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Fumbler
7th February 2019, 06:52 AM
L&G, I have been requested to have a crack at turning something very delicate, and was wondering how to approach it.

the job needs to be 380mm long and tapers from about 8-10mm, done to 5mm then on to the final 35 mm close to one end.

I have trimmed up a piece 11mm sq and was going to trap 1 end in the scroll shuck and very gently bring up the tail stock then turn down an end to fit into a mandrel saver (snuggly) to prevent undue pressure and causing flex when it thins out.

Can anyone else make any suggestions or give advice, that is, short of me hand shaping.

looking forward to the pearls of wisdom heading my way

arose62
7th February 2019, 07:05 AM
Google "trembleur" and "string steady".

Trembleurs (French for tremblers) are woodturning challenges which are very long, thin, and delicate. There are several videos showing techniques.

Skew ChiDAMN!!
7th February 2019, 09:58 AM
:whs:

String steadies are the traditional way for doing this sort of thing. They're easy enough to knock together, which is good 'cos you'll need a few; I'd have one every 100mm or so, so you'd need 3 or 4.

With these you shape and finish short lengths of the trembleur, working from the tailstock back towards the drive, placing steadies as you complete sections. Try not to start/stop the lathe while working... don't even vary the speed,,, as trembleurs are basically a series of small fly wheels and starting/stopping/varying can impart twist on the very, very thin shaft, causing breakage.

In all honesty, I like your idea of using a mandrel saver, provided it's of the right size. In the past I've used bushes in a live-centre for slightly larger dia pieces, which is pretty much the same... although I haven't gone full length. (Basically, I've turned finials as parts of lids or on rods rather than as add-ons.)

Again, work short lengths - probably only and inch or two - from the the tailstock end, leaving as much meat as possible on the unworked sections.

Unlike trembleurs, I'd stop the lathe when each section is finished to move the tailstock up. I've found (in similar jobs) that any wobble when unclamping and moving up the tailstock can have disastrous consequences if the lathe's still spinning. :B

Once I'd worked enough of the shaft so the end starts projecting beyond the tailstock... string steadies!

I wouldn't try putting a point on it. That'd be done by hand (linisher?) after the turning is complete.

I also suspect that it'd need a fair bit of hand sanding after turning. But if you get to that stage, it means you're winning! :D

Paul39
8th February 2019, 02:09 AM
Send the person to Cindy Drozda. Life is short, do you need that much aggravation. Says I, whose smallest spindle is a 35mm tool handle.

Or: https://youtu.be/OrwvgAIHXPA

Some years ago there was a "Who can make the longest thinnest finial / spindle video" Retired was part of it, there were many string centers involved. Do a search.

ian
8th February 2019, 05:03 AM
L&G, I have been requested to have a crack at turning something very delicate, and was wondering how to approach it.

the job needs to be 380mm long and tapers from about 8-10mm, done to 5mm then on to the final 35 mm close to one end.

Can anyone else make any suggestions or give advice, that is, short of me hand shaping.


https://youtu.be/OrwvgAIHXPA
Notice how Ashley is achieving the final surface mostly off the tool

Only thing I'd add is riven rather than sawn stock might make life a bit easier.

Paul39
8th February 2019, 06:59 AM
Only thing I'd add is riven rather than sawn stock might make life a bit easier.

I agree with that, You need everything in your favor, and grain running all the way down the center would help.

ian
8th February 2019, 07:25 AM
looking around, it appears that competent turners do these sorts of thin turnings without a tail stock or steadies. the key seems to be working in stages from the thinnest part back towards the head stock and never going back to the bit already fully completed.
apart from the final 35 mm that goes to a point, compared to a lace bobbin, the dimensions quoted are rather "large"

Fumbler
12th February 2019, 03:52 PM
String steadies almost complete,

449318 449319

And the 2 batons

449320

Of course nowhere near finished.

does anyone know what sort of string to use? Or how tightly to run the string? Actually how's best to string?

ian
12th February 2019, 04:21 PM
have you thought about trying go turn the finial using the technique demonstrated by Ashley Harwood -- as linked by Paul in post #4

Fumbler
12th February 2019, 05:08 PM
have you thought about trying go turn the finial using the technique demonstrated by Ashley Harwood -- as linked by Paul in post #4

Yes I have, and will give it a go, dut don't forget this is 380mm long, that's about 100. So I still need the steadies.

Skew ChiDAMN!!
12th February 2019, 06:57 PM
does anyone know what sort of string to use? Or how tightly to run the string? Actually how's best to string?

I use chalk line string, but w/out the chalk. I do wax it fairly heavily though.

I would suggest that you make all pegs (except the one you tie off the string ends on) of a fairly large diameter, so the string will slip around them fairly easily when you pull the end of the string taut. I also like to tie the free end of the string to a small expansion spring to maintain a constant tension... this also means that loosening (eg. to move it along) is a simple matter of slipping the spring off then back on the fiinal peg instead of going the route of manually tying/untying the string every time.

I've also seen blokes who tie a few weights to the end of the string as tensioners, letting them dangle down in front of the bed. I dislike this myself, but you do what you feel comfortable with.

How tightly you adjust the string is up to you and how the wood is cutting. You do NOT want it tight enough to mark the timber or start charring, all it should really be doing is damping down any vibrations along the work-piece and keeping it centred. I'd say "firm" tautness, but how many N that is I have no idea. :B

You'll have to suck it and see what works for you, I guess. ;)

Paul39
13th February 2019, 03:25 AM
String steadies almost complete,

Nice looking steadies.

Fumbler
13th February 2019, 02:58 PM
Nice looking steadies.

Thank you, its probably a plaster cast for a paper cut, and no where near as thin as a trembleur, but I just hope they do the trick.

Fumbler
3rd March 2019, 07:25 PM
Getting there on the Baton, I now have to switch to the string steady as getting a little flex in the middle.

450216

Lets try that again

450217
Ah, that's better.

Fumbler
4th March 2019, 06:57 PM
All strung up, and although my skill is not trembleur quality (and I don't want to jinx myself(touch wood)), I'm taking it an inch a day when my hands are at their steadiest.

the first one is there to help take the flex out of the centre. By the way the tail stock is free and not touching. Also the Brickies string was just a test but is fantastic. Until I can figure out how to tie a small knot with a bung thumb, the spanners as tensioner will suffice, the springs can wait.

450242 450243
This last photo is whilst lathe running at 1500 or so
450244
Pardon the pun but steady as she goes.