Machine Feet for my lathe

[cropwell]

Jim,

I just don't know the effect of a lathe bed being off level. I guess that the more important thing is that there are no forces distorting the bed. To my mind it might be more practicable to set up with a cheaper level. but before bolting down put the bed on some sort of metal filled epoxy cushions that settle out any twisting forces. Then, when they have set can the fixing bolts be tightened.
As I have said before, I am not an engineer, so some of my thinking is 'outside the box'. I am in the middle of raising my lathe off the tray to give me more room to clean up. So when I have made the platforms for the headstock and tailstock I will either need to get them surface ground or concoct some thing else like liquid metal shimming.

I am certainly following this thread for advice.

TTFN

Rob

[Neale]

I think the levelling business is to take the worst of the twist out of the bed and bring it close to its original just-ground level of accuracy. However, that isn't going to guarantee the accuracy that the lathe should be able to achieve. Once it's levelled as accurately as you can manage, then you switch to the "machining" test - the test bar machined at both ends. As long as the bed is not worn, there shouldn't be any need for grinding. That's already been done and you are just tweaking out any slight twist that develops in the casting as it ages and stresses release. The instruction manual for my lathe - cast iron integral stand, etc - recommends the "machining" test after setting up with a level, and then rechecking over the next few months. I think the BH 600 will be second-hand (although rather newer than my lathe) so it's likely to be fairly stable by now. I would set it up with a level as close as you can get and then fine-tune by machining. I can't see any point in using self-levelling techniques as they still won't give you the ultimate accuracy although it will certainly help overcome the problems of an uneven floor when first installing.

[EddyCurrent]

I've just been to the smallest room where I do my best thinking and I thought, things can be relative to a datum or relative to each other.
So using gravity as the datum, a level is placed at the headstock end for example and that is brought into alignment with the ground.
Next everything else is brought into the same alignment either by making it relative to the ground or relative to the headstock. I would suggest relative to the headstock being the most accurate in this instance.
The tools required for alignment should therefore be chosen to achieve these requirements.

[Neale]

I think you're right, Eddy - the bed does not have to be level to micron accuracy to work OK. However, it's just easier to aim at "level" across and along it than to get to take out twist by making it the same amount off-plumb all along. As to accuracy required - and I'm thinking out loud here so no guarantee of logic! - then a bed that's as about as wide as the centre height will need to be levelled to about the same accuracy as the lathe could be expected to cut. Say, 1 thou in 12" would be pretty good. That's 1 in 12000, which is about 0.005deg. That's a pretty good level...

[cncJim]

That's 1 in 12000, which is about 0.005deg. That's a pretty good level...

So this level could be just the job then?

And I found this "proper" level:-
300MM Precision Engineers Level
Accuracy 0.02mm/m (0.001°?)
£89.50
http://www.rdgtools.co.uk/cgi-bin/sh...%2ehtml#SID=63

[Neale]

Looks it - could you lend it to me when you're done?

Just joking - I still think that "reasonably level" followed by a machining test is the way to go, but certainly a decent level should get you pretty close more quickly.

[cncJim]

Looks it - could you lend it to me when you're done?

Just joking - I still think that "reasonably level" followed by a machining test is the way to go, but certainly a decent level should get you pretty close more quickly.

I agree, i must admit though, with my inexperience I have no idea what "reasonably level" looks like! Machining test after levelling will be done - I think i will be following pretty much what the guy in the videos (that Lee shared) does.

Maybe when I get more comfortable with the machine (and actually make some cuts!)/get some experience/learn about what kind of accuracy I am happy with etc, my feelings about the process may change! :)

Cheers

Jim
(PS - Neale - If I do buy one you would be more than welcome to borrow it anytime!)