Engineers level

[Michael GilliganParticipant @michaelgilligan61133]

Starting 2015 with a 'lightbulb moment'

This explanation works for me … I hope it works for the rest of you

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The matter of 'levelling' the lathe has been debated repeatedly, and without satisfactory conclusion.

The reason, I believe is the capricious semantics of the English language:

Levelling can mean making a thing, or a set of things, level … [whatever that term is taken to mean, in a particular context]

BUT

Levelling can also mean the process of using a level … This is the meaning that Surveyors use.

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If we accept that second definition, then the debate fizzles-out.

As I mentioned earlier; the level is a very efficient comparator, and its use is probably the most expedient way of checking for twist and warp when installing a lathe … It is not the only way of doing that check; and it is not essential for the lathe to be horizontal.

MichaelG.

 

[Clive HartlandParticipant @clivehartland94829]

Looking back in my notes I see that the curve polished inside a bubble vial of 20" quality has a radius of 60 mtrs.?

I am just quoting what was told to me as I have no way of checking. We were recently quoted a price for a bubble that was 20" and no longer available from LEICA and they wanted a £150 and a quantity of 50 to make it viable for them. We declined and scrapped the Instrument.

Clive

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Robert Dodds on 31/12/2014 18:08:50:

It is after all a 60 year old plain flat bed lathe. I have the Atlas version and enjoy using it but its not an ultra precision lathe! As long as you get the bed to be reasonably level at either end it will produce good parallel work for the hobbyist. It was never intended as a heavyweight machine and lacks the rigidity to take heavy cuts or carry heavy components.

Hmm…

After reading this I thought it is about time I checked my 60 year old Atlas clone for level (twist) having set it up in its present position about five years ago.

I put a length of 9/16 silver steel in the three jaw and a dial gauge set to centre height on the cross slide to measure in the horizontal direction. Next to the chuck there was 1 thou variation as I turned the chuck and I set the zero in the middle of that range. I then moved the saddle to bring the dial gauge to ten inches from the chuck and again rotated. This time there was 2.5 thou variation and the middle reading was only 1/2 thou off zero! I was expecting at least a couple of thou to need adjusting out.

The above method of checking for twist has, for some reason, become known as Rollie's Dad's method but I have used it for years – it just seems to be an obvious method. Using a level with 10" sensitivity would give about the same sensitivity but as most people have a dial gauge why bother?

Agreed, the Atlas won't take heavy cuts like a Colchester but it can certainly give accurate results.

Russell.

 

Edited By Russell Eberhardt on 01/01/2015 10:55:18

[BazyleParticipant @bazyle]

Goodness this thread has been dragging on since last year!

a couple more links for when this has been discussed before which are worth reading.

Lathe alignment.

New Lathe leveling

Is 0.1 deg good enough..

[NealebParticipant @nealeb]

Coming back to the original question – the "what" rather than the "why" – and always a difficult thing on a forum!

I bought one of these levels (the 200mm version) a few weeks ago. I was also concerned about the "bit of rust" comment but mine was clean, no rust apparent. What was a problem was that the bubble had fallen out! The thing comes in a fitted case with a bit of foam packing, and was well wrapped in bubble wrap, but had probably been dropped or thrown in transit. The bubble assembly – the vial – is plastic, and it's glued into a piece of channel section pivoted at one end and bearing on a spring-loaded adjuster screw at the other. The glue had given way and the vial was loose. I fixed it back with a bit of PVA glue (my thinking was strong enough to hold it, weak enough that I could remove it if necessary). I tweaked it on my carefully shimmed surface plate so that it read the same when turned end-for-end, and it seems to be holding its calibration fairly well. I cannot detect any rock on my surface plate (a 300x300x20 slab of plate glass). This is not Moore and Wright, Hilger, etc, quality but it works. If I put my thinnest feeler gauge under one end, the bubble moves the number of divisions that I would expect. Again, not metrology lab standards, but a reasonable sanity check.

I bought it to help align the profile rails on a CNC router that I am building. It's a welded steel structure with steel box sections about 1800mm long carrying the rails, and due to manufacturing and welding distortions, there was a dip in the middle of roughly 1.5mm. I used an epoxy bed to get close to level, bolted down the rail, then used the "precision" level (with feelers as necessary) to measure height differences every 200mm. I'm assuming that this was fairly accurate as I found a +-0.1mm variation; after inserting the calculated shim thickness and remeasuring I was within about 0.05mm which is more than good enough for this job.

So, as a level it's not the best in the world, but it's certainly not the most expensive either. You get what you pay for, it does the job, and even with the Christmas post, I ordered it one day and it arrived the next.

[Douglas JohnstonParticipant @douglasjohnston98463]

I notice the level Norman pointed to has a sensitivity of 3.5 thou per foot. I am no expert but that does not seem to be very sensitive to me. This whole area can be a minefield since there are a number of variables which can influence alignment. The bed should not have a twist or a sag, the headstock must point down the bed within fine limits, the headstock spindle must be parallel to the bed and so on. Get all these right then start screaming when you try to machine something and find the results are not to your liking.

In case you are wondering, I don't have an answer, I'm not sure there is one.

Doug

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Bogstandard2 on 01/01/2015 10:50:17:

Michael,

I think that is the explanation that I gave.

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John,

That's good to know

MichaelG.

[Bob Brown 1Participant @bobbrown1]

I did find this on the internet **LINK** and goes to show that a level is not final part in levelling a lathe as the guy in the clip has actually twisted the bed very slightly (1 division&nbsp to get the machine to cut parallel to within 1/10 of a thou over 10" which in my book is very good.

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by Douglas Johnston on 01/01/2015 11:27:22:

I notice the level Norman pointed to has a sensitivity of 3.5 thou per foot. I am no expert but that does not seem to be very sensitive to me. This whole area…………………………………………………

In case you are wondering, I don't have an answer, I'm not sure there is one.

Doug

Hi, am I not understanding something here.

The claim in the add is 0.02 mm/1000mm which is the same as 0.0007874 inchs/39.3700784 inchs near as dam, or a ratio 1/50000.

I'm no expert at maths but 1000mm is just a bit more 3 feet and 3.5 thou is quite a few tads more than 0.02mm.

0.2/1000 is quite sensitive, I have one that claims to be 0.0002"/10" and you only need thickness of the silver paper from a sweet wrapper under the very end of it to throw the bubble off the centre completly.

With levels of this sensitivity you will need it to be in the same area as the machine for at least a couple of hours for it to stabalize to the same temperature, before you start to use it and then you'll have to be carefull not to alter it's temperature with the heat of your hands. Even the temperature of the room it is in will alter the size of the bubble.

If your workshop has a wooden floor, or any floor that deflects when you walk on it, this kind of level is a waste of time, as you might as well go and chase rainbows.

Regards Nick

[jason udallParticipant @jasonudall57142]

Model engineer..some time ago published a precision level build.

The tube ( bubble) was made from parallel glasse tube ( drawn)
And a nominally straight tube was warped ( screw pressing between two supports) to achive the desired curve.
As to lathe leveling…this debate is old and pointless.
Those who believe will never convince the non believers and vice versa..

[Ian L2Participant @ianl2]

Thanks Guys Some interesting points. Thinking I will ask around at work see if I can find someone with something bit better than the brick layers level I have and just give it a go. Think one problem I have is mentioned by Nicholas Farr I'm in wooden shed with a wooden floor and home made wood bench so unless I do some more work and obtain a proper stand and remove some floor so it can sit it on the concrete underneath I could be chasing my tail.

But I might keep an eye out for reasonable second hand engineers level of known manufacture without spending silly money.

[jason udallParticipant @jasonudall57142]

Btw I have measured ( only in the lab)..deflection caused by the gravitational attraction between a few tens of kilos of mass.. anyone care to explain if the levels should be observed locally or from a remote?

[Douglas JohnstonParticipant @douglasjohnston98463]

The level mentioned by Ian L2 does indeed have a resolution of 0.02mm per m, but the Moore &Wright one mentioned by NJH has the resolution of 3.5 thou per foot or approximately 0.3mm per m. Quite a difference in resolution between the two when they are both intended for a similar purpose.

Doug

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Doug, thanks for pionting out my mistake, just a case of assumtion on my part that you were refering to the OP.

Regards Nick.

[Bob Brown 1Participant @bobbrown1]

I have a feeling that with all the best intentions there are likely to be other issues like movement of the floor be it wooden or even concrete. Taking the latter, foundations and concrete does move/bend all be it not a lot but possibly enough to the put the lathe out of level, if the sub soil is clay then this is a distinct possibility. Wooden floors are going to be more prone to movement as the moisture content of the timber changes with the seasons.

I remember back in the early 70's a wing jig for the production of wings for a twin engine light aircraft moving although it was set up on a concrete slab, it would move every 12 hours as the site was on an estuary and it was the tide causing the movement and had to be reset twice a day.

Bob

[martin perman 1Participant @martinperman1]

When I was earning a living as a machine tool fitter we had a problem with a multi spindle lathe which at certain times when out of true and work was scrapped, the floor it stood on turned out to be cracked and when a fork lift went over it it lifted one end of the machine twisting it, a pit was dug and a float was built for the machine.

Martin P

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Douglas Johnston on 01/01/2015 17:40:28:

The level mentioned by Ian L2 does indeed have a resolution of 0.02mm per m, but the Moore &Wright one mentioned by NJH has the resolution of 3.5 thou per foot or approximately 0.3mm per m. Quite a difference in resolution between the two when they are both intended for a similar purpose.

Doug

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Doug,

That is a very interesting difference, and may help explain why some find 'levelling' easier than others!

My guess is that 0.02mm per m is too sensitive for practical use.

MichaelG.

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P.S … The build quality of that 0.02 level is what really worries me … [See Nealeb's description, posted earlier today]

It's very easy to make a ridiculously senitive vial [in extremis; a straight tube]; but that doen't guarantee a useful instrument.

Edited By Michael Gilligan on 01/01/2015 20:22:17

Edited By Michael Gilligan on 01/01/2015 20:24:37

[Swarf, Mostly!Participant @swarfmostly]

Posted by Clive Foster on 31/12/2014 17:15:57:

SNIP

In my view the best all round instrument for this sort of thing is the once common WW2 era vintage 6 inch (nominal) base gunnery clinometer featuring a 30 second of arc vial and a nice adjusting system covering a few degrees scaled to 1 minute accuracy. That is a measuring instrument and supremely easy to use. Couple of pictures, not very good I'm afraid, of mine.

Clive

Edited By Clive Foster on 31/12/2014 17:21:13

Hi there, all,

Some time ago I bought a level (clinometer ?) like the one Clive shows in his post. Unfortunately, the bubble is longer than the scaled part of the tube – I suspect it has invited a few relatives in for Christmas!

I'd replace the tube if I could obtain a suitable one – what is members' experience regarding availability of spare tubes? I dimly remember a link to Cromwell's web-site but can't retrieve it now.

Best regards,

Swarf, Mostly!

[NealebParticipant @nealeb]

P.S … The build quality of that 0.02 level is what really worries me … [See Nealeb's description, posted earlier today]

It's not exactly the best-made tool in my garage! But the bottom is flat, the graduations are about right, and the adjusting screw is fine enough to be able to zero it with an end-for-end check. The great thing about a level is that it is self-checking. I'm happy that I have my money's worth, given the price of even second-hand levels from a recognised manufacturer. I would agree that 0.02mm/m is very sensitive. I'm using it with feelers to measure differences in level and I am regularly needing the 0.05mm feeler to bring the bubble on-scale.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Nealeb on 01/01/2015 21:27:07:

… I'm happy that I have my money's worth, given the price of even second-hand levels from a recognised manufacturer. I would agree that 0.02mm/m is very sensitive. I'm using it with feelers to measure differences in level and I am regularly needing the 0.05mm feeler to bring the bubble on-scale.

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Thanks for the update, Nealeb

I'm glad to know you're happy with it.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Swarf, Mostly! on 01/01/2015 21:08:03:

I'd replace the tube if I could obtain a suitable one – what is members' experience regarding availability of spare tubes?

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I haven't yet had need to use them, but Level Developments would be a good place to start.

MichaelG.

[Ian L2Participant @ianl2]

Posted by Michael Gilligan on 01/01/2015 21:44:23:

Posted by Swarf, Mostly! on 01/01/2015 21:08:03:

I'd replace the tube if I could obtain a suitable one – what is members' experience regarding availability of spare tubes?

.

I haven't yet had need to use them, but Level Developments would be a good place to start.

MichaelG.

Now there's a thought. after looking at the link above I have a bench drill in my shed not the best thing for accurate drilling as the thing has so many movements drilling anything thicker than 1mm and it's pain to get drill set up to run without being at an angle (its got them pointless stick on bits of tape with 1mm +/- divisions). So if I get some of these vials I can fix them around drill so I can see every thing is ok.

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by Michael Gilligan on 01/01/2015 19:55:44:

Posted by Douglas Johnston on 01/01/2015 17:40:28:

The level …………………………………………………….

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Doug,

That is a very interesting difference, and may help explain why some find 'levelling' easier than others!

My guess is that 0.02mm per m is too sensitive for practical use.

MichaelG.

.

P.S … The build quality of that 0.02 level is what really worries me … [See Nealeb's description, posted earlier today]

It's very easy to make a ridiculously senitive vial [in extremis; a straight tube]; but that doen't guarantee a useful instrument.

Hi Michael, I tend to agree, the one I have is not much use for general work, the slightest movement of the floor that you stand on moves the bubble significantly, even leaning more on one foot more than the other and even placing your hand on anything that potenionaly deflects will move the bubble.

Below is a photo of each end of the bubble mounting and to my mind the adjusting thread is a little too course to truely set it dead centre when level. It's a long and painstaking job to get it even close, one day I may attempt to replace the adjusting screw and nuts wirth finer ones.

Regards Nick.

[Neil WyattModerator @neilwyatt]

> anyone care to explain if the levels should be observed locally or from a remote?

It doesn't matter, the act of measuring will impact on the system, however you do it. Even placing a level on the lathe bed will deflect it…

Neil

*This is why the Lunar Society met at full moon, at least they could be sure the tidal forces on their experiments were constant.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 02/01/2015 10:14:01:

*This is why the Lunar Society met at full moon, at least they could be sure the tidal forces on their experiments were constant.

.

As my old pal Alec used to say: "B***S*** baffles brains"

MichaelG.

[Author]

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