Levelling a lathe question ..... again

[loose nut]

My lathe is sitting on adjustable levelers mounted under the two separate bases and the lathe is bolted to the top of these.

Is it better to roughly level the bases and then level the lathe by shimming the lathe to the bases OR bolt the lathe down tight to the bases, shimming as necessary to get even support all around and then level the lathe by adjusting the levelers under the two bases.

I have been getting conflicting answers on this. Does it make a difference which way it is done or is it just a matter of personnel preference.

Bolting to the floor is another thing that no one seem to be able to agree on.

[jep24601]

Lathes with cast iron legs bolted to the bed typically do not have any easy adjustment above the bottom of the legs so all the adjustment is between the feet and the floor. Since the aim is to level the lathe ways bolting the legs down on shims may be necessary to pull out any twist. If bolted down leveling can be acomplished with double nuts rather than shims.

If you have a lathe that bolts to a table then any twist in tha ways needs to be taken out between the table and the lathe so you do two leveling procedures, level the table, then the lathe ways.

[Blackadder]

Can we get this lathe levelling thing sorted a lathe does not have to be level ( it is better if it is ) to the big ball ( earth ) but it need to be in step with itself , no twist , in the same condition that it was when it was manufactured.

the HS end and the TS end should be in harmony with each other no twist thats what it means to be level .

Before you think my first statement was wrong many ships have machine shops as did the war ships in the last war the lathes in those cannot be level in relationship to the big ball unless the ship is in dry dock at sea the lathe could never be level yet they still turned (pun accepted ) accurate work

so get the support bolted down to the floor reasonable true bolt on the lathe and go from there a good machinist level will get you in the ball park as to the twist in the bed induced by the support shim ( adjust it ) out let the machine sift for a while use it if possible then do the turning tests without TS support , light cuts less than 0.5 mm and adult as required for the standard of work that you are producing

its not rocket science they have been doing it for over a hundred years , your aim is to support the lathe in the same plane as it was when it was manufactured , for thats when the thing was aligned in the first place

Stuart

[jep24601]

Blackadder is quite right - but if you have a machinist's level the whole process can go a little quicker if you are level to the " big ball". The test cut described can only indicate a no twist condition if all other parameters are right.

[bcassel]

Use this analogy, first you build the foundations for a house, then you build the floor, then you put in the appliances and you level them last.

Your lathe in an appliance, build your foundation first.

[RussZHC]

To me it is/was also a matter of where you want to "fiddle"...just saying trying to make fine adjustments crawling around on an uneven concrete floor v. standing up and just adjusting a bolt or adding shim stock at say elbow height...

[jep24601]

To me it is/was also a matter of where you want to "fiddle"...just saying trying to make fine adjustments crawling around on an uneven concrete floor v. standing up and just adjusting a bolt or adding shim stock at say elbow height...

All depends on the style of lathe. With this type of lathe mounting you will be a lot better off crawling around on the floor than trying to shimm at the leg/bed mounting:

[Dr Stan]

Use this analogy, first you build the foundations for a house, then you build the floor, then you put in the appliances and you level them last.

Your lathe in an appliance, build your foundation first.

Excellent explanation. BTW, Blackadder is absolutely correct. We had to hold +/- .0002" on pump shaft bearing diameters with .001" TIR max between the bearing diameters that were around 16 to 18 inches apart. BTW we only did this while tied up to the pier in port.

[Forrest Addy]

I'm not sure why resiliant mounts are so popular. Their intent was originally to attenuate floor borne vibrations to where they have little effect on the machine.

Here's an outlandish example. In the late '70's I toured a punch outfit that had dozens of high speed punch pressers making zillions of parts from coil stock. By high speed I mean thousands of hits per minute. The place hummed and jingled and the whole floor (8" concrete I was told) was like a drumhead. In some places the trash cans (galvanised steel in those days) had buzzed recessed circles right in the concrete floor. The shop had lost their lease on their die shop building so they'd moved it in and set up square in the middle of the punch shop - and they were having problems with finishes and they had the best isolation mounts in the business. I suggested the off-shift opeation and inflatable mounts as a desparate stab but in truth I had never entered an environment so hostile to machine tool function.

Machine tools don't vibrate much or introduce significant noise to the floor. So I suggest vibration isolation mounts as superfluous to actual need. They are resiliant and over time will settle in rough proportion to the weight they support assymptotically seaching zero as equalibrium is attained. This has been my experience because once a month checks were necessary for a year or more on any resiliantly mounted machines tool under my care.

It is important the load rating of the mount be matched to the load it supports. The head stock end of a mid-sized lathe may be twice the weight of the tailstock end and 4x that of a pedestal. How you adjust them is personal preference. I prefer to support the load directly on the mount and shim between mount and machine. Others get satisfactory performance by supporting the load on a nut under the machine.

Resilliant mounts make if difficult to tweak the machine into accurate alignment as the machine cannot be attached rigidly to the floor. Without attachment to the floor or foundation the whole armamentariun of the millwright is scotched. Side jacks, kickers, differential adjustments, ect are brute force adjustments making possible to align 20 ft or more of machine bed to linear perfection. The machine provides the bearing and motions whereas the forces against the foundation slightly deflects the bedways into their final linearity and alighment.

Most small shop owners never get into thiis level of refinement. Most of the time their machine tools don't even need to be bolted down. But it pays to have knowledge of the scale of things and how the work is done the next level up. Call it preparation for expansion, getting a sense of proportion, or just filling in the blanks but the whys and whens are good to know whether they apply to you directly or not.

Back to topic. It's a wash. Shim between machine foot or double nut; whatever floats your boat. Track your machine's level over the next several months. Chances are you'll need no re-tweaking if you mount the machine directly on concrete. Chances are you will need some adjustment if you use resiliant mounts. BTW knee mills need only rough leveling - they are so stiff the floor bearing has no effect on their alighment. A lathe however is long and limber. Carefrul leveling leads to accurate alighment.

Most important, read the installation manual. Every machine tool has its quirks.

[loose nut]

Forrest, what about bolting down to a thin concrete shop floor in a home shop or garage, are they prone to shifting and putting twist into the bed. I'm going to answer myself, correct me if I'm wrong but if the floor moves it should still stay in the same plain so that there isn't any twist put in the bed?

I should have said up front that the bases are 16" x 16" x 20" high made out of 1/4" steel with a 3/4" thick top and 4 mounting points on each bottom. Cast iron legs might be better but I've got what I've got.

Blackadder, we all know that it is taking the twist out of the bed but it ia generally referred to as levelling, right or wrong.

[Shade]

Can we get this lathe levelling thing sorted a lathe does not have to be level ( it is better if it is ) to the big ball ( earth ) but it need to be in step with itself , no twist , in the same condition that it was when it was manufactured.

Agreed it does not have to be level, but a level lathe is desirable, as it can eliminate
variables when troubleshooting other issues.

"in the same condition [as] manufactured."

In theory that is correct... Some of the poorer imports that might not be true...

Before you think my first statement was wrong many ships have machine shops as did the war ships in the last war the lathes in those cannot be level in relationship to the big ball unless the ship is in dry dock at sea the lathe could never be level yet they still turned (pun accepted ) accurate work

I have been in and out of dry dock 3 times in my Naval career, except when being built
a ship is never ever level again. Even in dry dock, albeit they did get close in the PI.

[darryl]

Everything in the chain affects the final outcome. I would prefer to have the stand secured to the floor and leveled fairly well, then do the lathe. But what happens to the floor over time- long or short- does it warp when you walk around on it, and does it warp with the seasons? It could be that the lathe helps to keep the floor from twisting, rather than the other way around. You have to consider everything, and figure the most reasonable way to maintain a reasonable alignment.

Here's another take on this whole thing. Suppose you built a form to pour some concrete into. At the top of the form, on each end, is a single pivot point. Also at each end you have some framework embedded that matches the mounting points of the lathe. Probably four points at the headstock and two at the tailstock, but of course it depends. Anyway, the stand then is a pair of triangular frames that rise from the floor and end at the pivot points. I'm assuming that the pivot points would be self-aligning.

At the bottom of the concrete casting would be some mounting points where you could bolt a single 'leg' which would end up in a rubber bushing held in the bottom shelf framework of the stand. This serves to keep the concrete casting basically stable so it can't roll. Now you bolt the lathe to it and align it. Now and then you would check the alignment, as the concrete casting twists and warps as it cures.

What you have now is a stable structure consisting of the casting and the lathe, with the casting contributing weight and rigidity to the lathe, while the pivoting mounts let the floor twist independently if it's going to do so. The stand can be secured to the floor, and it won't be important to try to level it, as the weight of the lathe and concrete casting will keep all the legs supporting weight in a shared way. Leveling in the traditional sense could still be done, and there's no reason not to do this anyway. A carpenters level is plenty good enough for this part. This 'decoupling' between the stand and the combined casting/lathe assembly is something you would not get with a four legged, four or six point lathe mounting point stand of ordinary design.

[firbikrhd1]

I agree with Blackadder and Shade regarding level and alignment.

To the point of where to shim, right or wrong, my Logan has cast iron legs similar to those shown in Jep24601's post. In my case I drilled my concrete floor where the holes in the legs would be and epoxied in threaded studs. (I suggest fine threads for easier adjustment) Then installed a nut, washer on top of each stud then set the lathe in place on the studs followed by another washer and nut. This eliminates all need for shims as the legs can be adjusted up or down as necessary to attain alignment. The alignment, once found, is secured by locking the two nuts together with the leg and washers between them. As mentioned, right or wrong, it's worked well for me for about 20 years.

[The Artful Bodger]

This is my concrete bench being delivered..



.... and this is how I mounted the lathe..



I packed cement under the lathe feet after everything was level.

The little tweak that was required a year later was easily done by adjusting the feet of the concrete bench.

Everyone should have a concrete machine bench in their home shop!

[ogre]

Someone has in the past brought up that the concrete "moves" from winter to summer so the lathe may need adjusted 2 or more times a year? When bolted to the floor with cast legs. I have no idea and im just throwing that in there cause i read it on here before. I personally like the threaded rod with nuts idea.