Levelling Table?

I am trying to identify what company made the levelling tables that were used for measuring flatness and perhaps other features. These were two steel plates approximately 8" square and had two solid steel 'hinges' between them and would likely be used on a surface plate. The bottom plate had a 3 point mounting system with one of the points being adjustable to level in one axis. The second plate mounted to the bottom plate with 2 solid steel hinges and one adjustment screw for adjusting the second axis. Main purpose was to be able to level a part/surface so you could then check it's flatness.

I have Googled it and looked in some old catalogs and can't find one now. I know they exist because over the years I have purchased two of them but now I don't recall what company made them. Perhaps they are called something other than a levelling table or plate....?

We could probably make one but purchasing one would be easier. Just want to measure flatness without resorting to the 3 jackscrew method.

Thanks in advance for any assistance you can provide.

-Jim

It might be that one of the photonics equipment suppliers like Newport or Thorlabs might have something you could use. I'd suggest that you could easily make a single plate with a 3-tapped hole arrangement so as to have the jackscrews mounted in the plate, and achieve what is required pretty easily. Round the tips of the screws for best result on a surface plate. I have found that use of 3 individual jacks under a part is often a bit cumbersome, depending on the part characteristics and klutziness of people involved.

Maybe searching compound sine tables will turn something up. I have one like the one used here :- Machining blade with distal taper using compound sine table..

Used to make them ourselves for optical lab use albeit with springs holding them together with ball and cup or rod and Vee pivots rather than hinges. Not aware of an off the shelf supplier in UK for new ones but can't say I've looked hard. Last one before I left was that sort of size done using the tapped hole aluminium breadboards from Thor labs to make the plates and off the shelf components for the adjusters (loose ball in a screw, screw in cups) as we'd lost direct access to local workshop by then.

Clive

Suburban Tool (Taft-Pierce) makes high-quality sine plates here in the US.
Website is: Suburban Tool, Inc. - PRECISION WORKHOLDING & INSPECTION EQUIPMENT

I had not suggested those earlier because I think they're much heavier than the OP envisioned, but perhaps they'll work OK.

- Leigh

Maybe this video will help.
https://www.youtube.com/watch?v=qmiHmSZEKvs

You know I do remember a discussion of a similar table, I think it was a Brown and sharpe product and of course have not been made in some time. If you dont get a better answer then repost your question in the Antiques subforum. I seem to remember that is where the original discussion was, someone had a table like you described and was asking what it was used for.

I just went to Ebay and had a quick look and came up with this...not exactly what you described but similar concept.

http://www.ebay.com/itm/FEDERAL-PRO...352?pt=LH_DefaultDomain_0&hash=item417931ed28

Charles

Hello Charles,

YES! That looks exactly like what I remember! I did try EBay and had no luck. I am a bit shocked at the price though but that is a serious inspection tool - as I recall they were selling new for under $1K before but admittedly that was back in the late 80's -early 90's. Perhaps as some of the other responders have suggested we might be better off making one ourselves. Thank you for finding that, and thank you to the others who responded.

-Jim

Jim --

A triple-plate fixture like the Federal listed on ebay has only one advantage over a Brown-and-Sharpe-type single-plate fixture that I can see . . . the triple-plate fixture can compensate for considerably-larger wedge angles than a single-plate fixture. If you don't ABSOLUTELY NEED the compensation range of a triple-plate fixture, "home-making" a single-plate fixture of the B&S type is pretty straight-forward and should be well worth the time and effort.

If you don't already know how a B&S leveling plate is configured, and can't find a photo of one, I should be able to describe it well enough. Let me know, by a response in this thread, if you need a description.

John

A triple-plate (two-hinge) fixture can set angles on two planes simultaneously, while a single-hinge plate can only do one plane.

That may or may not be significant, depending on what you're doing.

- Leigh

For the record, the Brown and Sharpe leveling plate is a single plate with no hinge(s); it is configured as a 45/90/45 triangle with a fixed pivot at the 90 degree corner, and plate-tilting screws at the 45 degree corners. The plate pivots about two lines at approximate right angles to each other, one of those lines connecting the fixed pivot and one leveling screw, the other line between the fixed pivot and the other leveling screw.

I've found the B&S-type leveling plate reasonably effective at angles of roughly five degrees in each of the two perpendicular directions, which works out to slightly over 7 degrees total tilt.

John

John,

Thank you for your reply. I had not seen the Browne and Sharpe version before. I had to find a picture of it to capture to full value of their version, and yes it would work well for our application - just measuring flatness. My original thought was that the adjusting screws were under the measuring platform which would obviously lead to stability problems. Moving those adjusting screws beyond the measuring platform provides the stability this tool requires. Sometimes my thinking doesn't extend beyond the box....... ;-) Thank you for opening my eyes to that! Yes we will consider that version as an option for our needs. I will say that the Federal version is more compact but since our parts aren't that big, that probably really isn't an issue for us.

-Jim