Surface plate support quick question

All of the higher end Standridge stands use two adjustable elevator bolts, and two more on a rocker arm, making the leveling as per a 3 point system, but supporting on all 4 Bessel points. For long term flatness, the surface plate (especially large ones) need to be supported equally on all 4 Bessel points. (.2204 from the edges, as I dimly recall)
 
All of the higher end Standridge stands use two adjustable elevator bolts, and two more on a rocker arm, making the leveling as per a 3 point system, but supporting on all 4 Bessel points. For long term flatness, the surface plate (especially large ones) need to be supported equally on all 4 Bessel points. (.2204 from the edges, as I dimly recall)

>.2204 from the edges... are you a suspect for photographic memory?

So after re-reading all this is it a yea or nay for 3 points? It sounds like on the large plates (3'x3' Or bigger?) that they need 4. At the largest I would have a 3' x 3' . I just wonder at what width or thickness would it start to flex, twist or distort. If I'm using it to scrape small ways my wooden workbench might not be where I want to set this thing up. I know my garage floor is bowed like >insert anything you want here< . I know I won't have a Harley in there. So I guess I'm still up in the air on this. Then it gets back to will I ever get my work to a level quality that would require this amount of OCD in advance. :chemist: Perhaps!

Paul
 
I have 3 surface plates, and here's what I'm doing with them:

- an 11"X 9"X2.5" (unknown grade) from China - used only as a bench plate, for lapping only. supported by bench. stored in a drawer.
- a 12"X18"X3", (B grade) - just unmounted it from its stand, because I'm reusing the stand. It will be mounted on 3 points, just because it's easier.
- a newly acquired 18" X 24" Mitutoyo A grade plate. see below...

... first a short story: I have a friend that bought a Mitutoyo AA grade surface plate in the 36 X 48 X 5 inch size - and mounted it using the 4 corners... After 36 years, it has dropped about .006 in the centre. It is now worse than a shop grade plate. I wouldn't take it if he gave it to me.

So being a little OCD and/or anal-retentitive (yes it does have a hyphen BTW), and because I'm not from Standridge Granite I am mounting my new surface plate on a rolling Tool and Die cart, also recently acquired, which is made of 10 gauge pressed steel. The plate will be mounted using 4 Bessel points with a pivot...

The best advice I can give to you is that if you are mounting it on a non-movable table, make the feet of the table adjustable so ti is properly supported( so the table won't twist) . No use twisting your surface plate for the lack of 1$ worth of leveling bolts. If it is on a moving base, the your plate's sub-base must be overly rigid, so as to support the plate properly. No matter what, the plate has to ber very rigidly supported to maintain calibration.

3 or 4? your choice - if your manufacturer won't commit, I'd use 4. If you go with a Standridge 24 X 36, they explicitly say use 3 because they calibrate them that way. I hope this is more helpful than confusing,...
 
This guy is great. I'm surprised he wasn't on my subscribed to list.
Paul
I have 3 surface plates, and here's what I'm doing with them:

- an 11"X 9"X2.5" (unknown grade) from China - used only as a bench plate, for lapping only. supported by bench. stored in a drawer.
- a 12"X18"X3", (B grade) - just unmounted it from its stand, because I'm reusing the stand. It will be mounted on 3 points, just because it's easier.
- a newly acquired 18" X 24" Mitutoyo A grade plate. see below...

... first a short story: I have a friend that bought a Mitutoyo AA grade surface plate in the 36 X 48 X 5 inch size - and mounted it using the 4 corners... After 36 years, it has dropped about .006 in the centre. It is now worse than a shop grade plate. I wouldn't take it if he gave it to me.

So being a little OCD and/or anal-retentitive (yes it does have a hyphen BTW), and because I'm not from Standridge Granite I am mounting my new surface plate on a rolling Tool and Die cart, also recently acquired, which is made of 10 gauge pressed steel. The plate will be mounted using 4 Bessel points with a pivot...

The best advice I can give to you is that if you are mounting it on a non-movable table, make the feet of the table adjustable so ti is properly supported( so the table won't twist) . No use twisting your surface plate for the lack of 1$ worth of leveling bolts. If it is on a moving base, the your plate's sub-base must be overly rigid, so as to support the plate properly. No matter what, the plate has to ber very rigidly supported to maintain calibration.

3 or 4? your choice - if your manufacturer won't commit, I'd use 4. If you go with a Standridge 24 X 36, they explicitly say use 3 because they calibrate them that way. I hope this is more helpful than confusing,...

Unreal how multi-million year old granite moves in a few years. This does help me quite a bit. I'll have to buy some really ridged box tubing to weld up once I select a plate. I've got a lot of measuring equipment to purchase going forward. Seems the surface plate is the base point for being able to measure with accuracy.

Being as new to it as I am I've got a long way to go. Since there is never an end to the learning on this topic I think I've picked the perfect hobby.

Paul
 
Being as new to it as I am I've got a long way to go. Since there is never an end to the learning on this topic I think I've picked the perfect hobby.

Yes there is! Door #3 has a tunnel with an infinite length filled with infinite cubby holes just waiting for someone to say; "I didn't know that."

Now, I'll say I was with him up to the point where he puts a beam on the third support. I still think we get stuck thinking **level** when all we are really striving for is flat. The plate is certified (if it is of certifiable quality) and it needs to be supported so there's no force or tension on any specific point. I don't think there's been proof that a plate supported on three points ends up with to of the corners drooping. I think if we replace the word support with suspend we arrive where we need to be.

With that said, I wouldn't want the workbench or support to be out of level to a point where things roll off the plate.
 
I think if I ever get room and need for a larger plate, I will build a heavy stand with leveling feet, just because it may have to move some time in the future.....never know. But I will build the top as a tray and fill it about an inch deep with self leveling floor compound. That stuff seems to flow out really nicely and should give even support. HOWEVER, the catch is that there is no guarantee that the top and bottom of any plate are parallel, nor that the bottom is actually flat. But if I time it right and sit the plate in the compound just before it sets up, then I would have virtually 100% contact and therefore support for the entire plate. It wouldn't matter so much if it weren't perfectly level at that point, as I would adjust it with the feet. It doesn't have to be level, but it sure is nice at times to have a known level surface. And I mean really level, so close I could use it (to a degree) to calibrate levels. Like the one I'm about to build as soon as I talk Ken into scrounging me a piece of nice, aged CI.
 
TW--that is bound to fail as changes in the mounting surface will impart stress on the surface plate. If that were a workable solution, the big guys would be using it already.
 
TW--that is bound to fail as changes in the mounting surface will impart stress on the surface plate. If that were a workable solution, the big guys would be using it already.

OK to take this a step beyond this. Could you mount the surface plate support system in a way that it would be stabilized and protected from vibration. Much like they earth quake proof buildings? Almost in a stiffened rubberized mount that would take the stress or any expansion of the bench material?
 
OK to take this a step beyond this. Could you mount the surface plate support system in a way that it would be stabilized and protected from vibration. Much like they earth quake proof buildings? Almost in a stiffened rubberized mount that would take the stress or any expansion of the bench material?
There's no such thing as an earthquake proof building. :grin big::grin big:

....but we do keep trying.
 
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