|David Thompson 1||16/08/2017 18:36:41|
|6 forum posts|
Why, when setting up a lathe, is the advice to make sure it is level?
Wouldn't it be ok if it wasn't level, as long as the bed wasn't twisted or distorted?
818 forum posts
David, not an expert but having the lathe level helps when setting it up. As you say though if there is no twist in the bed and no distortion then the lathe will still work at an angle. There are slant bed lathe which are definitely at an angle front to back but probably still levelish lengthwise. I think getting paranoid about level is unnecessary. When I was briefly in the Merchant Navy the lathe in the engine room was rarely, if ever, level. Come to that you had to hang on to it just to keep yourself level sometimes!
|Carl Wilson 4||16/08/2017 19:07:00|
671 forum posts
|Shoot me now.|
|802 forum posts|
There are slant bed lathe which are definitely at an angle front to back but probably still levelish lengthwise.
Slant bed lathes are leveled front-to-back using a fixture held in the turret that puts the level errr.... level.
Sometimes this is provided with the machine as part of the original equipment, sometimes the installation technician brings the factory tool along with him (and takes it away again) or, in my case, you make one when you get a second hand machine.
When (reasonable quality) lathes are manufactured, the alignments are set with the bed set in a known condition. Setting the bed back to that known condition on installation should, therefore, bring all the other alignments back to the values shown on the inspection record. In the greater (industrial) scheme of things, a precision level is cheap & easy to use, so using one to set the bed level is easy for both machine builder & end user to get to a known condition.
A 0.05mm/metre level can be obtained from Ebay from £40-ish (Item 272295866038 for example), which isn't a great deal for a precision measuring device.
Doubtless there will be other posts along shortly extolling the virtues of "Rollies Dad's Method" (whoever Rollie was ?) to set up a lathe & decrying the use of a precision level in the home workshop - to each their own !
|Ian Skeldon 2||16/08/2017 19:39:23|
|489 forum posts|
Firstly I want to point out that I am probably no more knowledgable than David Thompson 1, however David ask yourself this question;
If I am going to bother making sure that there is now twisting, bending and distortion in the lathe once it is set up, why would I not make sure it was level as well?
5488 forum posts
The engineering community need to invent a new word for levelling a lathe when they don't mean levelling it.
Like when the first cave man started to knock through an extra door hole but had a tea break after doing the top half. He got tired of explaining to everyone that it was half a door that he hadn't got round to finishing so invented a new word for it which made it much simpler.
|David Thompson 1||16/08/2017 20:12:35|
|6 forum posts|
Carl Wilson 4
Why write, "shoot me now"? Is this intended as an insult? If you don't have any knowledge on the subject why bother posting?
|David Thompson 1||16/08/2017 20:15:53|
|6 forum posts|
An enigmatic reply. Cavemen? Can you give a less obscure response?
|Alan Vos||16/08/2017 20:16:56|
|162 forum posts|
From what I have read (there is a lot of it), a straight bed is what counts. Level w.r.t. gravity is a means to that end.
So, is there a method for measuring twist when the bed is not level? I figure it can be done using the traditional precision spirit level with the addition of a sine bar and slip gauges. Those take the place of the factory tool mentioned by Ngel B. But that is getting expensive (or an excuse to buy a sine bar and slip gauges).
Whichever way you do it, you need to measure using the same surfaces the saddle runs on. If your lathe has a prismatic bed, this gets complicated.
|Nick Hulme||16/08/2017 20:20:24|
|743 forum posts|
Why would you ensure that there was twist in your bed? That's confusing!
1424 forum posts
The term simply means that the lathe is level within itself, i.e without twist of the guiding surfaces.
It's immaterial to its precision how the lathe is orientated in its environment.
|Peter G. Shaw||16/08/2017 20:31:56|
1170 forum posts
May I refer you to Chapter 9 of Tubal Cain's (pen name of T.D.Walshaw) book Workholding in the Lathe (Workshop Practice Series 15) where he goes into mounting a lathe, and then the reasons for, and how, to set up the lathe.
Peter G. Shaw
5488 forum posts
It was just that the word 'level' when used in reference to setting up a lathe has a different meaning to the usual 'horizontal' or 'flat'. For lathes it means lack of twist and since it can be achieved traditionally using a spirit-level the term has stuck. It causes endless confusion so it would be easier if we had a different word.
If you search this site you will find a lot of previous explanations of how to set up without a precision level as the subject comes up for 50% of the newcomers to the hobby so don't worry you are not alone in being confused by this.
Too many words or not enough? Bit off topic but I think the whole basis of the opposition to the Euro would have been smaller if they hadn't invented a new word for it and just called it the 'new pound' or 'new franc' etc in each country then people wouldn't have seen it as so alien.
|David Standing 1||16/08/2017 20:39:39|
|1289 forum posts|
Unless your comment was tongue in cheek, Ian obviously had a sausage fingers moment and typed 'now' instead of 'not'
6335 forum posts
My take on levelling is that it's a basic engineering tactic used to simplify construction. Buildings are levelled, roads are levelled, drains are installed at an angle to a level, distances are measured on a level, and machine installations are levelled. Levelling provides a reproducible reference both for the base and the verticals.
The construction, which could be a lathe, is designed to ground it's own weight and loadings without the forces involved causing the structure to bend or topple over. This is most easily done by reference to a level. It follows that an object designed with reference to a level should be installed to match the design so that the installation can be checked.
Levelling also provides a reference for ensuring alignment of parts during assembly. This is particularly important with any construction that's liable to bend. Everything bends, a big expensive lathe is likely to be more vulnerable to bending than a mini-lathe because the latter is short and stubby. Some machines require more care than others.
Another reason relates to balance: off-centre installation may cause vibration.
In the case of the average lathe, once it's installed, I don't think it matters much if it's operated off level. Lathes are used successfully at sea.
|3309 forum posts|
The Slant Bed lathe (example Willson Lathe Company of Halifax) was a means of using a larger swing over the bed, the spindle being set further back.
Nevertheless the bed is "level", albeit at a downward inclined angle front to back. (Hence jig Nigel B mentioned earlier above).
The axes of a lathe need to be set up true to each other, not of necessity in relation to any other plane. We have called it " levelling", Set true might be a better term?
|Russell Eberhardt||16/08/2017 21:05:02|
2600 forum posts
Google "Rolly's Dad's Method" for the simplest method.
|Carl Wilson 4||16/08/2017 21:33:33|
671 forum posts
|Hello David Thompson.|
I do have some knowledge on the subject. Not a lot, I admit, and probably not as much as many of the luminaries hereabouts.
My posting was intended to be taken with a certain degree of levity. The subject of lathe set up and levelling has been done to death and invariably results in a bun fight between respective camps on whose method us the best.
My words were intended as a bit of a laugh, a sigh and a "here we go again..."
I'm sorry if that didn't come across.
|802 forum posts|
You lot are slacking - 16 posts in before "Rolly's Dad's Method" came up !
Buy or borrow a proper level & do it right.
|Ian P||16/08/2017 23:00:33|
2420 forum posts
Is Rolly's father a different person to the Rollie you mentioned in your first reply (third not sixteenth post) to this thread?
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