light shear cuts with the 3/8" Oland-style tool. Should get there eventually.

[ptc]

Whats the latest on the Bike ?

[rsser]

... be a week before I hear ptc. First the quote has to be sent in, then the insurer sends the assessor out to see if I was using an unroadworthy tyre, etc etc.

[brind0g]

Here is my 2 cents worth.. A Custom made hollowing spade for goblets, and one of my latest goblets, i have only made goblets using cooking pear tree limbs (its not the nicest looking timber in the world, so its good to practise on, but it is VERY nice to turn)... The Spade bit was made by a mate, he just used a dead centre, cut the head off, and just used the morce taper and welded on the plate and did some grinding and presto!!

[rowie]

Got some more time in the goblet last night. Results improved with some more RPMs and light shear cuts with the 3/8" Oland-style tool. Should get there eventually.slow and easy wins the race Ern;)

[rsser]

hey brinddog, what's the diam of the tip?

Rowie, yep, go any slower and the horizontal and I will be in cryogenic suspension! But whatever it takes ... there's always something to learn.

And it's worth it with this 'horizontal' ... can't wait to get some DO on it to see how the figure comes up

[ptc]

Ern.
Sounds to me like your winning.
When is the Musk Getting the Treatment.

[Skew ChiDAMN!!]

Rowie, yep, go any slower and the horizontal and I will be in cryogenic suspension! But whatever it takes ... there's always something to learn.

Just so long as it doesn't slow to a "shelf stasis" state. In my shed, once an item achieves that level of unprogress, it becomes part of the shed collection and is almost impossible to kick-start again. :(

[tashammer]

curious, horizontal scrub, very hard, fine-grained, was tempted to say try a metal lathe cutter. Dunno why. i have a faded mental pic of some bloke using metal working tools, but darned if i know where that came from. Maybe i am talking out my foot here.

[brind0g]

2 inches.. or for you metric people around the 5cm mark...

[rsser]

ptc: that bit of musk just has me gobsmacked. Seems to me it could be put in a gallery as it is, and so whatever I do has to match/enhance what it is.

I'll be sitting with it for a while as I figure out what that will be.

Skew: yes, I know that temptation. Actually gave into it a while ago by buying a third chuck so I could have multiple jobs on the go but have realised it also encourages procrastination.

tashammer: effectively what I'm doing is using metal turning technique as best as I can understand it. That said, the outside shaped readily enough with a gouge with a fresh edge.

It's a lovely timber with some irregular grain; as posted elsewhere, my best guess is that speeding her up reduced the harmonics as Hughie described it so well, and using a scraper with more heft reduced tool flex. That said, I think the wood is 'whippy'. Can't get more technical than that!

But thanks all for taking the time to share your advice.

[ptc]

Ern
I think i might treat myself to a lump of that Musk for the fog locker.

[rsser]

Time to get a slow combustion stove in there my friend.

Plus carpet tiles on the floor.

Plus foil-backed fibreglass blanket on the walls and ceiling.

Missed anything?

Oh yep, ugg boots ;-}

[ptc]

Ern
Bit late for it now (spring is here ! ) Brrrrr!
Have a black bird nesting in the Flu.

[rsser]

So do the pets eat roast bird?

Gee, now I'm hijacking my own thread.

Got some good progress on the hollowing hassle last night, just taking it slowly and doing what I've mentioned. [Edit: with a good edge just getting very fine narrow ribbons out; kinda mesmerising].

Cleaned up the top inside with a toothpick.

Still got a peculiar dimple left in the bottom. Initially figured it was the point mark left by depth drilling but I can't seem to get rid of it with the 3/8" Oland style tool (aka round nose scraper). Wonder whether I'm recreating it somehow. Tried coming at it from outside in but the tool starts to catch.

Anycase, to revert to other irrelevancies, turns out that my 30kph slide on the Trumpy means she's a write-off ($11k damage would you believe) so it's time to choose another bike. Just like a lathe, if you can only have one it's hard to figure out the balance of trade-offs that you can live with esp when dealers won't give you one for a weekend to try out :mad:

[ptc]

No they only like canned stuff !!! (the cats )
Sorry to hear about the Write Off
You will have to put some wheels on the Beast.
I have cut the Horizontal.
Will try to get it away next week.

[rsser]

Many thanks Peter.

No rush.

Let me know the postage.

Yeah, what would the bike equiv be of a Stubby ... lol.

[Skew ChiDAMN!!]

Sorry to hear about the Trumpy, Ern.

I dunno about you, but my ol' girl was the worlds' best stress reliever, not just transport. Wish I could take her for a spin... :(

[ptc]

Ern.
A Vincent Twin "black Shadow."

[rsser]

Thanks Skew. Yep, half a day of fanging sorts out most of the world's problems!

Any case, think I've got the replacement lined up, and p.t.c. it won't be a Vincent. Once came close to buying a Velocette Thruxton new ... wish I had and had kept it but as they say, 'if wishes were horses ...'. Nope, back to a rice burner for me. Gasket Goo and broken bolts no longer hold any appeal.

[Skew ChiDAMN!!]

So, any news on the goblet front?

And any preference on the rice-burner? My ol' man has stored his '81 Suzuki GS650G & '96 Yamaha Diversion XJ900S (not even a 1000km on the clock... bought just before his stroke. :( ) in my shed and they're both in excellent condition. For purposes of maintenance, they're taken for the occasional spin, of course... even though we've let the rego's lapse. :o

I prefer hard iron, but both these bikes have tempted me to the aluminium side.

[rsser]

Skew, the goblet continues to throw up challenges. The latest is some deep scratches on the underside of the bowl left by the old 80 grit. Can't get below them with paper so it's back to steel.

As for the bike, yep, deposit down on a Honda Fireblade. Borrowed one for a day yesterday, did Black and Reefton spurs and had a hoot: fast, light, nimble and not as hard on the bones as expected.

Ah, an old Divvy in the shed. Seem to recall it has a steel frame at least ;-} Now there's a comfy tourer for you. And with springtime upon us ....

[ptc]

Is it a Red one ?

[OGYT]

Tashammer, I use metal lathe HSS cutters... 1/4 x 1/4 x 2.5"... should be able to get them at any metal supplier in Oz. I use them in my Oland tools.
For Goblet stems, high rpm and light cuts = easy-does-it, in my books.
Somewhere I heard of someone using a "string steady"... don't know what that is, though.

How the heck did this post get here? I was replying to Tashammer, now his post ain't here.... hmmmm. Still just a dumb yank, I guess.

[Gra]

Ern.
A Vincent Twin "black Shadow."


I know of one of those hanging on a wall in a shed, up country (No he wont part with it)

[Skew ChiDAMN!!]

Somewhere I heard of someone using a "string steady"... don't know what that is, though.

'Tis basically a cats' cradle of string. :)

Good for damping vibrations in long, thin, spindle turning but not very effective for goblets that're only supported at one end. :(

[ptc]

Never mind the Fireblade
Where's the Goblet ?

[Captain Chaos]

Never mind the Fireblade
Where's the Goblet ?
Yeah Ern,
Lets see how well "we turned our goblet" - Pictures please? ;):D:D ( Tongue firmly in cheek.)
Regards,
Barry

[rsser]

OK, OK ... I confess to a 140hp distraction :o ... another beast: smooth powerful and fast.

Will get down to the final chapter in the goblet saga.

[ptc]

I bet its a Honda Goblet !!!

[Captain Chaos]

Worlds fastest goblet?:p

Regards,
Barry

[ptc]

Its snowing over here !

[rsser]

Lucky sods.

Time to turn a nose for your snowman ;-}

[ptc]

I see its a yellow one ?

[rsser]

Update: the scratches were in fact heat checking I think so I've gone back over the inside and outside wet sanding. Much improved results. That said, the timber still scratches easily and a light touch is needed.

Bit more of that to do and then the stem gets thinned down.

Progress has been slow as my son dropped his bike last week and dad gets to help fix it.

[ptc]

Is your new bike a Yellow one ????

[Skew ChiDAMN!!]

Update: the scratches were in fact heat checking I think so I've gone back over the inside and outside wet sanding. Much improved results. That said, the timber still scratches easily and a light touch is needed.

:eek: What timber did you say it was?


Progress has been slow as my son dropped his bike last week and dad gets to help fix it.

It never rains but it pours, eh? ;)

[rsser]

ptc, yep, just as in the avatar. Richmond colours :( but at least it stands out on the road.

She is to the Triumph as a scalpel is to an axe ;-}

Skew: the timber is 'horizontal' ... as in Tassie horizontal scrub. Something grandulosum is the tech term I think.

Yeah, I'm getting an education in backyard fairing repairers and painters. The finish is a gorgeous candy red which needs a special undercoat and multiple translucent top coats followed by a clear coat. Paint alone costs a bomb.

[Skew ChiDAMN!!]

She is to the Triumph as a scalpel is to an axe ;-}

Huh? You mean it's useless for cutting wood? :confused:;):D

[rsser]

Huh? You mean it's useless for cutting wood? :confused:;):D

lol, it's a bit hard managing two obsessions at once.

[ptc]

Ern
is it finished yet ?

[tashammer]

Its snowing over here !

are you close to Paradise ? (that oughta get them guessing - them not us).

[ptc]

Not sure.
its a bit WINDY

[tashammer]

Paradise is over Sheffield way. But it has been years since i have been that way.

[ptc]

Tashammer.
Any wood shows on round your way ?

[ptc]

Ern
is it finished yet. ?

[rsser]

Peter, I'm hastening slowly ;-}

Got more W&D in but am also now working full-time.

I promise to post a pic as soon as she's done.