Thread: Lathe Levelling

Originally Posted by jack620

Here you go Bob:

Marshalltown Msw24 Skywalker Plasterers Stilts 24in

I'm guessing RD = Rollies Dad's Method. Its an excellent way to start an argument.

you mean I wasnt supposed to do it that way

I hope everyone is remembering that if the lathe has a set twist in it, you may not (probably wont) get it level with out bolting it down. ie weight alone of the offending corner of the lathe may not be enough to remove the twist.

Originally Posted by eskimo

I hope everyone is remembering that if the lathe has a set twist in it, you may not (probably wont) get it level with out bolting it down. ie weight alone of the offending corner of the lathe may not be enough to remove the twist.

Eskimo
Yes I agree.
I was speaking with BT Bob about this.
From my own experience,for my Hercus 260 I welded up a lathe stand from 2" square steel (very rigid) its bolted to the concrete floor.
Then the lathe was set on top of it with the drip tray under, & final adjustments made, to give the correct setting & get the lathe cutting parallel as per the Hercus book page 6
Thats how its been for 20years, It has not been disturbed or adjusted at any time & all is accurate & well.
The whole thing is not dead level, but that does not matter, as per GQs note.
I think in Bobs situation he wants to be able to move the lathe from time to time, within the workshop.
regards
Bruce

Originally Posted by simonl

Yep. I think strictly speaking you are supposed to use a couple of parallels sitting on each side of the flat. Or, a couple of precision V blocks straddling each side on the V's as long as the V's don't rest on the top because as pointed out and as I've learnt the top of the V's are purely an arbitrary flat piece of metal where the V finishes and not consistent.

As for levelling back to front, I don't even worry about that as long as the cross vial in my starret is roughly in the centre. I don't have coolant set up on my lathe so I don't see what difference it would make. If swarf was sliding down one end of the swarf tray I guess it may be a tad extreme?

Also I only have a starret No. 98 should I have a more sensitive level than this? I manage to level right on one of the graduations at both ends so I get maximum accuracy as I can out of it.

Simon

A 98 is plenty enough Simon
Like I have said on here a few times, years ago I used to use a carpenters level with good results.

Dave

Thanks every one I am learning alot about lathe leveling '

I think a better description for this type of thing is "To get the twist out of a lathe" not leveling a lathe. A level is only used to compare either end for twist.

As Simon said above, most if not all will find the top of the V's to running on a different plane to the ways. This is because the beds are machined or planned first after casting (you can see the lines on the top of them) and then the bed is ground, but only either side of the V and the flat ways. The top of the V goes untouched by the grinder on most lathes, so it's height might vary to that of the flat way which the carriage rides on.
You are best to use some type of parallel on the flat way to bridge the V way, and use the same parallel either side end to end so you taking any error of the parallel out of it.

When you put a lathe on say a ship, it will never be truly level and the ship could roll many degrees. As long as the lathe is set up on a sturdy platform and it has been shimmed for twist, the actual leveling of it doesn't matter other than for coolant run off.

Many years ago there used to be lathes with only on leg in the centre on the tailstock end, so there was no way to adjust twist, but these lathes where heavy built that you would be hard pressed to twist anyway. Some of these where made for this type of purpose and mounted on ships.

Dave

It is interesting that in Peter Hercus' Text Book of Turning, revised for the 260, there is a sectional detail showing the installation of that lathe's tailstock end foot when mounted on a bench.The foot is able to pivot on a single 5/16" ball sandwiched with clearance between two plates. The lower plate is fixed to the bench, the upper plate is fixed to the lathe foot via adjustable fixings. The headstock end is rigidly mounted to the bench. The removal of twist is achieved by the careful adjustment of the feet fixings.

I am going by memory here. Bruce might like to expand on my description but given that he performed his adjustments back in the early eighties, the chance of expansion might be slight.

BT

Hi Bob,
I posted it on another forum a while back, if your thinking about 6 feet this diagram might help.out.
The sequence came from an old book I have here about setting up industrial machinery.
In your case you would drop D

I dropped 63 dollars and bought 16 of those feet Dave so I might go for an 8 footer. Thanks for the drawing.

Originally Posted by Anorak Bob

It is interesting that in Peter Hercus' Text Book of Turning, revised for the 260, there is a sectional detail showing the installation of that lathe's tailstock end foot when mounted on a bench.The foot is able to pivot on a single 5/16" ball sandwiched with clearance between two plates. The lower plate is fixed to the bench, the upper plate is fixed to the lathe foot via adjustable fixings. The headstock end is rigidly mounted to the bench. The removal of twist is achieved by the careful adjustment of the feet fixings.

I am going by memory here. Bruce might like to expand on my description but given that he performed his adjustments back in the early eighties, the chance of expansion might be slight.

BT

Bob
I was reading that section in the Hercus book on the single ball bearing & it makes good sense.
You mentioned the 9" Hercus does not have the tapped holes in the cast feet for adjusters to get twist & bring the bed back to its factory produced precision grind.
So a plate with tapped holes & set screws clamped to the lathe foot under the tailstock end resting on a ball bearing & 2 seperate bolt holes in the top plate to clamp it all to tapped holes in a lower plate would work very well I believe. It would then be a simple matter of adjusting 2 hold down bolts to pivot on the ball bearing to get things right.
It does not require much twist to get back to the optimum factory produced precision.
I hope this makes sense.
regards
Bruce

Originally Posted by eskimo

I hope everyone is remembering that if the lathe has a set twist in it, you may not (probably wont) get it level with out bolting it down. ie weight alone of the offending corner of the lathe may not be enough to remove the twist.

Yep! I have that problem, hence the leveling went on hold indefinitely (until I find a suitable source of cheap thick walled RHS to build a good rigid stand)

Out of curiousity, people generally level over the ways in some fashion. Is there any reason you can't place the level on the carriage, and simply wind it back and forth between headstock and tailstock? Seems to me that would give a more accurate result, as the carriage is the part you want to be traveling flat anyway, and on my lathe at least, with its flimsy cabinet stands, the weight of the carriage shifting seems to be enough to throw it out of whack a little.... Not to mention you don't have to worry about repeatability of parallels placement or effects of body temperature on the level.....

If your gibs are not done up dead right it could travel with one corner up at one end and the introduce inaccuracies as well. If you start at the bed you then know it's right.

Dave

Originally Posted by Dave J

If your gibs are not done up dead right it could travel with one corner up at one end and the introduce inaccuracies as well. If you start at the bed you then know it's right.

Dave

That is true, but then what happens when you're actually making a cut? Won't the corner still lift, and then you'll get tapering or hourglass shapes anyway?

It all starts to hurt my head, this 'under 1mm society' as someone called it the other day...

Twist is not the only aspect to consider. the centre line of the spindle has to be parallel to the bed ways. Think of a railway line starting on level ground and then going up or down hill. If the headstock end of the lathe is bolted down first and provision is made to raise or lower the tailstock end via shims or jacking screws, both removing twist and maintaining parallelism can be achieved regardless of the floor being level or the tray (cabinets) being level. ( Assuming the Headstock has been aligned correctly when viewed from above ).
Russell