Diy Master Precision Level

I got some 10 second vials and I want to make a master precision level. Not having seen a master precision level I'm unsure of how the vial assembly is mounted. I know the vials are pretty sensitive to temperature so will be making a shield for the vial assy. are the vials mounted the same way as on a machinist level. I intend to use a 2 by 2 inch piece of Durabar for the base. Any suggestions.

From pictures as well as the one I own it seems most master precision levels have a pocket that the vial is sunk into, vs the less precise Starrett machinist type that have the vial protected in a tube. So if making your own I'd just mill a pocket into the dura bar then make fittings to allow tilt adjustment, I f desired you could make a plastic "cover" with a window for the vial. this would protect it a bit more and also hide the adjusters after you set them. Relieve the sides and lighten the bar up a bit before scraping it and also add some plastic handles to grab it so heat from your hands does not transfer to the metal as much. I had thought of doing the same myself till I stumbled on one for cheap.

Good luck
Paul

Is the vial adjusted the same way as on the machinist levels?
since I have it, it'll be carbon fiber for the cover.....

When constructing the level you need to include thermal insulation of some form so heat from your hands will not be conducted to the level components during handling.

Levels are all adjusted the same way...

Put it on a very smooth surface with a positional fixture (an "L") so it fits in the corner.
Note the reading.
Rotate it 180° and put it in the same reference location.
Note the new reading and determine the difference.
Adjust to remove one half of the error.
Note the reading.
Rotate it 180° and put it in the same reference location.
Note the reading and confirm that it is exactly the same as the previous reading.
Repeat if needed for final accuracy.

- Leigh

ISnt a 2x2 square kinda small fora level? Or do you mean 2x2 square by a foot long?

I believe he meant a 2x2 cross-section with an unspecified length, which is still awfully small for the intended purpose.

- Leigh

Master Precision Level Vial adjustment features.

What I meant was what type features are used to adjust the vial to level. Same as a machinist level? Spherical washers one end, post with two nuts the other?
I was thinking 2" by 2" section 12" long.
What would most people consider the 'right' length in terms of using it during a machine re-build. 12", 18"?
With luck the machine to be re-built will be a 10EE....... Fingers crossed.

I am also looking to get an autocollimator.

We were just talking about mounting a bubble on a King-Way Alignment instrument and RC99 posted some pictures of his level vial he purchased.
http://www.practicalmachinist.com/vb/general/mounting-vial-kingway-type-device-264089/#post2016652

I also have a picture of a Level my Father and I made. That I have on my Profile pictures.
http://www.practicalmachinist.com/v...g-classes-2011/48152-king-way-level-top-view/

I make my own tubes that the glass bubble sides into if you need info on that let me know. PM me please and I will come back to this thread.

15" length seems to be somewhat standard for US master precision levels as that is the length of the Starrett and P&W. WAG 2" wide is probably in the correct area (on checking starrett lists the width as 1 5/8, but they don't list the height), consider making the height more, like at least 3" probably a bit more. If you look at pictures of a starrett 199 you will see it is a casting to lighten it up significantly, the P&W has a nice open beam design which I think looks nice aesthetically. Listen to Leigh and Richard, they know there stuff far better than I.

Paul

I have been concerning myself re: rigidity and sag so was thinking taller section shape as well but....... Sag should not matter as long as the level is supported a symmetric distance from each end correct? As for rigidity / height of the cross section, the lower the height the more stable. As to the extra machining to recess the vial. Would you consider that a production feature to protect the vial more than a necessary requirement for a self made level.

The Starrett 199Z is 3" tall.

- Leigh

At RARDE we frequently made special purpose lab and demonstrator equipment incorporating sensitive levels. Normal practice was to seat the vial in a recessed carrier with a fibre sheet material protecting the vial from direct contact with the metal parts and, probably, giving a measure of insulation. Working to military temperature ranges a bit of compliance to cope with differences in thermal expansion between materials was pretty much essential. As I recall matters it looked like blotting paper, heck it might even have been blotting paper for all I know being very much on the user, not designer, end for that. Adjustment would be either by shims or some form of mount rotation. The one device still in my possession (an optical clinometer demonstrator issued as part of a post redundancy consultancy contract) effectively has a rotatable carrier.

I do wonder whether a DIY master precision level is the right way of going about things if you are mostly interested in having a tool to help machine tool refurbishment. I always preferred a clinometer style device with a short, accurately calibrated tilt scale for optics lab work and machine alignment. My favourite has a 6" base, 20 second vial and 10 degrees of tilt one way graduated down to 10 seconds of arc. Compact, easy to handle and you can do rough alignment with the adjuster. The master precision level came out of its box, I think, once in 20 odd years to confirm it was too much of a PIA to use. Naturally if you want the pride of (very considerable) accomplishment in making a master precision level its a different matter.

Clive

Good point on the clinometer. I've used them during aircraft boresighting procedures. It would be a joy to have one in the shop. I intend to get my hands on an autocollimator for much of the work of mapping the ways etc. The main reason I'm building it is because I got the vials for next to nothing pricewise. On closer inspection they might be closer to 15sec accuracy. Im building a jig to test/calibrate them.
As suggested above, I'll probably mount the vials on studs with springs below and a fiber spacer under the vial carrier. Spherical nut on one end and thumbnut on the other. All covered by a carbon fiber thermal shield with a small slot for viewing.

Simply posting to gloat. Logged on to E-Bay 3 minutes ago..... Someone posted a 18" Pratt .00025"/div level.

Buy it now:$150
Got it!
Anyone need a 10-15sec vial?
I'm still keeping one of them.
Now to find that autocollimator...............

Splendid catch.

Copy this to use up the vial you are keeping!



Very handy.

Sorry, mistake in previous post concerning scales. Top knob is calibrated to 1 minute of arc and can be estimated to 10 seconds, not read as I said.

Clive

Made me look at ebay to see an 18" level and nothing show's up searching on pratt level?
Search did turn up a pratt and whitney Master level that sold for all of $66 on April 16th, they listed it as "some damage" but pictures look like that is chips in the paint and long time wear on the box - someone got a super deal.

Paul

I snagged the Pratt level as soon as I saw it. The same seller has a few Starrett #199 levels for $199 but I have seen them go for less than $199 now and then. The Pratt level is twice as sensitive at the Starrett #199 so in all honesty probably will not get used that often.....

OK I think I found it ebay auction 281097282185
From that and the Starrett's they have for sale they must not own a tape measure - I think your going to find that the level is 15" long as are the Starrett's that are listed as 18". Also the Pratt and Whitney standard is the same as Starrett (.0005) so unless someone swapped the vial .... Leigh probably knows better. If you want to be a bit of an ass you can ask the seller for a discount as it will be missing 3" of length.
In any case I like the looks of the P&W better.

Paul

The Starrett 199Z is 15" long. At least both of mine are.

- Leigh

I got some 10 second vials and I want to make a master precision level.

Click to expand...

That's 0.054 mm/m. Almost factor 3 off of a precision level (they are 0.02 mm/m).
Common length is 200 or 250 mm. Many standards do require measuring deviation over a length of 200 mm.

Nick