Precision Level

Hi

I am about to embark on a surface grinder restoration project and I’m trying to get the right tools for it.

So I can scrape the ways coplanar I reckon I need a precision level. It would also be useful for my other machines, but particularly the surface grinder as I really want to get it as accurate as I can.

Some time ago I bought a little Rabone level, which looks like a precision level but isn’t. There are loads of similar “engineers” levels on eBay but very few of them have any info about the sensitivity. I guess I need 0.02mm/m or 0.05 mm/m or ideally the imperial equivalent. There are some Starrett master levels available but they are too expensive.

I could get a new one from RDG but I am a sucker for vintage stuff if I can get it.

How can Identify an appropriate level? Is there a model number / size that guarantees I get the right one?

thanks

Steve

There are 150mm long levels and 250mm long levels, graduated in 0.02mm/m

I have the 150mm long one and wish that I had got the 250 mm long version. The shorter on is more sensitive because it is short. Either one needs to be meticulously clean on the under side of the level and the surface it is placed on. Having said that, I have had a few occasion that the 250 would not have fitted inside the areas that I was checking. The Starrett one I have has no information on the graduations of the bubble , but one whole division is more than the full range of the 150mm precision level. I have a peices of fag paper in the box, and use that under each end, to see if the underlying surface is the issue or not. I don't use blue under my levels to check for high spots either. Having a 150mm flat reference definitely helps when scraping and bluing out a surface.

Could just replace the vial in your Rabone level?

Well, it all depends on exactly what you're trying to do, and how you propose to do it. I think I understand what you have in mind: the level would be one way to check that the ways were parallel to each other, along their length. However, you need to know their relationship, across their short dimensions, as well, to ensure their surfaces lie on the same plane. Using a level for this would be pretty awkward.

I don't believe that you need a level at all, to scrape the ways of a lathe, milling machine or a surface grinder, provided you have a large enough plane surface, which acts as the reference plane, against which the ways are checked, and a reference straightedge. Sometimes it's convenient to use a machined surface on the machine (say between the ways), although it may take some work to scrape that surface flat, and ensure it's correctly aligned with other appropriate surfaces (I'm thinking of a lathe saddle, for instance). It's a big subject, with many good and less-good approaches. Getting the right sequence of surfaces to be scraped is paramount.

Have you seen the book 'Machine Tool Reconditioning' by Edward F Connelly? It's a bit long in the tooth, and tediously repetitive, but covers the basics in considerable detail.

Look up "King Way alignment tool". Making one may well help.

Level Developments, as linked to by Pete, are very reasonably priced. I have a couple of their vials waiting for me to get around to getting ready to do my surface grinder.

The easiest way to make male dovetails co-planar is to scrape the female one first on a surface plate and use it as a gauge. You still need a straight edge because most female dovetails are shorter than the male but between that and a mating part that you have scraped you have all you need to match two flat ways either side of a dovetail.

Obviously doesn't work where a female dovetail rides on the internal ways which is thankfully not common.

Edited By Pete Rimmer on 27/08/2022 09:16:44

Great idea. Why didn’t I think of that.

I think, with a sensitive vial, you will need some sort of adjustment on the level like this:

Rod

Good morning, Steve,

Some time ago I replaced the vial in my Rabone 18" engineer's level. I described the process with photos in a thread on this forum - I had a quick search before coming to this post but I wasn't able to find it.

Here are a few observations in case you, or anyone else, decides to fit a new vial:

I bought the new vial from Level Developments. Some people thought that their price was expensive but I thought it fair considering that the vial is a precision component. I wouldn't like to try making them for that price!

The word at the time was that Level Developments make that sort of vial in batches and they aren't necessarily always in stock. But Level Developments themselves are, of course, the best source of information on that aspect.

There was a warning to be careful to protect the 'pip' on the end of the vial when back-filling the tube with plaster of Paris. I found this easy, my method is shown in the photos on the thread that I now can't find!!!

I do confess that I made a boo-boo - I should have painted the back of the new vial with white paint before fitting it. I backed mine with a piece of stiff paper, folded concertina fashion, but it shows through the rear of the vial and looks rubbish.

The plugs in the ends of the metal tube that houses the vial are (on the Rabone level, at least ) a push fit but it is a VERY TIGHT push fit. I found them tricky to remove, there isn't an easy way to hold the inner metal tube.

On refitting, the plugs need to be refitted with their flats level when the face of the vial is uppermost. And they are STILL a tight push fit and now there's an expensive new vial within the not inflexible metal tube.

My preferred sequence would be:
Fit one plug to the inner metal tube, taking care that the orientation of its flat extension aligns with the window in the metal tube,
Fit the outer metal tube and the two little leaf springs over the inner tube,
Fit the remaining plug, enuring that its flat extension aligns with the flat extension of the first plug and with the window in the inner metal tube,
Check your bench-top to ensure that you have no parts left over!
Refit the vial & tube assembly to the cast iron base of the level.

I hope that this helps.

Best regards,

Swarf, Mostly!

Edited By Swarf, Mostly! on 27/08/2022 10:20:21

I had another look for the earlier thread; it's at Fitting level vial

Best regards,

Swarf, Mostly!

no, it sounds good but it’s £300! I tried to find a pdf but couldn’t get it to download.

Machine Tool Reconditioning' by Edward F Connelly? link on this page

Iv'e never reconditioned a M/C tool but a level of any sort would not be my instrument of choice, a lot more research is needed.

Tony

When trying to make two separate V or V-and-flat ways parallel to each other there are very few techniqes other than the use of a level to eliminate 'twist'. ideally, the level will be mounted on a King Way jig or home-brewed equivalent so that the level can be adjusted and slid up and down the ways. If the ways are both V, then a dial gauge can be used on such a jig to verify that the ways are parallel in the horizontal direction as well.

Obviously, once one pair of ways has been aligned and scraped, they can then be used to align the matching set.

Note:- the US patent I linked to is excellent in that it gives the full description and operating principles of the tool, onlike many patents.

Edited By Mark Rand on 27/08/2022 20:49:38

The link to Connelly's book was well found! I thought my copy was expensive, when bought perhaps 20 years ago, but it was probably only 30 quid or so, or I wouldn't have bought it. Times change...

Mark Rand's comments about V ways illustrate why reconditioning these are tricky. However, levels really come into their own on bigger machines, where measurements can't easily be referenced directly to a reference surface. If one has a surface plate comparable in size to the machine elements that have to be checked, life is much easier, although some ingenuity may be needed to make jigs, etc., to hold dial gauges, etc.. My 2 ft square surface plate (bought cheaply, second-hand) was reconditioned to 'Inspection grade', and certificated to better than 1/10th of a thou over its entire surface *. It's therefore a better reference than an affordable level, and far easier to use - apart from anything else, you don't have to worry about the floor moving as you shift position...

* This, of course, only tells you something about the high spots, and only along the lines where the plate was checked (presumably by autocollimator, in this case). However, it 'should' be pretty good. It's now well over 20 years since it was reconditioned, and it's travelled half way round the world. It's cast iron, so now is probably out of calibration (not easy to get it calibrated in NZ, south island. I must dig out my autocollimator, before I recondition another machine...). These days, granite is a better bet, but was too expensive then. The reconditioners were The Surface Flatness Co., near Manchester. I don't know whether they're still going.

P.M sent

Steve.

I think that you'll find The Surface Flatness Co is in Birmingham

Which is near Manchester, by Antipodean standards.

I have replaced the vial in a 250 mm, Rabone Chesterman engineers level The end plugs are an over tight fit and breaking the new vial is a distinct possibility when replacing them. I simply took a skim off them in the lathe until they were a loose push fit. I then used superglue to fix them in place.

I was bothered about the vial "pip" and getting Plaster of Paris on it. I happened to have a small plastic cap, which I loctited over the pip and then the plaster could not get on the pip. Hope this helps anyone who is contemplating a similar repair. The vial came from Level Developments, a very helpful bunch

Andrew..

I have to admit the Connelly book is pretty good. The procedures he provides for the different machine types are superb and very detailed. Admittedly my surface grinder is more like his horizontal mill (knee type) but it’s a question of picking the right bits from the different machine procedures to match your machine.

Yes, it’s long winded and tedious but it’s an old book and they all were, It’s a treatise on the subject intended to be a guide but also to document it thoroughly for posterity.

in a similar vein, Cassel’s Carpentry is an amazing book if you have a Victorian house, and you want to make an authentic door or sash window, or if you want to know how the fancy moulding work in palaces and stately homes was actually done.

but I digress…. Looks like I need to start with the spindle. It all works from there, it needs to run with a tolerance of 0.0004. Then the column is trued to that, and on it goes. I was going to start with the table, I can see now why that would have been wrong,