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Lignum vitae under the saddle?

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ady08/12/2010 19:03:49
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I'm currently stripping down an old pultra and was surprised by the lightness of one of the blocks under the saddle.
They are used to position the underside of the saddle at right angles across the raised ways of the bed when it's screwed down, and I presume resist twisting forces when cutting.
 
One is metal, but the other is a very hard light material, wood I think.
 
Is anyone aware of this practice with these boley/pultra/watchmaker style of lathes with a fixed position saddle?
Alex gibson08/12/2010 19:08:02
35 forum posts
you should ask terryd cos he knows everything 
Richard Parsons09/12/2010 06:08:07
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As I remember Lignum which were used as the thrust blocks on the propeller shafts. It was quite heavy. Lignum is very hard, self lubricating and has good wearing properties.

My Lorch which is similar to the Boley-Linen uses normal gib strips in its compound/cross slide which is fixed by a clamp around or under bed.

 

 

Ian S C09/12/2010 09:07:16
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Lignum Vitae is heavy, I remember a young nephew being supprised when a large piece sank to the bottom of a tank of water, he was sure all wood floats.
on another tack. the bearings in the vintage turbine that I look after consist of 4 blocks of Lignum Vitae, 2" x4" x 6" held in clamps around the shaft. When we first started on the restoration 18yrs ago the bearing had been dry for many years, and had seized on the shaft. Ian S C
ady09/12/2010 09:15:46
612 forum posts
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I just tried my bit of wood in the sink and it sank straight to the bottom.
 
It's no bodge job either, it appears to have been carefully and accurately machined.
Chris Trice09/12/2010 10:20:21
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It obviously bears against a surface that the designers were keen not to have wear. I've an Emco Compact 5 (not the same league) which has hard plastic gib strips. This took me back a bit but seems to work OK and there's no wear I can see on any of the corresponding metal parts. Perhaps it's the same mind set?
 
Ian S C09/12/2010 10:35:33
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ady, the advantage of Lignum Vitae in engineering is that in water ie prop shafts on ships, our turbine is that it is a self lubricating bearing, also it can be machined asif it were metal. The bit my nephew was worrying about was an off cut from a floor grateing  my brother in law was making for the walkway  round the pens in his pig shed. There is another wood that on dry land is used for similar high strength uses, I just know it as Austrailian hard wood, its used for railway sleepers, power poles, and I'v seen it used as flooring in shearing sheds.  When I was into wood turning, afriend was refloring his shearing shed, and gave me some off cuts, you can turn it ,but you sharpen the chisel every second cut, another friend converted some old wooden lawn bowl into condiment sets and had the same problem, so both woods behave more like metal than wood.Ian S C
Nicholas Farr09/12/2010 11:23:47
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Hi. Lignum Vitae is one of of two tropical American trees. Guaiacum officinal or G. sancturn which have evergreen leaves and are heavy,durable,resinous woods. Machine bearings made from either of these woods. The name is derived from New Latin, from Late Latin; "tree or wood of life". There are sevral similar or related trees.
 
Regards Nick.
Terryd09/12/2010 12:30:08
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Hi Alex,
 
I see we are into the personal comments again, but don't worry I won't complain or spit out my dummy unlike some others.  Yes, I know a lot that has been garnered during a long and varied career (see my profile).   Some have specialisms which they spend their life on and have a very deep but narrow knowledge.  Unfortunately that can lead in some to a blinkered view.  I am one who has a wide but necessarily shallower range of knowledge (but contrary to your assertion I don't claim to know everything). I can discuss the contrapuntal form of Baroque composers and the work of Lalique and Frank Lloyd Wright as easily as the iron-carbon phase diagram.  The world needs both types of mind narrow and broad, logical and lateral. 
 
I simply offer views which sometimes challenges the narrow and blinkered perspectives in order to stimulate thought, debate and discussion to push the boundaries. That is how we progress, not by merely accepting the status quo. I also am prepared to do in-depth research on a topic in order to deepen my knowledge using a very wide range of sources to which I have access. I expect my views to be sometimes controversial and often contradicted, I accept that.  However some entrenched minds have difficulty accepting it and become involved in simple insults and personal comment which is unfortunate.  As I've quoted often, 'a mind is like a parachute, most efficient when open'.
 
with the best regards and respect you deserve,
 
Terry
John Haine09/12/2010 14:28:49
5563 forum posts
322 photos
Lignum Vitae was used by John Harrison in his clocks, I think for both arbor bearings and pallets, because it didn't need lubrication.  The Brocklesby clock has been working I think for a couple of centuries without lubrication.
Alex gibson09/12/2010 20:13:20
35 forum posts
Hi Terry,
                 my previous post was an attempt at light hearted humour, not a personal attack and I'm very sorry if I caused any offence. I have the greatest respect for your achievements over a long and varied career and look forward to your continued input.
 
kind regards
alex
 
ps; I'm not sure if hugging ex pupils in shopping centres is conducive to your continued wellbeing.
 
 
Stub Mandrel09/12/2010 20:25:38
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I can't help worrying that this website seems to have a shortage of humour and humility at times.
 
Neil
Andrew Johnston09/12/2010 21:23:15
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May I ever so 'umbly suggest that this website has no humour, humility, or any other emotion; but as for the people posting on it, well that's a whole different story!
 
Your 'umble servant,
 
Andrew
Sam Stones09/12/2010 22:44:45
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Andrew,
 
I can't pick your accent!
 
Sam
Andrew Johnston09/12/2010 23:22:27
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Sam,
 
When I wrote it I had Uriah Heep in mind (Dickens, not the rock band) so I suppose the accent would be Cockney!
 
Regards,
 
Andrew
John Olsen10/12/2010 01:32:04
1294 forum posts
108 photos
1 articles
Jarrah is a very strong tough Australian hardwood, it has a density of 913 kg/m^3, while lignum vitae is 1330. So jarrah will just float while LV will sink quite definitely. (Of course the densities will vary a bit depending on the sample.
 
Jarrah is used quite a lot for things like telephone poles, at least in Oz and NZ. It is also used for the keelson of my boat where it adds a lot of strength, and of course the weight it adds is low down. Off cuts make nice bases for stationary engines, the timber has a deep reddish colour.
 
Curiously enough balsa is technically a hardwood. The definition is not based on the actual hardness of the wood...conifers are softwoods and broadleaf trees are hardwoods. 
 
regards
John
Richard Parsons10/12/2010 05:11:01
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What the heck? The wood is probably (90% certain) Lignum. This is uncommon, I have not heard of it bring used in machine tools before but I do not see why it should not be. It could have been a war time-post war emergency job (Bronze was is short supply) As the ‘man’ said if it works use it. “Nuff said” – “job done”!

'John' you stole my thunder I was going to mention Harrison’s use of Lignum in his ‘Sea Clocks’. This was the first known use of the ‘Caged Roller Bearing’. He also invented the ‘bi-metal strip’, which are used by the million in electrical gear.

Please remember we indulge in a ‘Gentleman’s Hobby’. My workroom is referred to (on my Hungarian house plans as ‘Mühely’ followed in English by the words ‘Gentleman’s hobby workshop’. The authorities did this to ensure that it was not used as a business.

So please Gentlemen ‘Nihil nisi bonum dixit’!

ady10/12/2010 10:28:53
612 forum posts
50 photos
It's a pretty specialised old 1590 unit from the English Electric Luton works, where the British Thunderbird Missile program was.
 
It's got tapered gibs, zero backlash leadscrew nuts and the bed has no slot for the threading unit along the back (maybe the castings were a special order by EE from pultra specifically for prototype work), and now I've found lignum on the base.
 
She was in a bit of a state when I found her, which is probably why I got it so cheap, almost no-one recognised what lay within this pile of rusty metal on ebay.
Pultras were pretty pricey and from the little I know about them I get the impression most got literally worked to death to recoup the initial outlay, but we're slowly cleaning her up.

I've put a couple of piccies up.

Edited By ady on 10/12/2010 10:42:04

Richard Parsons10/12/2010 15:45:13
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645 forum posts
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Ady  Nice one son she is worth a lot of TLC! and you will have a nice plain lathe there
Chris Trice10/12/2010 21:47:47
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For what it's worth, I repaired an old war time mangle a few weeks ago and the blocks each metal roller was seated in was an unidentified hardwood.

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