Why wont my lathe stay level?

[moosesgunsmithing]

I've been struggling to keep my lathe level, to the point where I am leveling it weekly. I know my slab isn't any good but how does one actually keep their machine staying put on a mediocre slab?

It just rained and my machine was twisted enough to put a 1 thou taper in a two inch part. I'm trying to figure out an inexpensive and simple way to isolate the machine. Could I build a box with pea gravel and place the machine into the gravel on extra large feet? That may take up some of the slab twisting and heaving.

 

[lucky7]

I’m on clay soils that shift if you sneeze on em. Cut a hole in your slab and pour a reinforced isolating slab just for your lathe. Not cheap.

 

[Joe Gwinn]

What kind of lathe is this? It matters. As does where you are.

Also, contact with the floor should be at exactly three places, two under the headstock, and one at the tailstock end, so floor twist doesn't cause bedway twist.

 

[FredC]

Having the lathe on gravel would solve the problem of spilled cutting oil. After enough oil spilled in the gravel dust from the gravel would become a nonissue. I am not sure if it would do anything for your problem. There are probably other solutions that have been used successfully, a lot of smart people are members of this forum.

You might tell us how big your lathe is and where you are located as this info may be helpful in figuring something out.

What about gutters connected to buried pipes to get runoff away from your slab? I did this with my house and am happy with the results so far.

 

[moosesgunsmithing]

I have a cheapo Chinese 12×36 that weighs all of 1200 lbs. So very prone to twist and not terribly accurate to start with.

My slab sucks, not properly prepared and i cracked it when i moved in my bridgeport. Put French drains all the way around to divert surface water, but ground water here is about 7 feet down.

For budget reasons cutting a hole in the slab is not an option. Im a start up shop that's short on cash.

I'm on more than three points if contact, but how would one manage that in such a way that the machine is still stable? This rig is very top heavy and has a very unstable stand. I made outriggers so I couldn't rock the machine just by cranking on the handwheels.

 

[FredC]

Heavy tubing for the outrigger under the headstock with levelers under the ends and a short one under the tailstock feet with one leveler in the middle? Pretty easy to say that, not sure what your lathe feet look like to implement it.

French drain sounds helpful but does your roof runoff fill it up right after a rain? Might be helpful to get it a long way from your slab as the rain happens. Gound water at 6 feet! Wowsers.

 

[moosesgunsmithing]

Heavy tubing for the outrigger under the headstock with levelers under the ends and a short one under the tailstock feet with one leveler in the middle? Pretty easy to say that, not sure what your lathe feet look like to implement it.

French drain sounds helpful but does your roof runoff fill it up right after a rain? Might be helpful to get it a long way from your slab as the rain happens. Gound water at 6 feet! Wowsers.

I had a 3/4 x2 1/2 solid bar with a couple 5/8x11 bolts about 4 inches outboard of the base, enough to help stability but not enough to be a tripping hazard, one on each end. I actually popped it off the tailstock end today based on advice, and just have two 2 in round leveling feet from mcmaster carr under the tailstock end now. Not one point of contact, but I will see if it helps when the weather changes. I was hoping that the weight and vibration of the machine would settle it, but that hasn't been the case.

As to the drains, I have a dry well behind the shop that took an entire triaxle load of trap rock to intercept surface water run off. One trench is 5 ft deep with a pipe in it, the other is 1 ft deep surface drain (hard to get an excavator between the shop and a property line). The drainage system makes a U shape around both drip lines and the uphill side of the shop.

The only weather event that has overwhelmed them so far was when we got two and a half inches of rain in 24 hours in January when there was 2 ft of snowpack. When that refroze my shop heaved enough I had to kick the door in and re-frame it. That weather event got two inches of water in parts of the shop, but fortunately I planned everything to tolerate up to 6 in of standing water.

 

[Joe Gwinn]

I have a cheapo Chinese 12×36 that weighs all of 1200 lbs. So very prone to twist and not terribly accurate to start with.

I'm on more than three points of contact, but how would one manage that in such a way that the machine is still stable? This rig is very top heavy and has a very unstable stand. I made outriggers so I couldn't rock the machine just by cranking on the handwheels.

That's heavy enough. But cast iron will definitely twist. The three points of contact with the floor would be in a T-pattern, with the top bar of the T under the headstock and the bottom of the T under the tailstock end. The width of the T top is what prevents tip-over. The single contact at the tailstock end cannot twist the lathe bedway.

 

[guythatbrews]

You can pour a base on your existing floor. A 4" reinforced floating pad wouldn't cost much. Maybe on a sand base. Actual level isn't important so if the pad stayed flat it would work.

3 points under the lathe won't work well unless the base is heavy enough not to twist, like a 10EE.

Others with more concrete sense, and sense in general, will chime in.

 

[Tyrone Shoelaces]

I made a lot of money in my working career from customers who installed machinery on inadequate foundations.

Regards Tyrone

 

[EPAIII]

Yes, three points. Exactly what I was going to suggest. If you have two legs at the tailstock end, a piece of steel angle or channel running horizontal between them and a "foot" in the center of that runner. Adjust the existing feet on the two legs so they are a fraction of an inch off the floor - not touching it. This will be a safety measure to prevent it from accidentally falling over.

Then level it with those three feet. But a twist may still exist. So you will need to do the final level between the tailstock end of the bed where you should still have front and rear support points and the table it sits on.

You have a concrete slab floor. That is good. BUT, with actual experience I have seen that concrete floors, no matter how flat they may look, ARE MOUNTAIN RANGES when it comes to lathe leveling. So, if the legs of a four leg table are moved even a fraction of an inch, the level of the table and therefore of the lathe will be destroyed. I have long insisted that the legs, the feet of a lathe table MUST be fixed to one and ONLY ONE spot on a concrete floor. They MUST NOT be allowed to move, even minutely from vibrations of the lathe. I do this with simple angle brackets and lead anchors in the concrete.

My lathe table has a wide steel channel welded to it's top. My lathe sits on that channel and I can shim it on the channel as my final "leveling". This steel channel resists twists due to the floor changing, but it does not eliminate them. You need three point suspension and those three points must not be allowed to change/move.

What kind of lathe is this? It matters. As does where you are.

Also, contact with the floor should be at exactly three places, two under the headstock, and one at the tailstock end, so floor twist doesn't cause bedway twist.

 

[DDoug]

I've been struggling to keep my lathe level, to the point where I am leveling it weekly. I know my slab isn't any good but how does one actually keep their machine staying put on a mediocre slab?

It just rained and my machine was twisted enough to put a 1 thou taper in a two inch part. I'm trying to figure out an inexpensive and simple way to isolate the machine. Could I build a box with pea gravel and place the machine into the gravel on extra large feet? That may take up some of the slab twisting and heaving.

Wrong idea.
Sawcut slab around lathe (add 12" on a side)
dig out, at least 18" deep, deeper is better.
Build up with proper gravel, compact in 6" lifts.
Form new isolated slab at least 12" deep, #4 rebar in 6" grid near bottom and just under the top grade

 

[TaperPin]

I also have a lathe that’s in that weight range - it’s really old, but still not the best casting and way too light. My slab is stable, but the lathe is constantly moving. I’ve noticed temperature affects it more than it should. Weight on the bed causes it to move a measurable amount - moving the carriage and tailstock to the middle bows it. The bed wouldn’t be flat if leveled on three points - it relies on 4 points and so is always in a twisting tension.

With all that .001” in two inches is a lot. I cant help wondering if that is somewhat caused by deflection in the chuck. There was a really good video of deflection in parts before and after the jaws were ground while being preloaded at the ends, but I can’t remember if it was Robin Renzetti, or Stephan the German dude.

Im not much help, but I do feel for your predicament.