Machine Feet for my lathe

[Neale]

This levelling business set me wondering as well. I can think of a few reasons for doing it. One is that it puts the machine in exactly the same orientation as when it was originally ground, so you should be replicating the original accuracy. But I can't believe that you need a precision level to achieve that - I'm sure that you could get close enough with any decent level. But a precision level might be able to check for twist by checking in various places along the bed and save time spent in machining a test bar until you were very close. If you also set the machine very accurately, you could also use the level for setting work later? I've never done that, but I can see it might be useful on a milling machine.
By the way, don't use the tailstock for setting up. The initial setting up is all about getting the headstock aligned to the bed (or vice versa). That's why you don't use the tailstock when doing the initial checks. The tailstock is usually adjustable, and has to be aligned with the headstock and bed later. I wouldn't trust tailstock alignment on a fresh-from-the-factory machine.

[cropwell]

You are right about the tailstock as a primary reference it is inadequate. The first job would be to get the laser to point at a target at the tailstock end. When the dot doesn't move with the lathe turning (by hand) then the beam is directly on the axis. Then you can set up the tailstock centre, before checking the carriage. if you only want a relatively accurate level how about this one http://www.chronos.ltd.uk/cgi-bin/sh...html#a30316004
You can always put it on the bed, zero it and turn it 180deg to check for any slope.

[Neale]

A reasonable lathe is going to do better than 1 thou/20 micron accuracy - I'm not sure that a laser dot is small enough to do that well.

[cropwell]

The cheap laser pointers have quite a wide beam but you can shine it through a small aperture (pin hole). If you can make a 1 micron hole, then you have a 1 micron beam width, which would remain in good collimation over a couple of metres.

[Neale]

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

[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