Machine Feet for my lathe

[cropwell]

Use something smaller then and ream it to size ! Make sure you centre punch it first

[cncJim]

Dang - I'm fresh out of 1 micron drills!

Use something smaller then and ream it to size ! Make sure you centre punch it first

Lol! Nice replies!

Ok so I now have the cabinets drilled, tapped and have 4 adjustable feet on each! First time tapping anything so well pleased with the result!

Next step is to get the lathe on the cabinets.

Not sure what to do about the levelling part.... I would like to make sure the bed is accurately levelled but how accurate do I really need?

So there is this cheep and cheerful level:-
DIGITAL LEVEL BOX ANGLE SENSOR
ACCURACY: 1.75mm/m 3.5mm/m (O.1°/ OTHER O.2°)
£14.95
http://www.chronos.ltd.uk/acatalog/info-30316004.html

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

Obviously the more expensive one seems is better in terms of accuracy (by my calculations....) but will it really be worth it? Or will the cheaper level be good enough?

Cheers,

Jim

[EddyCurrent]

Jim, are you wanting the machine level or flat, I thought flat would be more important provided it's fairly level.

Also if you have a 0.1 angle over a length of 1000 mm the difference in height at each end would be 1.75 mm

[cncJim]

Thanks for the reply Eddy.

I guess I am mixing terms. The only thing I really am interested in is making sure the lathe cuts as straight and accurately as I can manage. So I think I need to be concentrating on getting the bed as flat (no twist) as possible.

I will level the cabinets first (to provide a solid base) then put the lathe on. Then shim between the lathe/base as required until the bed is flat?

I guess I am talking myself toward the more expensive level! It say an accuracy of 0.02mm/m which sounds crazy... Would you really be able to see that difference with a bubble!?!

[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