How often are you alligning your lathes?

My ML7 can be made to work quite parallel.

It is not too difficult to make it cutting with 0.5 thou per foot accuracy.

That is done by means of packing under one or another foot at the tailstock end. Machine is standing on original metal cabinet, bolted securely to reinforced concrete floor in my garage.

However within about 6 weeks from alligning lathe may cut 2-4 on even 6 thou per foot tapers, hence frequent allignements are needed to keep precision.

It seems to keep allignement for about 2-3 weeks and then slowly float off mark.

Is that a normal behavior and I must suffer with it, or some remedies related lets say to bolting methods are available?

I,ve had my super 7 for about thirty years it,s never moved and it,s bolted to an angle iron stand

Temperature changes within your garage? although miniscule within the metal itself possibly some differential between concrete & metal... just a thought

George.

Concrete and steel have very similar cofficients of expansion. Lucky, that, or a lot of reinforced concrete would not survive long...

It could possibly be the concrete floor moving about. Depending on construction, it may just be a flat slab of concrete "floating" on the ground below, depending on moisture content etc etc as to exactly where it lies.

You might help by reinforcing the cabinet with some stout steel square tubing or angle iron and leaving the floor bolts loose.

Or substitute rubber pads for the floor bolts and put a bracket from the top of the cabinet to the wall just for safety's sake so the top heavy lathe can't tip over.

This is a guess!

You are adjusting the lathe by twisting the lathe bed. The bed stores energy like a spring and will return to 'normal' if it possibly can. The problem may be that time and vibration gradually move the lathe, shimming, and/or stand such that the lathe bed relaxes and goes out of alignment again.

If so the cure might lie in finding out why the lathe bed needs to be corrected in the first place.

The problem may not be with the lathe at all. For example, if the floor or cabinet base aren't flat, then firmly bolting the cabinet down will twist the cabinet out of shape. This in turn could upset the alignment of a lathe balanced on top.

Some detective work is required.

Or:

Occasionally threads pop up questioning the need for lathes to be installed level. Some recent reading suggests that levelling isn't done because lathes 'must' be level. Rather, the installation process of any structure uses levelling at each stage as a way of ensuring that all the parts are fitted in proper alignment. Unpredictable things happen if they aren't.

It's much easier to get alignments correct when everything is orientated with a common reference like a level. You could try the same: make sure the floor is flat; make sure the cabinet base is flat and evenly seated on the floor; make sure the cabinet sides are vertical and the top flat; make sure that alignment is maintained when the bolts are tightened; make sure the lathe sits flat on the cabinet top. Then apply any shimming needed to get the lathe spot on.

Good luck,

Dave

Just an example - our house and garage is built on clay. A few years a go I started to have problems with pedestrian door to garage being difficult to open. After lots of investigation and abortive attempts at fixing, I eventually realised that the problem was a tree in neighbour's garden - over spring/summer tree grows, sucks water out of clay which shrinks, in winter tree is dormant and there is more rain (by the next spring I can open the door again).

Basically the whole raft the garage sits on was moving/bending. Thankfully new neighbour has hacked the tree right back and problem is vastly reduced.

Like Hopper says - the issue could be the concrete floor, so bear that in mind in addition to other possible causes.

I leveled the 2 lathes I have 15 years or so ago, checked them now and then but no movement at all. They stand on non reinforced concrete on sand, with ground water level at around 10 m. Niko.

The area of my workshop where my lathe stands has double thickness (over standard garage floor), and double the reinforcing, I first rechecked the levels about 4 years ago, about 18 months after our major earth quake, no changes noted.

Ian S C

The words "bolted securely to a concrete floor" ring alarm bells. The manual for my lathe (a Viceroy) details that the anchor bolts should be finger tight. If the lathe is pulled down hard onto a concrete floor then there is a good possibility that it will twist everything. Think about it, if the floor is out by just 1mm over the length of the machine (and how many pieces of concrete are this level?), then pulling it down hard can transfer this into the bed of the lathe. The anchor bolts are only there to stop the machine from falling over and don't need to be tight to do this. If vibration etc is a problem then use a rubber or similar pad around the anchors.

Edited By Martin Cargill on 05/11/2016 10:55:54

I found that my ML7 was VERY sensitive; half a flat on a holding down bolt would send the bubble in the level flying. As already said, slacken the bolts on the stand, / fit rubber pads, and level the lathe using the holding down bolts on the lathe feet, making very small adjustments, with repeated checks with the level.

I know to my cost that the present shop moves depending upon the moisture content of the ground, so try to isolate your lathe from such events.

Howard

The concreter floor is moving,small lathes should just sit on the floor i.e. not bolted ,if the lathe continues to "move " try mounting it on three pads,precision tools such as grinders only have three pads cast on the bottom of the machine ,with three pads it is bound to sit down without rocking.My myford has sat for 40 years on a home made sturdy timber cabinet, with a 7 inch wide length of channel iron mounted on top under the tray,the iron is very stable and is stiff enough to align the bed as per Myford instructions i.e. adjust it at the tailstock end. My large Colchester 7.5 in does suffer from alignment problems as the clay subsoil does move and the sheds concrete floor is a bit thin,I never thought I would have such a big lathe,the solution to this problem would be to dig out about 1 ft and make a "floating " base of reinforced concrete but I have got past it. The instructions for my surface grinder state that for the best operating conditions a it should stand on a concrete block 2 ft thick. A large Cincinnati Cnc mill I was involved with years ago sat on a concrete block 4 ft thick.So do not bolt a machine tool down to floor which is not stable,let it float.Unstable machines such as drills & power presses are bolted down as they are top heavy.

When referring to lathe leveling. I take it as comparing the level across the bed at the head stock end of the bed with the level across the bed at the tail stock end, ie., twist. the lathe doesn't have to be level length wise, although it does look better if it's not too far out. I suppose its possible for a lathe bed to droop so that the head stock is level, then the bed bends down, or up toward the tail stock, forming a bowed section of bed. I know, I'm rambling, I'v stopped now.

Ian S C

The cabinet is not rigid enough. I doubt if any modern ones are really. Lathe beds are pretty stiff things. Sheet steel plus bits of angle iron aren't and will give over time. The lathe wins eventually. Really the technique is from days when lathes were mounted on very stiff and rigid cast iron cabinets of one sort or another. Those days from what I can see are long gone.

John

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Re the garage door problem - the house footings on clay are likely to be much deeper than the garage, hence the problem even without tree roots (which will make things worse!).

For non-level surfaces, shims are the obvious way to be bolting anything down!

My 'flimsy' (not really!) 3.2mm folded and tapered cabinet is mounted on a 6'' plinth of 1/2'', or so, thick cast iron base which simply stands on a substantial concrete garage floor. Base weighs around 100kg, stand around the same and the lathe about 175kg. With about another 60kg of 'ballast' in the cupboard and in the base I ddon't think mine is going anywhere! It is a 5'' centre height lathe.

I may have overstated the problems a little but this gives some idea of the amount of correction that may be needed.

If it's any more than these sort of figures suggest it may well mean that the bed is worn or the headstock is out of alignment. Bearing wear / looseness will also cause taper - similar to the bar bending when cutting - larger towards the end. In short the lathe aught to cut to 0.001 / ft as it comes freely mounted and that is all the bed stressing is intended to fix. I have my doubts about if it will last though. Even I beams take a set eventually under their own weight.

What I would do if it was more than this and not due to wear is look at the headstock alignment first. 7's have some cap head screws coming in from the side which should allow minor adjustments. I'd guess if people have a lathe that doesn't meet these sort of figures there is a "problem" some where. It doesn't take much of one to exceed 0.001 / ft.

John

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Pretty much never, I wont touch it if i don't need to.

I don't subscribe to the idea of deliberately trying to twist a bed to desired shape will only lead to problems further down the line. 

Michael W

Edited By Michael Walters on 07/11/2016 10:01:29

I am amazed to read some of the methods to get a lathe to align, a small lathe does not need bedding down on concrete. With a stand just level the bed both ways and get rubber pads to fix to the stand first.

If you had a 14 foot bed lathe then, I agree that you need hard standing. The same thing applies to a mill or a shaper, their own weight is adequate for stability on the sizes that model maker work with!

Bolting down should be that the head or nut slightly clamped and backed off half a turn, job done. Why all the finesse. A good way to disperse ground force from a machine is set it down on lead sheet where it contacts a hard floor. All my optical stands were set on 2 thicknesses of lead sheet and after setting never moved, I worked to less than a half sec and a Collimator set and tested stayed the same year in year out.

Spend a bit more time turning or milling instead of fussing about where the machine is walking.

Clive