Levelling an ml7

[Chris MurphyParticipant @chrismurphy94983]

Hi all,

the thing I can’t understand about the levelling of the lathe is that in the manual it tells you to level the lathe with machinist levels, although I only have normal levels.

this is what I did and the lathe on my stand was reading level on my levels.

then in the manual it says to check for lathe body twist with a length of bar recessed in the middle and take light cuts on the two protruding bits.

but it says that if these are out you have to adjust the jack screws again to get twist out of the bed. Once I did this, the lathe was not level again.

I can’t understand this.

can someone enlighten me.

thanks

chris m….

[Chris MurphyParticipant @chrismurphy94983]

[Michael GilliganParticipant @michaelgilligan61133]

The subject has been worked to death on this forum, Chris

May I suggest that you search [using the box on the home-page NOT the one on this page] for the word levelling, and see what takes your fancy. …

MichaelG.

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Edited By Michael Gilligan on 06/07/2022 17:45:27

[HopperParticipant @hopper]

Getting it level is the first, and not necessary, step.

Getting it to turn parallel as you have done with a test turning piece is the final, and necessary, step.

As long as it turns parallel, actual level does not matter. Worn old lathes can have wear on the bed that throws a level out.

[Nick WheelerParticipant @nickwheeler]

The procedure is misnamed, as the lathe doesn't need to be level to turn accurately.

But to adjust it efficiently an easily acheivable(and easily repeatable) baseline is needed. And that's all you're doing with the most precise level you have.

As a beginner, fitting a hobby machine to its stand, or the bench it will live on, and just using it without stressing about the level has a lot to recommend it. There are more useful things for you to expend your efforts on.

My WM250 isn't even bolted to the bench, as I need to get in the cupboard next to the headstock and swing the bed away from the mill table when using that.

[Thor 🇳🇴Participant @thor]

Hi Chris,

If you haven't already checked Harold Hall's website, he has an explanation on how to set up the lathe here.

Thor

Edited By Thor 🇳🇴 on 06/07/2022 18:30:37

[John HaineParticipant @johnhaine32865]

PLEEAASSE, NOT AGAIN!

[SillyOldDufferModerator @sillyoldduffer]

Levelling for the purpose of eliminating bed twist can't be done with an ordinary builder's level – they're not sensitive enough. Errors caused by bed-twist are too small to detect with them.

You may be fixing a problem you don't have, maybe creating trouble in the process! What's the evidence? If you turn a stiff rod at least 25mm diameter to the same slightly smaller diameter over a length of, say 150 to 200mm, what's the difference in diameter at each end? The diameter has to be measured carefully with a micrometer, which requires practice. If the lathe cuts an unacceptable taper, then it's time to look at levelling or Rollies Dad.

Beware of precision measuring as required to set lathes up accurately. Often highly confusing at first and even experienced practitioners get it wrong. For example, the taper measurement I recommended will mislead unless you can reliably get a good finish by taking light cuts with a sharp tool – itself a learning challenge. And then it's best to know tapers also occur when metal rods flex under cutting pressure, even if the lathe is perfect. It's important to practice technique before taking results too seriously.

It may not matter either! When work is done close to the chuck, as much of it is, the error caused by bed twist is hard to detect. It only causes bother when cuts are taken over long distances.

Dave

Edited By SillyOldDuffer on 06/07/2022 18:37:06

[Howard LewisParticipant @howardlewis46836]

If you had bought and read Ian Bradley, (The Amateurs Workshop ), or "(The Myford 7 Series Manual" ) you would know how to adjust the level of a lathe so that it turns parallel.

Both books tell you how to go about it.

[Pete RimmerParticipant @peterimmer30576]

This is why you cannot use an ordinary level for aligning machine tools. They don't even register a movement that will send a sensitive level full scale.

**Link**

[Grizzly bearParticipant @grizzlybear]

Chris M,

Think about a lathe in a ships toolroom/workshop.

The sea is very rough today, the lathe is working fine.

OK, the crew may be feeling a little off.

Bear……….

[Michael GilliganParticipant @michaelgilligan61133]

Quite so, Bear

Which is why I pointed Chris towards all those previous threads

Levelling, in the sense used by surveyors and ‘lathe levellers’ is simply process of using a level to find the relative height of two points [and, if appropriate, to facilitate their adjustment].

A levelled lathe need not be an ‘orizontal lathe !

MichaelG.

[peak4Participant @peak4]

Just watch out for the tide tables; though this will obviously be for larger lathes than we use.
A friend of mine was telling me, that during his apprenticeship in Sheffield (the tides aren't an issue there), he was being taught to use one of the lathes in the big workshop; the best operator, an old hand, knew exactly where on the bed to change the depth of cut, with his foot, to maintain accuracy along the workpiece. It should be pointed out, that the lathe was large enough, that there was an operators seat on the carriage.

I recall reading this next story somewhere else, but I can't remember where, so the forum link will have to suffice – this isn't my tale.
https://bbs.homeshopmachinist.net/forum/general/80918-on-the-subject-of-lathe-leveling-a-funny-story#post1775889
On the subject of lathe leveling – a funny story
"This was posted to my local metalworking club today and I had to repost it:
Funny story about lathe levelling… my apprenticeship was as a maintenance machinist at a naval shipyard here locally and part of that job was installing (and moving) machinery. We got tasked with moving a couple old turret lathes from the north end of the machine shop to the south end. Got them moved and bolted down, and started the levelling process. One thing you need to do during that process once you get close to level is make a change and let the machine sit for several hours so they'll settle. This meant we'd make a change first thing in the morning, then check it in the afternoon and re-tweak. We went through several days of this and we'd get it dead on in the AM, by afternoon it would move a bit and we'd readjust. Normally you get it dialled in after a couple rounds. These things wouldn't take a set for anything.
Then I had an idea… we set it in the morning, checked it in the afternoon (it was off), then rechecked it the next morning (dead on).
South end of the building (built in 1936) is built on fill right next to the water… lathes were changing level as the tide went in and out and the floor swelled and receded. Machine shop wouldn't hear of putting them somewhere else so we told them "well they're accurate once a day, you get to guess when".

In response, another member wrote:

I talked to a guy from one of Boeing's plants on the Duwamish flats who said the same thing … they consulted the tide tables before doing accurate work.

metalmagpie"

Bill

Edited By peak4 on 08/07/2022 23:59:57

[HopperParticipant @hopper]

So, if a precision level gives an accuracy of half a thou per foot, and your old Myford has easily 4 thou wear on the front way in one place, and 2 thou wear on the rear way, which is common and within tolerance for not needing a regrind, that is a difference of 2 thou over the width of the bed, which is 4 inches. So that is equal to 6 thou per foot of difference between the ways due to uneven wear.

What is the point of putting a half-a-thou per foot accurate level on a bed with 6 thou per foot of wear? If you twist the bed to get a level reading, the rest of the relatively unworn bed will be 6 thou per foot out of level.

So with a used old Myford etc, it is best to not worry too much about super accurate levels and follow the instructions in the Myford factory User's Manual to bolt the lathe down without distortion by using a clock on a 12" piece of bar in the chuck while tightening down the mounting bolts. Any movement of the clock and that bolt needs a shim around it.

Then do the turning test as Chris has done on a test piece of 1" bar 4" to 6" long and measure it for taper and shim the tailstock end mountings accordingly, as per the Myford User's Manual. This is the ONLY test that really matters. All the rest is theory until you take a cut under real-world conditions and cutting forces and see what your worn old lathe is really doing.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hopper on 09/07/2022 06:06:07:

…

So with a used old Myford etc, it is best to not worry too much about super accurate levels and follow the instructions in the Myford factory User's Manual …

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Which, for sake of completeness, I an showing here:

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There is a lot of knowledge condensed into those approximately two pages worth of instruction ^^^

MichaelG.

[HopperParticipant @hopper]

Thank you Michael. A lot indeed. And that is about all that needs to be known to get your lathe set up, if you include my above proviso re the dangers of using sensitive levels on worn beds. (Although Myford above specifies levels with a sensitivity of 3 thou per foot which are not so sensitive by today's digital standards.) If you have a brand new unworn lathe bed, then page 1 will get you back to where the lathe left the factory, all nice and level and flat. Pages 2 and 3 are the relevant ones for old lathes with a bit of wear in them.

It's like they say: When all else fails, read the manual! Your post should be enshrined somewhere on this site as the standard reference to all levelling questions.

Edited By Hopper on 09/07/2022 07:03:08

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