Leveling a lathe vs. strong solid base

two-can · Nov 13, 2017

I have read in many places about the need to have the lathe level to avoid torquing the machine bed and frame.

Could someone explain why I cannot mount my South Bend 9A bench lathe on a 2" maple top supported by a welded angle iron frame which is about 1.5" over 6'-0" out of level.

I know that the lathe will be properly supported by the bench and should not be torqued due to fact that the tail stock is a little lower in the atmosphere.

What am I missing?

Capt. Art

Conrad Hoffman · Nov 13, 2017

There's no guarantee that the lathe will be untwisted when mounted to a flat surface, or even floating free in space. There is no escaping from the fact that you need to make the lathe straight with shims or similar. I don't like the word level because level itself isn't important.

Erich · Nov 13, 2017

The goal is a bed that is not twisted, but installed in the exact condition it was machined in.

Using a level front to back at each end of the lathe is a convenient method to ensure the bed has no twist.

There is no requirement that the lathe be level from headstock to tailstock.

Dobermann · Nov 13, 2017

In setting up the lathe, you're talking about dealing with bed twist angles in minutes rather than degrees. For this you need an accurate machinist's level. It seems to me that any sort of welded structure will not be that close to straight no matter how good a weldor you are.

The lathe will work perfectly well just plopped down on some sort of table or base but you'll never be able to achieve the accuracy that was designed into it. If you're turning baseball bats or rake handles it probably doesn't matter much. If you're working with engine parts, then you need the accuracy.

As with most things, there is no short-cut to getting it set up right.

Richard King · Nov 13, 2017

Yes we say you align the bed using a level. If the ways are worn you can twist the bed on purpose so it cuts straight. We use the example. How do you level a lathe on a ship ? On lathes that has a oil bath head stock or you use coolant I recommend level the lathe.

DMF_TomB · Nov 13, 2017

its more you want lathe attached to a stable base. wood changes shape and size with humidity changes.
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a big cnc is often mounted to a base thats 2 to 4 foot deep of steel reinforced concrete. why ? cause concrete cheaper than steel or cast iron.
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lathe can be mounted to slab of 2" or 3" thick steel or a combination 1.5" thick "sole" plate thats attached to concrete over 6" thick
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why bolt lathe down ? unbalanced turning load it will shake itself literally moving along the floor. i have seen 200 lb fan that was unbalance the weight of a 1/4-20 nut shake itself so bad it moved many inches per minute along the floor from vibration. when fan wheel balanced it would not move along floor. any lathe can potential be turning a unbalanced load easily especially if using a face plate. machine less likely to move if attached to something heavy preferably weighing tons

promacjoe · Nov 13, 2017

The above statement is correct. You could mount your machine to a flat and level piece of steel, that has been hand scraped to be perfectly flat, and still find a twist in your bed.

having said that, a good rigid Bench is an integral part of the rigidity of your machine. If you need accuracy, the more rigid the bench the better. In other words, don't skimp on the bench. And level your bench first. Then level your machine, and check for any twist that is left over. Readjusted as necessary. leveling your bench/machine is just a starting point. A starting point that should not be overlooked. and plan on rechecking your machine every so often. At least once a year. More often if you're Not In a climate controlled building.

stay safe and have fun.

Joe.

two-can · Nov 13, 2017

Richard King said:
Yes we say you align the bed using a level. If the ways are worn you can twist the bed on purpose so it cuts straight. We use the example. How do you level a lathe on a ship ? On lathes that has a oil bath head stock or you use coolant I recommend level the lathe.

Well, Richard, your question nailed it:

My lathe is going onto a boat, which is the reason I am unable to have a fixed reference point for "level".

I am going to have to use a method that measures "twist" of the bed so that I can install the proper shims to insure no twist remains when bolted down tight.

two-can · Nov 13, 2017

Erich said:
The goal is a bed that is not twisted, but installed in the exact condition it was machined in.

Using a level front to back at each end of the lathe is a convenient method to ensure the bed has no twist.

There is no requirement that the lathe be level from headstock to tailstock.

Erich, do prefer any particular method for measuring "twist" when a level reference surface is not available?

Conrad Hoffman · Nov 13, 2017

I'd go by what's been known in the hobbyist circles as "Rollie's dads method". One write up here- http://manuals.chudov.com/Rollies-Dads-Method-of-Lathe-Alignment.pdf

On stability, I find I should realign my lathe as the seasons change. Even the cement floor in my garage is subject to some warpage as the water table moves and the temperature changes. IMO, use of a lathe when the bed is warped is bad because the carriage, and to some extent, the ways, will wear unevenly and much more quickly than if everything is straight.

Amazingly, when I was balancing the wheel on my surface grinder, I found the amplitude of vibration changed noticeably depending on where I was standing. That sounds insane, but I was changing the coupling between the four legs and the floor, because cement isn't perfectly rigid. Understand that the actual wheel balance wasn't changing, only the amount of vibration transmitted to the table. Never assume anything is completely rigid and unmoving, especially over long periods of time.

two-can · Nov 13, 2017

Thanks for the Rollie's Dad's Method, Conrad.

I think that the reason for your experience with the surface grinder was due to your position moving the location of the "node" where the amplitude of the vibration equals zero.

In my case, the "floor" is not steady level. It changes with the balance of the vessel floating in the water. As the fuel tank or the waste tank is emptied or filled the attitude of the boat (and the "level" reference line will change. Let's not even talk about the effect of wave action.

That's why I posted this question. I had a feeling using "level" was the most convenient way to roughly get the lathe lined up to avoid inducing twist.

My preliminary plan is to solidly connect the maple top (which has been in the same area for 17 years) to the angle iron frame, then use shims under the feet of the lathe (only a South Bend 9" Model A w/ a 3' bed) to get the lathe itself mounted without stress in either direction.

Then keep track of work pieces accuracy and periodically check for any changes in twist.

Richard King · Nov 13, 2017

I'm not a big fan of the rollie test. I use actual cutting of the tool to the shaft. This is the way I teach and use. Your machine is smaller so you can use a piece of aluminum say 1 1/4 od x 7" sticking out of the chuck so you can turn 6" .
Monarch Lathe Test Cuts and Alignment - YouTube You would shim under one of the Tail Stock end. Some small South Bend lathes have a built in bed twist screw.

Look on the pedistal on right tail stock end below the ways, you see a red screw. That can be turned to twist the bed so you can cut straight. South Bend Lathe : South Bend Heavy 1 Tool Room Lathe - YouTube

promacjoe · Nov 13, 2017

for mounting on a boats/Truck/trailer, the bench should be as rigid as possible. But it should only contact the floor at 3 points. This helped prevent warpage simply from the wave action. Also make sure you bolt the bench to the floor at 2 points only. The third point should be floating. this also helps to prevent warpage in the bed

good luck.

Stay safe and have fun.

Joe.

Conrad Hoffman · Nov 13, 2017

Scroll down and have a look at the Leblond Portable Lathe-
http://www.lathes.co.uk/leblond/

In theory it's better to cut, as Richard says, following the rule of "test it the way you use it". Still, I find many people are perfectly capable of cutting a taper with a straight lathe due to dull tools and tools not on center, creating stock or spindle deflection. Thus the need for the stock size Richard states. Don't try to get away with less. IMO, both methods should give the same answer if done properly.

two-can · Nov 13, 2017

Thanks, Richard

two-can · Nov 13, 2017

promacjoe said:
for mounting on a boats/Truck/trailer, the bench should be as rigid as possible. But it should only contact the floor at 3 points. This helped prevent warpage simply from the wave action. Also make sure you bolt the bench to the floor at 2 points only. The third point should be floating. this also helps to prevent warpage in the bed

good luck.

Stay safe and have fun.

Joe.

Thanks, Joe.

If the bench has only 3 legs, I'm guessing that 2 are on the headstock side and one centered on the tail stock end.

Also, are the ones bolted to the floor, the legs under the headstock?

two-can · Nov 13, 2017

That's quite a setup.

I'm not sure I could be comfortable with the three legged monster loose in my hold.

I already rig for a hurricane each time I go to sea, and most items don't weigh any where near what that lathe does.

Seems to follow Joe's advice, though.

promacjoe · Nov 13, 2017

two-can said:
Thanks, Joe.

If the bench has only 3 legs, I'm guessing that 2 are on the headstock side and one centered on the tail stock end.

Also, are the ones bolted to the floor, the legs under the headstock?

two legs under the headstock, bolted to the floor. Tailstock end will be floating. For heavy weather, a chain-link from the top of the bed to the wall is preferable. You could also use a heavy Strap and Strap It down to the wall/floor.

Note, depending on what type of boat you have, the walls and floor tend to be very weak. Reinforcement may be necessary.

Stay safe and have fun.

Joe.

thomasutley · Nov 13, 2017

I had the pleasure of attending one of Richard King's scraping classes earlier this year at Keith Rucker's Georgia shop. Richard set up a sensitive machinist's vial level on Keith's granite surface plate with the group of us standing around it on the concrete floor that had been poured several months earlier. After the bubble settled, he asked Adam Booth, whom many of you will know as Abom79 on YouTube, to step sideways a few paces and for the rest of us to watch the bubble. It moved enough that we could see it, and it returned to its original location in the vial when Adam stepped back.

I also have a short video clip posted on my Instagram account (@kingtutley) where he demonstrated indicator sag for us. If you think sweeping a test indicator mounted on an adjustable arm around your tailstock to check concentricity is accurate, boy are you in for a surprise. He went on to teach us not to fight the sag, but to measure it and account for it in our calculations of how much material to add or remove to make things line up.

Lesson learned: If it matters for what you're doing, don't assume things are flat, square, level, or rigid unless you have a means of proving it either is, or isn't, and then have a plan for dealing with "isn't."

Link to indicator sag demonstration: Instagram

two-can · Nov 13, 2017

Thanks again, Joe

Leveling a lathe vs. strong solid base

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